Unnamed: 0 int64 0 2.34M | titles stringlengths 5 21.5M | abst stringlengths 1 21.5M |
|---|---|---|
8,100 | Survival after transcoronary ablation of septal hypertrophy in hypertrophic obstructive cardiomyopathy (TASH): a 10 year experience. | Catheter-based treatment of patients with hypertrophic obstructive cardiomyopathy (HOCM) by alcohol ablation (transcoronary ablation of septal hypertrophy, TASH) leads to symptomatic and haemodynamic improvement. However, little is known regarding the survival and its evolution since the introduction of the method in 1995. Theoretically, the method may be harmful, because widening of the obstructed left ventricular outflow tract is achieved by a septal infarction and subsequently by a potentially arrhythmogenic scar.</AbstractText>This study sought to determine the impact of TASH on the survival of all patients with HOCM treated in our institution between 1995 and 2005.</AbstractText>Survival was assessed from the early beginning in each of 644 consecutive patients to April 2005. Group A comprises a first series of 329 patients who were treated in a dose finding strategy with decreasing amounts of ethanol until December 2001, on average, from 2.9 ml to 0.93 ml/patient. The survival of this group was analysed using Kaplan-Meier estimates, multivariate Cox regression and Log-Rank testing. Group B comprises 315 patients of the following "low alcohol dose era" (mean amount of ethanol 0.8 +/- 0.4 ml, range 0.3-1.5 ml) and their mid-term survival (period to first regular 6-month post-procedural control).</AbstractText>All patients (age 58 +/- 15 years, 99.2% follow up, mean 1.4 years): 33 patients died (5.1% all cause mortality), including perioperative deaths. 14/33 (42%) died from cardiac reasons. Annual total (all cause) mortality was 3.2%, total in-hospital mortality 1.2% in all patients (8 of 644 patients, 6 of them with severe comorbidity) and 0.4% in low risk patients. Annual cardiac mortality after hospital discharge was 0.7% (6 patients, all with sudden death). Group A (age 58 +/- 15 years, 98.8% follow up, mean 2.1 years, maximum 6.2 years): 29 patients died (total annual mortality 4.3%), 10 of them from hypertrophic cardiomyopathy related reasons resulting in a total in-hospital mortality of 1.8% (6 deaths), a cardiac annual mortality of 1.5% (including hospital mortality) and 0.6%/year after hospital discharge. Age was identified as an independent predictor of increased overall mortality (P = 0.002) and lower alcohol dosage and the absence of atrial fibrillation as independent predictors of reduced cardiac mortality (P = 0.005 and P = 0.039, respectively). With focus on the median value of the alcohol quantity (2.0 ml), patients treated with high amounts (>2.0 ml) showed a higher total mortality than patients treated with small amounts (< or =2.0 ml) (P = 0.031) and alcohol turned out to be an independent predictor of survival (P = 0.047). The same holds true for a homogenous subset of 262 patients with respect to cardiac mortality (P = 0.018). Group B (age 57 +/- 14 years, 99.7% follow up, mean 7.3 months): Total in-hospital mortality was 0.6% (2 of 315 patients; P = 0.173, group A/B) and cardiac in-hospital mortality 0% (P = 0.016, group A/B). During follow up two patients died, both of them experienced a sudden death reflecting an annual mortality of 1.0%.</AbstractText>These data represent the largest available database on survival after alcohol septal ablation of HOCM from a single centre with large experience, and its evolution over 10 years with increasing procedural experience including the pronounced reduction of ethanol quantity in a systematic doses finding strategy. The in-hospital mortality has become very low. Cardiac survival during follow up was excellent, however, the well-known risk of sudden death is not completely eliminated. Longer follow-up time would be desirable for definite evaluation of this relatively new therapeutic option in the management of HOCM.</AbstractText> |
8,101 | Effectiveness of bystander-initiated cardiac-only resuscitation for patients with out-of-hospital cardiac arrest. | Previous animal and clinical studies suggest that bystander-initiated cardiac-only resuscitation may be superior to conventional cardiopulmonary resuscitation (CPR) for out-of-hospital cardiac arrests. Our hypothesis was that both cardiac-only bystander resuscitation and conventional bystander CPR would improve outcomes from out-of-hospital cardiac arrests of < or = 15 minutes' duration, whereas the addition of rescue breathing would improve outcomes for cardiac arrests lasting > 15 minutes.</AbstractText>We carried out a prospective, population-based, observational study involving consecutive patients with emergency responder resuscitation attempts from May 1, 1998, through April 30, 2003. The primary outcome measure was 1-year survival with favorable neurological outcome. Multivariable logistic regression analysis was performed to evaluate the relationship between type of CPR and outcomes. Among the 4902 witnessed cardiac arrests, 783 received conventional CPR, and 544 received cardiac-only resuscitation. Excluding very-long-duration cardiac arrests (> 15 minutes), the cardiac-only resuscitation yielded a higher rate of 1-year survival with favorable neurological outcome than no bystander CPR (4.3% versus 2.5%; odds ratio, 1.72; 95% CI, 1.01 to 2.95), and conventional CPR showed similar effectiveness (4.1%; odds ratio, 1.57; 95% CI, 0.95 to 2.60). For the very-long-duration arrests, neurologically favorable 1-year survival was greater in the conventional CPR group, but there were few survivors regardless of the type of bystander CPR (0.3% [2 of 624], 0% [0 of 92], and 2.2% [3 of 139] in the no bystander CPR, cardiac-only CPR, and conventional CPR groups, respectively; P<0.05).</AbstractText>Bystander-initiated cardiac-only resuscitation and conventional CPR are similarly effective for most adult out-of-hospital cardiac arrests. For very prolonged cardiac arrests, the addition of rescue breathing may be of some help.</AbstractText> |
8,102 | Exercise oscillatory ventilation: instability of breathing control associated with advanced heart failure. | Instability of breathing control due to heart failure (HF) manifests as exercise oscillatory ventilation (EOV). Prior descriptions of patients with EOV have not been controlled and have been limited to subjects with left ventricular ejection fraction (LVEF) of <or= 0.40. The aim of this study was to compare clinical characteristics including ventilatory responses of subjects with EOV to those of control subjects with HF matched for LVEF.</AbstractText>Subjects (n = 47) were retrospectively identified from 1,340 consecutive patients referred for cardiopulmonary exercise testing. Study inclusion required EOV without consideration of LVEF while control subjects (n = 47) were composed of HF patients with no EOV matched for LVEF. Characteristics for each group were summarized and compared.</AbstractText>For EOV subjects, the mean LVEF was 0.37 (range, 0.11 to 0.70), and 19 subjects (41%) had an LVEF of >or= 0.40. Compared to control subjects, EOV subjects had increased left atrial dimension, mitral E-wave velocity, and right heart pressures as well as decreased exercise tidal volume response, functional capacity, rest and exercise end-tidal carbon dioxide, and increased ventilatory equivalent for carbon dioxide and dead space ventilation (all p < 0.05). Multivariate analysis demonstrated atrial fibrillation (odds ratio, 6.7; p = 0.006), digitalis therapy (odds ratio, 0.27; p = 0.02), New York Heart Association class (odds ratio, 3.5; p = 0.0006), rest end-tidal carbon dioxide (odds ratio, 0.87; p = 0.005), and peak heart rate (odds ratio, 0.98; p = 0.02) were independently associated with EOV.</AbstractText>Patients with EOV have clinical characteristics and exercise ventilatory responses consistent with more advanced HF than patients with comparable LV systolic function; EOV may occur in HF patients with an LVEF of >or= 0.40.</AbstractText> |
8,103 | Repair of aortic arch and the impact of cross-clamping time, New York Heart Association stage, circulatory arrest time, and age on operative outcome. | Aortic arch replacement is associated with high morbidity and mortality.</AbstractText>We evaluated the postoperative complications and risk factors in 32 consecutive patients after aortic arch replacement.</AbstractText>The mean age was 61+/-15 years and male to female ratio was 24/8. Diameter of ascending aorta was 6.0+/-0.8 cm and diameter of aortic arch was 5.2+/-1.2 cm. The average New York heart association (NYHA) class was 2+/-1. The 30-day mortality was 6.2% (2 of 32 patients), one patient died intraoperatively (3%); all surviving 30 patients had f/u for at least six months, a total of 3 of 32 patients had died within six months, actuarial survival was 90% at six months. The overall incidence of neurologic adverse events was 9%; however, only one patient had a cerebrovascular accident (CVA) with a focal deficit (3%). The other two patients had global neurologic dysfunction. Other significant postoperative complications included atrial fibrillation in 15 patients (46%), ventricular fibrillation requiring cardiopulmonary resuscitation (CPR) in one patient (3%), and pericardial effusion requiring pericardicentesis in eight patients (25%). The need for blood transfusion correlated with the cross-clamping length (Pearson r 0.62; 95% confidence interval (CI), 0.35-0.79; P-value 0.0001; R(2)=0.38). Cross-clamp time (139+/-58 min) did not have an impact on length of intensive care unit (ICU) stay (Pearson r -0.09; 95% CI -0.39-0.23; P=0.58; R(2)=0.008) nor did the length of circulatory arrest (95% CI -0.44-0.21, P=0.44). The length of stay in the ICU (142+/-128 h) correlated with the NYHA stage of the patient (95% CI 0.001-0.62, P=0.04). The length of stay (LOS) (12+/-6 days) correlated with age of the patients (95% CI 0.03-0.57, P=0.03).</AbstractText>Elderly patients and patients with high NYHA class need close postoperative monitoring in the ICU. A short circulatory arrest and aortic clamp time do not extend the LOS in ICU or in the hospital.</AbstractText> |
8,104 | [Prevalence and risk factors of atrial tachyarrhythmia before and after percutaneous closure of secundum atrial septal defect in patients over 40 years of age]. | In this study, we attempted to observe the prevalence and risk factors of atrial tachyarrhythmias (AT) before and after transcatheter closure of atrial septal defect (ASD).</AbstractText>264 adult patients aged over 40 years (67 men and 197 women) who underwent transcatheter closure of ASD between September, 1997 and December, 2005 were included in this study. Incidence of preoperative and postoperative AT was analyzed, risk factors for AT were determined with multivariate stepwise logistic regression analysis.</AbstractText>Incidence of AT before closure was 9.1% (24/264). Twenty-nine patients (11.0 percent) developed AT after transcatheter closure (24 atrial fibrillation, 1 paroxysmal flutter, 4 paroxysmal atrial arrhythmia). The prevalence in patients of 40 to 49 years, 50 to 59 years and above 60 years was 4.3%, 14.6% and 26.3%, respectively. Most patients with atrial fibrillation were symptomatic. Compared to patients without AT, patients developed AT after closure were significantly older (53.0 +/- 7.6 years vs. 47.8 +/- 6.6 years, P < 0.01) and had larger defects (23.5 +/- 5.7 mm vs. 21.3 +/- 5.2 mm, P > 0.05), higher systolic pulmonary pressure (38.4 +/- 13.1 vs. 34.1 +/- 10.1, P < 0.05), larger left atrium dimension [(38.0 +/- 3.9) mm Hg (1 mm Hg = 0.133 kPa) vs. (33.6 +/- 4.4) mm Hg, P < 0.01], larger end diastolic right ventricular dimension [(34.7 +/- 5.9) mm vs. (32.1 +/- 6.8) mm, P > 0.05], higher incidence of tricuspid regurgitation (96.6% vs. 75.3%, P = 0.01), higher incidence of preoperative AT (51.7% vs. 3.8%, P < 0.01) and higher incidence of hypertension (27.6% vs. 10.2%, P = 0.013). Multivariate analysis showed that older age [odds ratio (OR) 2.659, 95 percent confidence interval (CI) 1.080 to 6.547, P < 0.05], presence of preoperative AT (OR 54.311, CI 9.819 to 300.395, P < 0.01), and left atrial enlargement (OR 8.529 per 10 mm increment, CI 2.162 to 33.643, P < 0.01) were independent predictors of AT after closure.</AbstractText>Incidence of AT was similar before and after percutaneous closure in patients with atrial septal defects aged 40 years and over. The risk of AT is related to the age at the time of transcatheter closure, the presence of preoperative AT and enlarged left atria.</AbstractText> |
8,105 | Deglutition induced atrial tachycardia and atrial fibrillation. | Deglutition induced supraventricular tachycardia is an uncommon condition postulated to be a vagally mediated phenomenon due to mechanical stimulation. Patients usually present with mild symptoms or may have severe debilitating symptoms. Treatment with Class I agents, beta blockers, calcium channel blockers, amiodarone and radiofrquency catheter ablation has shown to be successful in the majority of reported cases. We report the case of a 46-year-old healthy woman presenting with palpitations on swallowing that was documented to be transient atrial tachycardia with aberrant ventricular conduction as well as transient atrial fibrillation. She was successfully treated with propafenone with no induction of swallowing-induced tachycardia after treatment. This is also the first case to show swallowing-induced atrial tachycardia and atrial fibrillation in the same patient. |
8,106 | Pseudo crosstalk behavior in a patient with atrio-ventricular block and implanted biventricular defibrillator. | We present a 59-year-old man with a dilated cardiomyopathy (ejection fraction = 20%), congestive heart failure and atrio-ventricular (AV) block who underwent implantation of a biventricular defibrillator (BiV ICD). While undergoing cardiac transplant evaluation for drug-refractory ventricular fibrillation, his telemetry recorded findings resembling crosstalk inhibition. Device interrogation was normal. All episodes occurred at 1:00 a.m. suggesting a routine device operation. Left ventricular capture management, a new feature that automatically measures left ventricular pacing thresholds at 1:00 a.m., had been programmed to Monitor. Understanding this sophisticated pacing algorithm might avoid confusion when operative in patients with AV block. |
8,107 | Two cases of short QT interval. | The epidemiology of short QT interval remains unclear. We attempted to determine the incidence and clinical characteristics of short QT interval in a longitudinal cohort study.</AbstractText>A total of 19,153 subjects (7,525 male, 11,628 female) were enrolled in the study and all available electrocardiograms (ECGs) were investigated longitudinally from 1958 through 2003. We defined short QT interval as QTc of less than 350 ms.</AbstractText>Of the 19,153 subjects, two met the criteria of short QT interval and allowed for prevalence and incidence estimates for short QT interval as 0.01% and 0.39/100,000 person-years, respectively. Both cases had neither a family history of sudden cardiac death, nor a history of drug use that might have affected for QT interval. Case 1 was a female with history of ischemic heart disease. Case 2 was a 60-year-old male who exhibited a short QT interval for the first time when he was 26 years of age. He had sick sinus syndrome as an underlying heart disease.</AbstractText>Of the 19,153 subjects in this study, none were identified as having the short QT syndrome, with associated high risk of ventricular tachyarrhythmia, atrial fibrillation, and sudden death. Two subjects were identified as having QTc of less than 350 ms, and allowed prevalence and incidence estimates to be made of short QT interval. There observations were suggestive of clinical relationships between short QT interval and organic or electrophysiological heart disease.</AbstractText> |
8,108 | Morphology-enhanced atrial event classification improves sensing in pacemakers. | In atrial-based pacing, appropriate therapy and reliable diagnostics depend on detection and discrimination of atrial signals. Accurate classification of atrial events is mainly confounded by oversensing of ventricular far-field R-wave signals (FFRW), but attempts to reject FFRWs by manipulating atrial sensitivity and/or postventricular atrial blanking period (PVAB) may result in undersensing (especially of atrial fibrillation, AF) or in 2:1 atrial flutter detection. The objective of this study is therefore to evaluate if such methods can be improved by morphology-enhanced atrial event classification (MORPH).</AbstractText>Twenty-four-hour ambulatory atrial electrograms were recorded from continuous telemetry of digital pacemakers. Half of the recording was used for collecting two individual morphology parameters that discriminated P-waves from FFRWs in every patient (learning phase). The other half was used to test the MORPH algorithm against traditional methods (classification phase).</AbstractText>In 44/48 patients, data were suitable for analysis. Average P and FFRW amplitudes were 1.96 mV versus 0.61 mV (P < 0.001). The interval between ventricular events and FFRW oversensing (VA interval) averaged at 14 ms during sensing and at 118 ms during pacing in the ventricle. Compared to nominal ("Factory") settings, the MORPH algorithm improved the sensitivity for P-wave recognition from 97.2% to 99.2%, the specificity from 91.9% to 99.96%, and the accuracy from 95.3% to 99.4% (P < 0.01 for all).</AbstractText>By improving atrial signal discrimination, morphology analysis of atrial electrograms allows for high atrial sensitivity settings, and potentially improves the reliability of atrial arrhythmia diagnostics in heart rhythm devices.</AbstractText> |
8,109 | Noradrenaline reduces ischemia-induced arrhythmia in anesthetized rats: involvement of alpha1-adrenoceptors and mitochondrial K ATP channels. | We have evaluated the part played by the mitochondrial ATP-sensitive potassium (mK(ATP)) channels on effect of alpha(1)-adrenoceptor activation by noradrenaline in ischemia-induced ventricular arrhythmia.</AbstractText>Anesthetized rats were subjected to 25 minutes of regional ischemia, and infarct size (IS) and ischemia-induced ventricular arrhythmia were measured. Group I served as saline control with ischemia (n = 9). In group II (n = 9), the ischemic period was preceded by three short episodes of ischemia, followed by reperfusion. In group III, noradrenaline (2 microg/kg, IV, n = 9) was injected prior to ischemia. In group IV, an alpha(1)-adrenoceptor blocker (prazosin, 0.5 mg/kg, IV, n = 6) was administrated prior to noradrenaline injection. In Groups V and VI, rats received a specific mitochondrial K(ATP) channel inhibitor [5-hydroxydecanoic acid (5-HD), 10 mg/kg, IV, n = 6] prior to or after noradrenaline injection. Ischemic preconditioning (IPC) and noradrenaline markedly reduced incidences of ventricular fibrillation (VF) (0%, 0% vs. 55.5% in control, P < 0.05) and ventricular tachycardia (VT) (11%, 44.5% vs. 100% in control, P < 0.001 and P < 0.05), duration of VF + VT (3 +/- 1 seconds, 4.7 +/- 2.1 seconds vs. 52.9 +/- 6 seconds in control, P < 0.001), number of VF + VT episodes (1.7 +/- 1.7, 5.75 +/- 2.4 vs. 60.5 +/- 8 in control, P < 0.001), severity of arrhythmias (0.3 +/- 0.3, 1.7 +/- 0.5 vs. 3.9 +/- 0.3 in control rats, P < 0.001 and P < 0.01), and IS (13.6 +/- 1.8%, 18.2 +/- 1.5% vs. 49.6 +/- 2.4% in control, P < 0.001). Administration of prazosin or 5-HD prior to or after noradrenaline injection intensified incidences of VF (66.6%, 66.6% and 50%, P < 0.05) and VT (100%, 100%, and 100%, P < 0.05), duration of VF + VT episodes (70.2 +/- 10.5 seconds, 69.8 +/- 6.75 seconds, and 60.8 +/- 14.9 seconds, P < 0.001), number of VF + VT episodes (56 +/- 16.4, 67 +/- 11, and 45 +/- 3.5, P < 0.01, P < 0.001, and P < 0.05), severity of arrhythmias(3.8 +/- 0.3, 4 +/- 0.5, and 3.7 +/- 0.2, P < 0.01, P < 0.05, and P < 0.01), and IS (45.5 +/- 3%, 46.8 +/- 3.4%, and 43 +/- 2.5%, respectively, P < 0.001) compared with the noradrenaline-treated group.</AbstractText>Prazosin or 5-HD treatment eliminated the beneficial effects of noradrenaline on arrhythmogenesis and infarct size.</AbstractText> |
8,110 | [The clinical challenge of the atrial fibrillation]. | Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice. It consists in the triggering of 300 to 600 atrial waves per minute. The ventricular rate depends of the AV node refractory period that without treatment it is very high. This rapid response reduces the ventricular filling period with two consequences, the increase of venous pressures, and the reduction of the cardiac output, determining heart failure and myocardial ischaemia. The lack of atrial contraction, induces thrombus formation with high risk for systemic embolism. Cardioversion of atrial fibrillation is associated with an increased risk of stroke. Thromboembolism happens when atria recover the contraction, that in chronic AF can be several weeks after cardioversion. The management of AF involves three objectives: stroke prevention, rate control, and correction of rhythm disturbance. We need an appropriate approach to antithrombotic therapies for stroke prevention. A proper strategy and safe use of old and new Drugs for rate control or non electrical cardioversion to sinusal rhythm. The useful of statins, ARBII and ACEI for the primary and secondary prevention of AF. For symptomatic patients the electrical managing of the AF is the alternative. Cardioversion is performed as part of a rhythm-control treatment strategy but ablation of the perivenosos pulmonary circuits, ablation of the AV node and implantation of a pacemaker are another alternatives. |
8,111 | [New strategies in the treatment of atrial fibrillation]. | Atrial fibrillation (AFb) is the most common sustained cardiac arrhythmia. Once initiated, AFb alters atrial electrical and structural properties (remodeling) that promotes its maintenance and recurrence. Treatment is directed to restore and maintain the sinus rhythm, to control the ventricular rate and to prevent thromboembolic complications. Recent evidence indicates that angiotensin converting enzyme inhibitors, angiotensin AT1 receptor antagonists and statins modify atrial remodeling and reduce the incidence of AFb, thus possibly representing a new alternative in the treatment of the arrhythmia. |
8,112 | Detection of phase singularities in triangular meshes. | Phase singularities have become a key marker in animal and computer models of atrial and ventricular fibrillation. However, existing algorithms for the automatic detection of phase singularities are limited to regular, quadratic mesh grids. We present an algorithm to automatically and exactly detect phase singularities in triangular meshes.</AbstractText>For each node an oriented path inscribing the node with one unit of spatial discretization is identified. At each time step the phase information is calculated for all nodes. The so-called topological charge is also computed for each node. A non-zero (+/- 2pi) charge is obtained for all nodes with a path enclosing a phase singularity. Thus all charged nodes belonging to the same phase singularity have to be clustered.</AbstractText>With the use of the developed algorithm, phase singularities can be detected in triangular meshes with an accuracy of below 0.2 mm - independent of the type of membrane kinetics used.</AbstractText>With the possibility to detect phase singularities automatically and exactly, important quantitative data on cardiac fibrillation can be gained.</AbstractText> |
8,113 | Electromagnetic modelling of current flow in the heart from TASER devices and the risk of cardiac dysrhythmias. | Increasing use by law enforcement agencies of the M26 and X26 TASER electrical incapacitation devices has raised concerns about the arrhythmogenic potential of these weapons. Using a numerical phantom constructed from medical images of the human body in which the material properties of the tissues are represented, computational electromagnetic modelling has been used to predict the currents arising at the heart following injection of M26 and X26 waveforms at the anterior surface of the chest (with one TASER 'barb' directly overlying the ventricles). The modelling indicated that the peak absolute current densities at the ventricles were 0.66 and 0.11 mA mm(-2) for the M26 and X26 waveforms, respectively. When applied during the vulnerable period to the ventricular epicardial surface of guinea-pig isolated hearts, the M26 and X26 waveforms induced ectopic beats, but only at current densities greater than 60-fold those predicted by the modelling. When applied to the ventricles in trains designed to mimic the discharge patterns of the TASER devices, neither waveform induced ventricular fibrillation at peak currents >70-fold (for the M26 waveform) and >240-fold (for the X26) higher than the modelled current densities. This study provides evidence for a lack of arrhythmogenic action of the M26 and X26 TASER devices. |
8,114 | Sinus node disease and arrhythmias in the long-term follow-up of former professional cyclists. | Significant brady- and tachyarrhythmias may occur in active endurance athletes. It is controversial whether these arrhythmias do persist after cessation of competitive endurance training.</AbstractText>Among all 134 former Swiss professional cyclists [hereafter, former athletes (FAs)] participating at least once in the professional bicycle race Tour de Suisse in 1955-1975, 62 (46%) were recruited for the study. The control group consisted of 62 male golfers matched for age, weight, hypertension, and cardiac medication. All participants were screened with history, clinical and echocardiographic examination, ECG, and 24 h ECG. The time for the last bicycle race of FAs was 38 +/- 6 years. The mean age at examination was 66 +/- 6 years in controls and 66 +/- 7 years in FAs (P = 0.47). The percentage of study participants with >4 h current cardiovascular training per week was identical. QRS duration (102 +/- 20 vs. 95 +/- 13 ms, P = 0.03) and corrected QTc interval (416 +/- 27 vs. 404 +/- 18, P = 0.004) were longer in FAs. There was no significant difference in the number of isolated atrial or ventricular premature complexes, or supraventricular tachycardias in the 24 h ECG; however, ventricular tachycardias tended to occur more often in FAs than in controls (15 vs. 3%, P = 0.05). The average heart rate was lower in FAs (66 +/- 9 vs. 70 +/- 8 b.p.m.) (P = 0.004). Paroxysmal or persistent atrial fibrillation or flutter was reported more often in FAs (P = 0.028). Sinus node disease (SND), defined as bradycardia of <40 b.p.m. (10 vs. 2%), atrial flutter (6 vs. 0%), pacemaker for bradyarrhythmias (3 vs. 0%), and/or maximal RR interval of >2.5 s (6 vs. 0%), was more common in FA (16%) than in controls (2%, P = 0.006). Observed survival of all FAs was not different from the expected.</AbstractText>Among FAs, SND occurred significantly more often compared with age-matched controls, and there is trend towards more frequent ventricular tachycardias. Further studies have to evaluate prevention of arrhythmias with extreme endurance training, the necessity of regular follow-up of heart rhythm, and management of arrhythmias in former competitive endurance athletes.</AbstractText> |
8,115 | Protective mechanisms of resveratrol against ischemia-reperfusion-induced damage in hearts obtained from Zucker obese rats: the role of GLUT-4 and endothelin. | The resveratrol-induced cardiac protection was studied in Zucker obese rats. Rats were divided into five groups: group 1, lean control; group 2, obese control (OC); group 3, obese rats treated orally with 5 mg kg(-1) day(-1) of resveratrol (OR) for 2 wk; group 4, obese rats received 10% glucose solution ad libitum for 3 wk (OG); and group 5, obese rats received 10% glucose for 3 wk and resveratrol (OGR) during the 2nd and 3rd wk. Body weight, serum glucose, and insulin were measured, and then hearts were isolated and subjected to 30 min of ischemia followed by 120 min of reperfusion. Heart rate, coronary flow, aortic flow, developed pressure, the incidence of reperfusion-induced ventricular fibrillation, and infarct size were measured. Resveratrol reduced body weight and serum glucose in the OR compared with the OC values (414 +/- 10 g and 7.08 +/- 0.41 mmol/l, respectively, to 378 +/- 12 g and 6.11 +/- 0.44 mmol/l), but insulin levels were unchanged. The same results were obtained for the OG vs. OGR group. Resveratrol improved postischemic cardiac function in the presence or absence of glucose intake compared with the resveratrol-free group. The incidence of ventricular fibrillation and infarct size was reduced by 83 and 20% in the OR group, and 67 and 16% in the OGR group, compared with the OC and OG groups, respectively. Resveratrol increased GLUT-4 expression and reduced endothelin expression and cardiac apoptosis in ischemic-reperfused hearts in the presence or absence of glucose intake. Thus the protective effect of resveratrol could be related to its direct effects on the heart. |
8,116 | Altered expression of connexin43 contributes to the arrhythmogenic substrate during the development of heart failure in cardiomyopathic hamster. | Heart failure is known to predispose to life-threatening ventricular tachyarrhythmias even before compromising the systemic circulation, but the underlying mechanism is not well understood. The aim of this study was to clarify the connexin43 (Cx43) gap junction remodeling and its potential role in the pathogenesis of arrhythmias during the development of heart failure. We investigated stage-dependent changes in Cx43 expression in UM-X7.1 cardiomyopathic hamster hearts and associated alterations in the electrophysiological properties using a high-resolution optical mapping system. UM-X7.1 hamsters developed left ventricular (LV) hypertrophy by ages 6 approximately 10 wk and showed a moderate reduction in LV contractility at age 20 wk. Appreciable interstitial fibrosis was recognized at these stages. LV mRNA and protein levels of Cx43 in UM-X7.1 were unaffected at age 10 wk but significantly reduced at 20 wk. The expression level of Ser255-phosphorylated Cx43 in UM-X7.1 at age 20 wk was significantly greater than that in control golden hamsters at the same age. In UM-X7.1 at age 10 wk, almost normal LV conduction was preserved, whereas the dispersion of action potential duration was significantly increased. UM-X7.1 at age 20 wk showed significant reduction of cardiac space constant, significant decrease in conduction velocity, marked distortion of activation fronts, and pronounced increase in action potential duration dispersion. Programmed stimulation resulted in sustained ventricular tachycardia or fibrillation in UM-X7.1. LV activation during polymorphic ventricular tachycardia was characterized by multiple phase singularities or wavebreaks. During the development of heart failure in the cardiomyopathic hamster, alterations of Cx43 expression and phosphorylation in concert with interstitial fibrosis may create serious arrhythmogenic substrate through an inhibition of cell-to-cell coupling. |
8,117 | Driving and implantable cardioverter-defibrillator shocks for ventricular arrhythmias: results from the TOVA study. | This study examined the risk of implantable cardioverter-defibrillator (ICD) shocks for ventricular tachycardia (VT) or ventricular fibrillation (VF) associated with driving.</AbstractText>Concerns regarding VT/VF occurring during driving are the basis for driving restrictions in ICD patients; however, limited data are available to inform recommendations.</AbstractText>This study used a prospective nested case-crossover design to compare the risk of ICD shock for VT/VF both during and up to 60 min after an episode of driving as compared with that during other activities among 1,188 ICD patients enrolled in the TOVA (Triggers of Ventricular Arrhythmia) study.</AbstractText>Over a median follow-up of 562 days, there were 193 ICD shocks for VT/VF with data on exposure to driving before ICD shock. The absolute risk of ICD shock for VT/VF within 1 h of driving was estimated to be 1 episode per 25,116 person-hours spent driving. The ICD shocks for VT/VF were twice as likely to occur within 1 h of driving a car as compared with other times (relative risk [RR] 2.24, 95% confidence interval [CI] 1.57 to 3.18). This risk was specific for shocks for VT/VF and occurred primarily during the 30-min period after driving (RR 4.46, 95% CI 2.92 to 6.82) rather than during the driving episode itself (RR 1.05, 95% CI 0.48 to 2.30).</AbstractText>Although the risk of ICD shock for VT/VF was transiently increased in the 30-min period after driving, the risk was not elevated during driving and the absolute risk was low. These data provide reassurance that driving by ICD patients should not translate into an important rate of personal or public injury.</AbstractText> |
8,118 | Catheter ablation of atrial fibrillation. | Atrial fibrillation is a common arrhythmia associated with significant morbidity including angina, heart failure and stroke. Medical therapy remains suboptimal with significant side effects and toxicities, as well as a high recurrence rate. Catheter ablation or modification of the atrio-ventricular node with pacemaker implantation provides rate control but subjects the patient to the risks of an implantable device and does nothing to reduce the risk of stroke. Pulmonary vein antrum isolation offers a nonpharmacologic means of restoring sinus rhythm, thereby eliminating the morbidity of atrial fibrillation and the need for anti-arrhythmic drugs. |
8,119 | The role of pacemakers in the management of patients with atrial fibrillation. | Pacemakers have an important role in the major strategies for the management of atrial fibrillation, rate control and rhythm control. Of all the current non-pharmacologic therapies for atrial fibrillation, the use of pacemakers impacts the largest number of patients. Pacemakers are used to facilitate medical management of atrial fibrillation with rate control agents and anti-arrhythmic drugs. Atrioventricular junction ablation in conjunction with pacemaker implantation can be an effective therapy for controlling a rapid ventricular rate during atrial fibrillation. The minimization of right ventricular apical pacing in patients with paroxysmal atrial fibrillation is an important objective. Cardiac resynchronization therapy devices are likely to be beneficial in select patients with chronic atrial fibrillation. |
8,120 | Parasympathetic response in chick myocytes and mouse heart is controlled by SREBP. | Parasympathetic stimulation of the heart, which provides protection from arrhythmias and sudden death, involves activation of the G protein-coupled inward rectifying K+ channel GIRK1/4 and results in an acetylcholine-sensitive K+ current, I KACh. We describe a unique relationship between lipid homeostasis, the lipid-sensitive transcription factor SREBP-1, regulation of the cardiac parasympathetic response, and the development of ventricular arrhythmia. In embryonic chick atrial myocytes, lipid lowering by culture in lipoprotein-depleted serum increased SREBP-1 levels, GIRK1 expression, and I KACh activation. Regulation of the GIRK1 promoter by SREBP-1 and lipid lowering was dependent on interaction with 2 tandem sterol response elements and an upstream E-box motif. Expression of dominant negative SREBP-1 (DN-SREBP-1) reversed the effect of lipid lowering on I KACh and GIRK1. In SREBP-1 knockout mice, both the response of the heart to parasympathetic stimulation and the expression of GIRK1 were reduced compared with WT. I KACh, attenuated in atrial myocytes from SREBP-1 knockout mice, was stimulated by SREBP-1 expression. Following myocardial infarction, SREBP-1 knockout mice were twice as likely as WT mice to develop ventricular tachycardia in response to programmed ventricular stimulation. These results demonstrate a relationship between lipid metabolism and parasympathetic response that may play a role in arrhythmogenesis. |
8,121 | Simultaneous multi-vessel coronary artery bypass grafting, ischemic mitral regurgitation repair and descending aortic aneurysm replacement: analysis of technical points. | The combination of coronary artery disease and its complications (ischemic mitral regurgitation etc.) with the aneurysm of the descending thoracic aorta is not a rare case. The single-stage correction of coronary/intracardiac/aortic lesions may be considered as a way of managing the combined patients. Simultaneous multi-vessel coronary artery bypass grafting, suture mitral annuloplasty and descending aortic aneurysm replacement with synthetic prosthesis is described. The operation was performed through the left thoracotomy with cardiopulmonary bypass established by the cannulation of the ascending aorta and of the right atrial appendage. Ventricular fibrillation and no clamping of the ascending aorta were used. The circulatory arrest was induced for the construction of the proximal anastomosis between the descending aorta and the synthetic prosthesis. No complications related to the operation were diagnosed for the 14-month follow-up. Several technical points seem optimal for the combined procedure: (1) Minimization of manipulations on the ascending aorta (using of pedicled left internal thoracic artery; construction of the proximal anastomoses with synthetic aortic prosthesis; unclamped ascending aorta). (2) Revascularization of all coronary areas and correction of intracardiac lesions through the left thoracotomy. Individual planning of the procedural technical points for every patient may provide a safe feasibility of the combined procedure. |
8,122 | Effect of heterogeneous APD restitution on VF organization in a model of the human ventricles. | The onset of ventricular fibrillation (VF) has been associated with steep action potential duration restitution in both clinical and computational studies. Recently, detailed clinical restitution properties in cardiac patients were reported showing a substantial degree of heterogeneity in restitution slopes at the epicardium of the ventricles. The aim of the present study was to investigate the effect of heterogeneous restitution properties in a three-dimensional model of the ventricles using these clinically measured restitution data. We used a realistic model of the human ventricles, including detailed descriptions of cell electrophysiology, ventricular anatomy, and fiber direction anisotropy. We extended this model by mapping the clinically observed epicardial restitution data to our anatomic representation using a diffusion-based algorithm. Restitution properties were then fitted by regionally varying parameters of the electrophysiological model. We studied the effects of restitution heterogeneity on the organization of VF by analyzing filaments and the distributions of excitation periods. We found that the number of filaments and the excitation periods were both dependent on the extent of heterogeneity. An increased level of heterogeneity leads to a greater number of filaments and a broader distribution of excitation periods, thereby increasing the complexity and dynamics of VF. Restitution heterogeneity may play an important role in providing a substrate for cardiac arrhythmias. |
8,123 | In silico study on the effects of IKur block kinetics on prolongation of human action potential after atrial fibrillation-induced electrical remodeling. | Pharmacological treatment with various antiarrhythmic agents for the termination or prevention of atrial fibrillation (AF) is not yet satisfactory. This is in part because the drugs may not be sufficiently selective for the atrium, and they often cause ventricular arrhythmias. The ultrarapid-delayed rectifying potassium current (I(Kur)) is found in the atrium but not in the ventricle, and it has been recognized as a potentially promising target for anti-AF drugs that would be without ventricular proarrhythmia. Several new agents that specifically block I(Kur) have been developed. They block I(Kur) in a voltage- and time-dependent manner. Here we use mathematical models of normal and electrically remodeled human atrial action potentials to examine the effects of the blockade kinetics of I(Kur) on atrial action potential duration (APD). It was found that after AF remodeling, an I(Kur) blocker with fast onset can effectively prolong APD at any stimulus frequency, whereas a blocker with slow onset prolongs APD in a frequency-dependent manner only when the recovery is slow. The results suggest that the voltage and time dependence of I(Kur) blockade should be taken into account in the testing of anti-AF drugs. This modeling study suggests that a simple voltage-clamp protocol with a short pulse of approximately 10 ms at 1 Hz may be useful to identify the effective anti-AF drugs among various I(Kur) blockers. |
8,124 | Spontaneous stellate ganglion nerve activity and ventricular arrhythmia in a canine model of sudden death. | Little information is available on the temporal relationship between instantaneous sympathetic nerve activity and ventricular arrhythmia in ambulatory animals.</AbstractText>The purpose of this study was to determine if increased sympathetic nerve activity precedes the onset of ventricular arrhythmia.</AbstractText>Simultaneous continuous long-term recording of left stellate ganglion (LSG) nerve activity and electrocardiography was performed in eight dogs with nerve growth factor infusion to the LSG, atrioventricular block, and myocardial infarction (experimental group) and in six normal dogs (control group).</AbstractText>LSG nerve activity included low-amplitude burst discharge activity (LABDA) and high-amplitude spike discharge activity (HASDA). Both LABDA and HASDA accelerated heart rate. In the experimental group, most ventricular tachycardia (86.3%) and sudden cardiac death were preceded within 15 seconds by either LABDA or HASDA. The closer to onset of ventricular tachycardia, the higher the nerve activity. The majority of HASDA was followed immediately by either ventricular arrhythmia (21%) or QRS morphology changes (65%). HASDA occurred in a circadian pattern. HASDA occurred twice as often in the experimental group than in the control group. Electrical stimulation of LSG increased transmural heterogeneity of repolarization (Tpeak-end intervals) and induced either ventricular tachycardia or fibrillation in the experimental group but not in the control group. Immunohistochemical studies revealed increased synaptogenesis and nerve sprouting in the LSG in the experimental group.</AbstractText>Two distinct types of LSG nerve activity (HASDA and LABDA) are present in the LSG of ambulatory dogs. The majority of malignant ventricular arrhythmias are preceded by either HASDA or LABDA, with HASDA particularly arrhythmogenic.</AbstractText> |
8,125 | Acute defibrillation performance of a novel, non-transvenous shock pathway in adult ICD indicated patients. | The purpose of this study was to evaluate the efficacy of a totally subcutaneous, anteroposterior defibrillation shock pathway using a long time-constant shock waveform that emulates a proposed device having approximately twice the capacitance and thus twice the available energy of traditional transvenous devices.</AbstractText>A non-transvenous defibrillation system potentially offers advantages over a transvenous system including simplification of the implant procedure and reduction of the impact of device complications by eliminating the need to place a lead within the heart. Previous non-transvenous defibrillation efficacy studies have been reported using anterolateral and anterior-anterior shock vectors. An external anteroposterior shock vector has demonstrated superior efficacy compared to anterolateral shock vectors but a prospective study on an anteroposterior shock vector with implanted electrodes has not been previously reported.</AbstractText>The non-transvenous shock vector consisted of an anterior low pectorally-placed active can emulator electrode and a posterior subcutaneous coil electrode. The shock waveform was a biphasic with 50% tilt per phase and a time constant of decay of 12 ms. Defibrillation efficacy was characterized using a step-down defibrillation threshold protocol (35 J, 25 J, 15 J).</AbstractText>A total of 33 patients with standard ICD indications were enrolled in the study with 32 fully completing the protocol. The patient population was 69% male, with a mean age of 59 +/- 12 years. Mean ejection fraction was 27 +/- 12%. Of the 32 patients tested, 26 patients (81%) were successfully defibrillated at 35 J or less, 18 patients were defibrillated at 25 J or less and 9 patients were successfully defibrillated at 15 J.</AbstractText>Defibrillation using a long time-constant waveform delivered through an anteroposterior non-transvenous pathway including a pectoral active can emulator electrode and a posterior subcutaneous coil electrode is feasible with over 80% of patients defibrillated successfully using 35 J or less.</AbstractText> |
8,126 | Cardiac remodeling and predictors for cardiac death in long-term follow-up of subjects with chronic Chagas' heart disease: a mathematical model for progression of myocardial damage.<Pagination><StartPage>435</StartPage><EndPage>438</EndPage><MedlinePgn>435-8</MedlinePgn></Pagination><Abstract><AbstractText>In a prospective longitudinal study the occurrence of cardiac death was investigated and ongoing cardiac remodeling retrospectively analyzed in regard to adverse outcome. A cohort of 50 subjects with chronic Chagas' disease stratified according to Los Andes groups 1, 2 and 3 were followed-up for (mean+/-SD) 84.2+/-39.0 months. Follow-up was abbreviated by ventricular tachycardia ([VT] incidence: 3.0+/-7.0% year(-1)), first atrial fibrillation episode lasting >24 h ([AF] incidence: 3.3+/-1.0% year(-1)), nonfatal embolic stroke (incidence: 1.3+/-1.0% year(-1)), and cardiac death (mortality rate: 2.3+/-0.8% year(-1)). The relative risk of Los Andes group 3, VT, AF and stroke for cardiac death was, respectively, 25.3 (95%CI [3.5-182.6]), 3.0 (95%CI [1.2-7.3]), 3.6 (95%CI [1.2-10.9]) and 1.1 (95%CI [0.2-7.2]). In a multivariate Cox proportional-hazard model, Los Andes group 3 (hazard ratio=24.5; 95%CI [3.2-189.2]; p<0.01) was independent predictor for cardiac death. LAD and LV mass and not LVEF variation rates differed among group 1 (respectively, 0.03+/-0.1 cm year(-1); 2.4+/-5.7 g year(-1) and -0.1+/-2.4% year(-1)), group 2 (0.04+/-0.1 cm year(-1); 3.7+/-8.8 g year(-1) and -0.8+/-1.4% year(-1)) and group 3 (0.13+/-0.1 cm year(-1), p<0.001; 21.7+/-10.1 g year(-1), p<0.001 and -1.4+/-2.5% year(-1), p=0.26). Variables on admission were linearly related to respectively variation rates (r=0.71; p=0.02) composing a first order linear process with 0.07 months(-1) time constant. In chronic Chagas' disease, initial clinical status is an independent predictor for cardiac death and determines the progression rate of myocardial damage.</AbstractText></Abstract><AuthorList CompleteYN="Y"><Author ValidYN="Y"><LastName>Benchimol-Barbosa</LastName><ForeName>Paulo Roberto</ForeName><Initials>PR</Initials></Author></AuthorList><Language>eng</Language><PublicationTypeList><PublicationType UI="D016422">Letter</PublicationType></PublicationTypeList><ArticleDate DateType="Electronic"><Year>2007</Year><Month>11</Month><Day>28</Day></ArticleDate></Article><MedlineJournalInfo><Country>Netherlands</Country><MedlineTA>Int J Cardiol</MedlineTA><NlmUniqueID>8200291</NlmUniqueID><ISSNLinking>0167-5273</ISSNLinking></MedlineJournalInfo><CitationSubset>IM</CitationSubset><MeshHeadingList><MeshHeading><DescriptorName UI="D000328" MajorTopicYN="N">Adult</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D000368" MajorTopicYN="N">Aged</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D002598" MajorTopicYN="N">Chagas Cardiomyopathy</DescriptorName><QualifierName UI="Q000401" MajorTopicYN="Y">mortality</QualifierName><QualifierName UI="Q000473" MajorTopicYN="N">pathology</QualifierName><QualifierName UI="Q000503" MajorTopicYN="Y">physiopathology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D002908" MajorTopicYN="N">Chronic Disease</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D015331" MajorTopicYN="N">Cohort Studies</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D018450" MajorTopicYN="N">Disease Progression</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D005500" MajorTopicYN="N">Follow-Up Studies</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D006801" MajorTopicYN="N">Humans</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D008875" MajorTopicYN="N">Middle Aged</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D008955" MajorTopicYN="Y">Models, Cardiovascular</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D009206" MajorTopicYN="N">Myocardium</DescriptorName><QualifierName UI="Q000473" MajorTopicYN="Y">pathology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D011379" MajorTopicYN="N">Prognosis</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D012189" MajorTopicYN="N">Retrospective Studies</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D020257" MajorTopicYN="Y">Ventricular Remodeling</DescriptorName></MeshHeading></MeshHeadingList></MedlineCitation><PubmedData><History><PubMedPubDate PubStatus="received"><Year>2007</Year><Month>6</Month><Day>25</Day></PubMedPubDate><PubMedPubDate PubStatus="accepted"><Year>2007</Year><Month>7</Month><Day>7</Day></PubMedPubDate><PubMedPubDate PubStatus="pubmed"><Year>2007</Year><Month>12</Month><Day>7</Day><Hour>9</Hour><Minute>0</Minute></PubMedPubDate><PubMedPubDate PubStatus="medline"><Year>2009</Year><Month>5</Month><Day>19</Day><Hour>9</Hour><Minute>0</Minute></PubMedPubDate><PubMedPubDate PubStatus="entrez"><Year>2007</Year><Month>12</Month><Day>7</Day><Hour>9</Hour><Minute>0</Minute></PubMedPubDate></History><PublicationStatus>ppublish</PublicationStatus><ArticleIdList><ArticleId IdType="pubmed">18053595</ArticleId><ArticleId IdType="doi">10.1016/j.ijcard.2007.07.151</ArticleId><ArticleId IdType="pii">S0167-5273(07)01738-X</ArticleId></ArticleIdList></PubmedData></PubmedArticle><PubmedArticle><MedlineCitation Status="MEDLINE" Owner="NLM"><PMID Version="1">18051489</PMID><DateCompleted><Year>2008</Year><Month>01</Month><Day>23</Day></DateCompleted><DateRevised><Year>2007</Year><Month>12</Month><Day>05</Day></DateRevised><Article PubModel="Print"><Journal><ISSN IssnType="Print">0201-7563</ISSN><JournalIssue CitedMedium="Print"><Issue>5</Issue><PubDate><Year>2007</Year><Season>Sep-Oct</Season></PubDate></JournalIssue><Title>Anesteziologiia i reanimatologiia</Title><ISOAbbreviation>Anesteziol Reanimatol</ISOAbbreviation></Journal>[The cardiac performance recovery pattern and central hemodynamics in patients with coronary heart disease during coronary bypass surgery under extracorporeal circulation]. | In a prospective longitudinal study the occurrence of cardiac death was investigated and ongoing cardiac remodeling retrospectively analyzed in regard to adverse outcome. A cohort of 50 subjects with chronic Chagas' disease stratified according to Los Andes groups 1, 2 and 3 were followed-up for (mean+/-SD) 84.2+/-39.0 months. Follow-up was abbreviated by ventricular tachycardia ([VT] incidence: 3.0+/-7.0% year(-1)), first atrial fibrillation episode lasting >24 h ([AF] incidence: 3.3+/-1.0% year(-1)), nonfatal embolic stroke (incidence: 1.3+/-1.0% year(-1)), and cardiac death (mortality rate: 2.3+/-0.8% year(-1)). The relative risk of Los Andes group 3, VT, AF and stroke for cardiac death was, respectively, 25.3 (95%CI [3.5-182.6]), 3.0 (95%CI [1.2-7.3]), 3.6 (95%CI [1.2-10.9]) and 1.1 (95%CI [0.2-7.2]). In a multivariate Cox proportional-hazard model, Los Andes group 3 (hazard ratio=24.5; 95%CI [3.2-189.2]; p<0.01) was independent predictor for cardiac death. LAD and LV mass and not LVEF variation rates differed among group 1 (respectively, 0.03+/-0.1 cm year(-1); 2.4+/-5.7 g year(-1) and -0.1+/-2.4% year(-1)), group 2 (0.04+/-0.1 cm year(-1); 3.7+/-8.8 g year(-1) and -0.8+/-1.4% year(-1)) and group 3 (0.13+/-0.1 cm year(-1), p<0.001; 21.7+/-10.1 g year(-1), p<0.001 and -1.4+/-2.5% year(-1), p=0.26). Variables on admission were linearly related to respectively variation rates (r=0.71; p=0.02) composing a first order linear process with 0.07 months(-1) time constant. In chronic Chagas' disease, initial clinical status is an independent predictor for cardiac death and determines the progression rate of myocardial damage.</Abstract><AuthorList CompleteYN="Y"><Author ValidYN="Y"><LastName>Benchimol-Barbosa</LastName><ForeName>Paulo Roberto</ForeName><Initials>PR</Initials></Author></AuthorList><Language>eng</Language><PublicationTypeList><PublicationType UI="D016422">Letter</PublicationType></PublicationTypeList><ArticleDate DateType="Electronic"><Year>2007</Year><Month>11</Month><Day>28</Day></ArticleDate></Article><MedlineJournalInfo><Country>Netherlands</Country><MedlineTA>Int J Cardiol</MedlineTA><NlmUniqueID>8200291</NlmUniqueID><ISSNLinking>0167-5273</ISSNLinking></MedlineJournalInfo><CitationSubset>IM</CitationSubset><MeshHeadingList><MeshHeading><DescriptorName UI="D000328" MajorTopicYN="N">Adult</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D000368" MajorTopicYN="N">Aged</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D002598" MajorTopicYN="N">Chagas Cardiomyopathy</DescriptorName><QualifierName UI="Q000401" MajorTopicYN="Y">mortality</QualifierName><QualifierName UI="Q000473" MajorTopicYN="N">pathology</QualifierName><QualifierName UI="Q000503" MajorTopicYN="Y">physiopathology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D002908" MajorTopicYN="N">Chronic Disease</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D015331" MajorTopicYN="N">Cohort Studies</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D018450" MajorTopicYN="N">Disease Progression</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D005500" MajorTopicYN="N">Follow-Up Studies</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D006801" MajorTopicYN="N">Humans</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D008875" MajorTopicYN="N">Middle Aged</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D008955" MajorTopicYN="Y">Models, Cardiovascular</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D009206" MajorTopicYN="N">Myocardium</DescriptorName><QualifierName UI="Q000473" MajorTopicYN="Y">pathology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D011379" MajorTopicYN="N">Prognosis</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D012189" MajorTopicYN="N">Retrospective Studies</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D020257" MajorTopicYN="Y">Ventricular Remodeling</DescriptorName></MeshHeading></MeshHeadingList></MedlineCitation><PubmedData><History><PubMedPubDate PubStatus="received"><Year>2007</Year><Month>6</Month><Day>25</Day></PubMedPubDate><PubMedPubDate PubStatus="accepted"><Year>2007</Year><Month>7</Month><Day>7</Day></PubMedPubDate><PubMedPubDate PubStatus="pubmed"><Year>2007</Year><Month>12</Month><Day>7</Day><Hour>9</Hour><Minute>0</Minute></PubMedPubDate><PubMedPubDate PubStatus="medline"><Year>2009</Year><Month>5</Month><Day>19</Day><Hour>9</Hour><Minute>0</Minute></PubMedPubDate><PubMedPubDate PubStatus="entrez"><Year>2007</Year><Month>12</Month><Day>7</Day><Hour>9</Hour><Minute>0</Minute></PubMedPubDate></History><PublicationStatus>ppublish</PublicationStatus><ArticleIdList><ArticleId IdType="pubmed">18053595</ArticleId><ArticleId IdType="doi">10.1016/j.ijcard.2007.07.151</ArticleId><ArticleId IdType="pii">S0167-5273(07)01738-X</ArticleId></ArticleIdList></PubmedData></PubmedArticle><PubmedArticle><MedlineCitation Status="MEDLINE" Owner="NLM"><PMID Version="1">18051489</PMID><DateCompleted><Year>2008</Year><Month>01</Month><Day>23</Day></DateCompleted><DateRevised><Year>2007</Year><Month>12</Month><Day>05</Day></DateRevised><Article PubModel="Print"><Journal><ISSN IssnType="Print">0201-7563</ISSN><JournalIssue CitedMedium="Print"><Issue>5</Issue><PubDate><Year>2007</Year><Season>Sep-Oct</Season></PubDate></JournalIssue><Title>Anesteziologiia i reanimatologiia</Title><ISOAbbreviation>Anesteziol Reanimatol</ISOAbbreviation></Journal><ArticleTitle>[The cardiac performance recovery pattern and central hemodynamics in patients with coronary heart disease during coronary bypass surgery under extracorporeal circulation].</ArticleTitle><Pagination><StartPage>30</StartPage><EndPage>34</EndPage><MedlinePgn>30-4</MedlinePgn></Pagination><Abstract>Central hemodynamic parameters were retrospectively studied in 284 patients. After aortic declamping, sinus rhythm spontaneously restored in 179 patients (Group 1), ventricular fibrillation occurred in 105 (Group 2). The preoperative parameters were similar in both groups. The number of grafts and the time of aortic clamping and cardiopulmonary bypass (CPB) were higher in Group 1. In the groups, the volume of cardioplegic solution and the average dose of phenylephrine and nitroglycerin per perfusion did not differ. After CPB, the values of cardiac output (CO) and cardiac index (CI) were significantly higher in Group 1 than in Group 2. At the end of an operation and 3 hours after its termination, there were no differences between two groups. Twelve hours after surgery, cardiac output and systolic blood pressure were significantly higher in Group 1. Following 24 hours of surgery, heart rate was significantly greater in Group 1 than in Group 2 After surgery, all hemodynamic parameters were within normal physiological values. The mean duration and the degree of inotropic support did not differ in the groups. The incidence of atrial fibrillation, perioperative myocardial infarction, and low cardiac output syndrome were comparable in both groups. Thus, various modes of cardiac performance recovery affect perioperative hemodynamics; however, this impact is insignificant and does not make management policy be changed in such patients. After aortic declamping, ventricular fibrillation requiring for defibrillation is not a clinical sensitive factor that negatively affects the intra- and postoperative period. |
8,127 | Propagation velocity kinetics and repolarization alternans in a free-behaving sheep model of pacing-induced atrial fibrillation. | Experimental models have reported conflicting results regarding the role of dispersion of repolarization in promoting atrial fibrillation (AF). Repolarization alternans, a beat-to-beat alternation in action potential duration, enhances dispersion of repolarization when propagation velocity is involved.</AbstractText>In this work, original electrophysiological parameters were analysed to study AF susceptibility in a chronic sheep model of pacing-induced AF. Two pacemakers were implanted, each with a single right atrial lead. Right atrial depolarization and repolarization waves were documented at 2-week intervals. A significant and gradual decrease in the propagation velocity at all pacing rates and in the right atrial effective refractory period (ERP) was observed during the weeks of burst pacing before sustained AF developed when compared with baseline conditions. Right atrial repolarization alternans was observed, but because of the development of 2/1 atrioventricular block with far-field ventricular interference, its threshold could not be precisely measured. Non-sustained AF was not observed at baseline, but appeared during the electrical remodelling in association with a decrease in both ERP and propagation velocity.</AbstractText>We report here on the feasibility of measuring ERP, atrial repolarization alternans, and propagation velocity kinetics and their potential in predicting susceptibility to AF in a free-behaving model of pacing-induced AF using the standard pacemaker technology.</AbstractText> |
8,128 | Influence of diffuse fibrosis on wave propagation in human ventricular tissue. | During ageing, after infarction, in cardiomyopathies and other cardiac diseases, the percentage of fibrotic (connective) tissue may increase from 6% up to 10-35%. The presence of increased amounts of connective tissue is strongly correlated with the occurrence of arrhythmias and sudden cardiac death.</AbstractText>In this article, we investigate the role of diffuse fibrosis on wave propagation, arrhythmogenesis, and arrhythmia mechanism in human ventricular tissue using computer modelling. We show that diffuse fibrosis slows down wave propagation and increases tissue vulnerability to wave break and spiral wave formation. We also demonstrate that diffuse fibrosis increases the period of re-entrant arrhythmias and can suppress the restitution-induced transition from tachycardia to fibrillation.</AbstractText>The latter suggests that mechanisms different from restitution-induced spiral break-up might be more likely to account for the onset of fibrillation in the presence of large amounts of diffuse fibrotic tissue.</AbstractText> |
8,129 | The Brugada syndrome in Canada: a unique French-Canadian experience. | The Brugada syndrome (BS) is a clinical entity involving cardiac sodium channelopathy, typical electrocardiogram (ECG) changes and predisposition to ventricular arrhythmia. This syndrome is mainly recognized by specialized cardiologists and electrophysiologists. Data regarding BS largely come from multicentre registries or Asian countries. The present report describes the Quebec Heart Institute experience, including the clinical characteristics and prognosis of native French-Canadian subjects with the Brugada-type ECG pattern.</AbstractText>BS has been diagnosed in 35 patients (mean age 51 +/- 12 years) at the Quebec Heart Institute since 2001. Patients were referred from primary care physicians for ECG abnormalities, syncope or ventricular arrhythmia, or were diagnosed incidentally on an ECG obtained for other purposes. The abnormal ECG was recognized after a syncopal spell in four patients and during family screening in four patients. All of the others were incidental findings following a routine ECG. No patient had a family history of sudden cardiac death at younger than 45 years of age. In this population, right bundle branch block pattern with more than 2 mm ST segment elevation in leads V1 to V3 was recorded spontaneously in 25 patients and was induced by sodium blockers in 10 patients. The sodium channel blocker test was performed in 21 patients and was positive in 18 patients (86%). An electrophysiological study was performed in 20 of 35 patients, during which ventricular fibrillation was induced in five patients; three of the five patients were previously asymptomatic. An implantable cardioverter-defibrillator was implanted in six of 35 patients (17%), including three of four patients with a history of syncope. A loop recorder was implanted in three patients. After a mean follow-up of 36 +/- 18 months, one patient died from a noncardiac cause and one patient (with a history of syncope) received an appropriate shock from his implantable cardioverter-defibrillator. No event occurred in the asymptomatic population.</AbstractText>BS is present in the French-Canadian population and is probably under-recognized. Long-term prognosis of individuals with BS, especially in sporadic, asymptomatic cases, needs to be clarified.</AbstractText> |
8,130 | Catheter ablation for cardiac arrhythmias: a 14-year experience with 5330 consecutive patients at the Quebec Heart Institute, Laval Hospital. | Catheter ablation is a curative treatment with excellent success and minimal complication rates for patients with supraventricular or ventricular arrhythmias.</AbstractText>The acute outcomes and complications of all catheter ablation procedures for supraventricular and ventricular arrhythmias performed at the Quebec Heart Institute (Sainte-Foy, Quebec) during a 14-year period from January 1, 1993, to December 31, 2006, were prospectively assessed. The ablation procedures were classified according to the arrhythmias induced using standard electrophysiological techniques and definitions. Immediate success and complication rates were prospectively included in the database.</AbstractText>A total of 5330 patients had catheter ablation performed at the Institute during the period assessed. The mean (+/- SD) age of patients was 50 +/- 18 years (range four to 97 years), and 2340 patients (44%) were men. Most of the patients were younger than 75 years (group 1), and 487 (9%) were 75 years of age and older (group 2). Indications for ablations were as follows: atrioventricular nodal re-entry tachycardia (AVNRT) in 2263 patients, accessory pathways in 1147 patients, atrioventricular node ablation in 803 patients, typical atrial flutter in 377 patients and atrial tachycardia in 160 patients; 580 patients had other ablation procedures. The overall success rates were 81% for atrial tachycardia, 92% for accessory pathways or flutter, and 99% for AVNRT or atrioventricular node ablation. There was no difference in the success rates of the younger (group 1) and older (group 2) patients. Seventy-seven patients (1.4%) had complications, including 11 major events (myocardial infarction in one patient, pulmonary embolism in three patients and permanent pacemaker in seven patients). In patients undergoing AVNRT ablation, two had a permanent pacemaker implanted immediately after the procedure and three had a permanent pacemaker implanted at follow-up.</AbstractText>The results confirm that radiofrequency ablation is safe and effective, supporting ablation therapy as a first-line therapy for the majority of patients with cardiac arrhythmias.</AbstractText> |
8,131 | Electrical heart disease: Genetic and molecular basis of cardiac arrhythmias in normal structural hearts. | Purely electrical heart diseases, defined by the absence of any structural cardiac defects, are responsible for a large number of sudden, unexpected deaths in otherwise healthy, young individuals. These conditions include the long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia and the short QT syndrome. Collectively, these conditions have been referred to as channelopathies. Ion channels provide the molecular basis for cardiac electrical activity. These channels have specific ion selectivity and are responsible for the precise and timely regulation of the passage of charged ions across the cell membrane in myocytes, and the summation of their activity in cardiac muscle defines the surface electrocardiogram. Impairment in the flow of these ions in heart cells may mean the difference between a normal, prosperous life and the tragedy of a sudden, unexpected death due to ventricular arrhythmia. The present paper reviews the current clinical and molecular understanding of the electrical diseases of the heart associated with sudden cardiac death.</Abstract><AuthorList CompleteYN="Y"><Author ValidYN="Y"><LastName>Farwell</LastName><ForeName>David</ForeName><Initials>D</Initials><AffiliationInfo><Affiliation>Arrhythmia Service, University of Ottawa Heart Institute, Ottawa, Ontario.</Affiliation></AffiliationInfo></Author><Author ValidYN="Y"><LastName>Gollob</LastName><ForeName>Michael H</ForeName><Initials>MH</Initials></Author></AuthorList><Language>eng</Language><PublicationTypeList><PublicationType UI="D016428">Journal Article</PublicationType><PublicationType UI="D013485">Research Support, Non-U.S. Gov't</PublicationType><PublicationType UI="D016454">Review</PublicationType></PublicationTypeList></Article><MedlineJournalInfo><Country>England</Country><MedlineTA>Can J Cardiol</MedlineTA><NlmUniqueID>8510280</NlmUniqueID><ISSNLinking>0828-282X</ISSNLinking></MedlineJournalInfo><ChemicalList><Chemical><RegistryNumber>0</RegistryNumber><NameOfSubstance UI="D024642">Potassium Channels, Voltage-Gated</NameOfSubstance></Chemical></ChemicalList><CitationSubset>IM</CitationSubset><MeshHeadingList><MeshHeading><DescriptorName UI="D000328" MajorTopicYN="N">Adult</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D000367" MajorTopicYN="N">Age Factors</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D001145" MajorTopicYN="N">Arrhythmias, Cardiac</DescriptorName><QualifierName UI="Q000175" MajorTopicYN="N">diagnosis</QualifierName><QualifierName UI="Q000235" MajorTopicYN="Y">genetics</QualifierName><QualifierName UI="Q000401" MajorTopicYN="Y">mortality</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D053840" MajorTopicYN="N">Brugada Syndrome</DescriptorName><QualifierName UI="Q000175" MajorTopicYN="N">diagnosis</QualifierName><QualifierName UI="Q000235" MajorTopicYN="N">genetics</QualifierName><QualifierName UI="Q000401" MajorTopicYN="N">mortality</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D016757" MajorTopicYN="N">Death, Sudden, Cardiac</DescriptorName><QualifierName UI="Q000453" MajorTopicYN="Y">epidemiology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D004562" MajorTopicYN="N">Electrocardiography</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D005260" MajorTopicYN="N">Female</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D020022" MajorTopicYN="N">Genetic Predisposition to Disease</DescriptorName><QualifierName UI="Q000453" MajorTopicYN="Y">epidemiology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D006329" MajorTopicYN="N">Heart Conduction System</DescriptorName><QualifierName UI="Q000503" MajorTopicYN="Y">physiopathology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D006801" MajorTopicYN="N">Humans</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D015994" MajorTopicYN="N">Incidence</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D008133" MajorTopicYN="N">Long QT Syndrome</DescriptorName><QualifierName UI="Q000175" MajorTopicYN="N">diagnosis</QualifierName><QualifierName UI="Q000235" MajorTopicYN="N">genetics</QualifierName><QualifierName UI="Q000401" MajorTopicYN="N">mortality</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D008297" MajorTopicYN="N">Male</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D024642" MajorTopicYN="N">Potassium Channels, Voltage-Gated</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D012016" MajorTopicYN="N">Reference Values</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D012307" MajorTopicYN="N">Risk Factors</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D012720" MajorTopicYN="N">Severity of Illness Index</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D014693" MajorTopicYN="N">Ventricular Fibrillation</DescriptorName><QualifierName UI="Q000175" MajorTopicYN="N">diagnosis</QualifierName><QualifierName UI="Q000235" MajorTopicYN="N">genetics</QualifierName><QualifierName UI="Q000401" MajorTopicYN="N">mortality</QualifierName></MeshHeading></MeshHeadingList><OtherAbstract Type="Publisher" Language="fre">Les troubles purement électriques, définis comme l’absence de lésions cardiaques structurales, entraînent la mort subite d’un grand nombre de jeunes, par ailleurs en bonne santé. Ces troubles comprennent notamment le syndrome de l’allongement de l’intervalle QT, le syndrome de Brugada, la tachycardie ventriculaire polymorphe catécholaminergique et le syndrome du raccourcissement de l’intervalle QT. Ce type d’arythmie est désigné par le terme de maladie des canaux ioniques. Ceux-ci constituent la base moléculaire de l’activité électrique du cœur; ils ont une sélectivité ionique spécifique et ils sont responsables du passage régulier des ions chargés par la membrane cellulaire dans les myocytes, et l’ensemble de leur activité dans le muscle cardiaque est rendu visible par l’électrocardiogramme de surface. Ainsi, les troubles de la circulation des ions dans les cellules du cœur peuvent faire toute la différence entre une vie normale, heureuse et une mort subite, tragique, causée par l’arythmie ventriculaire. Le présent article fait le point sur les facteurs cliniques et moléculaires des troubles de la conduction électrique, liés à la mort cardiaque subite. |
8,132 | Non-pharmacological management of ventricular tachycardia. | Ventricular tachyarrhythmias (VTA), a major cause of sudden cardiac death, require meticulous management in order to prevent recurrent episodes. Recently, non-pharmacological interventions, including radiofrequency catheter ablation and implantable cardioverter defibrillators (ICD), have become important treatments of VTA. Catheter ablation is curative in a relatively high percentage of patients presenting with idiopathic monomorphic ventricular tachycardia (VT). For VT associated with structural heart disease, however, the efficacy of catheter ablation remains limited, and ICD is the first-line therapy. In a subset of patients presenting with recurrent episodes of ventricular fibrillation (VF), catheter ablation is a therapeutic option when the VF is triggered by specific premature ventricular complexes. In Japan, unlike in the United States and Europe, ICD have not yet been accepted as first-line prevention of sudden cardiac death caused by VTA. The efficacy of ICD is occasionally limited by intolerable complications, such as electrical storm, inappropriate shock delivery and infection. Catheter ablation and ICD therapy might need to be combined for problematic cases. |
8,133 | Drug therapy for ventricular tachyarrhythmia in heart failure. | Sudden cardiac death (SCD) accounts for approximately one-third of all deaths in patients with heart failure, and is generally the result of ventricular tachycardia (VT) and/or ventricular fibrillation (VF). The mechanisms of VT/VF associated with heart failure are complex and heterogeneous; they include functional and structural remodeling, as well as neurohormonal activation. The implantable cardioverter-defibrillator is very useful for preventing SCD, but the improvement of outcome is limited in patients with cardiac dysfunction and advanced heart failure. This article reviews the current status of drug therapy for the treatment of VT/VF in patients with heart failure. Chronic beta-blocker therapy reduces SCD and improves survival. Angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers and aldosterone antagonists are thought to reduce SCD by preventing ventricular remodeling. Amiodarone is potentially effective for preventing VT/VF in patients at high risk, especially those with nonischemic heart failure. This may be a result of the complex pharmacodynamics of amiodarone, which affects many kinds of ion channels/transporters, as well as thyroid function. The pure class III antiarrhythmic drug, nifekalant, is useful in the emergency treatment of VT/VF. |
8,134 | Brugada syndrome in Japan. | The incidence of Brugada syndrome (BS) is relatively high in Japan compared with the rest of the world, ranging between 0.1% and 0.2% in the general population. BS in Japan, as in other countries, is most prevalent in middle-aged men, and has characteristics ECG changes, a high recurrence rate in symptomatic patients, and relatively low incidence of SCN5A mutations. In contrast, both the incidence of a family history of BS and/or sudden cardiac death and the rate of developing cardiac events in asymptomatic patients are less in Japan than in other countries. Increased vagal tone and/or decreased sympathetic activity are suggested as provoking cardiac events. Several factors should be evaluated in risk stratification for recurrence of life-threatening arrhythmias, because there appears to be no single determinant for risk stratification: spontaneous ST elevation of coved-type (Type 1), family history of sudden cardiac death, inducible ventricular tachycardia/ventricular fibrillation and positive late potentials. An implantable cardioverter defibrillator is recommended for patients with aborted sudden cardiac death. |
8,135 | Mechanism and new findings in Brugada syndrome. | Brugada syndrome is a clinical entity characterized by coved type ST-segment elevation in the right precordial electrocardiographic leads (V(1-3)) and an episode of ventricular fibrillation in the absence of structural heart disease. Although a number of clinical and experimental reports have elucidated the electrocardiographic, electrophysiologic, cellular, and molecular aspects, several problems remain unsolved. Recently developed high-resolution optical mapping techniques in arterially-perfused wedge preparations enable recording of transmembrane action potentials from 256 sites simultaneously at the epicardial surface, thus providing further advances in the understanding of the cellular mechanism of the specific ST-segment elevation and subsequent ventricular arrhythmias. In this review article, new findings relating to several unresolved problems such as gender difference (male predominance) and ethnic difference (higher incidence in Asian population) are also presented. |
8,136 | Modulation of spiral wave reentry by K(+) channel blockade. | It is well established that spiral wave reentry is the primary mechanism of ventricular tachyarrhythmias (ventricular fibrillation/tachycardia, VF/VT), but information is still limited concerning pharmacological modification of spiral waves by ion channel blockers. In this brief review, the antiarrhythmic and proarrhythmic actions of K(+)-channel blockade (I(Kr) and I (K1)) are discussed in terms of spiral wave dynamics, primarily based on recent experimental findings in ventricular preparations perfused in vitro with the aid of high-resolution optical mapping, as well as their related theoretical studies using computer simulation. |
8,137 | Risk stratification for sudden cardiac death. | Sudden cardiac death (SCD) is a leading cause of mortality in industrialized countries, and ventricular fibrillation and sustained ventricular tachycardia are the major causes of SCD. Although there are now effective devices and medications that can prevent such serious arrhythmias, it is crucial to have methods of identifying patients at risk. Numerous studies suggest that most patients dying of SCD have coronary artery disease or cardiomyopathy. Functional or electrophysiological measurements are effective in risk stratification. Left ventricular ejection fraction measured by echocardiography or cardiac imaging techniques is the gold standard to detect high-risk patients. Electrophysiological studies have also been used for risk stratification. Noninvasive techniques and measurements, such as T-wave alternans, signal-averaged electrocardiography, nonsustained ventricular tachycardia, heart rate variability, and heart rate turbulence, have been proposed as useful tools in identifying patients at risk for SCD. This article reviews the epidemiology, mechanisms, substrates, and current status of risk stratification of SCD. |
8,138 | Ventricular fibrillation: dynamics and ion channel determinants. | Ventricular fibrillation (VF) is the leading cause of sudden cardiac death. This brief review addresses issues relevant to the dynamics of the rotors responsible for functional reentry and VF. It also makes an attempt to summarize present-day knowledge of the manner in which the dynamic interplay between inward and outward transmembrane currents and the heterogeneous cardiac structure establish a substrate for the initiation and maintenance of rotors and VF. The fragmentary nature of our current understanding of ionic VF mechanisms does not even allow an approach toward a "Theory of VF". Yet some hope is provided by recently obtained insight into the roles played in VF by some of the sarcolemmal ion channels that control the excitation-recovery process. For example, strong evidence supports the idea that the interplay between the rapid-inward sodium current and the inward-rectifier potassium current controls rotor formation, as well as rotor stability and frequency. Solid evidence also exists for an involvement of L-type calcium current in the control of rotor frequency and in determining VF-to-ventricular tachycardia conversion. Less clear, however, is whether or not time dependent outward currents through voltage-gated potassium channels affect the fibrillatory process. Hopefully, taking advantage of currently available approaches of structural, molecular and cellular biology, together with computational and imaging techniques, will afford us the opportunity to further advance knowledge on VF mechanisms. |
8,139 | Electrotonic remodeling following myocardial infarction in dogs susceptible and resistant to sudden cardiac death. | Passive electrical remodeling following myocardial infarction (MI) is well established. These changes can alter electrotonic loading and trigger the remodeling of repolarization currents, a potential mechanism for ventricular fibrillation (VF). However, little is known about the role of passive electrical markers as tools to identify VF susceptibility post-MI. This study investigated electrotonic remodeling in the post-MI ventricle, as measured by myocardial electrical impedance (MEI), in animals prone to and resistant to VF. MI was induced in dogs by a two-stage left anterior descending (LAD) coronary artery ligation. Before infarction, MEI electrodes were placed in remote (left circumflex, LCX) and infarcted (LAD) myocardium. MEI was measured in awake animals 1, 2, 7, and 21 days post-MI. Subsequently, VF susceptibility was tested by a 2-min LCX occlusion during exercise; 12 animals developed VF (susceptible, S) and 12 did not (resistant, R). The healing infarct had lower MEI than the normal myocardium. This difference was stable by day 2 post-MI (287 +/- 32 Omega vs. 425 +/- 62 Omega, P < 0.05). Significant differences were observed between resistant and susceptible animals 7 days post-MI; susceptible dogs had a wider electrotonic gradient between remote and infarcted myocardium (R: 89 +/- 60 Omega vs. S: 180 +/- 37 Omega). This difference increased over time in susceptible animals (252 +/- 53 Omega at 21 days) due to post-MI impedance changes on the remote myocardium. These data suggest that early electrotonic changes post-MI could be used to assess later arrhythmia susceptibility. In addition, passive-electrical changes could be a mechanism driving active-electrical remodeling post-MI, thereby facilitating the induction of arrhythmias. |
8,140 | Effects of dual endothelin receptor blockade on sympathetic activation and arrhythmogenesis during acute myocardial infarction in rats. | The effects of dual (ETA and ETB) endothelin receptor blockade on ventricular arrhythmogenesis during acute myocardial infarction are not well defined. We randomly allocated Wistar rats to bosentan (100 mg/kg daily, n=24), a dual endothelin receptor antagonist, or vehicle (n=23). After 7 days of treatment, myocardial infarction was induced by permanent coronary ligation. Ventricular tachyarrhythmias were evaluated for 24 h following ligation, using a miniature telemetry electrocardiogram recorder. Action potential duration was measured from monophasic epicardial recordings and sympathetic activation was assessed by heart rate variability and catecholamine serum level measurements. Compared to controls (1012+/-185 s), bosentan (59+/-24 s) markedly decreased (P<0.00001) the total duration of ventricular tachyarrhythmias during the delayed (1-24 h) phase post-ligation, with a modest effect during the early (0-1 h) phase (132+/-38 s, versus 43+/-18 s, respectively, P=0.053). Treatment did not affect infarct size or total mortality. Action potential duration at 90% repolarization prolonged in controls (from 93.1+/-4.7 ms to 117.6+/-6.9 ms), displaying increased temporal dispersion (from 4.14+/-0.45 ms to 10.42+/-2.51 ms, both P<0.001), but was preserved in treated animals. Bosentan decreased norepinephrine, but increased epinephrine levels 24 h post-ligation. Low frequency spectra of heart rate variability, an index of net sympathetic tone, were lower in bosentan-treated rats. Dual endothelin-1 receptor blockade decreases ventricular tachyarrhythmias during myocardial infarction without reperfusion, by preventing repolarization inhomogeneity. Diverse treatment effects on sympathetic activation may ameliorate the antiarrhythmic action. |
8,141 | Catheter-ablation of ventricular tachycardia in patients with coronary artery disease: influence of the endocardial substrate size on clinical outcome. | Ablation of symptomatic ventricular tachycardia (VT) in patients with coronary artery disease is frequently performed using the three dimensional mapping system CARTO. In the amplitude map, bipolar potentials of <1.5 mV are considered abnormal and represent damaged myocardium due to previous infarction. This pathological electrical area can be arrhythmogenic, serving as the substrate for reentrant VT. The purpose of this study was to correlate the size of the endocardial substrate with the success of VT catheter ablation. Included in this retrospective analysis were 69 consecutive patients with coronary artery disease who underwent ablation for symptomatic clinical VT using CARTO. The voltage maps were analyzed and the area with abnormal bipolar electrograms (<1.5 mV) was determined using geometric approximation models. The area of abnormal electrograms was divided into three sizes: small (<or=15 cm(2); 11 patients), medium (16-99 cm(2); 50 patients), and large (>or=100 cm(2); 8 patients). Patient characteristics were not different between the three substrate groups in regard to age, tachycardia cycle length, or number of radiofrequency applications, however differed significantly between the small, medium and large group in regard to left ventricular ejection fraction (44 +/- 12% vs. 32 +/- 9% vs. 21 +/- 7%, respectively; P = 0.001). Overall, there was a significant correlation between myocardial infarction locations and endocardial substrate sizes (P = 0.031), such that 73% of small substrates were found after inferior myocardial infarctions, and 100% of large substrates after anterior and multiple myocardial infarctions (P = 0.003). After ablation, inducibility of ventricular arrhythmias was more rare in patients with small substrates compared to patients with medium or large substrates (small substrates: 9%, medium and large substrates: 43%, P = 0.043). Although during follow-up of 25 +/- 17 months (1 day to 72 months) there was no significant difference between endocardial substrate sizes in regard to recurrence rates (small: 27%, medium: 38%, large: 50%, P = 0.588), patients with a small substrate did not have fast VT or ventricular fibrillation (VF), in contrast to 30% and 38% of patients with medium and large substrates, respectively. We conclude that in patients with coronary artery disease a small area of low amplitude bipolar potentials (<or=15 cm(2)) was seen more often after inferior myocardial infarction than after anterior and multiple infarctions. After ablation, patients with small substrates were rarely inducible and showed a more benign course during follow-up (trend towards fewer arrhythmia recurrences and no fast VT or VF). As a result smaller arrhythmogenic substrates appear to be better amenable to catheter ablation than larger substrates. |
8,142 | Emergency department use of intravenous procainamide for patients with acute atrial fibrillation or flutter. | Acute atrial fibrillation and flutter are very common arrhythmias seen in emergency department (ED) patients, but there is no consensus for their optimal management. The objective of this study was to examine the efficacy and safety of intravenous (IV) procainamide for acute atrial fibrillation or flutter.</AbstractText>This health records review included a consecutive cohort of ED patients with acute-onset atrial fibrillation or atrial flutter who received IV procainamide at one university hospital ED during a five-year period. The standard clinical protocol involved IV infusion of 1 g of procainamide over 60 minutes, followed by electrical cardioversion if necessary. A trained observer extracted data from the original clinical records. Outcome measurements included conversion to sinus rhythm, adverse events, and relapse up to seven days.</AbstractText>The 341 study patients had a mean age of 63.9 years (SD +/- 15.5 years), and 56.6% were male. The conversion rates were 52.2% (95% confidence interval = 47% to 58%) for 316 atrial fibrillation cases and 28.0% (95% confidence interval = 13% to 46%) for 25 atrial flutter cases. Mean dose given was 860.7 mg (SD +/- 231.2 mg), and median time to conversion was 55 minutes. Adverse events occurred in 34 cases (10.0%): hypotension, 8.5%; bradycardia, 0.6%; atrioventricular block, 0.6%; and ventricular tachycardia, 0.3%. There were no cases of torsades de pointes, cerebrovascular accident, or death. Most patients (94.4%) were discharged home, but 2.9% of patients returned with a recurrence of atrial fibrillation within seven days.</AbstractText>This study of acute atrial fibrillation or flutter patients treated in the ED with IV procainamide suggests that this treatment is safe and effective in this setting. Procainamide should be prospectively compared with other ED strategies.</AbstractText> |
8,143 | Pre-transplant predictors of cerebrovascular events after kidney transplantation. | We evaluated cerebrovascular events (CVE) after kidney transplantation (KTx) and sought to identify pre-transplant predictors of transient ischaemic attacks (TIA) and strokes post-transplantation.</AbstractText>A total of 1617 consecutive kidney and 16 kidney-pancreas recipients transplanted between 1995 and 2005 were analysed in this retrospective single-centre study. Risk factors for CVE, e.g. recipient and donor age and gender, diagnosis of chronic kidney disease, end-stage renal disease (ESRD) duration, histories of hypertension, hyperlipidaemia, smoking, atrial fibrillation (AF), diabetes mellitus (DM), ischaemic heart, peripheral- and cerebro-vascular disease, as well as pre-transplant myocardial infarction or CVE (i.e. TIA/strokes) were analysed. Furthermore, the predictive value of pre-transplant screening tests, i.e. echocardiography (n = 1184) and carotid ultrasound (n = 922), was investigated.</AbstractText>During a median follow-up of 4 years, 64 CVE (54 strokes and 10 TIA) were observed. Nineteen (5.1%) of 373 deceased patients died from fatal stroke. Recipient age, history of AF and hyperlipidaemia (P = 0.00, respectively), reduced left ventricular function (LVF) (P = 0.01) and the degree of stenosis by carotid ultrasound (P = 0.002), duration of ESRD (P = 0.03) and interstitial nephritis as renal disease cause (P = 0.04) evolved as predictors of TIA/stroke post-transplant in univariate analysis. In multivariable analysis, AF (P = 0.001) and DM (P = 0.037) were significant predictors for post-transplant CVE.</AbstractText>AF and DM are independent predictors of CVE after KTx. Beyond their general ability to detect sev- erely comorbid patients, pre-transplant screening tests (e.g. carotid ultrasound or echocardiography) were not able to identify renal transplant candidates at risk for CVE after transplantation.</AbstractText> |
8,144 | [Influence of the radiofrequency current on the left ventricular systolic function]. | Radio frequency catheter ablation (RFCA)--induced myocardial injury is caused by the thermal, electrical and biological effects of RF current.</AbstractText>To assess the changes in the left ventricular systolic function following RFCA.</AbstractText>Ejection fraction (EF) and shortening fraction (FS) were assessed in 24 pacing patients (10 females in age 44-79 years, mean age 64.8 +/- 11 years) before and 24 hours after successful RFCA of an atrio-ventricular node area due to medical refractory chronic atrial fibrillation.</AbstractText>The mean number of RFCA applications was 5.5 +/- 5.0, total application time--237.5 +/- 188 sec, cumulative energy--8916.7 +/- 6886.2 J and temperature measured at the tip of electrode--59.6 +/- 4.90 degrees C. We did not find the changes in EF and FS after the ablation. In addition, a non-significant correlation between the left ventricular systolic function and the cumulative RFCA energy was documented.</AbstractText>Non-significant correlation between the left ventricular contractility and the cumulative RFCA energy was observed.</AbstractText> |
8,145 | Relationship between serum magnesium level and arrythmias following post-coronary artery bypass grafting. | Atrial and ventricular arrhythmias are among the most common complications after coronary artery bypass graft (CABG) surgery. It is known that cardiopulmonary bypass reduces serum magnesium level. In this study, we evaluated the relationship between total blood magnesium level (TMG) and the incidence of perioperative arrhythmias.</AbstractText>TMG was measured in patients who were scheduled for CABG on three occasions: just before anesthesia, on intensive care unit (ICU) arrival and on the first morning after operation. Patients were evaluated for primary cardiac rhythm, serum creatinine, urine output in operating room and diuretic therapy. Supplemental magnesium (SMG) was also recorded in operating room and ICU. Patients were then evaluated for the rate and kind of arrhythmia occurring during the next 3 days.</AbstractText>Mean TMG level in 170 cases was 2.2 (0.5), 2.6 (0.6) and 2.4 (0.6) mg/dl on three occasions respectively. 53 patients developed post-operative arrhythmia (31%) [Atrial Fibrillation (AF) (7.1%), Non-AF Supraventricular arrhythmia (14.7%) and Ventricular arrhythmia (16.5%)]. Although there was a significant difference between TMG on three occasions (P <0.001), all values were within normal range. Although TMG was higher in arrhythmic patients compared to non- arrhythmics (2.26 vs. 2.14), both values were in normal range and there was no significant difference between two groups.</AbstractText>This study shows that routine magnesium administration has no significant effect on serum magnesium level. We conclude that though routine regimen of magnesium administration has no effect on incidence of perioperative arrhythmia, it is probably necessary for maintaining normal magnesium level.</AbstractText> |
8,146 | Electrical storm: clinical manifestations and management. | Electrical storm is the clustering of hemodynamically destabilizing ventricular tachycardia or ventricular fibrillation that typically requires multiple electrical cardioversions or defibrillations within a 24-hour period. Electrical storm is frequently seen in the acute phase of myocardial infarction, in patients with the genetic arrhythmia syndromes, and in patients with implanted cardioverters-defibrillators. The evaluation and management should focus on the immediate suppression of the arrhythmia, a search for possible reversible causes, and attempts to prevent recurrences. In this review we present the most common conditions associated with electrical storm, therapeutic options for suppression of electrical storm, and new investigational techniques emerging for the treatment of electrical storm in refractory cases. The management of this life threatening arrhythmia typically requires the coordinated efforts of emergency medicine, critical care, cardiology, cardiac electrophysiology, and pacemaker experts. |
8,147 | Pulsatile versus nonpulsatile flow to maintain the equivalent coronary blood flow in the fibrillating heart. | How much flow is required by a nonpulsatile pump to match the coronary blood flow equivalent to that of pulsatile pump? A cardiopulmonary bypass circuit from the right atrium to the ascending aorta was constructed in a ventricular fibrillation model using 13 Yorkshire swine. The animals were randomly divided into two groups: CONTROL (pulsatile T-PLS, n = 7) or EXPERIMENTAL (nonpulsatile Biopump, n = 6). The hemodynamic data at mid-LAD level was measured with a flow meter at baseline and every 20 minutes after pump flow initiation. The pump flow was started from 2 L/min in both groups (67 +/- 8 in CONTROL and 70 +/- 9 ml/kg/min in EXPERIMENTAL; p = NS), and the pump flow of the EXPERIMENTAL group was increased to match the coronary flow of the CONTROL group. To maintain mean velocity and flow in the LAD, the EXPERIMENTAL group required significantly higher pump flow at 20, 40, and 60 minutes (84 +/- 17 vs. 67 +/- 8, 87 +/- 24 vs. 67 +/- 8, 85 +/- 18 vs. 67 +/- 8 ml/kg/min, respectively, p < 0.05). The LAD diameter was substantially smaller in the CONTROL group and the resistance index was significantly lower in the CONTROL group at 80 minutes and 120 minutes after bypass (0.56 +/- 0.26 vs. 0.87 +/- 0.20 and 0.61 +/- 0.23 vs. 0.90 +/- 0.06; p < 0.05). In conclusion, we found that the nonpulsatile pump may require 25%-28% higher pump flow than the pulsatile pump to maintain equivalent coronary blood flow. |
8,148 | Effects of combined sildenafil-nitric oxide donor on defibrillation efficacy. | A previous study demonstrated that supra-therapeutic concentration of sildenafil citrate attenuates defibrillation efficacy. However, the effect of combined sildenafil and NTG administration on defibrillation efficacy is not known.</AbstractText>The present study investigated whether sildenafil administration at the therapeutic level increases the defibrillation threshold (DFT) when combined with NTG.</AbstractText>Twenty-four pigs (20-25 kg) were randomized into four groups. After the control DFT was obtained, a stock solution of 50-mg (group 1, therapeutic concentration) and 100-mg (group 2, supratherapeutic concentration) of sildenafil, and 100-mL of saline (groups 3 and 4) were infused at 2 mL/min. Then, NTG was administered in groups 1-3 at 5 microg/min, with an increment of 5 microg/min every 5 min. The DFT was determined again after NTG was infused for 20 minutes.</AbstractText>In group 1, the DFT (402 +/- 33V, 11 +/- 2J) was not different from the control (404 +/- 28V, 11 +/- 2J). In group 2, the DFT (521 +/- 18V, 19 +/- 1J) was higher (p < 0.004) than that in the control group (444 +/- 31V, 14 +/- 2J). Saline did not alter the DFT either individually or in combination with NTG.</AbstractText>Supratherapeutic dose of sildenafil-NTG combination significantly increased the DFT (17% of peak voltage, 37% of total energy). This effect on DFT appears to be driven by sildenafil and not NTG.</AbstractText> |
8,149 | Effect of epicardial fat on ablation performance: a three-energy source comparison. | To investigate the effect of epicardial fat on surgical atrial fibrillation ablation performance using an in vitro model. Two tissue models were employed to investigate standard penetration and maximal lesion depth performance of bipolar radiofrequency (RF), microwave, and laser energy sources.</AbstractText>Ventricular veal tissue was utilized in various thicknesses (3 mm, 5 mm, 7 mm, 15 mm). Epicardial fat was modeled by layering porcine fat (1 mm, 2 mm and 4 mm) on moistened tissue. In each group, 8 to 10 lesions were created. Post ablation, tissue samples were sectioned and ablation depth of each myocardial section measured using 1% tetrazolium tetrachloride dye solution.</AbstractText>The laser energy source produced nearly 100% transmural lesions in almost all study groups irrespective of myocardium thickness and fat thickness. The microwave device maintained transmurality in all 3-mm and most 5-mm myocardium trials but fell to near zero with all 7-mm myocardium trials. The bipolar RF maintained transmurality only when no fat was applied. In the maximal lesion depth models, the laser was capable of producing lesions >8 mm with no fat and >6 mm with either 2 mm or 4 mm of fat present. The microwave produced lesions in the no fat (>6 mm) and 2-mm (>4 mm) fat group. The bipolar RF produced 83% transmurality with no fat and zero percent transmurality with 2 mm of fat present.</AbstractText>Epicardial fat can severely limit transmurality in energy sources that utilize conductive heating. Laser energy was uniformly superior at producing both transmural and deep lesions irrespective of the presence of fat.</AbstractText> |
8,150 | Interference of electrical dental equipment with implantable cardioverter-defibrillators. | To determine whether electromagnetic interference with implantable cardioverter-defibrilllators (ICDs) occurs during the use of electrical dental equipment.</AbstractText>Ten different electrical dental devices were tested for their ability to interfere with the function of three types of ICDs at different intervals for 90 seconds, during which the ICD activity was monitored by telemetry.</AbstractText>Only one ultrasonic bath cleaner interfered with two of the ICDs tested up to a distance of 12.5 cm, both during continuous use and intermittent operation. In contrast, the dental chair, electrosurgical unit, both handpieces, ultrasonic tooth scaler, both amalgamators and two other types of ultrasonic bath cleaners failed to produce interference at the minimum distance of 2.5 cm.</AbstractText>Our results suggest that normal clinical use of dental electrical equipment does not have significant effects on the ICDs tested.</AbstractText> |
8,151 | Pilsicainide-induced Brugada-type ECG and ventricular arrhythmias originating from the left posterior fascicle in a case with Brugada syndrome associated with idiopathic left ventricular tachycardia. | The patient was a 50-year-old male in 2002, who was first suspected of having a Brugada-type electrocardiogram (ECG). A drug challenge test using pilsicainide was performed and unmasked a typical coved type ST elevation followed by ventricular arrhythmias (VAs) manifesting a QRS pattern with a right bundle branch block and left axis deviation. Three years later, he was transferred to the emergency room due to a wide QRS tachycardia with the same QRS morphology as the VA that previously occurred in the drug challenge test. An ECG just after the recorded termination of the tachycardia exhibited a typical Brugada-type ECG. In an electrophysiological study, ventricular fibrillation could be easily induced with reproducibility. Since the clinical tachycardia could not be sustained by an isoproterenol infusion, mapping and catheter ablation targeting the pilsicainide-induced VAs was performed. The successful ablation site was the left mid-lower septal wall where a Purkinje potential was recorded and a false tendon was attached just to it. |
8,152 | Rationale and design of a prospective study of the efficacy of a remote monitoring system used in implantable cardioverter defibrillator follow-up: the Lumos-T Reduces Routine Office Device Follow-Up Study (TRUST) study. | Increased implantable cardioverter defibrillator (ICD) implant volumes (and product advisories/recalls) pose management challenges. Most device interrogations at 3- to 6-month routine follow-up visits are "nonactionable," that is, require no clinically significant reprogramming, lead revision, or initiation or up-titration of antiarrhythmic medications. Conversely, implanted devices collect important diagnostic data (eg, atrial fibrillation onset, system integrity) that remain concealed between device interrogations. Remote monitoring may resolve some of these challenges, but has not been studied in a large-scale clinical trial. Home Monitoring (HM) uses automatic (without patient intervention) data and electrogram transmissions with rapid (<24 hours) event notification of significant (including silent) events. The Lumos-T Reduces Routine Office Device Follow-Up Study (TRUST) is a multicenter, prospective, randomized study enrolling 1000 ICD patients designed to test whether HM can safely reduce the number of scheduled nonactionable office device interrogations by 50% and provide early detection and notification of cardiac and/or device problems. After enrollment, TRUST patients are randomized 2:1 to either HM or to control (ie, HM off) arms and are seen for an in-office follow-up 3 months postimplant. At subsequent 3-month intervals, control patients have conventional office visits, whereas in HM, patient data are remotely retrieved and evaluated. In HM patients, early notification may automatically occur between periodic checks for compromised system integrity (battery, lead parameters, high-voltage circuitry) or arrhythmia occurrence (eg, atrial fibrillation, ventricular arrhythmia). All study patients will have a final office visit 15 months after implant. The results of TRUST may confirm the role of remote monitoring as an intensive surveillance mechanism for device management. |
8,153 | [Significance of the contralateral approach combined with venous deocclusion in a case of biventricular defibrillator implantation]. | The authors report the case of a patient in whom a biventricular defibrillator was successfully implanted from the right, following a failed approach from the left. The patient had chronic thrombosis of the subclavian vein, and this procedure was only possible after venous deocclusion and the positioning of an endoprosthesis. The authors underline the significance of the contralateral approach in case of difficulties in inserting pacing devices, as well as the complementary benefits of interventional radiological procedures in order to allow vascular access in cases of chronic venous thrombosis. |
8,154 | [Echocardiographic factors predictive of restoration and maintenance of sinus rhythm after reduction of atrial fibrillation]. | Atrial fibrillation (AF) is the most common cardiac arrhythmia. While the arrhythmia was initially thought to be little more than a nuisance, it is now clear that AF has a significant negative impact on quality of life and a corresponding increase in both morbidity and mortality.</AbstractText>The aim of this study was to identify Doppler echographic patterns that allow prediction of atrial fibrillation reduction and maintenance of sinus rhythm within 12 months.</AbstractText>One hundred and thirty patients having permanent atrial fibrillation, recent (51) or chronic (79) are included in the study, excepting those with valvular heart disease or thyroid dysfunction. The mean age was 63.5 +/- 11.3 years. Both transthoracic and transoesophageal echocardiography was performed using a Philips SONOS 5500 Echograph, before cardioversion. Were studied: end diastolic and systolic left ventricular diameters, left ventricular ejectionnal fraction, left atrial area (LAA), left atrial diameter, left atrial appendage area and peak emptying velocities of the left atrial appendage (PeV). Sinus rhythm was re-established in 102 patients (44 having recent and 58 chronic atrial fibrillation). Sinus rhythm was maintained for 12 months in 79 patients.</AbstractText>Within the echographic parameters studied, the left atrial area (LAA) and peak emptying velocities of left atrial appendage (PeV) before cardioversion were the best predictors of restoration of sinus rhythm. On monovariate analysis, SOG is significantly lower and PicV is significantly higher in patients whose sinus rhythm had been restored in comparison with those with permanent atrial fibrillation. (Mean SOG: 27.7 +/- 7.62 vs. 34 +/- 7,6 cm2, p<0.0001; Mean PicV: 44 +/- 15.8 vs. 31.4 +/- 13,7 cm/s, p<0.0001). This difference was maintained on multivariate analysis (p=0.002 for SOG and p=0.005 for PicV). In patients with recent atrial fibrillation, only left atrial area can predict on mono and multivariate analysis (p=0.05, OR=0.5, IC=0.36 à 3.56), re-establishing of sinus rhythm whereas in patients with chronic atrial fibrillation, peak emptying velocity of left atrial appendage predict better re-establishing of sinus rhythm (p=0.04, OR=1.29, IC=0.12 à 4.23). The threshold values of LAA and PeV for conversion of atrial fibrillation into sinus rhythm are respectively 25 cm2 and 20 cm/sec. In patients who converted into sinus rhythm; LAA predict maintenance of sinus rhythm at the end of 12 months of survey (p=0.04) with a threshold value of 25 cm2. In the subgroup of patients admitted with chronic atrial fibrillation, PeV predicts better the maintenance of sinus rhythm (p=0.05) with a threshold value of 60 cm/sec, p=0.06; whereas LAA remains better in patients with a recent atrial fibrillation. (p=0.02).</AbstractText>In addition to the anatomic study of cardiac structure and the search of intracavitary thromboses before reduction of atrial fibrillation, echocardiography allows prediction of cardioversion success (LAA and PeV) and maintenance of sinus rhythm within 12 months.</AbstractText> |
8,155 | [Evaluation of the cost of complications of automatic implantable defibrillators]. | The automatic implantable defibrillator (AID) has been shown to prevent sudden death but it frequently gives rise to complications. These complications seem to be costly but they do not figure in the economic assessments of AID. From 1989 to 2003, 202 patients (173 men, age 58 +/- 14 years) received consecutively 264 AID in the same centre of implantation. The authors studied the complications of these implantations. The medical indication was secondary (documented spontaneous ventricular tachycardia or fibrillation) in 145 patients (71.8%) and prophylactic in the remaining 57 patients (28.2%). During the 36 month (+/- 35) follow-up, 40.6% patients had an appropriate treatment: 50.3% in the secondary prevention group versus 15.8% in the prophylactic implantation group. The one year, 5 and 15 year survival rates were 99, 88 and 85% respectively. Eighty seven complications were observed resulting in a long term complication in 36.7% of patients. These complications were: inappropriate electric shock, n=24 (27.6%), fractured catheters, n=12 (13.6%), haematomas, n=12 (13.6%), loss of function of the AID, n=10 (11.4%), infection, n=6 (6.8%), pneumothorax, n=7 (8.0%), and others n=16 (18.4%). The cost of these complications was assessed in terms of hospital stay in intensive care (1010.40 euros per day) or in the general cardiology wards (546.70 euros per day). The complications resulted in 502 days of additional hospital stay (5.77 days per complication) with a total cost of 285 655.20 euros (3283.40 euros per complication). The most expensive complications in terms of hospital stay were: infections (24.5 days), fractured catheter (5.75 days), and postoperative haematoma (5.5 days). These results indicate a significant cost of complications which should be indicated in the economic evaluation of AID. |
8,156 | Cardiac arrest and left ventricular fibrosis in a Finnish family with the lamin A/C mutation. | We screened the candidate genes from a Finnish family in which the mother was resuscitated from ventricular fibrillation and the daughter died suddenly without any prior cardiac symptoms.</AbstractText>In addition to screening of potential structural gene mutations, phenotyping of the proband and medico-legal autopsy of the victim of the sudden death, including histopathological examinations, were performed. Genetic screening revealed an R541C mutation in the lamin A/C gene both in the proband and her daughter. None of the 16 first- or second-degree relatives, or 96 unrelated healthy subjects, carried the same mutation. In the proband, the size and the global function of the left ventricle (LV) were normal, but a local hypokinesia and thinning of inferoposterior area of the LV were seen in 2D echocardiography and magnetic resonance imaging. Coronary angiogram and the results of the electrophysiological study were normal. Autopsy of the victim of sudden death showed localized thinning and fibrosis in the inferoposterior area of the LV, with only minimal fibrosis in the right ventricle and no abnormalities in the interventricular septum.</AbstractText>These observations indicate that a fatal or near-fatal cardiac arrhythmia can be the first clinical manifestation of a "de novo" mutation R541C of the lamin A/C gene. Replacement of cardiac myocytes by fibrosis seems to be the predominant pathologic-anatomic finding.</AbstractText> |
8,157 | Prognostic value of 123I-metaiodobenzylguanidine in patients with various heart diseases. | It has been reported that (123)I-metaiodobenzylguanidine (MIBG) scintigraphy can predict the poor prognosis in patients with dilated cardiomyopathy (DCM). However, the prognostic significance of MIBG is still unknown in patients with other heart diseases. In this study, we compared the prognosis and MIBG findings in various heart diseases.</AbstractText>Consecutive 565 patients undergoing MIBG scintigraphy were enrolled (392 men, 52 +/- 16 years). Indications were that 127 had ischemic heart disease (IHD), 120 DCM, 101 hypertrophic cardiomyopathy (HCM), 21 hypertensive heart disease (HHD), 58 volume-load valvular disease (VVD), 38 pressure-load valvular disease (PVD), and 101 ventricular tachycardia or fibrillation (VTF). Heart-to-mediastinum ratio (H/M) and washout rate (WR) of MIBG were evaluated. Cardiac events were defined as sudden cardiac death, heart failure, and acute ischemic event (follow-up, 22.7 +/- 17.0 months).</AbstractText>A total of 106 cardiac events including 40 cardiac deaths occurred. Cox hazard model analysis showed that in the IHD, HCM, and DCM groups, H/M and WR were associated with cardiac death, but not in the HHD, PVD, VVD, or VTF groups. Only death and congestive heart failure (CHF) episodes were related to H/M and WR. On the other hand, fatal arrhythmia, myocardial infarction, or angina pectoris were not related to H/M and WR. The data indicated that WR or H/M may predict death and CHF but does not predict fatal arrhythmia or acute ischemic event.</AbstractText>MIBG WR and H/M were associated with heart failure, sudden death, and cardiac death events, and were useful to predict the prognosis in DCM, HCM, and IHD. In contrast, fatal arrhythmia events were not associated with MIBG indices, and thus it does not appear to be useful in predicting cardiac events in patients with VTF.</AbstractText> |
8,158 | Different effects of antiarrhythmic drugs on the rate-dependency of QT interval: a study with amiodarone and flecainide. | To describe the QT/RR relationship in normal subjects, a previous study validated experimentally and used in healthy subjects a function that separately considered rate-dependent and rate-independent components of ventricular repolarization. The analysis is now extended to the effects on the QT/RR relationship of amiodarone and flecainide, 2 widely used antiarrhythmic drugs affecting repolarization.</AbstractText>The QT/RR relationship was obtained in 45 subjects without heart disease (20 men, 25 women); 20 were taken as controls, and 30 were under antiarrhythmic prophylaxis for lone atrial fibrillation (15 with amiodarone, 15 with flecainide). All subjects underwent a bicycle stress test; RR and QT (V5) were measured at the end of each load step; QTc (Bazett's formula, lead II) was obtained at rest. The QT/RR relation was fitted (R > or = 0.90) by the function QT = QTmax*R/(RR50 + RR). Here, QTmax (QT extrapolated at infinite RR) is a rate-independent measure of repolarization, RR50 (RR at which 50% of QTmax is reached) and S evaluate the rate-dependency of QT.</AbstractText>In controls, QTmax was 436 +/- 67 ms, RR50 was 355 +/- 55 ms, and S was 2.9 +/- 0.2. Amiodarone increased QTc, QTmax, and RR50 and decreased S significantly. Flecainide slightly prolonged QTc, increased QTmax but did not modify RR50 or S.</AbstractText>The saturating dependency of human repolarization on cycle length, described by the proposed function, is differently affected by amiodarone and flecainide. These differences might reflect the specific effects of each drug on ionic currents and their properties.</AbstractText> |
8,159 | Aortic stenosis. | Patients with aortic stenosis (AS) have an increased prevalence of coronary risk factors, coronary artery disease, and other atherosclerotic vascular disease and an increased incidence of coronary events and death. Statins may reduce the progression of AS. Angina pectoris, syncope or near syncope, and heart failure are the three classic manifestations of severe AS. Prolonged duration and late peaking of an aortic systolic ejection murmur best differentiate severe AS from mild AS on physical examination. Doppler echocardiography is used to diagnose the presence and severity of AS. Once symptoms develop, aortic valve replacement (AVR) should be performed in patients with severe or moderate AS. Warfarin should be administered indefinitely after AVR in patients with a mechanical aortic valve and in patients with a bioprosthetic aortic valve who have either atrial fibrillation, prior thromboembolism, left ventricular systolic dysfunction, or a hypercoagulable condition. Patients with a bioprosthetic aortic valve without any of these four risk factors should be treated with aspirin 75-100 mg daily. |
8,160 | Predictors of paroxysmal atrial fibrillation in patients undergoing aortic valve replacement. | Atrial fibrillation is one of the most common complications after cardiac surgery. This study evaluates the risk factors of paroxysmal atrial fibrillation in patients who underwent aortic valve replacement.</AbstractText>The study comprised 300 patients with aortic valve defects of either aortic stenosis (n = 150) or regurgitation (n = 150) who underwent aortic valve replacement. For each patient, 2-mode and Doppler echocardiographic examinations were performed in the preoperative period, early postoperative period, and long-term observation, and selected hemodynamic parameters were analyzed.</AbstractText>Factors significantly associated with atrial fibrillation in patients with aortic stenosis were heart failure (odds ratio = 5.5), age 70 years or more (4.5), low (3.9) and high body mass index (1.7), maximal transvalvular gradient (3.7), low left ventricular ejection fraction (5.1), end-systolic (2.9) and end-diastolic intraventricular septum thickness (1.5), and insignificant mitral regurgitation (1.9) in the preoperative period; and left ventricular ejection fraction (4.4) and end-systolic intraventricular septum thickness (1.8) in the early postoperative period. In the aortic regurgitation group, factors significantly associated with atrial fibrillation were age (1.8), left ventricular ejection fraction (3.7), left ventricular end-systolic diameter (1.7), end-diastolic intraventricular septum thickness (1.7), left atrium dimension (4.1) and insignificant mitral regurgitation (2.5) in the postoperative period; essential arterial hypertension (3.3), diabetes mellitus (2.6), and heart failure in the history (4.5) in the preoperative period; and left ventricular ejection fraction (1.9) and left atrium dimension (2.9) in the early postoperative period.</AbstractText>On the basis of the separated risk factors, all patients should be preoperatively classified to applicable groups of risk of postoperative atrial fibrillation appearance, and the prophylactic treatment should be administered in the group of patients with the highest risk. It may essentially decrease the rate of complications and deaths, and, consequently, the costs of postoperative medical care.</AbstractText> |
8,161 | Characteristics of cardiac arrest and resuscitation by age group: an analysis from the Swedish Cardiac Arrest Registry. | The objective of this study was to describe patients who experienced an out-of-hospital cardiac arrest (OHCA) by age group.</AbstractText>All patients who suffered from an OHCA between 1990 and 2005 and are included in the Swedish Cardiac Arrest Registry (n = 40,503) were classified into the following age groups: neonates, younger than 1 year; young children, between 1 and 4 years; older children, between 5 and 12 years; adolescents, between 13 and 17 years; young adults, between 18 and 35 years; adults not retired, between 36 and 64 years; adults retired, between 65 and 79 years; and older adults, 80 years or older.</AbstractText>Ventricular fibrillation was lowest in young children (3%) and highest in adults (35%). Survival to 1 month was lowest in neonates (2.6%) and highest in older children (7.8%). Children (<18 years), young adults (18-35 years), and adults (>35 years) survived to 1 month 24.5%, 21.2%, and 13.6% of cases, respectively (P = .0003 for trend) when found in a shockable rhythm. The corresponding figures for nonshockable rhythms were 3.8%, 3.2%, and 1.6%, respectively (P < .0001 for trend).</AbstractText>There is a large variability in characteristics and outcome among patients in various age groups who experienced an OHCA. Among the large age groups, there was a successive decline in survival with increasing age in shockable and nonshockable rhythms.</AbstractText> |
8,162 | [Cross-sectional study of heart failure of patients intaked in an Internal Medicine Service in the third level hospital in mixed area. Part III: mortality analysis]. | To establish the characteristics of the deceased in intaked patients by heart failure.</AbstractText>A cross-sectional study of the intaked patients in the Internal Medicine Service in the Hospital Clínico Universitario de Santiago de Compostela between 1999 to 2003. The variables analized were: sex, age, days of hospital stay, number of intaked by failure cardiac, reason for admission (guide symptom), hypertension, diabetes mellitus, cardiac disease, fibrillation atrium, previous treatment with beta-blockers, blood pressure in the admission moment, to make echocardiography, disfunction systolic, etiology, deceased, treatment at the end. The statistical analysis was performed with cualitative and cuantitative measures, chi-cuadrado and t-student.</AbstractText>248 patients were accepted for the study, with the mortality rate rising 8.6% (21 patients). We did not observed differences between sexes, but the median age in death patients was greater than other patients. The median income was 5 days, letter than study population. The hypertension prevalence (30 vs. 42.6%, p = 0.27) and ischemic cardiopathy (30 vs. 27.7%, p = 0.82) did not showed differences with the population. The hypertension prevalence in women (16.7 vs. 35.7%, p = 0.21) and the ischemic cardiopathy prevalence in men (50 vs. 21.4%, p = 0.20) did not showed differences. It made echocardiography in 21.0% of death patients, p = 0.76. The systolic disfunction prevalence was bigger in death patients (80 vs. 41.3%), this difference was not significant statistically.</AbstractText>The older patients showed letter survival. We did not observe any influence of sex or left ventricular systolic function on mortality in patients with heart failure.</AbstractText> |
8,163 | Valvular heart disease: diagnosis and management. | Valvular heart disease is a leading cause of morbidity and mortality in India. Advances in both surgical and percutaneous techniques and a better understanding of timing for intervention accounts for the current increased rates of survival. Echocardiography remains the gold standard for diagnosis and periodic assessment of patients with valvular heart disease. Generally, patients with stenotic valvular lesions can be monitored clinically until symptoms appear and most can now benefit from percutaneous techniques. In contrast, patients with regurgitant valvular lesions require careful echocardiographic monitoring for left ventricular function and may require surgery even if no symptoms are present. Percutaneous therapy of valvular regurgitant lesions is yet to evolve fully. |
8,164 | [QT dynamicity in risk stratification in patients after myocardial infarction]. | Ventricular repolarization abnormalities are associated with increased risk of sudden cardiac death in patients after myocardial infarction. The aim of this study is to assess QT dynamicity - QT/RR relationship - in patients after myocardial infarction and its contribution to risk stratification of sudden cardiac death.</AbstractText>In a group of patients with diagnosis of acute myocardial infarction a long term ECG recording was performed 48-72 hours after myocardial infarction (MARS Unity Workstation, GE Medical Information Technologies). Patients with unstable circulation, artificial pulmonary ventilation, left bundle brach block, atrial fibrillation and paced rhythm were excluded. Analysis of QT dynamicity was performed by QT Guard software (GE Medical Information Technologies). QT/RR relationship is expressed by linear regression as QT = = aRR + b where "a" is termed "slope".</AbstractText>Assessment of QT dynamicity was possible in 215 ECG recordings. In 6-month follow-up 2 patients died and another was successfully resuscitated for primary ventricular fibrillation. Six-month mortality resp. mortality + resuscitation was 0.9 %, resp. 1.4 %. Therefore statistical evaluation was not possible. In the 3 mentioned individuals the slope values were 0.333, 0.249 and 0.342.</AbstractText>Mortality of up-to-date-treated patients after myocardial infarction is low. Therefore, in such patients it is not possible to assess QT dynamicity as a risk factor in midterm follow-up. Limitation of the method is the necessity of substantial selection of patients elegible for analysis and dependance on necessary equipment.</AbstractText> |
8,165 | [Early haemodynamic changes after radiofrequency ablation of the atrioventricular junction]. | The effect of radiofrequency ablation of the atrioventricular junction may be accompanied by undesired effect of right ventricular stimulation. The objective of the study was to evaluate early haemodynamic effects of catheter ablation in patients with permanent atrial fibrillation resistant to pharmacotherapy.</AbstractText>The study included 19 patients aged 66.9 +/- 12.4 years on an average. Depending on the basal ejection fraction (EF), we divided the patients in to two groups (the 1 st group patients had EF less than 50 %, the 2nd group patients had EF equal to 50 % or higher). The patients were underwent radiofrequency ablation of the atrioventricularjunction and a pacemaker implantation. Haemodynamic changes were evaluated by measuring the ejection volume (EV) and the minute volume (MV) using echocardiography basally prior to and after the intervention, at different stimulation frequencies. For a more precise evaluation of the patients' condition, we defined the EVi am MVi indices as the ratio between the above values at different stimulation frequencies and the basal value.</AbstractText>EV in patients with a low EF increases at all stimulation frequencies with the maximum effect observed in the frequency band from 60-100/min. At stimulation frequency of 60/min, the volume increased from 26.4 ml before ablation to 39.5 ml after ablation. MV grows or remains unchanged at all frequencies except for 60/min, at which the growth in EV cannot compensate the drop in MV due to a fall in frequency. Patients in the 2nd group had a high EV value (52.3 ml) before ablation. After the intervention, their EV increased only at stimulation frequency of 60 and 80/min (64.0 and 55.1 ml, respectively). Also these patients' MV was high before ablation (6,097 ml). After the intervention, their MV decreased for all stimulation frequencies, but showed a growing tendency. Statistical evaluation showed negative correlation between EVi and MVi on the one hand, and between EF and the average of the left ventricle in systole on the other.</AbstractText>Our results have shown that radiofrequency transcatheter ablation of the atrioventricular node (RFCA AVN) is beneficial for certain patients in both the groups, even though the mechanisms of improving their clinical condition are different.</AbstractText> |
8,166 | ECG monitoring after cardiac surgery: postoperative atrial fibrillation and the atrial electrogram. | Atrial fibrillation is one of the most common complications after cardiac surgery and is associated with adverse outcomes such as increased mortality, neurological problems, longer hospitalizations, and increased cost of care. Major risk factors for the development of postoperative atrial fibrillation include older age and a history of atrial fibrillation. beta-Blockers are the most effective preventive therapy, although sotalol and amiodarone can also be used for prophylaxis. In the postoperative period, the nurse plays an important role in the early detection of atrial fibrillation by the recording of an atrial electrogram, which is easily obtained from the bedside monitor. Because an atrial electrogram records larger atrial activity than ventricular activity, it can be invaluable in establishing the diagnosis of postoperative atrial fibrillation. Once atrial fibrillation begins, treatment can be started with either rhythm conversion or rate-controlling medications. |
8,167 | Narrow QRS complex tachycardias. | Narrow QRS complex tachycardias are either atrioventricular (AV) nodal passive or AV nodal active. AV nodal passive tachycardias do not require the participation of the AV node in maintenance of the tachycardia. Examples are atrial tachycardia, atrial flutter, and atrial fibrillation. Treatment is directed at ventricular rate control with calcium channel blockers or beta-blockers. AV nodal active tachycardias require active participation of the AV node in maintaining the tachycardia. Examples include AV nodal reentry tachycardia and circus movement tachycardia using an accessory pathway. Treatment with a vagal maneuver or adenosine usually terminates the tachycardia. Recognition of these tachycardias is reviewed. |
8,168 | A KCNE2 mutation in a patient with cardiac arrhythmia induced by auditory stimuli and serum electrolyte imbalance. | Auditory stimulus-induced long QT syndrome (LQTS) is almost exclusively linked to mutations in the hERG potassium channel, which generates the I Kr ventricular repolarization current. Here, a young woman with prior episodes of auditory stimulus-induced syncope presented with LQTS and ventricular fibrillation (VF) with hypomagnesaemia and hypocalcaemia after completing a marathon, followed by subsequent VF with hypokalaemia. The patient was found to harbour a KCNE2 gene mutation encoding a T10M amino acid substitution in MiRP1, an ancillary subunit that co-assembles with and functionally modulates hERG. Other family members with the mutation were asymptomatic, and the proband had no mutations in hERG or other LQTS-linked cardiac ion channel genes. The T10M mutation was absent from 578 unrelated, ethnically matched control chromosomes analysed here and was previously described only once-in an LQTS patient-but not functionally characterized.</AbstractText>T10M-MiRP1-hERG currents were assessed using whole-cell voltage clamp of transfected Chinese Hamster ovary cells. T10M-MiRP1-hERG channels showed <or=80% reduced tail current, left-shifted steady-state inactivation, and 50% slower recovery from inactivation when compared with wild-type channels, with mixed wild-type/T10M channels displaying an intermediate phenotype. Lowering bath K+ concentration reduced wild-type and T10M currents equivalently.</AbstractText>Data suggest a mechanism for reduced penetrance, inherited arrhythmia in which baseline I Kr current reduction by the T10M mutation is exacerbated by superimposition of arrhythmogenic substrates such as auditory stimuli, or electrolyte disturbances that reduce I Kr (hypokalaemia) or otherwise lower the ventricular threshold for fibrillation (hypomagnesaemia and hypocalcaemia). This first example of a MiRP1 mutation associated with auditory stimulus-induced arrhythmia is supportive of the hypothesis that MiRP1 regulates hERG in the human heart.</AbstractText> |
8,169 | New-onset heart failure after permanent right ventricular apical pacing in patients with acquired high-grade atrioventricular block and normal left ventricular function. | Emerging data have suggested that right ventricular (RV) apical pacing results in progressive left ventricular (LV) dysfunction and contributes to the development of heart failure (HF). This study aimed to investigate the prevalence and clinical predictors for the development of new-onset HF after long-term RV apical pacing in patients with acquired atrioventricular (AV) block who require permanent pacing.</AbstractText>We studied the clinical outcomes after long-term RV apical pacing for acquired AV block in 304 patients without a prior history of HF. All patients had >90% ventricular pacing as determined by device diagnostic data.</AbstractText>After a median follow-up of 7.8 years, 79 patients (26.0%) developed new-onset HF after RV apical pacing. Univariate Cox-regression analysis revealed that older age at the time of pacemaker implantation (P < 0.001), the presence of coronary artery disease (CAD) (P < 0.001) or atrial fibrillation (P = 0.03), VVI pacemaker (P < 0.001), wider paced QRS duration (P < 0.001), and new-onset myocardial infarction (P < 0.001) were predictors for HF. Multivariate analysis revealed that older age at implantation (Hazard ratio [HR] 1.06, 95% confidential interval [CI] 1.04-1.09, P < 0.001), CAD (HR 1.98, 95% CI 1.12-3.50, P < 0.05), and a wider paced QRS duration (HR 1.27 for each 10 ms increment, 95% CI 1.11-1.45, P = 0.001) were independent predictors of HF. Furthermore, cardiovascular mortality was significantly increased in those with HF (36.7% vs. 2.7%, P < 0.001).</AbstractText>After a median follow-up of 7.8 years, permanent RV apical pacing was associated with HF in 26% of patients. Elderly age at the time of implant, a wider paced QRS duration and the presence of CAD independently predicted new-onset HF. More importantly, HF after RV apical pacing was associated with a higher cardiovascular mortality.</AbstractText> |
8,170 | Ventricular artifacts cancellation from atrial epicardial recordings in atrial tachyarrhythmias. | Atrial tachyarrhythmias are a very common cardiovascular disease in clinical practice with an incidence that doubles with each advancing decade. A key issue to understand their pathophysiological mechanisms is the analysis and interpretation of atrial electrograms (AEG). To properly study these signals, ventricular artifacts have to be removed from the AEG. In this work, a new application of independent component analysis (ICA) to the AEG is presented where ventricular artifacts are removed from atrial recordings making use of only one reference lead. Therefore the technique is suitable when multi-lead recordings are unavailable as in atrial implantable cardioverter-defibrilators. The methodology has been compared with traditional techniques on a database of 20 patients. Performance was evaluated through atrial waveform similarity (S) and ventricular activity reduction (V D R) as a function of atrial rhythm regularity on a beat-by-beat basis. When the atrial tachyarrhythmia is quite regular, results show that ICA preserves the atrial waveform better than the other methods (median S = 99:64%) whereas maintaining ventricular reduction (median VDR = 6:32dB). |
8,171 | Ventricular arrhythmias assessment. | An integrated framework for ventricular arrhythmias (VA) assessment, composed of two levels, is proposed in this work. The first level consists of four independent neural networks (NN), designed for specific detection tasks: signal quality, premature ventricular contractions (PVC), ventricular tachycardia (VT) and ventricular fibrillation (VF). Time and frequency domain features, obtained from the electrocardiogram (ECG) and selected through a correlation analysis procedure, form the inputs to the neural modules. The outputs feed the second layer, which consists of a global classifier (ANFIS structure), returns the global result for the VA assessment scheme. Sensitivity and specificity values, evaluated from public MIT-BIH databases, show the effectiveness of the proposed strategy. |
8,172 | Cardiac arrhythmia detection by parameters sharing and MMIE training of Hidden Markov Models. | This paper is concerned to the cardiac arrhythmia classification by using Hidden Markov Models and Maximum Mutual Information Estimation (MMIE) theory. The types of beat being selected are normal (N), premature ventricular contraction (V), and the most common class of supra-ventricular arrhythmia (S), named atrial fibrillation (AF). The approach followed in this paper is based on the supposition that atrial fibrillation and normal beats are morphologically similar except that the former does not exhibit the P wave. In fact there are more differences as the irregularity of the RR interval, but ventricular conduction in AF is normal in morphology. Regarding to the Hidden Markov Models (HMM) modelling this can mean that these two classes can be modelled by HMM's of similar topology and sharing some parameters excepting the part of the HMM structure that models the P wave. This paper shows, under that underlying assumption, how this information can be compacted in only one HMM, increasing the classification accuracy by using MMIE training, and saving computational resources at run-time decoding. The algorithm performance was tested by using the MIT-BIH database. Better performance was obtained comparatively to the case where Maximum Likelihood Estimation training is used alone. |
8,173 | The effect of internal DC shocks on the atrial fibrillation frequency. | The objective of this study, was to investigate the effect of internal DC shocks on the atrial fibrillation frequency (AFF). AFF has previously been shown to predict the success and energy requirements in patients undergoing internal cardioversion (IC) of atrial fibrillation (AF). However the possibility that unsuccessful shocks during IC may influence the AFF has not been before studied. Thirty eight patients with AF, suggested for DC cardioversion at the Royal Victoria Hospital in Belfast, were included in our study. Two catheters were positioned in the right atrial appendage (RAA) and the coronary sinus (CS), to deliver a biphasic shock waveform, synchronized with the R wave of the electrocardiogram (ECG) signal. A voltage step-up protocol (50-300 V) was used for patient cardioversion. The ECG was analyzed for a mean of 52,8+/-10.1 seconds (corresponding to segments before and after nonsuccessful shocks). Atrial fibrillatory activity was extracted by means of bandpass filtering and ventricular activity (QRST) cancellation. QRST complexes were cancelled using a recursive least squared (RLS) adaptive filter. FFT was applied to the residual atrial fibrillatory signal. AFF was estimated from the dominant frequency within the 3-12 Hz band of the power spectrum. R-R intervals during the segments were also analyzed. A total of 26 patients were successfully cardioverted, employing 167 shocks (141 nonsuccessful). AFF, computed with 10 s of signal, showed significant reduction (mean 0.3052 +/- 1.1055 Hz, P=0.028) comparing segments immediately before and after shocks, and AFF significantly increases (mean 0.2582 +/- 0.609 Hz, P=0.007) between segments immediately after shocks and those 35 s after. AFF showed distinct behavior according to the energy level of the shocks. In conclusion, intracardiac electric shocks could cause transitory changes in the AFF of patients with atrial fibrillation. |
8,174 | Non-linear organization analysis of paroxysmal atrial fibrillation. | Atrial fibrillation (AF) is a common supraventricular arrhythmia with episodes that, in the first stages of the disease, may terminate spontaneously. This fact is referred as paroxysmal atrial fibrillation. The analysis of its termination or maintenance could avoid unnecessary therapy and contribute to take the appropriate decisions on its management. The aim of this work is to study if an AF episode terminates spontaneously or not by analyzing the increase of atrial activity (AA) organization prior to AF termination. The organization varies as a consequence of the decrease in the number of reentries into the atrial tissue. The analysis was carried out noninvasively through the use of surface electrocardiogram (ECG) recordings. Sample entropy was selected as non-linear organization index. It was observed that noise and ventricular residues degrade AA organization estimation performance, therefore the use of selective filtering to get the main atrial wave (MAW) was necessary. Using the MAW organization analysis, that is the signal produced by the main reentry wandering the atrial tissue, 46 out of 50 of the terminating and non-terminating analyzed AF episodes were correctly classified (92%). The obtained outcomes allow to conclude that the dominant atrial frequency, and therefore, the main atrial reentry, contains the most relevant information about spontaneous AF termination. |
8,175 | Phase-rectified signal averaging: a useful tool for the estimation of the dominant frequency in ECG signals during atrial fibrillation. | Atrial fibrillation (AF) is the most common type of human cardiac arrhythmia. An important parameter that can be extracted from surface electrocardiogram (ECG) during AF is the dominant frequency (DF) of AF. Unfortunately, AF signal components are always highly contaminated by the ventricular QRST complexes, and the cancellation of these components is never perfect. The remaining artifacts tend to induce DF overestimates. In this paper we report on the use of phase-rectified signal analysis, a technique introduced recently to enhance quasi-periodic signal components, for improving DF estimation. The potential of phase-rectified analysis is demonstrated through experiments both on synthetic and clinical ECG signals. |
8,176 | Arrhythmogenic right ventricular cardiomyopathy/dysplasia. | Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a heart muscle disease clinically characterized by life-threatening ventricular arrhythmias. Its prevalence has been estimated to vary from 1:2,500 to 1:5,000. ARVC/D is a major cause of sudden death in the young and athletes. The pathology consists of a genetically determined dystrophy of the right ventricular myocardium with fibro-fatty replacement to such an extent that it leads to right ventricular aneurysms. The clinical picture may include: a subclinical phase without symptoms and with ventricular fibrillation being the first presentation; an electrical disorder with palpitations and syncope, due to tachyarrhythmias of right ventricular origin; right ventricular or biventricular pump failure, so severe as to require transplantation. The causative genes encode proteins of mechanical cell junctions (plakoglobin, plakophilin, desmoglein, desmocollin, desmoplakin) and account for intercalated disk remodeling. Familiar occurrence with an autosomal dominant pattern of inheritance and variable penetrance has been proven. Recessive variants associated with palmoplantar keratoderma and woolly hair have been also reported. Clinical diagnosis may be achieved by demonstrating functional and structural alterations of the right ventricle, depolarization and repolarization abnormalities, arrhythmias with the left bundle branch block morphology and fibro-fatty replacement through endomyocardial biopsy. Two dimensional echo, angiography and magnetic resonance are the imaging tools for visualizing structural-functional abnormalities. Electroanatomic mapping is able to detect areas of low voltage corresponding to myocardial atrophy with fibro-fatty replacement. The main differential diagnoses are idiopathic right ventricular outflow tract tachycardia, myocarditis, dialted cardiomyopathy and sarcoidosis. Only palliative therapy is available and consists of antiarrhythmic drugs, catheter ablation and implantable cardioverter defibrillator. Young age, family history of juvenile sudden death, QRS dispersion > or = 40 ms, T-wave inversion, left ventricular involvement, ventricular tachycardia, syncope and previous cardiac arrest are the major risk factors for adverse prognosis. Preparticipation screening for sport eligibility has been proven to be effective in detecting asymptomatic patients and sport disqualification has been life-saving, substantially declining sudden death in young athletes. |
8,177 | Reducing events in patients with chronic heart failure (REDUCEhf ) study design: continuous hemodynamic monitoring with an implantable defibrillator. | The use of implantable cardioverter defibrillators (ICDs) has been proven effective in the prevention of sudden cardiac death (SCD) and constitutes standard of care in appropriate populations. Combining a pressure sensing system with ICD therapy represents the first attempt to provide continuous hemodynamic monitoring using a device previously designed exclusively for SCD protection.</AbstractText>REDUCE is a prospective, multicenter, randomized, single-blind, parallel-controlled trial designed to assess the safety of the Chronicle ICD system (single chamber ICD with a hemodynamic monitoring system) and the effectiveness of a management strategy guided by intracardiac pressure information among ICD-indicated New York Heart Association (NYHA) Class II or III heart failure (HF) patients. Those successfully implanted with a Chronicle ICD will be randomized to the Chronicle group or Control group. All patients will receive optimal medical therapy, but the hemodynamic information from the device will be used to guide patient management only in the Chronicle group. Primary endpoints include freedom from system-related complications and relative risk reduction of one or more HF-related events (hospitalizations, and emergency department and urgent care visits requiring intravenous therapy for HF). Approximately 850 patients will be enrolled in at least 75 centers in the United States to accrue the 419 events needed to test the primary effectiveness endpoint. Enrollment began in April 2006, and is expected to end during 2009.</AbstractText>REDUCE will assess the safety of the Chronicle ICD system and the effectiveness of a patient management strategy based on remote access to continuous intracardiac pressures in reducing HF-related events.</AbstractText> |
8,178 | Cardiomyocyte Ca2+ overload in atrial tachycardia: is blockade of L-type Ca2+ channels a promising approach to prevent electrical remodeling and arrhythmogenesis? | Electrical remodeling paradigm has important implications for the understanding of atrial fibrillation (AF) and improvement of current treatment. Cardiomyocyte Ca(2+) overload is generally accepted as the initiating signal for the tachycardia-induced changes in atrial electrical properties (electrical remodeling). The precise role of cardiomyocyte Ca(2+) overload in AF-related ion channel alterations that contribute to AF maintenance is not fully understood. Clinically, patients with AF are often treated with Ca(2+) channel blockers such as verapamil to control their ventricular rate and to improve the success rate of cardioversion procedures. However, verapamil may produce an increased L-type Ca(2+) channel current (I(Ca,L)) that may reinforce Ca(2+) overload thereby promoting AF in the atrium. Ca(2+) channel blockers which target T-type Ca(2+) channels in addition to I(Ca,L) (for instance, efonidipine) may be more efficient at preventing Ca(2+) overload and arrhythmogenic electrical remodeling, but the potential benefits of these drugs have usually been tested in experimental models where drug administration preceded the initiation of electrical remodeling. Studies in animal models with established atrial tachycardia remodeling and in patients with AF are clearly warranted to prove the efficacy of Ca(2+) channel blockers that additionally target T-type Ca(2+) channels. |
8,179 | The dependence of successful resuscitation on electrocardiographically documented cardiac rhythm in case of out-of-hospital cardiac arrest. | To determine the influence of electrocardiographically documented cardiac rhythm during sudden cardiac arrest on successful resuscitation among out-of-hospital deaths in Kaunas city.</AbstractText>An observational prospective study was conducted between 1 January, 2005, and 30 December, 2005, in Kaunas city with a population of 360,627 inhabitants. In this period, all cases of cardiac arrest were analyzed according to the guidelines of the Utstein consensus conference. Cardiac arrest (both of cardiac and noncardiac etiology) was confirmed in 72 patients during one year. Effective cardiopulmonary resuscitation was performed in 18 patients.</AbstractText>The total number of deaths from all causes in Kaunas during 1-year study period was 6691. Sixty-two patients due to sudden death of cardiac etiology were resuscitated by emergency medical services personnel. Return of spontaneous circulation was achieved in 11 patients. Ventricular fibrillation was observed in 33 (53.2%) patients. Asystole was present in 11 (17.7%) and other rhythms in 18 (29.1%) cases. Patients with ventricular fibrillation as an initial rhythm were more likely to be successfully resuscitated than patients with asystole.</AbstractText>Ventricular fibrillation was the most common electrocardiographically documented cardiac rhythm registered during cardiac arrest in out-of-hospital settings. Ventricular fibrillation as a mechanism of cardiac arrest was associated with major cases of successful resuscitation.</AbstractText> |
8,180 | Improved neurological outcome with continuous chest compressions compared with 30:2 compressions-to-ventilations cardiopulmonary resuscitation in a realistic swine model of out-of-hospital cardiac arrest. | The 2005 Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care changed the previous ventilations-to-chest-compression algorithm for bystander cardiopulmonary resuscitation (CPR) from 2 ventilations before each 15 chest compressions (2:15 CPR) to 30 chest compressions before 2 ventilations (30:2 CPR). It was acknowledged in the guidelines that the change was based on a consensus rather than clear evidence. This study was designed to compare 24-hour neurologically normal survival between the initial applications of continuous chest compressions without assisted ventilations with 30:2 CPR in a swine model of witnessed out-of-hospital ventricular fibrillation cardiac arrest.</AbstractText>Sixty-four animals underwent 12 minutes of ventricular fibrillation before defibrillation attempts. They were divided into 4 groups, each with increasing durations (3, 4, 5, and 6 minutes, respectively) of untreated ventricular fibrillation before the initiation of bystander resuscitation consisting of either continuous chest compression or 30:2 CPR. After the various untreated ventricular durations plus bystander resuscitation durations, all animals were given the first defibrillation attempt 12 minutes after the induction of ventricular fibrillation, followed by the 2005 guideline-recommended advanced cardiac life support. Neurologically normal survival at 24 hours after resuscitation was observed in 23 of 33 (70%) of the animals in the continuous chest compression groups but in only 13 of 31 (42%) of the 30:2 CPR groups (P=0.025).</AbstractText>In a realistic model of out-of-hospital ventricular fibrillation cardiac arrest, initial bystander administration of continuous chest compressions without assisted ventilations resulted in significantly better 24-hour postresuscitation neurologically normal survival than did the initial bystander administration of 2005 guideline-recommended 30:2 CPR.</AbstractText> |
8,181 | Predictors of arrhythmia recurrence in patients with lone atrial fibrillation. | The need for antiarrhythmic drugs (AAD) after a first episode of atrial fibrillation (AF) is determined by the probability of recurrence. The aim of this study was to asses the probability of relapse and the predictors of recurrence in patients with idiopathic AF.</AbstractText>A cohort of 98 consecutive patients younger than 65 years admitted at the emergency room because of an episode of symptomatic idiopathic (lone) AF was included in this study. On admission, a complete medical history was taken, and an echocardiogram and 24-h Holter monitoring were performed. Patients were seen at 3 and 6 months after the index episode. There were 35 (35.7%) patients with a new-onset AF episode and 63 (64.3%) with a recurrent AF episode. A majority of them were male (71%), with a mean age of 48+/-11 years. Patients with new-onset AF episodes did not receive AAD. At 6 month follow-up, 57% of all patients suffered at least one symptomatic AF relapse. Patients with AF relapses belong more often to the recurrent group vs. new-onset group of AF (65.1 vs. 34.9%, respectively, P = 0.03); they had larger LA diameter indexed for body surface area (BSA) (22.6+/-3.7 vs. 19.8+/-3.2 mm/m(2), P = 0.001), larger left ventricular end-systolic diameter (18.4+/-3.1 vs. 17.2+/-2.5 mm/m(2), P = 0.05) and a tendency towards a higher proportion of atrial tachycardia runs on Holter (66.7 vs. 50%, P = 0.09). Logistic regression analysis showed that the presence of previous episodes of AF (OR: 3.2; 95% CI; 1.0-8.0, P = 0.04) and a larger anteroposterior LA diameter (OR: 1.3; 95% CI; 1.1-1.6, P = 0.001) were independent predictors of AF recurrences at 6 months.</AbstractText>The recurrence rate in lone AF patients is high. The presence of previous episodes and a mildly enlarged anteroposterior LA diameter increase the probability of relapse of lone AF.</AbstractText> |
8,182 | Influence of diabetes on cardiac resynchronization therapy with or without defibrillator in patients with advanced heart failure. | We performed a post hoc analysis to determine the influence of cardiac resynchronization therapy with a defibrillator (CRT-D) or without a defibrillator (CRT-P) on outcomes among diabetic patients with advanced heart failure (HF).</AbstractText>In patients with systolic HF, diabetes is an independent predictor of morbidity and mortality. No data are available on its impact on CRT-D or CRT-P in advanced HF.</AbstractText>The database of the Comparison of Medical Therapy, Pacing and Defibrillation in Heart Failure trial was examined to determine the influence of CRT (CRT-D and CRT-P) on outcomes among diabetic patients. All-cause mortality or hospitalization, all-cause mortality or cardiovascular hospitalization, all-cause mortality or HF hospitalization, and all-cause mortality were analyzed among diabetic patients (n = 622). A Cox proportional hazard model, adjusting for age, gender, New York Heart Association, ischemic status, body mass index, left ventricular ejection fraction, heart rate, QRS, left or right bundle branch block, blood pressure, comorbidities (renal failure, carotid artery disease, peripheral vascular disease, hypertension, coronary artery bypass grafting, and atrial fibrillation), medications, and device (with or without defibrillator), was used to estimate hazard ratios (HRs) and significance.</AbstractText>The overall outcome of diabetic patients was similar to that of nondiabetic patients in the optimal pharmacologic therapy arm. With CRT, diabetic patients experienced a substantial reduction in all-cause mortality or all-cause hospitalization (HR = 0.77, 95% confidence interval [CI] 62-0.97), all-cause mortality or cardiovascular hospitalization (HR = 0.67, 95% CI 0.53-0.85), all-cause mortality or HF hospitalization (HR = 0.52, 95% CI 0.40-0.69), and all-cause mortality (HR = 0.67, 95% CI 0.45-0.99) compared with optimal pharmacologic therapy. Procedure-related complications and length of stay were identical in diabetic and nondiabetic patients.</AbstractText>In diabetic patients with advanced HF, there is a substantial benefit from device therapy with significant improvement in all end points.</AbstractText> |
8,183 | Prognostic usefulness of anemia and N-terminal pro-brain natriuretic peptide in outpatients with systolic heart failure. | N-terminal pro-brain natriuretic peptide (NT-pro-BNP) and anemia are predictors of outcome in systolic heart failure. It is currently unclear how these 2 markers interact in particular with regard to the prognostic information carried by each risk marker. We therefore tested the hypothesis that anemia (World Health Organization criteria, hemoglobin levels <7.5 mmol/L for women and <8.0 mmol/L for men) and NT-pro-BNP are associated and evaluated how a possible association affects the prognostic value of each risk marker. Clinical data from 345 patients with systolic heart failure were obtained prospectively at the baseline visit to our heart failure clinic (inclusion criterion left ventricular ejection fraction <0.45, no exclusion criteria). Follow-up was 30 months (median), and 70 events (mortality) occurred. Prevalence of anemia was 27%. In a multivariate logistic regression model, anemia (p = 0.041) was closely associated with NT-pro-BNP levels above the median (1,381 pg/ml) after adjustment for traditional confounders (left ventricular ejection fraction, age, body mass index, atrial fibrillation, chronic kidney disease). In an adjusted Cox proportional hazard model, the 2 parameters were associated with mortality after adjustment for traditional confounders (hazard ratio for anemia 1.73, 95% confidence interval 1.06 to 2.83, p = 0.029; hazard ratio for NT-pro-BNP >1,381 pg/ml 2.68, 95% confidence interval 1.58 to 4.66, p <0.001). Patients with anemia and high NT-pro-BNP levels had a fivefold increased risk for mortality (hazard ratio 4.77, 95% confidence interval 2.47 to 9.18, p <0.001). In conclusion, anemia is closely associated with NT-pro-BNP in patients with systolic heart failure, and anemia and NT-pro-BNP carry independent prognostic information. Patients with anemia and high levels of NT-pro-BNP have a markedly increased mortality risk. |
8,184 | Control of electrical alternans in simulations of paced myocardium using extended time-delay autosynchronization. | Experimental studies have linked alternans, an abnormal beat-to-beat alternation of cardiac action potential duration, to the genesis of lethal arrhythmias such as ventricular fibrillation. Prior studies have considered various closed-loop feedback control algorithms for perturbing interstimulus intervals in such a way that alternans is suppressed. However, some experimental cases are restricted in that the controller's stimuli must preempt those of the existing waves that are propagating in the tissue, and therefore only shortening perturbations to the underlying pacing are allowed. We present results demonstrating that a technique known as extended time-delay autosynchronization (ETDAS) can effectively control alternans locally while operating within the above constraints. We show that ETDAS, which has already been used to control chaos in physical systems, has numerous advantages over previously proposed alternans control schemes. |
8,185 | Evaluating intramural virtual electrodes in the myocardial wedge preparation: simulations of experimental conditions. | While defibrillation is the only means for prevention of sudden cardiac death, key aspects of the process, such as the intramural virtual electrodes (VEs), remain controversial. Experimental studies had attempted to assess intramural VEs by using wedge preparations and recording activity from the cut surface; however, applicability of this approach remains unclear. These studies found, surprisingly, that for strong shocks, the entire cut surface was negatively polarized, regardless of boundary conditions. The goal of this study is to examine, by means of bidomain simulations, whether VEs on the cut surface represent a good approximation to VEs in depth of the intact wall. Furthermore, we aim to explore mechanisms that could give rise to negative polarization on the cut surface. A model of wedge preparation was used, in which fiber orientation could be changed, and where the cut surface was subjected to permeable and impermeable boundary conditions. Small-scale mechanisms for polarization were also considered. To determine whether any distortions in the recorded VEs arise from averaging during optical mapping, a model of fluorescent recording was employed. The results indicate that, when an applied field is spatially uniform and impermeable boundary conditions are enforced, regardless of the fiber orientation VEs on the cut surface faithfully represent those intramurally, provided tissue properties are not altered by dissection. Results also demonstrate that VEs are sensitive to the conductive layer thickness above the cut surface. Finally, averaging during fluorescent recordings results in large negative VEs on the cut surface, but these do not arise from small-scale heterogeneities. |
8,186 | Cellular basis for triggered ventricular arrhythmias that occur in the setting of compensated hypertrophy and heart failure: considerations for diagnosis and treatment. | Malignant ventricular tachyarrhythmias are common among patients with hypertrophy and heart failure, and these arrhythmias can initiate by triggered activity. Abnormal repolarization and disturbed calcium handling due to remodeling processes are common features of the hypertrophied and failing heart that conspire to facilitate triggering events. These changes have a different cellular origin in compensated hypertrophy as compared with failure, which underscores the complexity of mechanisms that predispose the remodeled heart to arrhythmias. This hampers the identification of the vulnerable patient and adequate antiarrhythmic pharmacotherapy. Beat-to-beat variability of repolarization has been proposed as an early (noninvasive) electrographic detection method of triggered activity. An increase of variability heralds an enhanced risk of arrhythmias, and controlling this repolarization parameter by pharmacological agents is antiarrhythmic. Different drugs (flunarizine, ranolazine, K201, calmodulin kinase blockers) that are able to prevent and/or suppress triggered arrhythmias by specific mechanisms of action will be discussed. |
8,187 | Eight (or more) kinds of alternans. | Cardiac electrical alternans is an alternating rhythm in the electrical properties of the heart, such as cellular action potential duration, conduction velocity, and/or intracellular calcium (Ca) concentrations. These alternations can initiate reentrant arrhythmias and can also break up ongoing reentry, creating ventricular fibrillation. Alternans can take several forms. The alternation in time can be uniform in space (concordant alternans) or can have regions that are out of phase with other regions (discordant alternans). Alternans can be driven by voltage instabilities (involving electrical restitution) or by Ca instabilities. In addition, the relation between voltage and Ca can be positive or negative. Anatomical factors can play a role in generating spatially discordant alternans, but there is also a critical role for instabilities that are dynamically generated and can only be understood as the response of a nonlinear medium to periodic excitation. This is especially true of spatially discordant alternans, the most deadly form. We will review the role of factors such as action potential duration, conduction velocity, and Ca, which interact with each other to produce alternans. Simulations of cardiac conduction support these conclusions, as do experiments in a variety of animal and human preparations. |
8,188 | Imaging fibrillation/defibrillation in a dish. | Sheets of cultured cardiac cells constitute an emerging experimental model of cardiac tissue electrophysiology and arrhythmia. It has been used to study fundamental properties of reentrant (spiral) waves and electric field interactions with tissue structure and thus constitutes a valuable model for investigations of fibrillation and defibrillation.</AbstractText>Optical mapping can be used to visualize action potential propagation or calcium waves in confluent monolayers of neonatal rat ventricular cells. Spiral waves can be initiated by burst pacing and terminated by an electric field shock.</AbstractText>Work from this laboratory and others is reviewed regarding the behavior of single and multiple spiral waves in this model system as they pertain to fibrillation (dynamic instabilities) and defibrillation (interaction of electric fields with reentrant waves).</AbstractText>Subject to limitations, the cultured cell monolayer is a controlled experimental model that will be useful for further study of basic aspects of fibrillation and defibrillations.</AbstractText> |
8,189 | Imaging ventricular fibrillation. | Ventricular fibrillation (VF) had been traditionally considered as a highly disorganized process of random electrical activity emanating from multiple, short-lived, reentrant electrical waves. It is the incessant breakup of wave fronts and the creation of new daughter waves (wavebreaks) that perpetuate VF. Other studies described VF as a process with a substantial degree of structure embedded in seemingly random events where VF is spatially organized as a small number of relatively large domains, each with a single dominant frequency. Ventricular fibrillation is then driven by the domain with the highest activation frequency representing a "mother rotor" that drives the surrounding myocardium except at boundaries with more refractory tissues. Voltage-sensitive dyes and optical mapping provide a powerful technique that has been extensively applied to study the structure and organization of VF and has revealed how cellular properties, fiber orientation, and metabolism influence VF. This brief review will discuss signal processing methods used to investigate mechanisms underlying VF, namely, (a) fast Fourier transform, (b) time-frequency domain analysis, (c) time-lag correlation, (d) mutual information analysis, and (e) phase reconstruction techniques to identify phase singularities and wavebreak locations. In addition, several cellular properties that have been shown to influence the structure of VF such as (a) the dispersion of repolarization, (b) the low tonicity/osmolarity, and (c) the amplitude of K(+) currents will be discussed as determinants of VF. Finally, recent image analysis routines were used to identify wavebreak sites and revealed that wavebreaks are caused by abrupt spatial dispersion of voltage (V(m)) oscillations. |
8,190 | Cardiac electrical dynamics: maximizing dynamical heterogeneity. | The relationships between key features of the cardiac electrical activity, such as electrical restitution, discordant alternans, wavebreak, and reentry, and the onset of ventricular tachyarrhythmias have been characterized extensively under the condition of constant rapid pacing. However, it is unlikely that this scenario applies directly to the clinical situation, where the induction of ventricular tachycardia (VT) typically is associated with the interruption of normal cardiac rhythm by several premature beats. To address this issue, we have developed a general theory to explain why specific patterns of premature stimuli increase dynamic heterogeneity of repolarization and precipitate conduction block. The theory predicts that conduction block is caused by (1) creation of a spatial gradient in diastolic interval (DI) by waves traveling at slightly different velocities (ie, conduction velocity dispersion) and (2) amplification of the spatial gradient in DI over subsequent action potentials, secondary to a strong dependence of action potential duration on the preceding DI (ie, a steep action potential duration restitution function). Tests of this theory have been conducted in computer models of homogeneous tissue, where increased spatial dispersion of repolarization during premature stimulation can be attributed solely to the development of dynamical heterogeneity, and in a canine model exhibiting spontaneously occurring VT and sudden death. Our results thus far indicate that the probability of inducing ventricular fibrillation (VF) in the animal model is highest for those sequences predicted to cause conduction block in the computer model. An understanding of the mechanisms underlying these observations will help to identify key electrical phenomena in the onset of VT and fibrillation. Drug and electrical therapies can then be improved by targeting these specific phenomena. |
8,191 | Genetic predisposition and cellular basis for ischemia-induced ST-segment changes and arrhythmias. | Recent reports have highlighted the importance of a family history of sudden death as a risk for ventricular fibrillation (VF) in patients experiencing acute myocardial infarction (AMI), pointing to the possibility of a genetic predisposition. This report briefly reviews 2 recent studies designed to examine the hypothesis that there is a genetic predisposition to the development of arrhythmias associated with AMI. Ventricular tachycardia and VF (VT/VF) complicating AMI as well as arrhythmias associated with Brugada syndrome, a genetic disorder linked to SCN5A mutations, have both been linked to phase 2 reentry. Because of these mechanistic similarities in arrhythmogenesis, we examined the contribution of SCN5A mutations to VT/VF complicating AMI in patients developing VF during AMI. A missense mutation in SCN5A was found in a patient who developed an arrhythmic electrical storm during an evolving myocardial infarction. All VT/VF episodes were associated with ST-segment changes and were initiated by short-coupled extrasystoles. G400A mutation and H558R polymorphism were on the same allele, and functional expression in TSA201 demonstrated loss of function of sodium channel activity. These results suggest that a subclinical mutation in SCN5A resulting in a loss of function may predispose to life-threatening arrhythmias during acute ischemia. In another cohort of patients who developed long-QT intervals and torsade de pointes arrhythmias in days 2 to 11 after an AMI, a genetic screening of all long-QT genes was performed. Of 8 patients in this group, 6 (75%) displayed the same polymorphism in KCNH2, which encodes the alpha-subunit of the rapidly activating delayed rectifier potassium current, I(Kr). The K897T polymorphism was detected in only 3 of 14 patients with uncomplicated myocardial infarction and has been detected in 33% of the white population. Expression of this polymorphism has previously been shown to cause a loss of function in HERG current consistent with the long-QT phenotype. These observations suggest a genetic predisposition to the development of long-QT intervals and torsade de pointes in the days after an AMI. These preliminary studies provide support for the hypothesis that there is a genetic predisposition to the type and severity of arrhythmias that develop during and after an AMI, and that additional studies are warranted. |
8,192 | Detection of cardiac tachyarrhythmias in implantable devices. | Implantable devices such as pacemakers and implantable cardioverter/defibrillators (ICDs) use algorithms to sense cardiac depolarizations and to detect tachyarrhythmias by analysis of timing and morphology of sensed events. The purpose of tachyarrhythmia detection in these devices is to guide electrical therapies delivered by the pacemaker or ICD and/or to provide clinical diagnostics for medical management of patients. Unlike electrocardiographic analysis methods that rely on postanalysis of recorded signals using desktop computers, implantable devices must make detection decisions on a beat-by-beat basis with algorithms that can be implemented in battery-powered devices with longevities of up to several years. Cardiac sensing in implantable devices is achieved using amplifiers, bandpass filters, and adaptive thresholds to avoid oversensing of cardiac and noncardiac activity, while avoiding undersensing of low-amplitude cardiac activations during fibrillation. The tachyarrhythmia detection algorithms are formed by combining different building blocks of rhythm information extracted from timing of cardiac activations and from electrogram morphology information. Tachyarrhythmia detection algorithms in ICDs were originally designed to achieve high sensitivity for detection of life-threatening tachyarrhythmias such as ventricular tachycardia and ventricular fibrillation. Much of the progress in ICD detection algorithms in the past 15 years has been in the development of supraventricular tachycardia discrimination algorithms to reduce the number of inappropriate therapies delivered by ICDs. This article provides an overview of current tachyarrhythmia detection approaches, describe challenges facing tachyarrhythmia detection algorithm performance in ICD patients with primary prevention indications, and presents future directions in cardiac tachyarrhythmia detection for implantable devices. |
8,193 | Full recovery of an avalanche victim with profound hypothermia and prolonged cardiac arrest treated by extracorporeal re-warming. | Survival of hypothermic avalanche victims with cardiac arrest is rare. This report describes full recovery of a 29-year-old backcountry skier completely buried for 100 min at 3.0m (9.8 ft) depth. On extrication he was unconscious, but breathing spontaneously into an air pocket; core body temperature measured 22.0 degrees C (71.6 degrees F). He was intubated and ventilated on site. Ventricular fibrillation commenced during helicopter transportation, whereby chest compression was lacking for 15 min. At the nearest hospital continuous cardiopulmonary resuscitation was initiated, but defibrillation failed. Tympanic core body temperature measurement confirmed life-threatening hypothermia of 21.7 degrees C (71.1 degrees F) and serum K(+) was 4.3 mmol/l, necessitating transferral to a hospital with cardiopulmonary bypass facilities. Defibrillation finally succeeded following re-warming, by femoral veno-arterial bypass, to 34.5 degrees C (94.1 degrees F). Total duration of cardiac arrest was 150 min. The patient developed pulmonary oedema, treated by extracorporeal membrane oxygenation, but progressed well and was discharged from hospital on day 17, fit to resume professional and social activities. Follow-up cerebral magnetic resonance imaging 2 years after avalanche burial demonstrated only minimal changes attributable to unrelated, prior cranial trauma. Extensive neurological and psychological investigations gave excellent results. This report confirms previous literature that an air pocket with patent airways is essential for survival of a completely buried avalanche victim after 35 min and endorses the recommended management strategies of the International Commission for Mountain Emergency Medicine ICAR MEDCOM. In particular, all hypothermic victims extricated with an air pocket and free airways must be treated optimistically, even despite prolonged cardiac arrest. This remarkable case documents the fastest drop in core temperature ever recorded during snow burial, namely 9.0 degrees C (16.2 degrees F)/h, and the second-lowest reversible core temperature in avalanche literature. |
8,194 | The tissue distribution of fluoride in a fatal case of self-poisoning. | The purpose of this paper is to report a case of fluoride poisoning along with a discussion of poisoning characteristics, analytical procedures, and a review of previous reports of fatal intoxications with analytical data. A case of suicidal ingestion of 40 mL of a rust removal agent containing hydrofluoric acid and ammonium fluoride by a 33-year-old white male is presented. He had an organic personality disorder with residual schizophrenia and previous suicide attempts with therapeutic drugs and cleaning products. At admission, he presented with a Glasgow coma score of 3, third degree atrioventricular block, and asystole. Resuscitation efforts were performed during which the patient suffered two episodes of ventricular fibrillation followed by asystole. In spite of advanced resuscitation efforts and the administration of calcium chloride, he died 2.5 h after the ingestion. Analytical data in the hospital showed calcium levels of 3.1 mg/dL and metabolic acidosis. Internal findings were erosive gastritis, brain edema, and pulmonary and hepatic congestion. Quantitation of fluoride was performed using an ion-selective electrode for the anion. Disposition of fluoride in the different tissues was as follows: peripheral blood, 19.4 mg/L; urine, 670 mg/L; vitreous humor, 2.5 mg/L; liver, 40.0 mg/kg; kidney, 60.0 mg/kg; lung, 17.5 mg/kg; brain, 2.5 mg/kg; spleen, 30.0 mg/kg; bone, 0.5 mg/ kg; and gastric content, 1120 mg/L (67 mg total). Validation of the analytical method was performed using different spiked tissues, in a range of concentrations from 2.4 to 475 mg/L or mg/kg, and submitting them to dilution (1:25) to avoid the matrix effect and to bring these concentrations to the range of the aqueous calibration curve (0.19-19 mg/L). Limits of detection and quantitation were 0.02 and 0.1 mg/L, respectively. The linearity of the method, for all studies tissues, was excellent, with r(2) values of 0.999. Accuracy and precision were within 10.5% and 5.7%, respectively. Fluoride analyses using the ion selective electrode are simple, sensitive, and rapid. This report provides an extensive tissue distribution study of fluoride after a well documented case of acute poisoning. Based on the autopsy findings, patient history, toxicology results, and previously reported data the forensic pathologists ruled that the cause of death was due to a fluoride poisoning, and the manner of death was listed as suicide. |
8,195 | Percutaneous occlusion of patent ductus arteriosus with the Nit-Ccclud device in an adult patient. | We report a case of an adult patient with patent ductus arteriosus (PDA), a large aortic ampulla and moderate pulmonary hypertension. The PDA was successfully closed using a Nit-Occlud device designed for PDA closure. The day before the programmed procedure, the patient was admitted for signs and symptoms of cardiac heart failure and atrial fibrillation with rapid ventricular response. The procedure was postponed for 6 days, and in the meantime, she was successfully treated with diuretics, negative water balance and heart rate control. This device is frequently used in the pediatric population. The same procedure in an adult patient may present some technical difficulties, and the merging of pediatric and adult interventional cardiologists is necessary. The technique and management of the procedure are discussed here. |
8,196 | In vivo porcine model of reperfused myocardial infarction: in situ double staining to measure precise infarct area/area at risk. | The aim of this study is to evaluate a catheter-based porcine model for reperfused myocardial infarction and investigate the appropriate location and duration of the occlusion.</AbstractText>A balloon catheter was placed in the left descending coronary artery (LAD) in 78 swine, and used to occlude the LAD. To evaluate this model, left ventricular ejection fraction (LVEF), infarct size, incidence of ventricular fibrillation (VF), and mortality was compared among three groups: 60-min proximal LAD occlusion (60P), 60-min mid LAD occlusion (60M), and 30-min proximal LAD occlusion (30P).</AbstractText>In 72 of the 78 pigs, the procedures were successfully completed. Both mortality and incidence of VF were highest in the 60P group (66.7% and 91.7%, respectively). Myocardial infarction was successfully induced in all 72 animals and in situ double-staining with Evans blue dye and 2,3,5-triphenyltetrazolium chloride was performed to delineate area at risk for ischemia and infarcted myocardium. There was no difference in infarct size, expressed as a percentage of the area at risk, between the 60P and 60M groups (49.5% +/- 3.9% vs. 45.4% +/- 13.3%, respectively). Serial changes in LVEF of the 60M group demonstrated that until 14 days after reperfusion, LVEF improved naturally over time (36.4% +/- 6.6% at 24 hr, and 47.3% +/- 10.1% at 14 days).</AbstractText>This model and methodology could provide a reproducible and consistent infarct size. The current study demonstrated that 60-min mid LAD occlusion can be the most feasible to serve as a porcine reperfused myocardial infarction model.</AbstractText>Copyright 2008 Wiley-Liss, Inc.</CopyrightInformation> |
8,197 | Intracardiac thrombosis and embolism in patients with cardiac amyloidosis. | Patients with primary amyloidosis (AL type) have a poor prognosis, in part due to frequent cardiac involvement. Although intracardiac thrombus has been reported in anecdotal cases, neither its frequency nor its role in causing mortality is known. Furthermore, the clinical and echocardiographic variables that may be associated with thromboembolism in cardiac amyloidosis have not been defined.</AbstractText>A total of 116 autopsy or explanted cases of cardiac amyloidosis (55 AL and 61 other type) were identified in the Mayo Clinic. Forty-six fatal nonamyloid trauma cases served as controls. Each heart was examined for intracardiac thrombus. The cause of death was determined from autopsy and clinical notes. Intracardiac thrombosis was identified in 38 hearts (33%). Twenty-three had 1 thrombus, whereas 15 had 2 to 5 thrombi. Although subjects in the AL group were younger and had less atrial fibrillation than those with other types of amyloidosis, the AL group had significantly more intracardiac thrombus (51% versus 16%, P<0.001) and more fatal embolic events (26% versus 8%, P<0.03). Control hearts had no intracardiac thrombus. The presence of both atrial fibrillation and AL was associated with an extremely high risk for thromboembolism (odds ratio 55.0 [95% confidence interval 8.1 to 1131.4]). By multivariate analysis, AL type (odds ratio 8.4 [95% confidence interval 1.8 to 51.2]) and left ventricular diastolic dysfunction (odds ratio 12.2 [95% confidence interval 2.7 to 72.7]) were independently associated with thromboembolism.</AbstractText>A high frequency of intracardiac thrombosis was present in cardiac amyloidosis. Furthermore, thromboembolism caused significant fatality. Several risk factors for thromboembolism were identified. Early screening, especially in high-risk patients, and early anticoagulation might reduce morbidity and mortality.</AbstractText> |
8,198 | Azithromycin/chloroquine combination does not increase cardiac instability despite an increase in monophasic action potential duration in the anesthetized guinea pig. | Prolongation of the electrocardiogram QT interval by some, but not all drugs, has been associated with increased incidence of sudden cardiac death. Current preclinical regulatory assays cannot discriminate the arrhythmia liability of these drugs. Consequently, many new medications that prolong the QT interval are not developed despite their potential therapeutic benefit. Alternans (action potential duration alternations) is a measure of cardiac instability in humans and animals associated with the onset of ventricular fibrillation. Due to potential arrhythmia risk from observed QT prolongation, alternans was assessed in the anesthetized guinea pig after azithromycin or chloroquine alone and after combination treatment at clinically relevant concentrations proposed for the management of malaria. Chloroquine alone, but not azithromycin, caused a profound increase in action potential duration but with only minimal effects on alternans (approximately 10 ms). Azithromycin alone and in combination with chloroquine showed no increase in alternans beyond vehicle baseline responses indicating no additional arrhythmia liability. |
8,199 | Loss of luminal Ca2+ activation in the cardiac ryanodine receptor is associated with ventricular fibrillation and sudden death. | Different forms of ventricular arrhythmias have been linked to mutations in the cardiac ryanodine receptor (RyR)2, but the molecular basis for this phenotypic heterogeneity is unknown. We have recently demonstrated that an enhanced sensitivity to luminal Ca(2+) and an increased propensity for spontaneous Ca(2+) release or store-overload-induced Ca(2+) release (SOICR) are common defects of RyR2 mutations associated with catecholaminergic polymorphic or bidirectional ventricular tachycardia. Here, we investigated the properties of a unique RyR2 mutation associated with catecholaminergic idiopathic ventricular fibrillation, A4860G. Single-channel analyses revealed that, unlike all other disease-linked RyR2 mutations characterized previously, the A4860G mutation diminished the response of RyR2 to activation by luminal Ca(2+), but had little effect on the sensitivity of the channel to activation by cytosolic Ca(2+). This specific impact of the A4860G mutation indicates that the luminal Ca(2+) activation of RyR2 is distinct from its cytosolic Ca(2+) activation. Stable, inducible HEK293 cells expressing the A4860G mutant showed caffeine-induced Ca(2+) release but exhibited no SOICR. Importantly, HL-1 cardiac cells transfected with the A4860G mutant displayed attenuated SOICR activity compared with cells transfected with RyR2 WT. These observations provide the first evidence that a loss of luminal Ca(2+) activation and SOICR activity can cause ventricular fibrillation and sudden death. These findings also indicate that although suppressing enhanced SOICR is a promising antiarrhythmic strategy, its oversuppression can also lead to arrhythmias. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.