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8,200 | Higher prevalence of cardiovascular events among patients with abnormal atrial depolarization and coronary artery disease at 18 months' post-exercise tolerance testing. | Abnormal atrial depolarization, denoted as interatrial block (IAB; P wave >110 ms), is associated with myocardial ischemia during exercise. The authors conducted an 18-month follow-up for cardiovascular events in 31 consecutive patients with IAB and 60 controls without IAB at rest; participants had coronary artery disease and hypertension and had undergone coronary angiography following positive exercise tolerance test (ETT) results. Atrial fibrillation and need for repeat ETT and coronary artery revascularization were significant with IAB (77.4% vs 20%; P<.001). In patients with such events, IAB, left atrial dilatation, left ventricular hypertrophy, increased left ventricular end-diastolic volume, poorer Duke prognostic treadmill (DPT) scores, and significant coronary artery stenoses were predominant. IAB (hazard ratio [HR], 4.9; 95% confidence interval [CI], 1.3-19.7; P=.02) and DPT scores (HR, 0.84; 95% CI, 0.72-0.98; P=.03) were independently associated with these events. At 18 months' follow-up, IAB at rest was associated with cardiovascular events among those with known coronary artery disease and hypertension. |
8,201 | Depressive symptoms predict recurrence of atrial fibrillation after cardioversion. | The aim of this study was to evaluate whether depressive symptoms and the type-D personality are predictive of early recurrence of atrial fibrillation (or atrial flutter; AF) after successful electrical cardioversion (CV).</AbstractText>Depressive symptoms are associated with an adverse prognosis in patients with coronary artery disease, congestive heart failure, and ventricular arrhythmias. Anger and hostility have been shown to be predictive of development of AF. However, little is known about the effects of depression on AF.</AbstractText>Fifty-four patients with persistent AF completed the Hospital Anxiety and Depression Scale (HADS) and the Type D Scale (DS-14) prior to elective electrical CV. Patients with a successful CV were followed for 2 months.</AbstractText>During the follow-up period, 27 patients (50%) had recurrence of the arrhythmia. Depressive mood (HADS depression scale >7) was the only significant nonsomatic predictor of recurrence, which was observed in 85% of depressed versus 39% of nondepressed patients [odds ratio=8.6; 95% confidence interval (CI)=1.7-44.0, P=.004]. HADS anxiety scores and the presence of the type-D personality pattern were not associated with recurrence of AF. On multivariate Cox regression analysis, including variables with a prevalence >10% of the total study population and a univariate discriminative effect yielding a P value of <.2, a HADS depression score >7 was found to be the only independently predictive variable of arrhythmia recurrence (hazard ratio=2.7; 95% CI=1.05-7.2; P=.046).</AbstractText>Our results indicate that depressive mood is a major risk factor for recurrence of AF after electrical CV. Heightened adrenergic tone and a proinflammatory state are possible mechanisms responsible for the observed association. Identification of depression may be of value prior to the decision to perform electrical CV.</AbstractText> |
8,202 | Effects of tamoxifen on myocardial ischemia-reperfusion injury model in ovariectomized rats. | The purpose of this study is to examine the antiarrhythmic and antioxidant effects of tamoxifen, one of the selective estrogen modulators, in ovariectomized rats subjected to myocardial ischemia-reperfusion (I/R) injury. A month after ovariectomy, rats were divided into four groups: (I) ovariectomized controls without any treatment, (II) ovariectomized rats treated with vehicle dimethylsulfoxide (DMSO), (III)-(IV) ovariectomized rats treated with tamoxifen 1 or 10 mg/kg,sc daily for 14 days. To produce arrhythmia, the left main coronary artery was occluded for 7 min, followed by 7 min of reperfusion. The blood pressure (BP), heart rate (HR), electrocardiography (ECG) was recorded before and during the ischemia-reperfusion period. The blood levels of malondialdehyde (MDA), creatine kinase (CK), glutathione (GSH), glutathione peroxidase (GSH-Px), glutathione reductase (GR), and catalase (CAT) were measured after the rats were killed. Tamoxifen reduced the incidence of ventricular tachycardia (VT) on ischemia and reperfusion as well as the incidence and duration of reversible ventricular fibrillation (VF) on reperfusion. I/R injury caused a significant fall in GSH, GSH-Px as well as an increase in MDA and CK levels in the control group when compared to tamoxifen treated groups. The changes in levels of CAT and GR were however, not significant. In conclusion, our findings suggest that tamoxifen has cardioprotective effects against I/R injury in rats, likely its antioxidant properties. |
8,203 | Beta-blocker use and the changing epidemiology of out-of-hospital cardiac arrest rhythms. | The incidence of ventricular fibrillation (VF) as the presenting rhythm in out-of-hospital cardiac arrest (OHCA) is declining, whereas pulseless electrical activity (PEA) is increasing. This changing epidemiology has occurred concomitant with an increase in beta-blocker use.</AbstractText>The aim of this study was to measure the association of beta-blocker use among prehospital cardiac arrest patients with PEA versus VF as presenting rhythm.</AbstractText>In this retrospective cohort study, records of all OHCA patients presenting to a single municipal hospital between 1 January 2001 and 31 December 2006 were reviewed. Age, sex, race, first documented rhythm, estimated down time, presence of bystander CPR, return of spontaneous circulation, beta-blocker use, and comorbid illnesses were noted. A Mantel-Haenzel chi-square was computed to describe the association between beta-blocker use and PEA, compared to beta-blocker use and VF. A sensitivity analysis was also performed to account for missing data, misclassification of beta-blocker use, misclassification of initial rhythm, confounding by unknown factors, and random error.</AbstractText>After exclusion of patients with asystole and patients in whom beta-blocker use was unclear/unknown, a cohort of 179 arrests was evaluated. The odds ratio for beta-blocker use among PEA versus VF patients was 3.7 (95% CI 1.9-7.2), and probabilistic adjustment for exposure and outcome misclassification, confounding, and random error increased the odds ratio to 5.0 (95% CI 1.1-31.0).</AbstractText>There appears to be an association between beta-blockers and the changing epidemiology of arrest rhythms, which may account for the increasing incidence of PEA and concomitant decrease in VF.</AbstractText> |
8,204 | Idiopathic cardiac electrical storm. | Cardiac electrical storm has been described as three or more distinct episodes of ventricular fibrillation or hemodynamically destabilizing ventricular tachycardia in a 24-h period, typically requiring treatment with electrical cardioversion or defibrillation. We report the case of a 45-year-old man who presented to the Emergency Department with idiopathic cardiac electrical storm, ultimately requiring defibrillation over 30 times in the Emergency Department and infusion of multiple antidysrhythmic agents for dysrhythmia control. Treatment of cardiac electrical storm entails immediate resuscitative therapy during the hemodynamically destabilizing episode (including cardioversion/defibrillation and the timely administration of antidysrhythmic agents), concurrent identification and correction of any factors that are potentially contributing to the acute dysrhythmia (i.e., electrolyte disturbances, myocardial ischemia), and ultimately, institution of long-term preventive therapy (such as an implantable cardioverter defibrillator) to quell recurrence. Amiodarone and beta-adrenergic blockers seem to be the agents of greatest clinical benefit to patients with cardiac electrical storm. Despite its potentially devastating nature, the majority of patients with cardiac electrical storm may have favorable clinical outcomes if the dysrhythmias are treated swiftly and aggressively. |
8,205 | Inappropriate defibrillator shocks from depolarization--repolarization mismatch in a patient with hypertrophy cardiomyopathy. | Despite wide use of dedicated bipolar sensing electrodes in implantable cardioverter-defibrillator (ICD) systems, oversensing occasionally occurs, leading to unwarranted shocks or antitachycardia pacing. This case report highlights an individual with hypertrophic cardiomyopathy (HCM) who experienced inappropriate shocks from oversensing of repolarization electrograms (T-waves). During the implantation procedure, no excessive T-wave amplitudes were detected during sinus rhythm, ventricular pacing, or induced ventricular fibrillation. T-wave oversensing leading to shocks only developed after maturation of the lead-tissue interface. An adequate safety margin for discrimination between ventricular electrograms and T-waves could not be assured. Thus, insertion of a new dedicated pacing-sensing electrode was required. The degree to which intracardiac repolarization signals may be heightened in patients with HCM has not been investigated systematically. However, a relative decrease in the ventricular electrogram amplitude without a concomitant decline of the intracardiac T-wave amplitude appears to have led to the problem in this patient. Special caution in technique and device selection with a particular emphasis on T-wave sensing may be prudent when ICDs are implanted in individuals with HCM. Additional programmable variables may also be beneficial in such cases. |
8,206 | Cardiac resynchronization therapy response is associated with shorter duration of atrial fibrillation. | Atrial fibrillation (AF) is commonly associated with heart failure. The benefit of cardiac resynchronization therapy (CRT) on atrial remodeling has been demonstrated. However, biventricular pacing did not reduce the global incidence of AF. We evaluated the relationship between CRT response and AF duration.</AbstractText>We retrospectively analyzed data from 96 patients (59 +/- 15 years; 78% male) who underwent CRT. All patients had class III-IV New York Heart Association (NYHA) symptoms despite maximal medical therapy, left ventricular ejection fraction (LVEF) < or = 35%, QRS >130 ms, and sinus rhythm before implantation. CRT response in patients who survived at six months of follow-up was defined as: (1) no hospitalization for heart failure and (2) improvement of one or more grades in the NYHA classification.</AbstractText>CRT responders (n = 54) and non-responders (n = 42) had similar baseline characteristics, including the incidence of persistent AF within six months before implantation. Six months after implantation, when compared to baseline, CRT responders exhibited a significant decrease in left atrial size (47.5 +/- 7.1 mm vs 44.6 +/- 7.7 mm, P < 0.01) and in the incidence of persistent AF (17% vs 2%, P = 0.02). At six months, CRT responders demonstrated shorter mean AF duration (7.5 +/- 43.3 hours vs 48.8 +/- 129.0 hours, P = 0.03) and lower incidence of persistent AF (2% vs 19%, P = 0.004) compared to nonresponders.</AbstractText>CRT response is associated with a reversal of atrial remodeling and a shorter AF duration.</AbstractText> |
8,207 | [Experimental studies on antiarrhythmic effect of jumi extraction]. | To investigate the antiarrhythmic effect of jumi (JM) extraction.</AbstractText>The conventional antiarrhythmic methods were used.</AbstractText>Administration of JM extraction reduced the occurrence of ventricular fibrillation induced by chloroform in a dose-dependent manner in mice. Quinidine significantly decreased the number of ventricular premature beats and ventricular tachycardia, shortened the duration of arrhythmia in aconitine-treated rats. But JM extraction had no effect on aconitine-induced arrhythmia. Compared with control, arrhythmia score was lower in ischemia/reperfusion rats which pretreated with 2.0 g/kg of JM extraction.</AbstractText>JM extraction has obvious protection effects in chloroform- and ischemia-induced arrhythmia, but has no effect in aconitine-induced arrhythmia.</AbstractText> |
8,208 | Clinical and echocardiographic parameters and score for the left atrial thrombus formation prediction in the patients with mitral stenosis. | Rheumatic mitral stenosis is one of the important health problems, especially in Thailand. Thromboembolic complications from this disease remain the major problem in these patients. These complications are usually related to the left atrial thrombus formation.</AbstractText>To determine the parameters that can predict the presence of left atrial thrombus in these patients.</AbstractText>Two hundred and sixty Thai patients with mitral stenosis from Siriraj Hospital were prospectively recruited in the study. The baseline clinical characteristics of these patients which were related to thrombus formation were properly collected. All patients underwent the transthoracic and transesophageal echocardiography with the standard technique to detect the mitral valve area, mitral valve score, left atrial size, LV ejection fraction, right ventricular systolic pressure, spontaneous echo contrast (SEC) and associated valvular lesions. Transesophageal echocardiography was used as the gold standard for evaluation of left atrial thrombus. These parameters were analyzed to demonstrate association with the presence of left atrial thrombus by univariate and multiple logistic regression analysis. Equation with score for prediction of left atrial thrombus was also purposed.</AbstractText>There were 77 men and 183 women in the present study. Left atrial thrombus was detected in 26% and previous thromboembolic complications occurred in 16.5%. Atrial fibrillation presented in 52.5%. From univariate analysis, atrial fibrillation (81.2% vs. 42.9%, p < 0.001), male sex (37.7% vs 25.6%, p < 0.050), left atrial enlargement by electrocardiogram (45.5% vs 15.4%, p < 0.001), left atrial diameter (7.26 vs 6.97 cm, p < 0.030), left atrial volume (132. 7 vs. 113.5 cm2, p < 0.001), EFby Teich method (58.9 vs 62.5%, p < 0.011), EF by MOD-bp (60.7 vs. 64.6%, p < 0.005), tricuspid regurgitation (46.4% vs. 28.8%, p < 0.008), mitral regurgitation (10.1 vs. 3.1%, p < 0.022), and RVSP (57.0 vs. 49.7 mmHg, p < 0.005) can predict the presence of left atrial thrombus formation with statistical significance. Using multiple logistic regression model, only atrial fibrillation (OR 5.95, 95% CI 1.21-29.3, p < 0.02) and RVSP (OR 1.02, 95%CI 1.01-1.04, p < 0.04) were independent predictors. The authors proposed score for predicting probability of left atrial thrombus formation that equal to -3.61 + 1.79 AF + 0.03 RVSP with AUC of 0.764. The best cut-off point for this score was -1.49, which gave a sensitivity of 91%, specificity of 56%, PPV of 48%, and NPV of 90%.</AbstractText>Prevalence of thromboembolic complications and thrombus formation is high in patients with mitral stenosis in Thailand. From the present study, the predictors for left atrial thrombus formation in the patients with mitral stenosis were atrial fibrillation and RVSP The model for predicting left trial thrombus formation was also proposed with high sensitivity and NPV.</AbstractText> |
8,209 | [Drugs for heart rate control and non-antiarrhythmic drugs in atrial fibrillation]. | Multiple drugs are helpful for rate control in different tachyarrhythmias, in particular atrial fibrillation (AF). Betablockers (betaB) and calcium channel blockers have been used as monotherapy or as adjunctive therapy to antiarrhythmics for mantaining an acceptable ventricular rate. In recent years new concepts about auricular remodelation process as a consequence of AF has shown benefits with drugs as angiotensin-renin system blockers (ARSB) like angiotensin conversing enzime inhibitors (ACEI) and angiotensin receptor blockers (ARB). In this article it will be reviewed the benefits of rate control in AF by using betaB and calcium channel blockers and also the benefits in atrial remodelation process and the prevention of AF with ARSB drugs. |
8,210 | [Arrhythmias in pregnancy. How and when to treat?]. | Cardiac arrhythmias can develop during pregnancy. The risk of arrhythmias is relatively higher during labor and delivery. Potential factors that can promote arrhythmias in pregnancy or during labor and delivery, include the direct cardiac electrophysiological effects of hormones, changes in autonomic tone, hemodynamic perturbations, hypokalemia, and underlying heart disease. In this review, the basis for treatment of supraventricular and ventricular tachycardias are described. No drug therapy is usually needed for the management of supraventricular or ventricular premature beats, but potential stimulants, such as smoking, caffeine, and alcohol should be eliminated. In paroxysmal supraventricular tachycardia, vagal stimulation maneuvers should be attempted first. In pregnant women with atrial fibrillation, the goal of treatment is conversion to sinus rhythm by electrical cardioversion. Rate control can be achieved by a cardioselective beta-adrenergic blocker drug and/ or digoxin. Ventricular arrhythmias may occur in the pregnant women, specially when cardiomyopathy, congenital heart disease, valvular heart disease, or mitral valve prolapse exists. Electrical cardioversion or treatment with sotalol may be used (amiodarone is not safe for the fetus). Finally, in women with congenital long QT syndrome, beta-blocker therapy must be continued during pregnancy and postpartum period. |
8,211 | Preserved left ventricular ejection fraction following atrioventricular junction ablation and pacing for atrial fibrillation. | Right ventricular apical (RVA) pacing creates ventricular dyssynchrony and may compromise left ventricular ejection fraction (LVEF). The impact of RVA pacing in patients who have undergone atrioventricular junction (AVJ) ablation for atrial fibrillation (AF) is unclear. We sought to determine whether RVA pacing after AVJ ablation for patients with AF compromises LVEF in the short- or long-term.</AbstractText><AbstractText Label="METHODS/RESULTS" NlmCategory="RESULTS">We studied 286 patients with AF who underwent AVJ ablation and RVA pacing at our institution between 1990 and 2002. Patients were stratified into a short-term follow-up group (LVEF reassessed by echocardiography within a year after AVJ ablation, n = 134) and a long-term group (LVEF reassessed after a year, n = 152). Among all 286 patients (mean follow-up 20 months), we observed no change in mean LVEF after AVJ ablation and RVA pacing (48% before vs. 48% after, P = 0.42). Short-term follow-up patients had a statistically significant improvement in mean LVEF (46% before vs. 49% after, P = 0.03), whereas there was no statistically significant change in mean LVEF in long-term follow-up patients (49% before vs. 48% after, P = 0.37). Only 9% of short-term patients, 15% of long-term patients, and 1% of patients with baseline LVEF <or= 40% experienced >or=10% absolute decrease in LVEF. Baseline LVEF > 40% was a multivariate predictor of LVEF decline.</AbstractText>RVA pacing after AVJ ablation does not compromise LVEF in the short- or long-term for the vast majority of patients. Better predictors are needed to help us select patients for biventricular pacing after AVJ ablation.</AbstractText> |
8,212 | Brugada syndrome subject to depolarization abnormality of the conduction system. | We report a patient who first developed Brugada syndrome (BS) after the conduction in atrioventricular (AV) node and the ventricular conduction system was disturbed. A type-1 Brugada ECG was unexpectedly unmasked after administration of a class IC antiarrhythmic agent for suppressing paroxysmal atrial fibrillation (paf), which had never been documented in the absence of such conduction disturbances, even after giving antiarrhythmic agents for paf. In addition, this patient was accompanied by sick sinus syndrome. This was an intriguing overlap syndrome case in that the development of BS might have been associated with the incidence of a conduction system disturbance. |
8,213 | Electrical storm in patients with an implanted defibrillator: a matter of definition. | The term "electrical storm" (ES) indicates a state of cardiac electrical instability manifested by several episodes of ventricular tachyarrhythmias (VTs) within a short time. In patients with an implantable cardioverter defibrillator (ICD), ES is best defined as 3 appropriate VT detections in 24 h, treated by antitachycardia pacing, shock or eventually untreated but sustained in a VT monitoring zone. The number of shocks and inappropriate detections are irrelevant for the definition. ES occurs in approximately 25% of ICD patients within 3 years, with typically 5-55 individual VTs within one storm. Potential triggers can be found in approximately 66% of patients and include new/worsened heart failure, changes in antiarrhythmic medication, context with other illness, psychological stress, diarrhea, and hypokalemia. In most patients, ES consists of monomorphic VT indicating the presence of reentry while ventricular fibrillation indicating acute ischemia is rare. ES seems to have a low immediate mortality (1%) but frequently (50-80%) leads to hospitalization. Long-term prognostic implications of ES are unclear. The key intervention in ES is reduction of the elevated sympathetic tone by beta blockers and frequently benzodiazepines. Amiodarone i.v. has also been successful and azimilide seems promising while class I antiarrhythmic drugs are usually unsuccessful. Substrate mapping and VT ablation may be useful in treatment and prevention of ES. Prevention of ES requires ICD programming systematically avoiding unnecessary shocks (long VT detection, antitachycardia pacing where ever possible) which otherwise can fuel the sympathetic tone and prolong ES. |
8,214 | Mutation in glycerol-3-phosphate dehydrogenase 1 like gene (GPD1-L) decreases cardiac Na+ current and causes inherited arrhythmias. | Brugada syndrome is a rare, autosomal-dominant, male-predominant form of idiopathic ventricular fibrillation characterized by a right bundle-branch block and ST elevation in the right precordial leads of the surface ECG. Mutations in the cardiac Na+ channel SCN5A on chromosome 3p21 cause approximately 20% of the cases of Brugada syndrome; most mutations decrease inward Na+ current, some by preventing trafficking of the channels to the surface membrane. We previously used positional cloning to identify a new locus on chromosome 3p24 in a large family with Brugada syndrome and excluded SCN5A as a candidate gene.</AbstractText>We used direct sequencing to identify a mutation (A280V) in a conserved amino acid of the glycerol-3-phosphate dehydrogenase 1-like (GPD1-L) gene. The mutation was present in all affected individuals and absent in >500 control subjects. GPD1-L RNA and protein are abundant in the heart. Compared with wild-type GPD1-L, coexpression of A280V GPD1-L with SCN5A in HEK cells reduced inward Na+ currents by approximately 50% (P<0.005). Wild-type GPD1-L localized near the cell surface to a greater extent than A280V GPD1-L. Coexpression of A280V GPD1-L with SCN5A reduced SCN5A cell surface expression by 31+/-5% (P=0.01).</AbstractText>GPD1-L is a novel gene that may affect trafficking of the cardiac Na+ channel to the cell surface. A GPD1-L mutation decreases SCN5A surface membrane expression, reduces inward Na+ current, and causes Brugada syndrome.</AbstractText> |
8,215 | Atrial antifibrillatory effects of structurally distinct IKur blockers 3-[(dimethylamino)methyl]-6-methoxy-2-methyl-4-phenylisoquinolin-1(2H)-one and 2-phenyl-1,1-dipyridin-3-yl-2-pyrrolidin-1-yl-ethanol in dogs with underlying heart failure. | Drug discovery efforts have focused recently on atrial-selective targets, including the Kv1.5 channel, which underlies the ultrarapid delayed rectifier current, I(Kur), to develop novel treatments for atrial fibrillation (AF). Two structurally distinct compounds, a triarylethanolamine TAEA and an isoquinolinone 3-[(dimethylamino)-methyl]-6-methoxy-2-methyl-4-phenylisoquinolin-1(2H)-one (ISQ-1), blocked I(Kur) in Chinese hamster ovary cells expressing human Kv1.5 with IC(50) values of 238 and 324 nM, respectively. In anesthetized dogs, i.v. infusions of TAEA and ISQ-1 elicited comparable 16% increases in atrial refractory period, with no effect on ventricular refractory period or QTc interval. Plasma concentrations at end infusion for TAEA and ISQ-1 were 58.5 +/- 23.6 and 330.3 +/- 43.5 nM, respectively. The abilities of TAEA and ISQ-1 to terminate AF, with comparison to the rapidly activating component of delayed rectifier potassium current blocker (+)-N-[1'-(6-cyano-1,2,3,4-tetrahydro-2(R)-naphthalenyl)-3,4-dihydro-4(R)-hydroxyspiro(2H-1-benzopyran-2,4'-piperidin)-6-yl]methanesulfonamide] monohydrochloride (MK-499) and the class IC 1-[2-[2-hydroxy-3-(propylamino)-propoxy]phenyl]-3-phenyl-1-propanone (propafenone), were assessed in conscious dogs with heart failure and inducible AF (entry criterion). All test agents administered in i.v. bolus regimens terminated AF in at least half of animals tested; conversely no agent was universally effective. MK-499, ISQ-1, TAEA, and propafenone terminated AF in five of six, four of seven, four of six, and five of six animals at plasma concentrations of 32.6 +/- 18.7, 817 +/- 274, 714 +/- 622, and 816 +/- 240 nM, respectively. Directed cardiac electrophysiologic studies in anesthetized dogs using i.v. bolus (consistent with AF studies) plus infusion regimens with TAEA and ISQ-1 demonstrated significant increases in atrial refractory period (12-15%), A-H and P-A intervals, but no effects on ventricular refractory period, H-V, and HEG intervals. The demonstration of AF termination with TAEA and ISQ-1 in the dog heart failure model extends the profile of antiarrhythmic efficacy of Kv1.5 blockade. |
8,216 | Ventricular fibrillation and the use of automated external defibrillators on children. | The use of automated external defibrillators (AEDs) has been advocated in recent years as a part of the chain of survival to improve outcomes for adult cardiac arrest victims. When AEDs first entered the market, they were not tested for pediatric usage and rhythm interpretation. In addition, the presumption was that children do not experience ventricular fibrillation, so they would not benefit from use of AEDs. Recent literature has shown that children do experience ventricular fibrillation, and this rhythm has a better outcome than do other cardiac arrest rhythms. At the same time, the arrhythmia software on AEDs has become more extensive and validated for children, and attenuation devices have become available to downregulate the energy delivered by AEDs to allow their use in children. Pediatricians are now being asked whether AED programs should be implemented, and where they are being implemented, pediatricians are being asked to provide guidance on the use of AEDs in children. As AED programs expand, pediatricians must advocate on behalf of children so that their needs are accounted for in these programs. For pediatricians to be able to provide guidance and ensure that children are included in AED programs, it is important for pediatricians to know how AEDs work, be up-to-date on the literature regarding pediatric fibrillation and energy delivery, and understand the role of AEDs as life-saving interventions for children. |
8,217 | 'Unexpected' sudden death avoided by implantable cardioverter defibrillator in Emery Dreifuss patient. | A female patient just over 20 years of age developed first grade atrioventricular block, and later atrial fibrillation. When she was 41 years old she was diagnosed with Emery-Dreifuss muscular dystrophy (EDMD). A VVIR pacemaker was implanted in 2002, replaced in 2003 with an ICD. Nine months later, during febrile illness, the patient experienced three appropriate ICD discharges. No further ICD interventions occurred. The transient course of arrhythmic activity and the possible influence of triggering factors lessen the role of electrophysiologic study to identify risk of sudden death, and suggest that in patients with EDMD requiring pacemaker implantation, an ICD would be more properly indicated. |
8,218 | Omega-3 polyunsaturated fatty acids prevent atrial fibrillation associated with heart failure but not atrial tachycardia remodeling. | There is epidemiological evidence that omega-3 polyunsaturated fatty acids (PUFAs) reduce the risk of atrial fibrillation (AF), but clinical data are conflicting. The present study assessed the effects of PUFA on AF in experimental models.</AbstractText>We studied the effects of oral PUFA supplements in 2 experimental AF paradigms: electrical remodeling induced by atrial tachypacing (400 bpm for 1 week) and congestive heart failure-associated structural remodeling induced by ventricular tachypacing (240 bpm for 2 weeks). PUFA pretreatment did not directly change atrial effective refractory period (128+/-6 [mean+/-SEM] versus 127+/-2 ms; all effective refractory periods at 300-ms cycle lengths) or burst pacing-induced AF duration (5+/-4 versus 34+/-18 seconds). Atrial tachypacing dogs had shorter refractory periods (73+/-6 ms) and greater AF duration (1185+/-300 seconds) than shams (119+/-5 ms and 20+/-11 seconds; P<0.01 for each). PUFAs did not significantly alter atrial tachypacing effects on refractory periods (77+/-8 ms) or AF duration (1128+/-412 seconds). PUFAs suppressed ventricular tachypacing-induced increases in AF duration (952+/-221 versus 318+/-249 seconds; P<0.05) and attenuated congestive heart failure-related atrial fibrosis (from 19.2+/-1.1% to 5.8+/-1.0%; P<0.001) and conduction abnormalities. PUFAs also attenuated ventricular tachypacing-induced hemodynamic dysfunction (eg, left ventricular end-diastolic and left atrial pressure from 12.2+/-0.5 and 11.4+/-0.6 mm Hg, respectively, to 6.4+/-0.5 and 7.0+/-0.8 mm Hg; P<0.01) and phosphorylation of mitogen-activated protein kinases (extracellular-signal related and P38 kinase).</AbstractText>PUFAs suppress congestive heart failure-induced atrial structural remodeling and AF promotion but do not affect atrial tachycardia-induced electrical remodeling. The beneficial effects of PUFAs on structural remodeling, possibly related to prevention of mitogen-activated protein kinase activation, may contribute to their clinical anti-AF potential.</AbstractText> |
8,219 | Secular trends of heart failure among US male physicians. | Heart failure (HF) remains a major public health issue. Data on long-term trends in the incidence of HF and survival after its onset are limited.</AbstractText>A prospective cohort study conducted between 1985 and 2004 in 21,906 participants of the Physicians' Health Study I who were alive and free of HF on January 1, 1985.</AbstractText>After an average follow-up of 16.8 years, a total of 909 incident cases of HF occurred in this cohort. There was no evidence for a substantial change in the incidence rate of HF across the 4 periods (P for trend .29). From 1985 through 2004, there were 457 deaths among 909 subjects with HF. Compared with the period of 1985 to 1989, the age-adjusted hazard ratio of all-cause mortality after onset of HF was 0.61 (0.46-0.81), 0.37 (0.28-0.48), and 0.10 (0.07-0.15) in the second, third, and fourth period, respectively (P for trend <.0001). Additional adjustment for treatment arm, diabetes, myocardial infarction, hypertension, atrial fibrillation, coronary angioplasty or bypass, valvular heart disease, and left ventricular hypertrophy did not alter these results. Similar findings were seen in subjects with HF with and without antecedent myocardial infarction (P for trend <.0001 each).</AbstractText>Over the past 20 years, we observed a lower risk of all-cause mortality after onset of HF whereas no major change in the incidence of HF was seen among US male physicians.</AbstractText> |
8,220 | [Perioperative cardiac arrhythmias in patients undergoing surgical treatment for lung cancer]. | Thoracic surgery is associated with a high risk of morbidity and mortality. Cardiac arrhythmias are the most common and severe complications in early postoperative period.</AbstractText>Evaluation of the prevalence and causes of cardiac arrythmias, factors that predispose to their occurrence and their influence on general state of health in short-term postoperative period.</AbstractText>The study was performed in 80 patients with proven primary non-small cell lung cancer. We analyzed demographic data, type of carcinoma, presence of other diseases, laboratory results, and echocardiograms performed 2 times before and after operation and 24-hour Holter monitoring obtained 3 times--a day before thoracotomy and on the 1st and 5th postoperative day.</AbstractText>There were no significant changes in a total number of supraventricular ectopic beats during 3 consecutive 24-hour Holter recordings. The second Holter recording performed on the 1st postoperative day showed a statistically significant increase (p < 0.05) in the number of ventricular premature beats, which persisted on a similar, higher level on the 5th day. Twenty-four patients (30%) developed atrial fibrillation (AF) in the postoperative period. The average time of the duration of AF was 2.62 days with the peak incidence during 1st and 2nd day after operation (total 62.5%). Apart from cigarette smoking, no other epidemiological and clinical variables affected the occurrence of postoperative AF (p > 0.05).</AbstractText>Paroxysmal atrial fibrillation is the most common type of arrhythmias in early postoperative period after thoracic surgery. Patients who underwent thoracic surgery should be under cardiological surveillance during the first postoperative days. Routine prevention with anticoagulants in patients after pulmonary tumor resection should be implemented based on their current clinical condition.</AbstractText> |
8,221 | Electromechanical characterization of cinnamophilin, a natural thromboxane A2 receptor antagonist with anti-arrhythmic activity, in guinea-pig heart. | Cinnamophilin, a thromboxane A(2) receptor antagonist, has been identified as a prominent anti-arrhythmic agent in rat heart. This study aimed to determine its electromechanical and anti-arrhythmic effects in guinea-pig hearts.</AbstractText>Microelectrodes were used to study action potentials in ventricular papillary muscles. Fluo-3 fluorimetric ratio and whole-cell voltage-clamp techniques were used to record calcium transients and membrane currents in single ventricular myocytes, respectively. Intracardiac electrocardiograms were obtained and the anti-arrhythmic efficacy was determined from isolated perfused hearts.</AbstractText>In papillary muscles, cinnamophilin decreased the maximal rate of upstroke (V(max)) and duration of action potential, and reduced the contractile force. In single ventricular myocytes, cinnamophilin reduced Ca(2+) transient amplitude. Cinnamophilin decreased the L-type Ca(2+) current (I(Ca,L))(IC(50)=7.5 microM) with use-dependency, induced a negative shift of the voltage-dependent inactivation and retarded recovery from inactivation. Cinnamophilin also decreased the Na(+) current (I(Na)) (IC(50)=2.7 microM) and to a lesser extent, the delayed outward (I(K)), inward rectifier (I(K1)), and ATP-sensitive (I(K,ATP)) K(+) currents. In isolated perfused hearts, cinnamophilin prolonged the AV nodal conduction interval and Wenckebach cycle length and the refractory periods of the AV node, His-Purkinje system and ventricle, while shortening the ventricular repolarization time. Additionally, cinnamophilin reduced the occurrence of reperfusion-induced ventricular fibrillation.</AbstractText>These results suggest that the promising anti-arrhythmic effect and the changes in the electromechanical function induced by cinnamophilin in guinea-pig heart can be chiefly accounted for by inhibition of I(Ca,L) and I(Na).</AbstractText> |
8,222 | Value of echo-Doppler derived pulmonary vascular resistance, net-atrioventricular compliance and tricuspid annular velocity in determining exercise capacity in patients with mitral stenosis. | The present study sought to determine if echo-Doppler-derived pulmonary vascular resistance (PVR echo), net-atrioventricular compliance (Cn) and tricuspid peak systolic annular velocity (Sa), as parameters of right ventricular function, have value in predicting exercise capacity in patients with mitral stenosis (MS).</AbstractText>Thirty-two patients with moderate or severe MS without left ventricular systolic dysfunction were studied. After comprehensive echo-Doppler measurements, including PVR echo, tricuspid Sa and left-sided Cn, supine bicycle exercise echo and concomitant respiratory gas analysis were performed. Measurements during 5 cardiac cycles representing the mean heart rate were averaged. Increment of resting PVR(echo) (r=-0.416, p=0.018) and decrement of resting Sa (r=0.433, p=0.013) and Cn (r=0.469, p=0.007) were significantly associated with decrease in %VO(2) peak. The predictive accuracy for %VO2 peak could increase by combining these parameters as Sa/PVR echo (r=0.500, p=0.004) or Cn. (Sa/PVR echo) (r=0.572, p=0.001) independent of mitral valve area, mean diastolic pressure gradients or presence of atrial fibrillation.</AbstractText>Measurement of PVR echo, Cn and Sa might provide important information about the exercise capacity of patients with MS.</AbstractText> |
8,223 | Mid-ventricular obstructive hypertrophic cardiomyopathy associated with an apical aneurysm: evaluation of possible causes of aneurysm formation. | Mid-ventricular obstructive hypertrophic cardiomyopathy (MVOHCM) is a rare type of cardiomyopathy, associated with apical aneurysm formation in some cases. We report a patient presenting with ventricular fibrillation, an ECG with an above normal ST segment, and elevated levels of cardiac enzymes but normal coronary arteries. Left ventriculography revealed a left ventricular obstruction without apical aneurysm. There was a significant pressure gradient between the apical and basal sites of the left ventricle. Cine magnetic resonance imaging (MRI), performed on the 10th hospital day, showed asymmetric septal hypertrophy, mid-ventricular obstruction, and an apical aneurysm with a thrombus. The first evaluation by contrast-enhanced imaging showed a subendocardial perfusion defect and delayed enhancement. It was speculated that the intraventricular pressure gradient, due to mid- ventricular obstruction, triggered myocardial infarction, which subsequently resulted in apical aneurysm formation. |
8,224 | Bone marrow mononuclear stem cells transplanted in rat infarct myocardium improved the electrical conduction without evidence of proarrhythmic effects. | The arrhythmogenic effect of stem cells transplantation (SCT) in an infarct myocardium is still unknown. We investigated arrhythmogenicity of SCT in rat cryo-infarct model.</AbstractText>In rat cryo-infarct model, bone marrow mononuclear stem cells (MNSC, 1 x 10(7) cells) were transplanted into the infarct border zone (BZ) of the LV epicardium. We compared the optical mapping and inducibility of ventricular tachycardia/fibrillation (VT/VF) among normal (n=5), cryo-infarct (n=6), and SCT rats (n=6).</AbstractText>The VT/VF inducibility was higher in the cryo- infarct (47.2%, p=0.001) and SCT groups (34.6%, p=0.01) than in the normal group (12.8%). The induced VT/VF episodes persisted for more than 2 minutes in 4.3%, 26.4% and 17.3% in the normal, cryo-infarct and SCT group, respectively. In the SCT group, the action potential duration at 70% was shorter at the SCT site than the BZ during SR (75.2 +/- 8.1 vs. 145.6 +/- 4.4 ms, p=0.001) and VT (78.2 +/- 13.0 vs. 125.7 +/- 21.0 ms, p= 0.001). Conduction block was observed at the SCT site and BZ during VT. However, no reentry or ectopic foci were observed around the SCT sites.</AbstractText>The electrical conduction was improved by SCT without evidence of augmentation of arrhythmia in the rat cryo-infarct model.</AbstractText> |
8,225 | Commotio cordis as a result of a fight: report of a case considered to be imprudent homicide. | Commotio cordis is a clinic-pathological syndrome related to sudden death in young people involved in sports activities. It has been described, mainly, in athletes without previous cardiac anomalies who received a minor blow to the chest which produces ventricular fibrillation and cardiac arrest in the absence of structural damage to the ribs, sternum, or heart. There are few reported cases of commotio cordis associated with violent, non-sports related actions, which are commonly considered to be imprudent homicides. We present the case of a 20-year-old man, who was kicked in the chest during a fight; he suddenly collapsed although advanced cardio-respiratory resuscitation started shortly. Autopsy showed no cardiac lesions concluding that death was due to commotio cordis (blunt trauma to the chest). Toxicological analysis determined the presence of 5.14 mg/L benzoylecgonine in blood. On the basis of medico-legal investigation, the official prosecution considered the death to be imprudent homicide and the aggressor was sentenced to 4 years in prison. We emphasize the importance of the knowledge of the death circumstances through the witnesses' testimony, prior to beginning the autopsy, to confirm this important medico-legal diagnosis. Arrhythmogenic effects of cocaine and its contribution in the production of these deaths are also exposed. |
8,226 | [Tpeak-Tend interval and risk of cardiac events in patients with Brugada syndrome]. | To evaluate the possible association between Tpeak-Tend (Tp-e) interval in surface standard ECG and cardiac events in patients with Brugada syndrome (BrS).</AbstractText>Tp-e interval in surface standard ECG was compared between BrS patients (n = 23, all males) and paroxysmal supraventricular tachycardia (PSVT) patients (n = 20, all males) as well as between BrS patients with (n = 16) or without (n = 7) cardiac events.</AbstractText>There was significant difference in Tp-e interval between BrS patients and PSVT patients [(109.57 +/- 22.86) ms vs. (88.50 +/- 13.08) ms, P < 0.05]. Tp-e interval was also significantly longer in BrS patients with cardiac events (syncope, clinical ventricular fibrillation and induced VF during electrophysiological study) than BrS patients without cardiac events [(118.12 +/- 20.40) ms vs. (90.00 +/- 15.27) ms, P < 0.05] while Tp-e interval was similar between BrS patients without cardiac events and PSVT patients (P > 0.05).</AbstractText>The prolongation of Tp-e (> or = 120 ms) was associated with higher cardiac events in BrS patients.</AbstractText> |
8,227 | Clinical significance of chemosensitivity in chronic heart failure: influence on neurohormonal derangement, Cheyne-Stokes respiration and arrhythmias. | Increased chemosensitivity has been observed in HF (heart failure) and, in order to clarify its pathophysiological and clinical relevance, the aim of the present study was to investigate its impact on neurohormonal balance, breathing pattern, response to exercise and arrhythmic profile. A total of 60 patients with chronic HF [age, 66+/-1 years; LVEF (left ventricular ejection fraction), 31+/-1%; values are means+/-S.E.M.] underwent assessment of HVR (hypoxic ventilatory response) and HCVR (hypercapnic ventilatory response), neurohormonal evaluation, cardiopulmonary test, 24-h ECG monitoring, and assessment of CSR (Cheyne-Stokes respiration) by diurnal and nocturnal polygraphy. A total of 60% of patients had enhanced chemosensitivity. Those with enhanced chemosensitivity to both hypoxia and hypercapnia (i.e. HVR and HCVR), compared with those with normal chemosensitivity, had significantly (all P<0.01) higher noradrenaline (norepinephrine) and BNP (B-type natriuretic peptide) levels, higher prevalence of daytime and night-time CSR, worse NYHA (New York Heart Association) class and ventilatory efficiency [higher VE (minute ventilation)/VCO(2) (carbon dioxide output) slope], and a higher incidence of chronic atrial fibrillation and paroxysmal non-sustained ventricular tachycardia, but no difference in left ventricular volumes or LVEF. A direct correlation was found between HVR or HCVR and noradrenaline (R=0.40 and R=0.37 respectively; P<0.01), BNP (R=0.40, P<0.01), N-terminal pro-BNP (R=0.37 and R=0.41 respectively, P<0.01), apnoea/hypopnoea index (R=0.57 and R=0.59 respectively, P<0.001) and VE/VCO(2) slope (R=0.42 and R=0.50 respectively, P<0.001). Finally, by multivariate analysis, HCVR was shown to be an independent predictor of both daytime and night-time CSR. In conclusion, increased chemosensitivity to hypoxia and hypercapnia, particularly when combined, is associated with neurohormonal impairment, worse ventilatory efficiency, CSR and a higher incidence of arrhythmias, and probably plays a central pathophysiological role in patients with HF. |
8,228 | Secondary prevention of ischemic stroke: evolution from a stepwise to a risk stratification approach to care. | Survivors of ischemic stroke are at significant risk for recurrent stroke. Appropriate therapy for stroke prevention is needed given the significant morbidity and mortality associated with stroke, the high financial costs, and the neurologic disability associated with treatment failure. A treatment strategy based on assessed risk represents an appropriate use of medical resources and results in improved outcomes. This approach requires evaluation of major risk factors, the most serious of which is a history of ischemic stroke or transient ischemic attack. The annual risk for recurrent stroke is 6% during the first 5 years after an initial stroke. Non-modifiable risk factors include age, race, ethnicity, gender, family history, and geography. The most important modifiable risk factor is hypertension. Diabetes mellitus, hyperlipidemia, left ventricular hypertrophy, atrial fibrillation, and lifestyle factors such as smoking, alcohol abuse, and obesity contribute to stroke risk. Antihypertensive, lipid-lowering, and antiplatelet therapies have been successful in reducing the incidence of secondary stroke. Clinical trials validate the benefits of statin therapy in reducing the risk for secondary stroke. Studies of antiplatelet agents, including aspirin, clopidogrel, and aspirin combined with extended-release dipyridamole, have evaluated the risk reduction in recurrent stroke and have been concerned particularly with the risk for hemorrhage. Therapy for stroke prevention based on risk stratification can identify patients who are appropriate targets for aggressive intervention. |
8,229 | Evaluation of pacemaker dependence in patients on ablate and pace therapy for atrial fibrillation. | In patients with atrial fibrillation (AF) and uncontrolled ventricular rate, radiofrequency (RF) ablation of the atrioventricular (AV) node and pacemaker (PM) implantation (ablate and pace) is a valid therapeutic approach, especially in elderly patients. The aim of our study was to evaluate the PM dependence and the incidence of correlated clinical phenomena in a patients population with AV block induced by RF ablation of the AV junction.</AbstractText>One-hundred and sixty-three patients (71 men; mean age 71 +/- 8 years) who had undergone ablate and pace therapy were evaluated. The patients underwent assessment of quality of life, impairment of consciousness, stroke/transient ischaemic attack (TIA), hospitalizations for heart failure, episodes of palpitations, and instrumental evaluation of PM dependence during PM inhibition (absence of escape rhythm; asystolic pause >5 s; escape rhythm <30 bpm after rhythm stabilization). Correlation between instrumentally evaluated PM dependence and clinical history was analysed. Hundred and thirty-two patients were evaluated after a mean follow-up period of 36 months [31 subjects (19%) died before the evaluation]; 55 patients (42%) were classified as PM-dependent: 38 (69%) complained of disturbances (19 dizziness, 15 pre-syncope, 4 syncope); 77 patients (58%) were considered non-PM-dependent: symptoms (dizziness, flush) were reported by only 3 (4%). No significant differences emerged between PM-dependent and non-PM-dependent patients with regard to episodes of pre-syncope, syncope, stroke/TIA, hospitalizations for heart failure, and quality of life.</AbstractText>This study confirms that ablate and pace is an effective and safe approach in subjects with chronic or recurrent AF and uncontrolled ventricular rate.</AbstractText> |
8,230 | Different effects of cardiac resynchronization therapy on left atrial function in patients with either idiopathic or ischaemic dilated cardiomyopathy: a two-dimensional speckle strain study. | In dilated cardiomyopathy (DCM), attenuation of left atrial (LA) booster pump function has been observed, and attributed both to altered LA loading conditions owing to left ventricular (LV) diastolic dysfunction and to LA involvement in the myopathic process. The aim of the present study was to detect LA systolic dysfunction in DCM using speckle-tracking two-dimensional strain echocardiography (2DSE), and to assess the effects of cardiac resynchronization therapy (CRT) on LA myocardial strain during 6 month follow-up.</AbstractText>A total of 90 patients (aged, 52.4 +/- 10.2 years) with either idiopathic (n = 47) or ischaemic (n = 43) DCM underwent standard Doppler echo and 2DSE analysis of atrial longitudinal strain in the basal segments of LA septum and LA lateral wall, and in LA roof. The two groups were comparable for clinical variables (NYHA class: III in 72.2%; IV in 27.8%). LV volumes, ejection fraction, stroke volume, and mitral valve effective regurgitant orifice were similar between the two groups. No significant differences were evidenced in Doppler transmitral inflow measurements. LA diameter and maximal volume were also similar between the two groups. Conversely, LA active emptying volume and fraction were both lower in patients with idiopathic DCM. Peak systolic myocardial atrial strain was significantly compromised in patients with idiopathic DCM compared with ischaemic DCM in all the analysed atrial segments (P < 0.001). At follow-up, 64 patients (71.1%) (37 idiopathic and 27 ischaemic) were responders, and 26 (28.9%) (10 idiopathic; 16 ischaemic) were non-responders to CRT (responder: decrease of LV end-systolic volume >15%). A significant improvement in LA systolic function was obtained only in patients with ischaemic DCM responders to CRT (P < 0.001). By multivariable analysis, in the overall population, it was found that ischaemic aetiology of DCM (beta-coefficient = 0.62; P < 0.0001) and positive response to CRT (beta-coefficient = 0.42; P < 0.01) were the only independent determinants of LA lateral wall systolic strain.</AbstractText>Two-dimensional strain represents a promising non-invasive technique to assess LA atrial myocardial function in patients with DCM. LA pump and reservoir function at baseline and after CRT are more depressed in idiopathic compared with ischaemic DCM patients. Future longitudinal studies are warranted to understand further the natural history of LA myocardial function, the extent of reversibility of LA dysfunction with CRT, and the possible prognostic impact of such indexes in patients with congestive heart failure.</AbstractText> |
8,231 | [New aspects of cardiopulmonary resuscitation]. | To analyse the current knowledge based on the experimental and clinical research studies focused on cardiopulmonary resuscitation.</AbstractText>International guidelines and recent review articles. Data collected from the Medline database with the keyword: cardiac arrest (CA).</AbstractText>Research studies published during the last ten years were reviewed. Relevant clinical information was extracted and discussed.</AbstractText>Last guidelines include significant modification in the management of cardiac arrest patient. Recognition of CA by lay rescuers is done on the absence of vital sign (no reactivity, no breathing) and it is now only recommended for healthcare providers to check the pulse. It is confirmed that chest compression has to prevail over ventilation and has to be done at a rate of 100 compressions per minutes with a compression-ventilation ratio of 30: 2. A short period of CPR before attempting defibrillation may be considered in adults with out-of-hospital ventricular fibrillation (VF) or pulseless ventricular tachycardia and a delay to EMS response. Defibrillation is provided with biphasic waveform at 150-200 J and is immediately followed by a 2 min period of CPR. Adrenaline remains the drug of choice in cardiac arrest whatever the first rhythm because no benefit has been demonstrated with vasopressin in term of survival. Amiodarone is the first line antiarrhythmic, improves short-term survival and is currently recommended after the second shock for resistant VF. Postresuscitation treatment is now receiving greater emphasis in emergency cardiovascular care, but there is little evidence to support specific therapies with the exception of hypothermia (12-24 h at 32-34 degrees C) that is currently recommended if patient remains unconscious after VF. Revascularization should also be discussed if CA is presumed to be from ischemic origin.</AbstractText>The last international 2005 guidelines include significant modifications of CPR. However, many questions remain unresolved and controlled studies are still needed before other changes could be recommended for routine practice. Our greatest challenge and highest priority is the training of lay rescuers and healthcare providers in simple, high-quality CPR skills that can be easily taught, remembered, and implemented to save lives.</AbstractText> |
8,232 | Reversal of isoproterenol-induced downregulation of phospholamban and FKBP12.6 by CPU0213-mediated antagonism of endothelin receptors. | The downregulation of phospholamban (PLB) and FKBP12.6 as a result of beta- receptor activation is involved in the pathway(s) of congestive heart failure. We hypothesized that the endothelin (ET)-1 system may link to downregulated PLB and FKBP12.6.</AbstractText>Rats were subjected to ischemia/reperfusion (I/R) to cause heart failure (HF). 1 mg/kg isoproterenol (ISO) was injected subcutaneously (sc) for 10 d to worsen HF. 30 mg/kg CPU0213 (sc), a dual ET receptor (ETAR/ETBR) antagonist was given from d 6 to d 10. On d 11, cardiac function was assessed together with the determination of mRNA levels of ryanodine receptor 2, calstabin-2 (FKBP12.6), PLB, and sarcoplasmic reticulum Ca2+-ATPase. Isolated adult rat ventricular myocytes were incubated with ISO at 1X10(-6) mol/L to set up an in vitro model of HF. Propranolol (PRO), CPU0213, and darusentan (DAR, an ETAR antagonist) were incubated with cardiomyocytes at 1X10(-5) mol/L or 1X10(-6) mol/L in the presence of ISO (1X10(-6) mol/L). Immunocytochemistry and Western blotting were applied for measuring the protein levels of PLB and FKBP12.6.</AbstractText>The worsened hemodynamics produced by I/R were exacerbated by ISO pretreatment. The significant downregulation of the gene expression of PLB and FKBP12.6 and worsened cardiac function by ISO were reversed by CPU0213. In vitro ISO 1X10(-6) mol/L produced a sharp decline of PLB and FKBP12.6 proteins relative to the control. The downregulation of the protein expression was significantly reversed by the ET receptor antagonist CPU0213 or DAR, comparable to that achieved by PRO.</AbstractText>This study demonstrates a role of ET in mediating the downregulation of the cardiac Ca2+-handling protein by ISO.</AbstractText> |
8,233 | [Adult cardio-respiratory arrest: guidelines 2005-2010]. | At the end of 2005 the new guidelines for the treatment of cardiac arrest were published. The diagnostic criteria of cardiac arrest were simplified and priority is given to thoracic compressions. The ratio of thoracic compressions to insufflations is 30/2. The frequency of thoracic compression is 100/min. In ventricular tachycardia (VT) without pulse or in ventricle fibrillation (VF), defibrillation is attempted with a single external electric shock per cycle. The reanimation cycles are divided in periods of 2 minutes. The two drugs, used to treat VF and VT without pulse, are amiodarone and adrenaline. Adrenaline is not given before the fourth minute into the reanimation and it is administered before the third electrical external shock. In case of asystole or pulse less electrical activity adrenaline is administered as early as possible. Atropine is used in case of pulse less electrical activity with a ventricular response lower than 60/min. In advanced life support a priority is given to whether or not there are treatable secondary causes (4H, 4T), furthermore controlled hypothermia is installed when systemic circulation is restored and optimal support to all vital functions is given. |
8,234 | Effect of induced ventricular fibrillation and shock delivery on brain natriuretic peptide measured serially following a predischarge ICD test. | Brain natriuretic peptide (BNP) was a marker for heart failure and cardiac wall tension. We analysed the trend of BNP after predischarge testing in order to get non-invasive details about the cardiac stress during predischarge testing.</AbstractText>4-5 days after ICD implant we measured BNP, myoglobin, cardiac troponin I and creatine kinase in 20 patients before and 1, 5, 10, 20, 40, 60, 80, 100, 120 minutes and at the next day after predischarge testing. We evaluated actual values and percentage alterations of BNP.</AbstractText>BNP significantly increased with a maximum after 5 minutes (804.0 +/- 803.4 vs. 475.7 +/- 629.5 pg/ml, P < 0.0001) and in terms of the percentage values (100 vs. 199.4 +/- 61.4 %, P < 0.0001) compared with baseline BNP. BNP decreased after that with the last significantly increased BNP value after 20 minutes (540.2 +/- 604.9 vs. 475.7 +/- 629.5 pg/ml, P = 0.017). We excluded a cardiac necrosis during predischarge testing because of similar values of myoglobin, cardiac troponin I and creatine kinase during the 2-hour follow-up.</AbstractText>Our data showed a great increase with a doubling of BNP after 5 minutes as a result of induced ventricular fibrillation during predischarge test. This increase was not generated by myocardial necrosis but rather caused by an acute cardiac failure as a consequence of induced ventricular fibrillation in predischarge testing.</AbstractText> |
8,235 | The role of abnormal trafficking of KCNE1 in long QT syndrome 5. | LQTS (long QT syndrome) is an important cause of cardiac sudden death. LQTS is characterized by a prolongation of the QT interval on an electrocardiogram. This prolongation predisposes the individual to torsade-de-pointes and subsequent sudden death by ventricular fibrillation. Mutations in a number of genes that encode ion channels have been implicated in LQTS. Hereditary mutations in the alpha- and beta-subunits, KCNQ1 and KCNE1 respectively, of the K(+) channel pore I(Ks) are the commonest cause of LQTS and account for LQTS types 1 and 5 respectively (LQT1 and LQT5). Recently, it has been shown that disease pathogenesis in LQT1 can be influenced by the abnormal trafficking of KCNQ1. In comparison, whether defective trafficking of KCNE1 plays a role in LQT5 is less well established. |
8,236 | Breakfast cereals and risk of heart failure in the physicians' health study I. | Heart failure (HF) is the leading cause of hospitalization among the elderly population in the United States. Consumption of grain products and dietary fiber has been shown to reduce the risk of hypertension and myocardial infarction. However, it is not known whether a higher consumption of breakfast cereals is associated with risk of HF.</AbstractText>This study evaluated prospectively the association between breakfast cereal intake and incident HF among 21 376 participants of the Physicians' Health Study I. Cereal consumption was estimated using a semiquantitative food frequency questionnaire. Incident HF was ascertained through annual follow-up questionnaires and validated using Framingham criteria. We used Cox regression models to estimate adjusted relative risk of HF across categories of cereal intake.</AbstractText>During an average follow-up of 19.6 years, 1018 incident cases of HF occurred. For average weekly cereal consumption of 0 servings, 1 or fewer, 2 to 6, and 7 or more, hazard ratios (95% confidence intervals) for HF were 1 (reference), 0.92 (0.78-1.09), 0.79 (0.67-0.93), and 0.71 (0.60-0.85), respectively (P<.001 for trend), adjusting for age, smoking, alcohol consumption, vegetable consumption, use of multivitamins, exercise, and history of atrial fibrillation, valvular heart disease, and left ventricular hypertrophy. However, the association was limited to the intake of whole grain cereals (P <.001 for trend) but not refined cereals (P = .70 for trend).</AbstractText>Our data demonstrate that a higher intake of whole grain breakfast cereals is associated with a lower risk of HF. Additional studies are warranted to confirm these findings and determine specific nutrients that are responsible for such a protection.</AbstractText> |
8,237 | Ventricular arrhythmia storms in postinfarction patients with implantable defibrillators for primary prevention indications: a MADIT-II substudy. | Much of prognostic implications of ventricular arrhythmia storms remain unclear.</AbstractText>We evaluated the risk associated with electrical storm in patients with defibrillators in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II) study.</AbstractText>Electrical storm was defined as > or =3 episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF) in 24 hours.</AbstractText>Of the 719 patients who received internal cardiac defibrillator (ICD) implants and had follow-up in the MADIT-II, 27 patients (4%) had electrical storm, 142 (20%) had isolated episodes of VT/VF, and the remaining 550 patients had no ICD-recorded VT events. Baseline clinical characteristics among the groups were similar. Patients who experienced electrical storm had a significantly higher risk of death. After adjustments for relevant clinical covariates, the hazard ratio (HR) for death in the first 3 months after the storm event was 17.8 (95% confidence interval [CI] 8.0 to 39.5, P <.01) in comparison with those with no VT/VF. This risk continued even after 3 months for those with electrical storm (HR of 3.5, 95% CI 1.2 to 9.8, P = .02). Study patients with isolated VT/VF episodes also were at an increased risk of dying (HR = 2.5, 95% CI 1.5 to 4.0, P <.01) when compared with patients without VT/VF episodes. Statistically significant predictors of electrical storm were interim postenrollment coronary events (myocardial infarction or angina) HR 3.1 (95% CI 1.2 to 8.1, P = .02) and isolated VT or VF HR 9.2 (95% CI 4.0 to 20.9, P <.01).</AbstractText>Postinfarction patients with severe left ventricular dysfunction in whom electrical storm developed have significantly higher mortality than patients with only isolated VT/VF as well as those without any episodes of VT/VF. Patients who experienced postenrollment ventricular arrhythmias and/or interim coronary events during follow-up were at higher risk for VT/VF storms.</AbstractText> |
8,238 | Atrial paroxysmal tachycardia in dogs and its management with homeopathic Digitalis--two case reports. | Homeopathic Digitalis 6c was evaluated in two clinical cases of atrial paroxysmal tachycardia in dogs. Tachycardias are common cardiac problems in dogs, and atrial paroxysmal tachycardia is a serious cardiac arrhythmia that may lead to syncope. Both adult dogs (Labrador and German Shepherd) were treated with Digitalis 6c, 4 drops orally four times daily for 7 days. Following treatment with Digitalis 6c heart rate stabilised and synchronized atrial and ventricular electrical activity was restored in 7 days. |
8,239 | [Influence of recording mode (unipolar or bipolar) on the spectral characteristics of epicardial recordings in ventricular fibrillation. An experimental study]. | The aim of this study was to examine the hypothesis that the recording mode (i.e., unipolar or bipolar) affects the information obtained using spectral analysis techniques during ventricular fibrillation by carrying out an experiment using epicardial electrodes.</AbstractText>Recordings of ventricular fibrillation were obtained in 29 isolated rabbit hearts using a multiple-electrode probe located on the left ventricular free wall. The parameter values obtained in the frequency domain (by Fourier analysis) using unipolar or bipolar electrodes, different interelectrode distances, and different orientations (i.e., horizontal, vertical or diagonal) were compared.</AbstractText>Changing the recording mode (i.e., unipolar to bipolar) or the interelectrode distance significantly altered the mean frequency (P< .0001) and the normalized energy of the spectrum (+/-1 Hz) around the dominant frequency (P< .05), though the changes were small relative to the dominant frequency. Cross-spectral analysis showed that the coherence between unipolar recordings decreased as the interelectrode distance increased, while the opposite occurred with the coherence between unipolar and bipolar recordings. The two coherences were inversely correlated such that the greater the former coherence, the less the coherence between unipolar and bipolar recordings (r=0.29; P< .0001; n=348).</AbstractText>The recording mode (i.e., unipolar or bipolar) used influenced the information obtained using spectral analysis techniques from epicardial recordings of ventricular fibrillation. Differences were observed in the mean frequency and in the frequency distribution, but they were very small relative to the dominant frequency.</AbstractText> |
8,240 | [Left atrium diameter: a simple echocardiographic parameter with high prognostic value in heart failure]. | Left atrium diameter (LAD) is a very simple and easy parameter to obtain by echocardiography. It is influenced by systolic and diastolic ventricular dysfunction and by the coexistence of mitral regurgitation. We evaluated LAD as a predictor of prognosis (2 year mortality) in a heart failure (HF) population admitted to an outpatient HF unit. We compared LAD (mm/m2) with other echocardiographic parameters (left ventricular ejection fraction, left ventricular end-diastolic and end-systolic diameters [mm/m2], mitral regurgitation, degree of diastolic dysfunction and pulmonary artery pressure).</AbstractText>We studied 368 patients (73% men; mean age [standard deviation]: 65.2 [11] years; 60% of ischemic etiology). The mean left ventricular ejection fraction by echocardiography was 32.3% (13.1%). The majority of patients were in NYHA (New York Heart Association) class II (48%) or III (43%).</AbstractText>Two years mortality was 20.6%. In the univariate analysis LAD (p < 0.001), left ventricular end-diastolic diameter (p < 0.001), left ventricular end-systolic diameter (p = 0.003), the degree of mitral regurgitation (p = 0.002) and the pattern of diastolic dysfunction (p = 0.004) showed a significant relationship with 2 years mortality, but not left ventricular ejection fraction and pulmonary pressure. In the echocardiographic multivariate analysis, only LAD remained significantly associated with mortality. In the multivariate analysis including important clinical parameters such as age, sex, etiology, time lapsed since symptoms onset, NYHA functional class, and the presence of diabetes, hypertension and atrial fibrillation, LAD remained as independent predictor of 2 years mortality. Patients with LAD less than 25 mm/m2 have a 10.9% mortality, whereas those with LAD equal or greater than 25 mm/m2 have a 30.1% mortality (p < 0.001).</AbstractText>LAD was a good predictor of 2 years mortality, better than other echocardiographic parameters in patients of our outpatient HF unit and was independent of strong clinical parameters.</AbstractText> |
8,241 | Atrial fibrillation-related cardiomyopathy: a case report. | Sustained chronic tachyarrhythmias often cause a deterioration of cardiac function known as tachycardia-induced cardiomyopathy or tachycardiomyopathy.The incidence of tachycardia-induced cardiomyopathy is unknown, but in selected studies of patients with atrial fibrillation, approximately 25% to 50% of those with left ventricular dysfunction had some degree of tachycardia-induced cardiomyopathy. It is an important clinical entity due to the high incidence and potential reversibility of the disease process.This case describes a cardiomyopathy induced by excess caffeine consumption. Six months following withdrawal of caffeine from the subject's diet, full resolution of symptoms occurred. |
8,242 | Electrophysiological consequence of adipose-derived stem cell transplantation in infarcted porcine myocardium. | Aim of this study was to investigate the effect of intracoronary administration of freshly isolated adipose-derived mononuclear cells (ADMCs) on myocardial vulnerability to arrhythmia induction after infarction.</AbstractText>A transmural myocardial infarction in an experimental porcine model was induced by occlusion of the mid-left anterior descending artery with an angioplasty balloon for 3 h. Upon reperfusion, a cellular suspension with freshly isolated ADMCs (1.5 x 10(6) cells/kg BW) or vehicle alone was injected into the infarct artery. All animals underwent a programmed ventricular stimulation at 8 weeks follow-up for possible induction of ventricular arrhythmias using a train of 8 S1 stimuli. Cell injections did not cause acute ventricular arrhythmia, bradycardia, or conduction block. The cycle length of the ventricular arrhythmia was compared at 1 and 10 s following its induction. Despite comparable infarct size in both groups, we found that the cycle length of the induced ventricular arrhythmia in the ADMC-treated group was significantly longer compared with control animals (P < 0.05). We also found that extra-stimuli were required for arrhythmia induction in the ADMC-treated group compared with control animals.</AbstractText>Freshly isolated autologous stem cell therapy is not proarrhythmic in pigs.</AbstractText> |
8,243 | Comparison of the incidences of cardiac arrhythmias, myocardial ischemia, and cardiac events in patients treated with endovascular versus open surgical repair of abdominal aortic aneurysms. | This study examines differences in cardiac arrhythmias, perioperative myocardial ischemia, troponin T release, and cardiovascular events between endovascular and open repair of abdominal aortic aneurysms (AAAs). Of 175 patients, 126 underwent open AAA repair and 49 underwent endovascular AAA repair. Continuous 12-lead electrocardiographic monitoring, starting 1 day before surgery and continuing through 2 days after surgery, was used for cardiac arrhythmia and myocardial ischemia detection. Troponin T was measured on postoperative days 1, 3, and 7 and before discharge. Cardiac events (cardiac death or Q-wave myocardial infarction) were noted at 30 days and at follow-up (mean 2.3 years). New-onset atrial fibrillation, nonsustained ventricular tachycardia, sustained ventricular tachycardia, and ventricular fibrillation occurred in 5%, 17%, 2%, and 1% of patients, respectively. Myocardial ischemia, troponin T release, and 30-day and long-term cardiac events occurred in 34%, 29%, 6%, and 10% of patients, respectively. Significantly higher heart rates and less heart rate variability were observed in the open AAA repair group. Cardiac arrhythmias were less prevalent in the endovascular AAA repair group (14% vs 29%, p = 0.04). Endovascular repair was also significantly associated with less myocardial ischemia (odds ratio 0.14, 95% confidence interval 0.05 to 0.40, p <0.001) and troponin T release (odds ratio 0.10, 95% confidence interval 0.02 to 0.32, p <0.001) and lower 30-day mortality (zero vs 8.7%, p = 0.03) and 30-day cardiac event rates (zero vs 7.9%, p = 0.04). Long-term mortality and cardiac event rates were not significantly lower in the endovascular AAA repair group. In conclusion, endovascular AAA repair is associated with a lower incidence of perioperative cardiac arrhythmias, myocardial ischemia, troponin T release, cardiac events, and all-cause mortality compared with open AAA repair. |
8,244 | Value of preoperative echocardiography in the prediction of postoperative atrial fibrillation following isolated coronary artery bypass grafting. | The value of echocardiography, especially tissue Doppler imaging (TDI), in the assessment of risk of postoperative atrial fibrillation (AF) after coronary artery bypass grafting (CABG) is not clear. One hundred two consecutive patients (80 men; mean age 61 +/- 10 years) who underwent elective isolated CABG were included in the study. All patients underwent conventional transthoracic echocardiography and TDI of the left and right heart before surgery. Also, 24-hour Holter recordings were obtained for all patients. The study end point was the development of postoperative AF. The surgical mortality rate was 2%. Postoperative AF occurred in 18 patients (18%). Patients with postoperative AF have been significantly older than patients without postoperative AF (73 +/- 7 vs 58 +/- 9 years, respectively; p <0.001). Compared with patients without postoperative AF, a significantly higher proportion of patients with postoperative AF experienced paroxysmal AF before surgery (6% vs 33%, respectively; p = 0.001). Patients with postoperative AF had a significantly larger mean left atrial diameter compared with patients without postoperative AF (37 +/- 3 vs 35 +/- 3 mm, respectively; p = 0.012). Multivariate logistic regression analysis identified age as the most significant predictor of postoperative AF (odds ratio 1.254, 95% confidence interval 1.127 to 1.396; p <0.001). Of the echocardiographic variables, only left atrial diameter was identified as a significant predictor of postoperative AF (odds ratio 1.250, 95% confidence interval 1.055 to 1.562; p = 0.047). In conclusion, in the prediction of postoperative AF after isolated CABG, preoperative transthoracic echocardiography, including both conventional echocardiography and TDI, is of little value. |
8,245 | Early right coronary vasospasm presenting with malignant arrhythmias in a heart transplantation recipient without allograft vasculopathy. | In heart transplant recipients, the aetiology of coronary vasospasm is largely unknown but it has been reported to be related to coronary vasculopathy or allograft rejection. We report a case of acute, reversible coronary vasospasm which caused malignant arrhythmias in a cardiac transplant recipient one month after transplantation without evidence of coronary vasculopathy or allograft rejection. The patient had a normal post-operative course with no other complications; this case supports the hypothesis that coronary vasospasm is not necessarily related to epicardial coronary artery disease or allograft rejection, but rather may be due to an abnormal reversible vasoreactivity. |
8,246 | Cardiac surgery in nonagenarians. | To evaluate outcomes following cardiac surgery in nonagenarians.</AbstractText>A retrospective analysis of patients > or = 90 years of age undergoing cardiac surgery at Barnes-Jewish Hospital from 1996-2006 was performed. The Social Security Death Index was used to determine late survival.</AbstractText>Twenty-two subjects were identified. The mean age was 91 years (range 90-94) and 64% were women. The most common comorbidities included hypertension in 91% and heart failure (HF) in 65%. Mean New York Heart Association class was 3.5, mean left ventricular ejection fraction was 50% (range 27-80%), and mean creatinine clearance was 34 +/- 11 cc/min. No patients had prior cardiac surgery. Nine patients underwent coronary bypass grafting only, 11 had valve replacement only, and 2 had both. Concurrent operations included 1 ventricular septal defect repair, 2 carotid endarterectomies, and 1 ascending aortic patch angioplasty. Two cases were urgent, 2 were emergent, and the remainder were elective. There was one intraoperative death (5%), during urgent mitral valve replacement. The most common postoperative complications included atrial fibrillation and need for vasopressors for >48 hrs. Mean length of intensive care and total hospital stay were 3.4 +/- 4.5 and 12.2 +/- 8.5 days, respectively. Independent predictors of increased hospital stay were higher serum creatinine (P=0.028) and the presence of HF (P=0.050). Survival to 30, 90 and 365 days were, respectively: 86%, 77%, and 64%. At study conclusion, 7 patients (32%) were alive at a mean follow-up of 4.1 years.</AbstractText>Despite higher morbidity and mortality, in carefully selected nonagenarians referred for cardiac surgery, short-term complication rates and long-term outcomes appear to be acceptable.</AbstractText> |
8,247 | Laminar arrangement of ventricular myocytes influences electrical behavior of the heart. | The response of the heart to electrical shock, electrical propagation in sinus rhythm, and the spatiotemporal dynamics of ventricular fibrillation all depend critically on the electrical anisotropy of cardiac tissue. A long-held view of cardiac electrical anisotropy is that electrical conductivity is greatest along the myocyte axis allowing most rapid propagation of electrical activation in this direction, and that conductivity is isotropic transverse to the myocyte axis supporting a slower uniform spread of activation in this plane. In this context, knowledge of conductivity in two directions, parallel and transverse to the myofiber axis, is sufficient to characterize the electrical action of the heart. Here we present new experimental data that challenge this view. We have used a novel combination of intramural electrical mapping, and experiment-specific computer modeling, to demonstrate that left ventricular myocardium has unique bulk conductivities associated with three microstructurally-defined axes. We show that voltage fields induced by intramural current injection are influenced by not only myofiber direction, but also the transmural arrangement of muscle layers or myolaminae. Computer models of these experiments, in which measured 3D tissue structure was reconstructed in-silico, best matched recorded voltages with conductivities in the myofiber direction, and parallel and normal to myolaminae, set in the ratio 4:2:1, respectively. These findings redefine cardiac tissue as an electrically orthotropic substrate and enhance our understanding of how external shocks may act to successfully reset the fibrillating heart into a uniform electrical state. More generally, the mechanisms governing the destabilization of coordinated electrical propagation into ventricular arrhythmia need to be evaluated in the light of this discovery. |
8,248 | Predictive value of programmed ventricular stimulation in patients with ischaemic cardiomyopathy: implications for the selection of candidates for an implantable defibrillator. | The present study assessed the role of programmed ventricular stimulation (PVS) in risk stratification of patients with ischaemic cardiomyopathy (ICM), candidates for implantable cardioverter-defibrillator (ICD).</AbstractText>Consecutive patients with ICM and LVEF < or = 40% (n = 106, age 61 +/- 7 years, LVEF 27 +/- 7%) underwent PVS. This was considered positive in case of inducibility of monomorphic ventricular tachycardia (VT) with < or =3 extrastimuli; polymorphic VT, ventricular fibrillation (VF), and fast monomorphic VT (CL < or = 230 ms) with < or =2 extrastimuli. Primary end-point was the combination of arrhythmic death and VF requiring ICD shock. Forty-nine patients (46%) were inducible at PVS; 74 (70%) were implanted with ICD. During a 24-month follow-up, the primary end-point occurred more frequently in positive PVS patients among the overall population, among patients with LVEF < or = 30% (n = 80) and among patients with an ICD. The negative predictive value of PVS was 96% in each group. In the overall population, both PVS (HR 7.32, 95% CI 1.6-32) and LVEF (HR 4.59, 95% CI 1.6-13) predicted the primary end-point.</AbstractText>PVS may still have a role in predicting the arrhythmic risk in patients with ICM. A negative PVS identifies a subgroup with a very low risk of arrhythmic events even in patients with LVEF < or = 30%.</AbstractText> |
8,249 | Development of an algorithm for detection of fatal cardiac arrhythmia for implantable cardioverter-defibrillator using a self-organizing map. | In this study, we have introduced the pattern classifier using the self-organizing map (SOM) for detecting fatal cardiac arrhythmia in implantable cardioverter-defibrillators (ICDs). The SOM has learned patterns of sinus rhythm, ventricular fibrillation and ventricular tachycardia with the feature vectors extracted from electrocardiogram and right ventricular volume measured during an arrhythmia induction experiment of a dog. After learning, neurons of the SOM were labeled by using the k-Nearest Neighbor method. It was shown that the accuracy of the proposed method was higher than other competitive methods applied to the same test data. |
8,250 | Maintenance of ventricular fibrillation in heterogeneous ventricle. | Although ventricular fibrillation (VF) is the prevalent cause of sudden cardiac death, the mechanisms that underlie VF remain elusive. One possible explanation is that VF is driven by a single robust rotor that is the source of wavefronts that break-up due to functional heterogeneities. Previous 2D computer simulations have proposed that a heterogeneity in background potassium current (IK1) can serve as the substrate for the formation of mother rotor activity. This study incorporates IK1 heterogeneity between the left and right ventricle in a realistic 3D rabbit ventricle model to examine its effects on the organization of VF. Computer simulations show that the IK1 heterogeneity contributes to the initiation and maintenance of VF by providing regions of different refractoriness which serves as sites of wave break and rotor formation. A single rotor that drives the fibrillatory activity in the ventricle is not found in this study. Instead, multiple sites of reentry are recorded throughout the ventricle. Calculation of dominant frequencies for each myocardial node yields no significant difference between the dominant frequency of the LV and the RV. The 3D computer simulations suggest that IK1 spatial heterogeneity alone can not lead to the formation of a stable rotor. |
8,251 | Development of a remote handheld cardiac arrhythmia monitor. | In this paper we present the design and development of a real-time remote handheld cardiac arrhythmic monitoring system (RCAM). A client-server model based on Internet protocols was used. ECG data was transmitted from the remote handheld client to a centralized server, where the QRS and premature ventricular contraction detection algorithms were implemented and graded depending on the number and pattern of PVCs present. The QRS sensitivity and specificity on ECG records from Physionet archives in absence of arrhythmia was 100% and 99.62%, while in presence of arrhythmia was 99.34% and 99.31%. The average 'negative time' measured on ventricular tachyarrhythmia records was 92 seconds. The RCAM can provide remote detection of cardiac abnormalities and give specific diagnosis and recommendations of actions to be taken immediately. The limitation due to the inability of the PDA to perform complex computations was overcome by the use of the remote server. |
8,252 | Cardiac current density distribution by electrical pulses from TASER devices. | TASERs deliver electrical pulses that can temporarily incapacitate subjects. The goal of this paper is to analyze the distribution of TASER currents in the heart and understand their chances of triggering cardiac arrhythmias. The models analyzed herein describe strength-duration thresholds for myocyte excitation and ventricular fibrillation induction. Finite element modeling is used to compute current density in the heart for worst-case TASER electrode placement. The model predicts a maximum TASER current density of 0.27 mA/cm(2) in the heart. It is conclude that the numerically simulated TASER current density in the heart is about half the threshold for myocytes excitation and more than 500 times lower than the threshold required for inducing ventricular fibrillation. Showing a substantial cardiac safety margin, TASER devices do not generate currents in the heart that are high enough to excite myocytes or trigger VF. |
8,253 | Development of arrhythmia diagnosis algorithm for effective control of antitachycardia pacing and high energy shock of ICD. | In this paper, we propose a modified arrhythmia diagnosis and therapy control algorithm based on VENTAK PRIZM 2 algorithm of the Guidant corp. Existing arrhythmia detection and therapy control algorithms control arrhythmia through two steps. First step is event detection using peak-to-peak interval detection, and the second step is duration detection. We modify these stages to improve diagnosis time delay and treatment efficiency. |
8,254 | Structural barrier increases QT-peak dispersion in swine left ventricle in vivo. | QT dispersion (QTD) is thought to represent the regional nonuniformity of ventricular repolarization and can serve as a prognostic marker for vulnerability to ventricular arrhythmias and risk for sudden cardiac death (SCD). In this study, we used an in vivo swine model to investigate the change of QT-peak dispersion before and after the introduction of a left-ventricular (LV) free-wall structural barrier (SB). Baseline and post-ablation pacing were delivered to: (i) the epicardial LV base, (ii) the epicardial LV apex, and (iii) the right ventricular (RV) endocardium. Four unipolar electrograms were measured from LV free wall epicardial sites referenced to an intrathorax electrode. An SB (approximately 4 x 1 x 1 cm (length, width, depth)) was created by cryoablation in the middle of the two electrode pairs. QTD was computed as the difference between QT-peak intervals for each beat from two electrodes across the SB region from one another. A significant increase of QTD occurred (p<0.05) after the introduction of the SB in all six animals. These results may reflect the accentuation of anatomical repolarization heterogeneity due to SB disruption of electrotonic coupling. Given the link between dispersion of repolarization and initiation of reentry, these findings are consistent with the increased arrhythmia risk of structural heart disease. |
8,255 | Automatic classification of heartbeats using neural network classifier based on a Bayesian framework. | This paper presents a method of automatic processing the electrocardiogram (ECG) signal for the classification of heart beats. Data were obtained from 48 records of the MIT-BIH arrhythmia database (only one lead). Five types of arrhythmic beats were classified using our method, Premature Ventricular Conduction beat (PVC), Atrial Premature Conduction beat (APC), Right Bundle Branch Block beat (RBBB), Left Bundle Branch Block beat (LBBB), and Paced Rhythm Beat (PRB), in addition to the Normal Beat (NB). A learning dataset for the neural network was obtained from a five records set (124, 214, 111, 100, and 107) which were manually classified using MIT-BIH Arrhythmia Database Directory and documentation, taking advantage of the professional experience of a cardiologist. Feature set was based on ECG morphology and time intervals. Our system resulted in a minimal sensitivity of 86% and minimal specificity of 90% |
8,256 | Calcium transients modulate action potential repolarizations in ventricular fibrillation. | Action potential alternans has been an indicator of ischemic disease and vulnerability to ventricular fibrillation (VF). The mechanisms of alternans are linked to the anomalies in intracellular Ca2+ (Cai) handling by either spontaneous Ca2+ release or modulation of action potential duration (APD), which may promote wave breaks in VF. We investigated possible role of Ca2+ in wave breaks by simultaneously measuring transmembrane potential (Vm) and intracellular Ca2+ concentration with voltage sensitive dye (RH237) and Ca2+ (Rhod-2) fluorescence probes. VF was induced by burst stimulation and the relationship between Vm and Ca2+ oscillations in VF were analyzed with cross-correlation analysis. The maximum correlation occurred at 12 ms delay between Vm and Cai, suggesting Vm still triggers Ca2+ release in VF as in normal excitation-contraction coupling. In addition, inverse correlation was found -20 ms between Vm and Cai, suggesting the amplitude of Cai can modulate action potential recovery in VF. In conclusion, Cai can influence action potential durations, which may promote wave breaks in VF. |
8,257 | Comparison of current densities measured in a pig heart during states of ventricular fibrillation and post-mortem for different defibrillation electrode positions. | Current density imaging (CDI) is an MRI technique used to quantitatively measure current density vectors in biological tissue. A fast CDI sequence was developed that can image the whole body of a 4 kg pig in about 15 minutes. A state of ventricular fibrillation (VF) can be sustained for nearly 30 minutes allowing two complete CDI scans of the same subject. A single parameter, i.e. electrode position, is adjusted between the two scans for comparative analysis. This study compares the current density vector directions and current density magnitudes measured for two typical electrode positions, i.e. apex anterior (AA) and apex posterior (AP). The comparative experiment is repeated on the same subjects for states of immediate post-mortem and one hour post-mortem. Further, the acquired vector datasets are used to compute conductivity images of the heart. |
8,258 | Method of post-shock synchronized pacing in the excitable gaps. | Ventricular fibrillation (VF) can be synchronized with a novel synchronized pacing technique (SyncP) using low-energy pacing pulses, which causes pace termination of VF. Synchronized pacing (SyncP) is defined as optical recording guided real-time detection and stimulation of spatiotemporal excitable gaps. In this paper, we investigate the effect of post-shock SyncP strategy on improvement of defibrillation efficacy. After a near-threshold defibrillation shock, when the reference site detected the earliest activation of the reinitiated VF, a 5-mA electric stimulus was delivered from the post-shock pacing electrode to depolarize the excitable gap. This area of wavefront synchronization may lead to a change in the timing of VF propagation, which is important for VF termination. Here, we implemented the concept of post-shock synchronized pacing by a real-time feedback mechanism and demonstrated a successful VF termination by the post-shock SyncP strategy. Further optimization of this technique may prove effective in improving the defibrillation efficacy for low-energy ventricular defibrillation. |
8,259 | Transmural electrophysiological heterogeneities in action potential duration increase the upper limit of vulnerability. | Transmural dispersion in action potential duration (APD) has been shown to contribute to arrhythmia induction in the heart. However, its role in termination of lethal arrhythmias by defibrillation shocks has never been examined. The goal of this study is to investigate how transmural dispersion in APD affects cardiac vulnerability to electric shocks, in an attempt to better understand the mechanisms behind defibrillation failure. This study used a three- dimensional, geometrically accurate finite element bidomain rabbit ventricular model. Transmural heterogeneities in ionic currents were incorporated based on experimental data to generate the transmural APD profile recorded in adult rabbits during pacing. Results show that the incorporation of transmural APD heterogeneities in the model causes an increase in the upper limit of vulnerability from 26.7 V/cm in the homogeneous APD ventricles to 30.5 V/cm in the ventricles with heterogeneous transmural APD profile. Examination of shock-end virtual electrode polarisation and postshock electrical activity reveals that the higher ULV in the heterogeneous model is caused by increased dispersion in postshock repolarisation within the LV wall, which increases the likelihood of the establishment of intramural re-entrant circuits. |
8,260 | Successful defibrillation in water: a preliminary study. | Mild hypothermia (32-34 deg C) treatment alleviates vital organ damage after cardiac arrest. A new cooling device, the Thermosuit operates by applying of a thin layer of water directly to the body surface. Hypothermic patients may experience sequential fibrillation. Therefore, we examined whether defibrillation could be administered safely and effectively in water. A 35 kg swine was anesthetized and placed inside the Thermosuit system. This consists of a water containing surround and pumping system. Conventional AED disposable defibrillation electrodes were applied to the animal's chest. Fibrillation was created by applying a 50-volt signal to a pacing wire introduced into the heart. Following a 30-second period of fibrillation, defibrillation was attempted using Medtronic AED 1000 defibrillator. Defibrillation voltage and current were measured. There were three test cases: dry in the system, wet in the functioning system, and damp. Cooling water in the system was contaminated with saline to simulate potential conditions in clinical application. In each fibrillation-defibrillation sequence, the heart was restarted successfully; this required less than 220 joules. Only a small difference was measured in the overall defibrillation voltage and current as applied to the electrodes for the different cases. Thus, underwater defibrillation is safe and can be performed effectively. |
8,261 | Validation of a novel atrial fibrillation model through simulated atrial pacing protocols. | We have previously reported a novel model to elucidate the effects of ventricular pacing (VP) on RR intervals during atrial fibrillation (AF). This model treats the AV junction (AVJ) as a lumped structure with defined conductivity, refractoriness and automaticity. We have shown that this model could account for various patterns of RR intervals that are consistent with experimental observations. In this study, we further validate this model by comparing its behavior with that of a real AVJ obtained in isolated rat heart preparation, through application of programmed atrial pacing protocols. We demonstrate that the AV conduction time and ventricular response of the present model are consistent with experimental findings, thus providing additional evidence to support the validity of our model. |
8,262 | Zoniporide preserves left ventricular compliance during ventricular fibrillation and minimizes postresuscitation myocardial dysfunction through benefits on energy metabolism. | To investigate whether sodium-hydrogen exchanger isoform-1 (NHE-1) inhibition attenuates myocardial injury during resuscitation from ventricular fibrillation through effects on energy metabolism, using an open-chest pig model in which coronary perfusion was controlled by extracorporeal circulation.</AbstractText>Randomized controlled animal study.</AbstractText>University research laboratory.</AbstractText>Male domestic pigs.</AbstractText>Ventricular fibrillation was electrically induced and left untreated for 8 mins, after which extracorporeal circulation was started and its flow adjusted to maintain a coronary perfusion pressure of 10 mm Hg. After 10 mins of extracorporeal circulation, restoration of spontaneous circulation was attempted by epicardial defibrillation and gradual reduction in extracorporeal flow. Two groups of eight pigs each were randomized to receive the NHE-1 inhibitor zoniporide (3 mg.kg-1) or vehicle control immediately before starting extracorporeal circulation.</AbstractText>Identical extracorporeal flows (approximately = 9% of baseline cardiac index) were required in zoniporide and control groups to attain the target coronary perfusion pressure, resulting in comparable left anterior descending coronary artery blood flow (9 +/- 1 and 10 +/- 1 mL.min-1) and resistance (0.10 +/- 0.01 and 0.10 +/- 0.01 dyne.sec.cm(-5)). Yet zoniporide prevented reductions in left ventricular volume and wall thickening while favoring higher myocardial creatine phosphate to creatine ratios (0.14 +/- 0.03 vs. 0.06 +/- 0.01, p < .05), lower myocardial adenosine (0.7 +/- 0.1 vs. 1.3 +/- 0.2, p < .05), and lower myocardial lactate (80 +/- 9 vs. 125 +/- 6 mmol.kg-1, p < .001). Postresuscitation, zoniporide-treated pigs had higher left ventricular ejection fraction (0.57 +/- 0.07 vs. 0.29 +/- 0.05, p < .05) and higher cardiac index (4.8 +/- 0.4 vs. 3.4 +/- 0.2 L.min-1.m-2, p < .05).</AbstractText>Zoniporide ameliorated myocardial injury during resuscitation from ventricular fibrillation through beneficial effects on energy metabolism without effects on coronary vascular resistance and coronary blood flow.</AbstractText>(C) 2007 Lippincott Williams & Wilkins, Inc.</CopyrightInformation> |
8,263 | Does the prognosis of cardiac arrest differ in trauma patients? | It is proposed to not resuscitate trauma patients who have a cardiac arrest outside the hospital because they are assumed to have a dismal prognosis. Our aim was to compare the outcome of patients with traumatic or nontraumatic ("medical") out-of-hospital cardiac arrest.</AbstractText>Cohort analysis of patients with out-of-hospital cardiac arrest included in the European Epinephrine Study Group's trial comparing high vs. standard doses of epinephrine.</AbstractText>Nine French university hospitals.</AbstractText>A total of 2,910 patients.</AbstractText>Patients were successively and randomly assigned to receive repeated high doses (5 mg each) or standard doses (1 mg each) of epinephrine at 3-min intervals.</AbstractText>Return of spontaneous circulation, survival to hospital admission and discharge, and secondary outcome measures of 1-yr survival and neurologic outcome were recorded. In the trauma group, patients were younger (42 +/- 17 vs. 62 +/- 17 yrs, p < .001), presented with fewer witnessed out-of-hospital cardiac arrests (62.3% vs. 79.7%), and had fewer instances of ventricular fibrillation as the first documented pulseless rhythm (3.4% [95% confidence interval, 1.2-5.5%] vs. 17.3% [15.8-18.7%]). A return of spontaneous circulation was observed in 91 of 268 trauma patients (34.0% [28.3-39.6%]) compared with 797 of 2,642 medical patients (30.2% [28.4-31.9%]), and more trauma patients survived to be admitted to the hospital (29.9% [24.4-35.3%] vs. 23.5% [22.0-25.2%]). However, there was no significant difference between trauma and medical groups at hospital discharge (2.2% [0.5-4.0%] vs. 2.8% [2.1-3.4%]) and 1-yr survival (1.9% [0.3-3.5%] vs. 2.5% [1.9-3.1%]). Among patients who were discharged, a good neurologic status was observed in two trauma patients (33.3% [4.3-77.7%]) and 37 medical patients (50% [38.1-61.9%]).</AbstractText>The survival and neurologic outcome of out-of-hospital cardiac arrest were not different between trauma and medical patients. This result suggests that, under the supervision of senior physicians, active resuscitation after out-of-hospital cardiac arrest is as important in trauma as in medical patients.</AbstractText>(C) 2007 Lippincott Williams & Wilkins, Inc.</CopyrightInformation> |
8,264 | Myocardial function, ischaemia and n-3 polyunsaturated fatty acids: a membrane basis. | Long-chain n-3 polyunsaturated fatty acids (PUFAs) are selectively incorporated into cardiac cell membranes from the diet in a dose-related manner. Regular intake can slow the heart rate, reduce myocardial oxygen consumption, and increase coronary reserve. These properties contribute to preconditioning-like effects of resistance to myocardial ischaemic damage and improved post-ischaemic recovery. These effects can be demonstrated in isolated hearts independently of the effects of n-3 PUFAs on neural or blood parameters. The enrichment of myocardial membranes with n-3 PUFA also reduces vulnerability to cardiac arrhythmias, particularly ventricular fibrillation during myocardial ischaemia and reperfusion, and attenuates heart failure and cardiac hypertrophy. n-3 PUFA concentrations can increase from 7% to 15% in the myocardial membranes of rats (mainly in the form of docosahexaenoic acid [22: 6 n-3]) with dietary intakes of only 0.3% fish oil, equivalent to two meals of salmon per week in the human diet. Dietary fish oil produces changes in cardiac function that might contribute to cardiovascular health benefits in humans and does so by modifying cardiac membranes within a dose range achievable in the human diet. |
8,265 | [Thyrometabolic disorders and heart failure]. | Thyroid hormones are essential to maintain normal function of many systems including the cardiovascular system. Their excess or deficiency may upset human body homeostasis. Hyperthyroidism leads to cardiovascular system's hyperdynamic status which is characterized by tachycardia, increased difference between systolic and diastolic arterial pressure, significant increase of the stroke volume and improvement of the left ventricular diastolic function. Long-lasting thyrotoxicosis in patient with heart disease may result in atrial fibrillation, deterioration of angina pectoris or congestive heart failure. Hypothyroidism leads to hemodynamic disturbances which are quite different than those observed in hyperthyroidism, but cardiac symptoms are scant in clinical practice. Hypothyroidism's clinical significance is limited to atherosclerosis progression and intensification of ischaemic heart disease symptoms. Both leads to symptomatic cardiovascular system failure or its deterioration. We should emphasize that cardiovascular system dysfunction associated with thyrometabolic disturbances subsides when euthyreosis is restored. It sounds promising that there are reports suggesting a potential advantage of thyroxin treatment in patients with acute or chronic cardiovascular system diseases. These hypotheses result from the observations that heart dysfunction in hypothyroidism is similar to that observed in heart failure. |
8,266 | Enhanced dispersion of atrial refractoriness as an electrophysiological substrate for vulnerability to atrial fibrillation in patients with paroxysmal atrial fibrillation. | Atrial electrical remodeling plays a part in recurrence of atrial fibrillation (AF). It has been related to an increase in heterogeneity of atrial refractoriness that facilitates the occurrence of multiple reentry wavelets and vulnerability to AF.</AbstractText>To examine the relationship between dispersion of atrial refractoriness (Disp_A) and vulnerability to AF induction (A_Vuln) in patients with clinical paroxysmal AF (PAF).</AbstractText>Thirty-six patients (22 male; age 55+/-13 years) with > or =1 year of history of PAF (no underlying structural heart disease--n=20, systemic hypertension--n=14, mitral valve prolapse--n=1, surgically corrected pulmonary stenosis--n=1), underwent electrophysiological study (EPS) while off medication. The atrial effective refractory period (AERP) was assessed at five different sites--high (HRA) and low (LRA) lateral right atrium, high interatrial septum (IAS), proximal (pCS) and distal (dCS) coronary sinus--during a cycle length of 600 ms. AERP was taken as the longest S1-S2 interval that failed to initiate a propagation response. Disp_A was calculated as the difference between the longest and shortest AERP. A_Vuln was defined as the ability to induce AF with 1-2 extrastimuli or with incremental atrial pacing (600-300 ms) from the HRA or dCS. The EPS included analysis of focal electrical activity based on the presence of supraventricular ectopic beats (spontaneous or with provocative maneuvers). The patients were divided into group A--AF inducible (n=25) and group B--AF not inducible (n=11). Disp_A was analyzed to determine any association with A_Vuln. Disp_A and A_Vuln were also examined in those patients with documented repetitive focal activity. Logistic regression was used to determine any association of the following variables with A_Vuln: age, systemic hypertension, left ventricular hypertrophy, left atrial size, left ventricular function, duration of PAF, documented atrial flutter/tachycardia and Disp_A.</AbstractText>There were no significant differences between the groups with regard to clinical characteristics and echocardiographic data. AF was inducible in 71% of the patients and noninducible in 29%. Group A had greater Disp_A compared to group B (105+/-78 ms vs. 49+/-20 ms; p=0.01). Disp_A was >40 ms in 50% of the patients without A_Vuln and in 91% of those with A_Vuln (p=0.05). Focal activity was demonstrated in 14 cases (39%), 57% of them with A_Vuln. Disp_A was 56+/-23 ms in this group and 92+/-78 ms in the others (p=0.07). Using logistic regression, the only predictor of A_Vuln was Disp_A (p=0.05).</AbstractText>In patients with paroxysmal AF, Disp_A is a major determinant of A_Vuln. Nevertheless, the degree of nonuniformity of AERP appears to be less important as an electrophysiological substrate for AF due to focal activation.</AbstractText> |
8,267 | Are maximum P wave duration and P wave dispersion a marker of target organ damage in the hypertensive population? | High blood pressure, left ventricular hypertrophy and diastolic dysfunction may cause hemodynamic and morphological changes in the left atrium, consequently instability and heterogeneity in atrial conduction. This is seen as an increase in maximum P wave duration (P(max)) and P wave dispersion (PD) on the electrocardiogram (ECG). P wave dispersion on ECG has been encountered as a risk factor for atrial fibrillation (AF). The aim of this study is to examine whether PD and P(max) can be used as a non-invasive marker of target organ damage (LVH and diastolic dysfunction) in a hypertensive population.</AbstractText>The study registered a total of 120 cases (mean age 46.9 +/- 10.6 years; 58 [48.3%] males and 62 [51.7%] females), of whom 60 were patients diagnosed as essential hypertension (group 1), and 60 were healthy individuals, who constituted the control group (group 2). Systolic and diastolic functions of all cases were evaluated by echocardiography, and maximum P wave duration (P(max)), and PD was calculated.</AbstractText>Maximum P wave duration was 91.6 +/- 10.2 ms in group 1, and 64 +/- 10.2 ms in group 2 (p < 0.01), while PD was 56.1 +/- 5.8 ms in group 1, and 30.3 +/- 6.6 ms in group 2 (p < 0.01). Blood pressure, left atrium diameter, DT, IVRT, and E/A ratio, as well as left ventricular mass index increased markedly in group 1.</AbstractText>High blood pressure, LVH, diastolic dysfunction and increased left atrium diameter and volume shows parallelism in hypertensive cases. These physiopathological changes may cause different and heterogeneous atrial electrical conduction. This led to a marked increase in P(max) and PD in our cases. Thus, the results support the hypothesis that PD can be used as a non-invasive marker of target organ damage (LVH and LV diastolic dysfunction) in the hypertension population.</AbstractText> |
8,268 | Awareness of guidelines for use of automated external defibrillators in children within emergency medical services. | Ventricular fibrillation occurs in 10-20% of pediatric cardiac arrests. Survival rates in children with ventricular fibrillation can be as high as 30% when the rhythm is identified and treated promptly. In the last 5 years, recommendations have been made for the use of automated external defibrillators in children between 1 and 8 years of age.</AbstractText>The goal of this study was to determine the awareness of the ILCOR guidelines and statewide protocols concerning AED use in children ages 1-8 among emergency medical providers after new guideline release. Availability of pediatric capable AED equipment was also assessed.</AbstractText>Surveys were distributed to EMS providers in Iowa and Montana within 1 year of the ILCOR advisory statement in 2003 recommending use of AEDs in children ages 1-8, and again approximately 1 year after the 2005 ILCOR guidelines on cardiopulmonary resuscitation were published. In Iowa, there were concentrated efforts to disseminate information about AED use in children, while there were minimal efforts in Montana.</AbstractText>Awareness of ILCOR guidelines for use of AEDs in children was low in both states in 2003 (29% in Iowa vs. 9% in Montana, p<0.001). After release of the 2005 guidelines, awareness improved significantly in both states but was still significantly greater in Iowa (83% vs. 60%, p<0.002). In 2003, less than 20% of respondents in both states reported access to pediatric capable AEDs. Availability of pediatric pads and cables increased significantly in 2006 but remained low in Montana (74% in Iowa vs. 37% in Montana, p<0.001).</AbstractText>At the present time, publication of new or interim guidelines in the scientific literature alone is insufficient to ensure that new protocols are implemented. An effective and efficient method to disseminate new pediatric out-of-hospital protocols emergency care to become standard of care in a timely matter must be developed.</AbstractText> |
8,269 | Clinical experience with a low-energy pulsed biphasic waveform in out-of-hospital cardiac arrest. | The efficiency of a pulsed biphasic waveform (PBW) was compared with that of biphasic truncated exponential (BTE) waveforms. First defibrillation shock outcome was studied in a population of 104 out-of-hospital cardiac arrest patients in ventricular fibrillation as the presenting rhythm. The call to first shock time was 8.2+/-5.4 min. At 5s post-shock, defibrillation efficiency was 90%. The arrest was witnessed in only 50% of the patients and only 5% received bystander CPR. Despite these limitations 38% of the patients achieved restoration of a spontaneous circulation at departure from scene and 9.8% were discharged from the hospital. These observations demonstrate a rate of first shock success in termination of ventricular fibrillation comparable to that reported with biphasic truncated exponential waveforms in out-of-hospital cardiac arrest. |
8,270 | Is there a role for remodeled connexins in AF? No simple answers. | Gap junctions provide direct cytoplasmic continuity between cells forming a low resistivity barrier to electrical propagation. As such, aberrant regulation of these low resistive conduits has been blamed for electrical conduction disorders in diseased myocardium. While there is a plethora of evidence that abnormalities in gap junctional communication underlie many forms of ventricular arrhythmias, the role of gap junctions in atrial conduction disorders has been less well studied. The atria are the most heterogeneous cardiac structures in terms of the gap junction proteins, connexins (Cx), which are present. Cx40 is the primary, or most abundant, gap junction protein in atria although Cx43 is also abundantly expressed. Cx45 is also expressed in atria, although at low levels. This heterogeneity in connexins leads to a complexity that makes understanding the role of cell coupling in conduction disorders and arrhythmogenesis difficult. In this review we focus on what is known about atrial connexins and their role in atrial fibrillation but also on the challenges presented in understanding the complex interplay between the individual connexin isoforms. |
8,271 | Phenotypic spectrum and clinical characteristics of apical hypertrophic cardiomyopathy: multicenter echo-Doppler study. | The aim of this study was to define the phenotypic spectrum of apical hypertrophic cardiomyopathy (ApHCM) and clinical characteristics pertaining to identified subtypes.</AbstractText>In 182 consecutive ApHCM patients (58.9 +/- 11.2 years; 142 men) with left ventricular ejection fraction > or =50%, we measured end-diastolic wall thickness of all 16 left ventricular segments to determine patterns of hypertrophy. Echo-Doppler parameters, electrocardiography patterns, and clinical findings were analyzed.</AbstractText>ApHCM was classified into three types as pure focal (n = 81), pure diffuse (n = 70) and mixed type (n = 31) according to patterns of hypertrophy. Incidence of atrial fibrillation (5% for pure focal vs. 11% for pure diffuse vs. 23% for mixed type, p < 0.05) and left atrial volume index (30.9 +/- 11.8, 35.7 +/- 14.8, and 41.3 +/- 15.9 ml/m(2), respectively, p < 0.001) were significantly different among subtypes. Peak systolic (6.6 +/- 1.0 vs. 6.3 +/- 1.2 vs. 5.9 +/- 1.1 cm/s, respectively, p < 0.05), diastolic (5.1 +/- 1.8 vs. 5.0 +/- 1.2 vs. 4.1 +/- 1.3 cm/s, respectively, p < 0.05) mitral annular velocity, E/E' (13.3 +/- 4.2 vs. 13.7 +/- 5.4 vs. 16.1 +/- 6.1, respectively, p < 0.05) were also significantly different.</AbstractText>ApHCM contains three morphologically distinct phenotypes and detailed subtyping is important in the prediction of development of atrial fibrillation, left atrial volume index and left ventricular longitudinal function.</AbstractText> |
8,272 | T5 spinal cord transection increases susceptibility to reperfusion-induced ventricular tachycardia by enhancing sympathetic activity in conscious rats. | We recently documented that paraplegia (T(5) spinal cord transection) alters cardiac electrophysiology and increases the susceptibility to ventricular tachyarrhythmias induced by programmed electrical stimulation. However, coronary artery occlusion is the leading cause of death in industrially developed countries and will be the major cause of death in the world by the year 2020. The majority of these deaths result from tachyarrhythmias that culminate in ventricular fibrillation. beta-Adrenergic receptor antagonists have been shown to reduce the incidence of sudden cardiac death. Therefore, we tested the hypothesis that chronic T(5) spinal cord transection increases the susceptibility to clinically relevant ischemia-reperfusion-induced sustained ventricular tachycardia due to enhanced sympathetic activity. Intact and chronic (4 wk after transection) T(5) spinal cord-transected (T(5)X) male rats were instrumented to record arterial pressure, body temperature, and ECG. In addition, a snare was placed around the left main coronary artery. The susceptibility to sustained ventricular tachycardia produced by 2.5 min of occlusion and reperfusion of the left main coronary artery was determined in conscious rats by pulling on the snare. Reperfusion culminated in sustained ventricular tachycardia in 100% of T(5)X rats (susceptible T(5)X, 10 of 10) and 0% of intact rats [susceptible intact, 0 of 10 (P < 0.05, T(5)X vs. intact)]. Beta-adrenergic receptor blockade prevented reperfusion-induced sustained ventricular tachycardia in T(5)X rats [susceptible T(5)X 0 of 8, 0% (P < 0.05)]. Thus paraplegia increases the susceptibility to reperfusion-induced sustained ventricular tachycardia due to enhanced sympathetic activity. |
8,273 | Right atrial infarction, atrial arrhythmia and inferior myocardial infarction form a missed triad: a case report and review of the literature. | Atrial infarction is rarely diagnosed before death because of its characteristically subtle and nonspecific electrocardiographic findings. These findings may be overshadowed by changes associated with concomitant ventricular infarction. A case of right atrial infarction accompanied by inferior myocardial infarction with rapid decompensated atrial fibrillation is reported. To increase awareness and knowledge of a complicated diagnosis, the present case is described in the context of a review of the relevant literature.</Abstract><AuthorList CompleteYN="Y"><Author ValidYN="Y"><LastName>Shakir</LastName><ForeName>Douraid K</ForeName><Initials>DK</Initials><AffiliationInfo><Affiliation>Cardiology Department, Hamad Medical Corporation, Doha, Qatar. dshakir@hotmail.com</Affiliation></AffiliationInfo></Author><Author ValidYN="Y"><LastName>Arafa</LastName><ForeName>Salah O E</ForeName><Initials>SO</Initials></Author></AuthorList><Language>eng</Language><PublicationTypeList><PublicationType UI="D002363">Case Reports</PublicationType><PublicationType UI="D016428">Journal Article</PublicationType></PublicationTypeList></Article><MedlineJournalInfo><Country>England</Country><MedlineTA>Can J Cardiol</MedlineTA><NlmUniqueID>8510280</NlmUniqueID><ISSNLinking>0828-282X</ISSNLinking></MedlineJournalInfo><CitationSubset>IM</CitationSubset><MeshHeadingList><MeshHeading><DescriptorName UI="D015906" MajorTopicYN="N">Angioplasty, Balloon, Coronary</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D001281" MajorTopicYN="N">Atrial Fibrillation</DescriptorName><QualifierName UI="Q000175" MajorTopicYN="Y">diagnosis</QualifierName><QualifierName UI="Q000209" MajorTopicYN="N">etiology</QualifierName><QualifierName UI="Q000628" MajorTopicYN="N">therapy</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D017023" MajorTopicYN="N">Coronary Angiography</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D004554" MajorTopicYN="N">Electric Countershock</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D004562" MajorTopicYN="N">Electrocardiography</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D006325" MajorTopicYN="Y">Heart Atria</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D006801" MajorTopicYN="N">Humans</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D008297" MajorTopicYN="N">Male</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D008875" MajorTopicYN="N">Middle Aged</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D009203" MajorTopicYN="N">Myocardial Infarction</DescriptorName><QualifierName UI="Q000150" MajorTopicYN="N">complications</QualifierName><QualifierName UI="Q000175" MajorTopicYN="Y">diagnosis</QualifierName><QualifierName UI="Q000628" MajorTopicYN="N">therapy</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D015607" MajorTopicYN="N">Stents</DescriptorName></MeshHeading></MeshHeadingList><OtherAbstract Type="Publisher" Language="fre">L’infarctus de l’oreillette est rarement diagnostiqué avant le décès en raison de ses caractéristiques électrocardiographiques discrètes et non spécifiques. Les modifications associées à un infarctus ventriculaire concomitant peuvent éclipser ces observations. On présente le cas d’un infarctus de l’oreillette droite accompagnée d’un infarctus du myocarde inférieur et d’une fibrillation auriculaire à décompensation rapide. Pour mieux faire connaître ce diagnostic complexe, le présent cas est décrit dans le contexte d’une analyse bibliographique pertinente. |
8,274 | Spatiotemporal relationship between intracellular Ca2+ dynamics and wave fragmentation during ventricular fibrillation in isolated blood-perfused pig hearts. | Normal "master-slave" relationship between the action potential (AP) and intracellular Ca2+ transient (Ca(i)T) is sometimes altered during ventricular fibrillation (VF). The nature of AP/Ca(i)T dissociation during VF and its role in inducing wavebreaks (WBs) remain unclear. We simultaneously mapped AP (RH237) and Ca(i)T (Rhod-2) during VF in blood-perfused pig hearts. We computed AP and Ca(i)T dominant frequency (DF) and Ca(i)T delay in each AP cycle. We identified WBs as singularity points in AP phase movies and sites of conduction block (CB) as sites where an AP wavefront failed to propagate. We analyzed spatiotemporal relationship between abnormal AP/Ca(i)T sequences and CB sites. We used a calcium chelator (BAPTA-AM) to abolish Ca(i)T and test its involvement in WB formation. During VF, the DF difference between AP and Ca(i)T was <10% of the respective values in 95% of pixels, and 80% of all Ca(i)T upstrokes occurred during the initial 25% of the excitation cycle. Aberrant sequences of AP and Ca(i)T occurred almost exclusively near CB sites but could be traced to normal wavefront sequences away from CB sites. Thus, apparent AP/Ca(i)T dissociation was largely attributable to spatial uncertainty of the absolute position of block of each wave. BAPTA-AM reduced Ca(i)T amplitude to 30.5+/-12.9% of control and the DF of AP from 12.2+/-1.6 to 10.4+/-1.3 Hz (P<0.01), but did not significantly alter WB incidence (0.76+/-0.19 versus 0.72+/-0.19 SP/mm2). These results do not support presence of spontaneous, non-voltage-gated Ca(i)Ts during VF and suggest that AP/Ca(i)T dissociation is a consequence rather than a cause of wave fragmentation. |
8,275 | Dispersion of refractoriness and induction of reentry due to chaos synchronization in a model of cardiac tissue. | Ventricular fibrillation is a lethal condition caused by multiple chaotically wandering electrical wavelets in the heart, reentering their own and each other's territories. The development of effective therapies requires a detailed understanding of how these reentrant waves are initiated. In this Letter, we demonstrate a novel mechanism for inducing reentry, in which chaos synchronization causes large-scale heterogeneities of refractoriness transverse to the direction of propagation. These regions of increased refractoriness create localized conduction block, which induces spiral wave reentry. |
8,276 | Noncompaction and neuromuscular disease with positive troponin-T in a nonagenerian. | In a 94-year-old male with a history of atrial fibrillation, aortic stenosis, heart failure, apical thrombus, arterial hypertension, aneurysm of the abdominal aorta, and a urinary bladder carcinoma, cardiologic investigations revealed pulmonary rales, enlarged heart, absolute arrhythmia, and positive troponin-, myocardial thickening, enlarged cardiac cavities, hypocontractility, aortic stenosis, slight aortic insufficiency, severe mitral insufficiency, and surprisingly left ventricular hypertrabeculation. Upon neurological investigations, a polyneuropathy was suspected but a myopathy not completely excluded. The presented case shows that LVHT occurs also in nonagenarians and is associated with neuromuscular disease and positive troponin-T, in the absence of ischemic heart disease or severe renal failure. The cause of troponin-T-positivity remains multi-factorial. |
8,277 | Strict versus moderate glucose control after resuscitation from ventricular fibrillation. | Elevated blood glucose is associated with poor outcome in patients resuscitated from out-of-hospital cardiac arrest (OHCA). Our aim was to determine whether strict glucose control with intensive insulin treatment improves outcome of OHCA patients.</AbstractText>A randomized, controlled trial.</AbstractText>Two university hospital intensive care units.</AbstractText>Ninety patients resuscitated from OHCA with ventricular fibrillation detected as the initial rhythm were treated with therapeutic hypothermia.</AbstractText>Patients were randomized into two treatment groups: a strict glucose control group (SGC group), with a blood glucose target of 4-6 mmol/l, or a moderate glucose control group (MGC group), with a blood glucose target of 6-8 mmol/l. Both groups were treated with insulin infusion for 48 h, because a control group with no treatment was considered unethical.</AbstractText>Baseline data were similar in both groups. In the SGC group 71% of the glucose measurements were within the target range compared with 41% in the MGC group. Median glucose was 5.0 mmol/l in the SGC group and 6.4 mmol/l in the MGC group. The occurrence of moderate hypoglycemic episodes was 18% in the SGC group and 2% in the MGC group (p = 0.008). No episodes of severe hypoglycemia occurred. Mortality by day 30 was 33% in the SGC group and 35% in the MGC group (p = 0.846); the difference was 2% (95% CI -18% to +22%).</AbstractText>We found no additional survival benefit from strict glucose control compared with moderate glucose control with a target between 6 and 8 mmol/l in OHCA patients.</AbstractText> |
8,278 | [Patch angioplasty for superior vena cava syndrome after pacemaker implantation and maze procedure for chronic atrial fibrillation; report of a case]. | In 1984, the patient, a 68-year-old male, underwent pacemaker implantation for the treatment of sick sinus syndrome. Because of a postoperative pocket infection, the atrial lead was removed ; but it was difficult to extract the ventricular lead, which was therefore left in place. While under observation, transient facial edema, atrial fibrillation, chest discomfort were noted. Chest X-ray revealed that the ventricular lead had gradually moved to the side of the pulmonary artery. Pre-operative phlebography of the internal jugular vein led to a diagnosis of obstruction of the superior vena cava (SVC). Maze procedure was performed and the lead was readily removed through the right atriotomy. The obstruction was incised and the lesion reconstructed by using a patch by the autologous pericardium. The satisfactory return of circulation was confirmed by postoperative imaging. At the discharge, an electrocardiograph indicated a sinus rhythm and a heart rate was 82 ppm. The facial edema and thoracic symptoms had been completely eliminated. |
8,279 | Effect of electrode surface area on thresholds for AC stimulation and ventricular fibrillation. | Unintended, weak AC stimulation (leakage currents) from medical devices can cause blood pressure collapse and ventricular fibrillation (VF), potentially even death. Yet, little is understood about AC cardiac stimulation. The objective of this paper is to establish the relationship between the stimulation and VF thresholds for electrode size and stimulation frequency. Twenty-four retired male breeder guinea pigs were anesthetized with isoflurane, a tracheotomy and thoracotomy were performed, and vitals were monitored using the lead II ECG and an optical plethysmograph. The circular flat ends of eleven stainless steel rods were used as electrodes with areas ranging from 0.1 to 26.79 mm2. In the first study, 60-Hz AC stimuli of 5 s duration were delivered with strengths from 25-3000 microA or until VF was induced. In the second group, the current thresholds at 20, 40, 80, and 160 Hz were determined at electrode areas of 0.2, 2.01, and 16.4 mm2. Reactions were categorized as having no effect, having some effect (EFFECT, typically blood pressure collapse), and inducing VF. On a log-log scale, electrode radii had a piecewise-linear relationship with the current thresholds for EFFECT (p < 0.005) and VF (p < 0.01). The liminal area determined by the piecewise-linear fit was 2.0 and 2.84 mm2 for EFFECT and VF, respectively. Above the liminal area, the threshold increased proportional to r(1.25) and r(0.95) (r = radius of electrode), for EFFECT and VF, respectively. Based on these experimental results, we present a theoretical framework to explain the electrode size-stimulation threshold variation for both low strength AC stimulation and VF initiation. |
8,280 | In-hospital arrhythmias in patients with acute myocardial infarction - the relation to the reperfusion strategy and their prognostic impact. | Arrhythmias are frequent complication in patients with acute myocardial infarction (MI). The importance of accelerated idioventricular rhythm (AIVR), ventricular fibrillation or tachycardia (VF, VT), atrial fibrillation or flutter (AF) and bradycardias is considered and discussed in this review article. The value of the presence of AIVR as a marker of reperfusion is small, but in combination with other non-invasive markers (ST-segment resolution), its presence is connected with a high probability of successful reperfusion. Early ventricular arrhythmias are a serious complication of MI. However, if they are revealed and treated in time, they apparently do not represent a negative prognostic factor. Later occurred VF or VT are more a symptom of larger MI. AF, which is not directly life-threatening for the patients, frequently occurs in patients with larger MI and it is an independent predictor of a poor long-term prognosis of these patients. The early and successful reperfusion therapy is the best anti-arrhythmic therapeutic method in patients with MI. |
8,281 | Obstructive hypertrophic cardiomyopathy is associated with enhanced thrombin generation and platelet activation. | To investigate the association of left ventricular outflow tract (LVOT) obstruction with blood coagulation, platelet activity and inflammatory response in patients with hypertrophic cardiomyopathy (HCM) and sinus rhythm.</AbstractText>In 42 patients with HCM with sinus rhythm, including 16 patients with resting LVOT obstruction (gradient > or = 30 mm Hg) and 29 age- and sex-matched controls, markers of thrombin generation (thrombin-antithrombin complex (TAT), prothrombin fragment 1+2 (F1+2)), platelet activation (soluble CD40 ligand (sCD40L), beta-thromboglobulin (beta-TG), P-selectin) and inflammation (C-reactive protein (CRP), interleukin (IL)6, tumour necrosis factor-alpha (TNFalpha)) were determined.</AbstractText>Thrombin, platelet and inflammatory markers were higher in the entire HCM group than in controls (p<0.005 for all compared parameters). Compared with non-obstructive HCM, obstructive HCM was associated with increased thrombin formation (TAT, F1+2), platelet activation (sCD40L, beta-TG, P-selectin) and both CRP and IL6 levels. Only the level of TNFalpha was similar in both forms of HCM. In contrast, a comparison of non-obstructive HCM with controls showed that all these variables (except for P-selectin) were similar; P-selectin was higher in non-obstructive HCM. The LVOT gradient correlated positively with all the raised blood markers (r from 0.39 to 0.73; p<0.05), except for TNFalpha. In multiple regression analysis models, the LVOT gradient was the only independent predictor of TAT (R(2) = 0.61; p<0.001), sCD40L (R(2) = 0.59; p<0.001), F1+2 (R(2) = 0.55; p = 0.002), P-selectin (R(2) = 0.49; p = 0.004) and beta-TG (R(2) = 0.38; p = 0.005) in patients with HCM.</AbstractText>LVOT obstruction is independently associated with enhanced thrombin generation and platelet activity in patients with HCM with sinus rhythm.</AbstractText> |
8,282 | Impact of atrial fibrillation in heart failure with normal ejection fraction: a clinical and echocardiographic study. | The clinical significance of atrial fibrillation (AF) in heart failure with normal ejection fraction (HFNEF) remains undetermined.</AbstractText>We compared the clinical and echocardiographic characteristics among 238 patients hospitalized for HF. Using the cutoff of left ventricular EF of 50%, there were 146 patients with HFNEF (AF = 42) and 92 with systolic HF (AF = 30). When compared among HFNEF, the New York Heart Association (NYHA) class (2.61 +/- 0.51 versus 2.21 +/- 0.46; P < .05), 6-minute walk distance (279.7 +/- 66.0 versus 338.0 +/- 86.1 m; P < .01), quality of life score (26.1 +/- 14.3 versus 19.5 +/- 10.3; P < .05), and previous HF hospitalization were significantly worse in the AF group. These variables were significantly better in HFNEF than systolic HF with sinus rhythm, but the differences were not detected among those with AF. Patients with HFNEF and AF were associated with more severe diastolic dysfunction when compared to sinus rhythm. With a median follow-up of 10.5 months, the proportion of HFNEF patients in AF with recurrent HF hospitalization or death was significantly higher than those in sinus rhythm (28.6% versus 10.6%; P < .01). Both AF and restrictive diastolic dysfunction were independent predictors of HF hospitalization or death in HFNEF.</AbstractText>Patients with HFNEF and AF were associated with more severe diastolic dysfunction and worse clinical outcomes than those in sinus rhythm.</AbstractText> |
8,283 | [Early and middle outcomes of total arterial revascularization using exclusively internal mammary artery and radial artery]. | To evaluate the early and mid-results of the use of the radial artery alongside the internal mammary artery for complete arterial revascularization in coronary bypass surgery.</AbstractText>From January 1999 to January 2005, 123 patients with coronary artery disease with lesions in more than one branch (target vessel), 114 males and 9 females, aged 51.9 +/- 9.4 (32 approximately 74) underwent coronary artery surgery after the complete arterial revascularization pattern. Before the operation the left ventricular ejection fraction (EF) value ranged 30% approximately 78%, and 24 patients (21.1%) had poor ejection fraction (with the EF < 50%). Sixty-four patients (52%) had previous myocardial infarction. Four patients with unstable angina received urgent operation. 36 patients (29.3%) had disease of the left main trunk. 74% of the patients underwent off-pump bypass technique. The mean number of distal anastomoses was 2.6 +/- 0.4 per patient. 20 patients were followed up for 62 +/- 12.8 months (36 approximately 80 months).</AbstractText>The early mortality was 0.8%. Postoperative complications included arterial fibrillation in seven patients (5.7%). One patient underwent IABP insertion because of low cardiac output, 3 patients were re-admitted because of heart failure, angina and arrhythmias. Three patients died of cardiac events. One patient underwent redo-CABG due to recurrent myocardial infarction and one patient underwent percutaneous coronary intervention because of stenosis of the arterial graft.</AbstractText>Complete arterial revascularization using radial and mammary arteries provides excellent early results, showing a low mid-term complication rate and surgical morbidity.</AbstractText> |
8,284 | Electric field perturbations of spiral waves attached to millimeter-size obstacles. | Reentrant spiral waves can become pinned to small anatomical obstacles in the heart and lead to monomorphic ventricular tachycardia that can degenerate into polymorphic tachycardia and ventricular fibrillation. Electric field-induced secondary source stimulation can excite directly at the obstacle, and may provide a means to terminate the pinned wave or inhibit the transition to more complex arrhythmia. We used confluent monolayers of neonatal rat ventricular myocytes to investigate the use of low intensity electric field stimulation to perturb the spiral wave. A hole 2-4 mm in diameter was created in the center to pin the spiral wave. Monolayers were stained with voltage-sensitive dye di-4-ANEPPS and mapped at 253 sites. Spiral waves were initiated that attached to the hole (n = 10 monolayers). Electric field pulses 1-s in duration were delivered with increasing strength (0.5-5 V/cm) until the wave terminated after detaching from the hole. At subdetachment intensities, cycle length increased with field strength, was sustained for the duration of the pulse, and returned to its original value after termination of the pulse. Mechanistically, conduction velocity near the wave tip decreased with field strength in the region of depolarization at the obstacle. In summary, electric fields cause strength-dependent slowing or detachment of pinned spiral waves. Our results suggest a means to decelerate tachycardia that may help to prevent wave degeneration. |
8,285 | [Electrical storm]. | Electrical storm is defined as repeated occurrence of severe ventricular arrhythmias requiring multiple cardioversions, two or more or three or more following different studies. The clinical aspect can sometimes be made of multiple, self aggravating, life threatening accesses. There are three main clinical circumstances of occurrence: in patients equipped with intracardiac defibrillators, during the acute phase of myocardial infarction and in Brugada syndrome. 10 to 15% of patients with cardiac defibrillators are subject to electrical storms in a period of two years. The causative arrhythmia is most often ventricular tachycardia than ventricular fibrillation, especially in secondary prevention and if the initial arrhythmias justifying the device was a ventricular tachycardia. Precipitaing factors are present in one third of cases, mainly acute heart failure, ionic disorders and arrhythmogenic drugs. Predictive factors are age, left ventricular ejection fraction<35% and renal insufficiency. Arrhythmia reduction is obtained by electrical shock in 50% of cases, antitachycardi stimulation in 30% and in 20% by association of the two. Treatment, after elimination of inappropriate shocks, is mainly based on beta-blockers and amiodarone, class I antiarrhythmics, lidocaïne or bretylium in some cases, and sedation pushed to general anesthesia in some cases. Radio-frequency ablation and even heart transplantation have been proposed in extreme cases. Quinidine has been proved efficient in cases of Brugada syndrome. |
8,286 | Prognostic value of exercise tolerance testing in asymptomatic chronic nonischemic mitral regurgitation. | In many heart diseases, exercise tolerance testing (ETT) has useful functional correlates and/or prognostic value. However, its predictive value in mitral regurgitation (MR) is undefined. To determine whether ETT descriptors predict death or indications for mitral valve surgery in patients with MR, we prospectively followed, for 7 +/- 3 end-point-free years, a cohort of 38 patients with chronic severe nonischemic MR who underwent modified Bruce ETT; all lacked surgical indications at study entry. Their baseline exercise descriptors were also compared with those from 46 patients with severe MR who, at entry, already had reached surgical indications. End points during follow-up in the cohort included sudden death (n = 1), heart failure symptoms (n = 2), atrial fibrillation (n = 4), left ventricular (LV) ejection fraction <60% (n = 2), LV systolic dimensions > or =45 mm (n = 12) and >40 mm (n = 11), LV ejection fraction <60% plus LV systolic dimensions > or =45 mm (n = 3), and heart failure plus LV systolic dimensions > or =45 mm plus LV ejection fraction <60% (n = 1). In univariate analysis, exercise duration (p = 0.004), chronotropic response (p = 0.007), percent predicted peak heart rate (p = 0.01), and heart rate recovery (p <0.02) predicted events; in multivariate analysis, only exercise duration was predictive (p <0.02). Average annual event risk was fivefold lower (4.62%) with an exercise duration > or =15 versus <15 minutes (average annual risk 23.48%, p = 0.004). Relative risks in patients with and without exercise-inducible ST-segment depression were comparable (< or =1.3, p = NS) whether defined at entry and/or during follow-up. Exercise duration, but not prevalence of exercise-inducible ST-segment depression, was lower (p <0.001) in patients with surgical indications at entry versus initially end-point-free patients. In conclusion, in asymptomatic patients with chronic severe nonischemic MR and no objective criteria for operation, progression to surgical indications generally is rapid. However, those with excellent exercise tolerance have a relatively benign course. Exercise-inducible ST-segment depression has no prognostic value in this population. |
8,287 | Comparison of Afro-Caribbean patients presenting in heart failure with normal versus poor left ventricular systolic function. | Data suggest that heart failure (HF) in Afro-Caribbean patients may be more often associated with preserved left ventricular (LV) systolic function, LV hypertrophy, and probable LV diastolic dysfunction than in other populations. Echocardiographic results on all patients referred for HF in a contemporary Afro-Caribbean population were reviewed, comparing findings in patients with and without preserved LV systolic function with. Echocardiographic findings included left atrial dimension, LV systolic and diastolic dimensions, ventricular septal and posterior wall thicknesses, right ventricular dimension, valve abnormality, or pericardial effusion. LV shortening fraction and ejection fraction were calculated. Age, gender, and presence of atrial fibrillation were recorded. Results from patients with preserved LV systolic function (LV shortening fraction >0.27) were compared with those with poor LV systolic function. There were 505 patients with HF with adequate studies; mean age +/- SD was 64 +/- 15 years, 46% were men, 17% had atrial fibrillation, and 285 of 505 (57%) had preserved LV systolic function. Those with preserved LV systolic function were no different in age (64 +/- 15 vs 64 +/- 14 years, p = 0.98) but were less likely to be men (40% vs 54%, p <0.01). They were less likely to have a dilated left atrium (61% vs 81%, p <0.001) or increased LV diastolic dimension (8% vs 63%, p <0.001). They were more likely to have increased ventricular septal or posterior wall hypertrophy (84% vs 66%, p <0.001) or other abnormal findings, including an abnormal valve, right ventricular enlargement, increased septal to posterior wall thickness ratio, or pericardial effusion (25% vs 6%, p <0.001). The presence of atrial fibrillation was no different (14% vs 20%, p = 0.10). In conclusion, most Afro-Caribbean patients with HF have preserved LV systolic function with high rates of LV hypertrophy, septal hypertrophy, and other echocardiographic abnormalities. |
8,288 | Near miss sudden cardiac death on a young patient with repaired atrioventricular septal defect. | Patients with congenital heart disease often face the prospect of long-term haemodynamic or arrhythmic complications for which lifelong follow-up in specialist adult congenital heart disease (ACHD) centres is required. We describe the case of a 25-year-old man with repaired atrioventricular septal defect who was referred to our centre after a ventricular fibrillation arrest. Serial echocardiograms in previous years had shown progressive severe left ventricular outflow obstruction, but the patient had not been operated on as he was deemed asymptomatic and reluctant to consider surgery. Management and criteria for further intervention in ACHD patients often differ from those of patients with acquired heart disease and reliance on symptoms alone is not good practice and may prove catastrophic. |
8,289 | Preoperative clinical status but not waiting time predicts in-hospital outcomes of surgery in patients with left main coronary artery stenosis. | Contoversy exists about the optimal operation time of the patients with left main coronary artery (LMCA) stenosis. We therefore, aimed to investigate the effect of waiting time on in-hospital morbidity and mortality in patients with LMCA stenosis and identify the risk factors associated with adverse cardiovascular events before and during surgery. One hundred seventy six patients with LMCA stenosis were divided into two groups according to the time period between coronary angiography and coronary artery bypass surgery (group 1: <or= 7 days, 94 patients; and group 2: > 7 days, 82 patients). Primary end points were death and major adverse cardiac event (MACE): in-hospital death, sustained ventricular tachycardia or ventricular fibrillation development, postoperative stay in the intensive care > 48 hrs and in hospital > 9 days. Demographic and clinical characteristics of patients in groups 1 and 2 were comparable. There was no difference between the two groups in terms of in-hospital morbidity, mortality and MACE. When we analyzed the differences between the patients with and without MACE, the patients who experienced MACE were older (p = 0.001), and had higher degree of LMCA stenosis (p = 0.01), higher degree of right coronary artery stenosis (p = 0.02), higher blood urea level (p = 0.003), and higher incidence of unstable angina or myocardial infarction within 2 weeks (p = 0.001). Independent risk factors for MACE were unstable angina or myocardial infarction within 2 weeks, age more than 70 years and stenosis more than 75% in the LMCA. These results suggest that preoperative clinical status but not waiting time predicts in-hospital surgical outcomes in LMCA stenosis. |
8,290 | Therapeutic trial of granulocyte-colony stimulating factor for dilated cardiomyopathy in three dogs. | Three dogs were presented to us for evaluation of cardiac problems. Electrocardiographic recordings revealed severe tachyarrhythmia and atrial fibrillation with ventricular tachycardia in 2 of the 3 dogs. The echocardiographic findings of the 3 dogs revealed markedly decreased fractional shortening and a marked increase in E-point septal separation. Based on the results of electrocardiographic and echocardiographic evaluation, the 3 dogs were diagnosed as dilated cardiomyopathy (DCM). The dogs were treated with conventional cardiac medication, but cardiac function did not improve and the clinical signs remained. We subsequently attempted treatment with granulocyte-colony stimulating factor (G-CSF; 10 microg/kg, subcutaneously). The specific purpose of G-CSF therapy for DCM was to improve cardiac function and a significant improvement in cardiac function was confirmed. The three dogs had no treatment side effects. This case report suggests that G-CSF might have therapeutic effects for medically refractory DCM in dogs. |
8,291 | The transmural activation sequence in porcine and canine left ventricle is markedly different during long-duration ventricular fibrillation. | Humans are more similar in transmural Purkinje and cardiac ion channel distributions to dogs than pigs. The Purkinje network in pigs is transmural but confined to the endocardium in dogs. Little is known about intramural activation during long-duration ventricular fibrillation (LDVF) given these differences. We tested the hypothesis that the transmural activation sequence is similar in sinus rhythm (SR) and LDVF in dogs as well as pigs, but different between species.</AbstractText>In six pigs and seven dogs, 50-60 plunge needles (six electrodes, 2-mm spacing) were placed throughout the left ventricle. Unipolar recordings were made for >10 minutes of LDVF. SR and LDVF activation times were grouped into waves by linking activations along each needle. Origin (earliest activation) and propagation direction were determined for each wave. The mean wave origin was significantly more endocardial in dogs than pigs for SR and 1 through 10 minutes of LDVF. Predominant propagation direction in LDVF and SR was endocardial to epicardial in dogs, but the opposite or equal in both directions in pigs. Fastest activation rate was epicardial in pigs, but endocardial in dogs with an increasing endocardial-to-epicardial activation rate gradient as LDVF progressed in dogs but not pigs.</AbstractText>The transmural activation sequence in SR and LDVF is markedly different between pigs and dogs. These differences may be related to differences in Purkinje fiber and ion channel distributions and suggest that dogs are a better model for investigating activation sequences during LDVF, given the similarities with humans.</AbstractText> |
8,292 | Clinical significance of macroscopic T-wave alternans after sodium channel blocker administration in patients with Brugada syndrome. | Macroscopic T-wave alternans (TWA) is sometimes observed after sodium channel blocker administration in patients with Brugada syndrome (BS), but little is known about the association between occurrence of TWA and clinical characteristics in BS patients. We investigated the association between spontaneous ventricular fibrillation (VF) occurrence and TWA after pilsicainide, a sodium channel blocker administration in BS patients.</AbstractText>We administered pilsicainide at a dose of 1 mg/kg to 77 BS patients (76 males and one female; mean age, 48.4 years) and examined the association between TWA after pilsicainide administration and clinical characteristics, including age, spontaneous VF, syncope, family history of sudden death, spontaneous coved ST elevation, late potentials (LP), induction of VF by programmed electrical stimulation, and SCN5A mutation. None of the patients had TWA before pilsicainide administration, but TWA became apparent in 17 (22.1%) of the patients after pilsicainide administration. Patients with TWA had a significantly higher incidence of spontaneous VF (52.9% vs 8.3%, P < 0.001) and syncope (58.8% vs 26.7%, P < 0.05) than did patients without TWA. Then, we focused on the association between spontaneous VF and clinical characteristics. Patients with spontaneous VF had a significantly higher incidence of TWA (64.3% vs 12.7%, P < 0.001) and LP positive (92.9% vs 56.5%, P < 0.01) than did patients without spontaneous VF. In multivariate analysis, TWA (P = 0.001) and LP (P = 0.047) appeared as the independent predictor for spontaneous VF.</AbstractText>TWA after pilsicainide administration is associated with a high risk of clinical VF in patients with BS.</AbstractText> |
8,293 | Early recurrence of ventricular fibrillation after successful defibrillation during prolonged global ischemia in isolated rabbit hearts. | The mechanisms that lower the efficacy of electrical defibrillation during prolonged global ischemia remain unclear.</AbstractText>Epicardial activation patterns during attempted electrical defibrillation were studied in 18 Langendorff-perfused rabbit hearts at baseline, after 5-minute no-flow global ischemia and after 10-minute reperfusion. DFT(50) (voltage required to achieve 50% probability of successful defibrillation) was determined at each stage. Defibrillation was considered successful if postshock sinus/idioventricular rhythm was present. Prolonged global ischemia converted type 1 VF (multiple wandering wavelets) into type 2 VF (repetitive epicardial breakthroughs, REBs). The mean DFT(50) after 5-minute ischemia (96 +/- 39 V) was significantly lower when compared with that at baseline (154 +/- 47 V, P < 0.0001) and after 10-minute reperfusion (145 +/- 47 V, P < 0.001). However, the incidence of early (within 10 seconds) VF recurrence after successful shock during prolonged global ischemia (23 of 78, 29.5%) was much higher than that at baseline (2 of 60, 3.3%) and after 10-minute reperfusion (5 of 63, 7.9%; P < 0.0001). Mapping data showed that the VF wavefronts during prolonged global ischemia were initially halted by the shock, followed by one to five ventricular escape beats. These beats then triggered REBs and early VF recurrence. In eight out of 11 episodes, the REBs before and after successful shock arose from the same location near the interventricular septum.</AbstractText>There is a significant reduction of DFT(50) during prolonged global ischemia. However, defibrillation appears to fail when the preexisting REBs near the interventricular septum induce early VF recurrence. Shock per se cannot eliminate the substrates of these REBs.</AbstractText> |
8,294 | Azimilide for the treatment of atrial fibrillation, atrial flutter, and paroxysmal supraventricular tachycardia: results of a randomized trial and insights on the concordance of symptoms and recurrent arrhythmias. | Azimilide hydrochloride is an investigational antiarrhythmic medication that had shown evidence of efficacy in prolonging the time to recurrence of atrial fibrillation (AF) or atrial flutter (AFL) and paroxysmal supraventricular tachycardia (PSVT). This study was designed to confirm efficacy of 125 mg daily azimilide.</AbstractText>The primary endpoint was ECG-documented recurrence of AF, AFL, or PSVT, followed for a maximum of 180 days. Four hundred eighty-two patients were enrolled in the United States and Canada (422 with AF or AFL and 60 with PSVT). The primary efficacy analysis included 402 patients with AF-AFL and 56 patients with PSVT. There was no significant difference in the time to first recurrence of symptomatic supraventricular arrhythmia in the AF-AFL stratum (median of 38 days for azimilide versus 27 days for placebo; hazard ratio [HR] of 1.14, P = 0.29). Similarly, there was no difference in time to recurrence in the PSVT stratum (>180 days for azimilide versus 135 days for placebo; HR = 1.28, P = 0.55). There were three deaths in the azimilide group and one in the placebo group. Four patients had nonsustained ventricular tachycardia (one torsades de pointes), all in the azimilide group. Asymptomatic recurrence was frequent in the AF-AFL group (8% with azimilide and 11% with placebo), but was absent in the PSVT group. False recurrence was common in both groups.</AbstractText>Azimilide 125 mg daily was not associated with significant prolongation of the time to recurrent symptomatic supraventricular arrhythmias. There was substantial discordance between symptoms and recurrence.</AbstractText> |
8,295 | A pilot study in hemodialysis of an electrophysiological tool to measure sudden cardiac death risk. | The hemodialysis procedure may play a role in the elevated risk of sudden cardiac death seen in hemodialysis patients.</AbstractText>Microvolt T wave alternans, a promising noninvasive electrophysiological test developed to measure sudden cardiac death risk, was used to test the hypotheses that high-risk hemodialysis patients commonly manifest cardiac electrophysiology that is associated with higher sudden death risk in nondialysis patients and that the hemodialysis procedure modifies cardiac electrophysiology in a manner predisposing to malignant ventricular arrhythmias. To test this hypothesis, microvolt T wave alternans tracings were done in 9 patients before and immediately after an early week hemodialysis session.</AbstractText>7 of 9 individuals had non-negative (i.e. higher risk) tracings either before or after hemodialysis. 2 of 4 subjects with tracings initially negative before hemodialysis became non-negative after hemodialysis.</AbstractText>This pilot study provides the first objective preliminary evidence using microvolt T wave alternans that high-risk hemodialysis patients commonly exhibit abnormal cardiac repolarization and that hemodialysis treatments can acutely alter repolarization in a potentially harmful manner.</AbstractText> |
8,296 | Modelling of the ventricular conduction system. | The His-Purkinje conduction system initiates the normal excitation of the ventricles and is a major component of the specialized conduction system of the heart. Abnormalities and propagation blocks in the Purkinje system result in abnormal excitation of the heart. Experimental findings suggest that the Purkinje network plays an important role in ventricular tachycardia and fibrillation, which is the major cause of sudden cardiac death. Nowadays an important area in the study of cardiac arrhythmias is anatomically accurate modelling. The majority of current anatomical models have not included a description of the Purkinje network. As a consequence, these models cannot be used to study the important role of the Purkinje system in arrhythmia initiation and maintenance. In this article we provide an overview of previous work on modelling of the Purkinje system and report on the development of a His-Purkinje system for our human ventricular model. We use the model to simulate the normal activation pattern as well as abnormal activation patterns resulting from bundle branch block and bundle branch reentry. |
8,297 | [Clinical, echocardiographic and prognostic evaluation of atrial fibrillation in patients with heart failure]. | We aimed to assess the prevalence of atrial fibrillation (AF) in a general heart failure (HF) population admitted to a HF unit, analyze the parameters associated with AF, and evaluate its prognostic significance.</AbstractText>389 patients, 64 with AF at the first visit. Mean (SD) age was 65.38 (10.77) years and 72.5% were men. The main etiology was ischemic heart disease (59.9%). Mean ejection fraction (EF) was 32.25% (13%). Vital status at 2 years was available in 377 patients (97%), 314 in sinus rhythm (SR) and 63 in AF.</AbstractText>The prevalence of AF was 15.8%. AF was associated with: older age, female gender, valvular and hypertensive etiology, longer time since the onset of HF symptoms, higher EF, higher left atrium diameter, degree of mitral regurgitation, and lower quality of life, but not with the NYHA functional class. The 2-years mortality (16.7%) was significantly higher in patients with AF (33.3% vs 18.4%; OR = 2.20; 95% confidence interval, 1.21-4). However, when adjusted for other relevant variables such as age, NYHA functional class, ejection fraction, sex and etiology, AF did not remain as an independent prognostic factor. The strongest mortality differences between patients with AF and those with SR where observed in ischemic heart disease and dilated cardiomyopathy.</AbstractText>AF was associated mainly with age, valvular and hypertensive etiology, higher left atrium diameter and lower end-systolic left ventricular diameter. Two years mortality was significantly higher in patients with AF, although other parameters such as age and NYHA functional class had a higher prognostic value.</AbstractText> |
8,298 | Angiotensin II type 1 receptor inhibition is associated with reduced tachyarrhythmia-induced ventricular interstitial fibrosis in a goat atrial fibrillation model. | Using a goat animal model, we tested the hypothesis that angiotensin-II inhibition reduces fibrotic degeneration of both the atrial and ventricular myocardium as well as AF induction susceptibility.</AbstractText>We studied three groups of five goats over a 6-month period. The study animals in the first two groups were implanted with a pacemaker capable of maintaining AF with burst pacing. Additionally, in one group, goats were administered candesartan (AF+candesartan group). The third group (SR group) of animals served as control. Animals were tested for AF induction on day 0, 1, 30, 90 and 180. A "Vulnerability Index" (VI) for AF induction was calculated, defined as the ratio of total time in AF per number of bursts needed to induce sustained AF, in each session. At the end of the study, all four heart chambers were examined and fibrosis quantified.</AbstractText>Both AF goat groups developed cardiomegaly due to tachy-cardiomyopathy. Although, the VI was significantly increased in AF group over time (28.8+/-43 to 284.7+/-291, p=0.045), this was not the case for AF+candesartan group (30.3+/-40 to 170.8+/-243, p=0.23). Histology revealed a significant increase of fibrous tissue in goats with induced AF, noticeable in all four heart chambers, compared to controls. However, the degree of fibrosis was significantly lower in AF animals on candesartan.</AbstractText>Our study demonstrated a beneficial effect of angiotensin II inhibition on tachyarrhythmia-induced ventricular fibrosis. It is also consistent with previous studies indicating a reduction in burst-induced AF susceptibility in goats and confirms the favorable effects in atrial structural remodeling.</AbstractText> |
8,299 | Decreased right and left ventricular myocardial performance in obstructive sleep apnea. | Obstructive sleep apnea (OSA) may predispose patients to congestive heart failure (CHF), suggesting a deleterious effect of OSA on myocardial contractility.</AbstractText>A cross-sectional study of 85 subjects with suspected OSA who had undergone their first overnight polysomnogram, accompanied by an echocardiographic study. Patients were divided according to the apnea-hypopnea index as follows: < 5 (control subjects); 5 to 14 (mild OSA); and >or= 15 (moderate-to-severe OSA). Right and left ventricular function was evaluated using the myocardial performance index (MPI) and other echocardiographic parameters. For the right ventricle analyses, we excluded patients with a Doppler pulmonary systolic pressure of >or= 45 mm Hg, while for the left ventricle we excluded patients with an ejection fraction of <or= 45%.</AbstractText>The mean (+/- SD) age was 60 +/- 15 years, and 83% were men. Right and left ventricular function were altered in patients with OSA, especially in those with the moderate-to-severe OSA, even after adjustment for potential confounders. The mean right MPI was 0.23 +/- 0.10 in control subjects, 0.26 +/- 0.16 in patients with mild OSA, and 0.37 +/- 0.11 in patients with moderate-to-severe OSA (p value for trend, < 0.01). The mean left MPI values were 0.28 +/- 0.05, 0.27 +/- 0.07, and 0.41 +/- 0.14, respectively (p value for trend, 0.04). Right and left MPI correlated positively and significantly with the apnea-hypopnea index (rho = 0.40, p = 0.002; and rho = 0.27, p = 0.02, respectively). Mean left atrial volume index was increased in patients with OSA (control subjects, 26.8 +/- 11; patients with mild OSA, 32.5 +/- 15; and patients with moderate-to-severe OSA, 30.4 +/- 11; p value for trend, 0.04).</AbstractText>OSA, particularly when moderate to severe, is associated with impaired right and left ventricular function and increased left atrial volume. These findings support the notion that OSA may contribute to the development of atrial fibrillation and CHF.</AbstractText> |
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