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5,000
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[Study on ultrastructure of cardioprotection of ramipril against ischemia/reperfusion injury in diabetic rats].
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To investigate the effects of ramipril on myocardial ischemia/reperfusion injury in diabetic rats, and to explore its mechanism according to the observation on myocardial ultrastructure.</AbstractText>Streptozotocin induced diabetic rats were divided randomly into three groups (n = 16): ischemia/reperfusion (I/R), ischemic preconditioning (IPC) and ramipril (RAM) group. Rats in RAM group were administered by RAM(1 mg x kg(-1) x d(-1)) orally for 4 weeks, the others were administered by normal saline. Then all rats were subjected to myocardial ischemia/ reperfusion injury. Rats in IPC group were preconditioned before ischemia. The ECG and the infarct size were examined. The changes of myocardial morphology were examined by light and electron microscopes.</AbstractText>Compared with I/R group, the elevation of ST segment and the incidence of ventricular tachycardia and ventricular fibrillation during ischemia were significantly decreased, the infarct size at the end of reperfusion was remarkably reduced, the myocardial morphology were significantly improved, special structure of myofilaments and mitochondria remained clearly, blood vessels were unobstructed, injury of endothelium were decreased in PC and RAM groups.</AbstractText>Ramipril administered for 4 weeks induces myocardial protection in diabetic rats, which is similar to that of IPC. The mechanism may be involved in protection of cardiocytes and mitochondria, and improvement of endothelial function.</AbstractText>
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5,001
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Bepridil facilitates early termination of spiral-wave reentry in two-dimensional cardiac muscle through an increase of intercellular electrical coupling.
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Bepridil is effective for conversion of atrial fibrillation to sinus rhythm and in the treatment of drug-refractory ventricular tachyarrhythmias. We investigated the effects of bepridil on electrophysiological properties and spiral-wave (SW) reentry in a 2-dimensional ventricular muscle layer of isolated rabbit hearts by optical mapping. Ventricular tachycardia (VT) induced in the presence of bepridil (1 µM) terminated earlier than in the control. Bepridil increased action potential duration (APD) by 5% - 8% under constant pacing and significantly increased the space constant. There was a linear relationship between the wavefront curvature (κ) and local conduction velocity: LCV = LCV₀ - D·κ (D, diffusion coefficient; LCV₀, LCV at κ = 0). Bepridil significantly increased D and LCV₀. The regression lines with and without bepridil crossed at κ = 20 - 40 cm⁻¹, resulting in a paradoxical decrease of LCV at κ > 40 cm⁻¹. Dye transfer assay in cultured rat cardiomyocytes confirmed that bepridil increased intercellular coupling. SW reentry in the presence of bepridil was characterized by decremental conduction near the rotation center, prominent drift, and self-termination by collision with boundaries. These results indicate that bepridil causes an increase of intercellular coupling and a moderate APD prolongation, and this combination compromises wavefront propagation near the rotation center of SW reentry, leading to its drift and early termination.
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5,002
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Comparison of a novel, single-lead atrial sensing system with a dual-chamber implantable cardioverter-defibrillator system in patients without antibradycardia pacing indications: results of a randomized study.
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Supraventricular tachyarrhythmias are the main cause for inappropriate therapy by implantable cardioverter-defibrillators (ICDs). For better rhythm discrimination, an atrial electrogram is helpful and usually obtained from an additional atrial lead, even in the absence of sinus node or atrioventricular nodal disease. An A+-ICD system with integrated atrial sensing rings mounted 15 to 18 cm from the tip of an ICD lead may obviate the need to implant a separate atrial lead. The aim of the study was to compare the novel A+-ICD and a conventional dual-chamber (DR)-ICD.</AbstractText>Two hundred forty-nine patients with standard ICD indications but no requirement for antibradycardia pacing were randomized to receive an A+-ICD (n=124) or a DR-ICD (n=125). Implantation details, need for ICD system revision, long-term sensing, documented arrhythmia episodes, and the respective rhythm discrimination during follow-up were analyzed. The implantation time was significantly shorter in the A+-ICD group (67±30 vs 79±30 minutes, P=0.003). Mean P-wave amplitudes were 3.5±0.8 mV (A+-ICD) and 3.2±0.6 mV (DR-ICD) and remained stable during the follow-up period of 12 months. Surgical revision was necessary in 13 patients in the DR-ICD and 10 in the A+-ICD group. All 593 ventricular tachyarrhythmia episodes were correctly discriminated. Sensitivity and specificity of supraventricular tachyarrhythmia discrimination were not different between the study groups.</AbstractText>The novel A+-ICD system can be implanted faster and is equivalent to a standard DR-ICD with regard to the detection of ventricular tachyarrhythmias and supraventricular tachyarrhythmias. It represents a useful alternative to obtain atrial sensing.</AbstractText>
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5,003
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Isoproterenol administration during general anesthesia for the evaluation of children with ventricular preexcitation.
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Rapid anterograde conduction in the setting of ventricular preexcitation is associated with an increased risk of sudden cardiac death. The effect of isoproterenol in this setting is unclear, particularly in younger anesthetized patients. The aim of this study was to determine the effect of isoproterenol on accessory-pathway conduction in children undergoing general anesthesia and its role in the risk-stratification process.</AbstractText>The records of 151 pediatric patients with preexcitation undergoing electrophysiologic study under propofol anesthesia during a 5-year period were reviewed. Data included accessory-pathway effective refractory period, minimum 1:1 accessory pathway conduction with atrial pacing, and shortest preexcited R-R interval in atrial fibrillation. Measurements were repeated after administration of low-dose isoproterenol (mean, 0.013 μg/kg per min; range, 0.003 to 0.027). All accessory-pathway characteristics were significantly shortened with isoproterenol (P<0.001). Accessory-pathway effective refractory period increased modestly with age, both in the baseline state (r=0.172, P=0.04) and with isoproterenol (r=0.267, P<0.01) as did minimum 1:1 accessory pathway conduction with atrial pacing (r=0.178, P=0.034, and r=0.175, P<0.01, respectively). Accessory-pathway effective refractory period ≤250 ms was observed in only 5% of patients at baseline vs 25% after isoproterenol, and Shortest preexcited R-R interval in atrial fibrillation ≤250 ms was noted in 16% vs 41%. Tachycardia was induced in 48 of 151 patients before and in 102 of 151 after isoproterenol.</AbstractText>In anesthetized children with ventricular preexcitation, accessory pathways display shorter conduction properties at younger ages and important adrenergic sensitivity at all ages. Use of low-dose isoproterenol resulted in a substantial increase in the number of patients who would otherwise meet typical criteria for ablation.</AbstractText>
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5,004
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Effects of a highly selective acetylcholine-activated K+ channel blocker on experimental atrial fibrillation.
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The acetylcholine-activated K(+) current (I(K,ACh)) is a novel candidate for atrial-specific antiarrhythmic therapy. The present study investigates the involvement of I(K,ACh) in atrial fibrillation (AF) using NTC-801, a novel potent and selective I(K,ACh) blocker.</AbstractText>The effects of NTC-801, substituted 4-(aralkylamino)-2,2-dimethyl-3,4-dihydro-2H-benzopyran-3-ol, on I(K,ACh) and other cardiac ionic currents (I(Na), I(CaL), I(to), I(Kur), I(Kr), I(Ks), I(Kl), I(KATP), and I(f)) and on atrial and ventricular action potentials were examined in vitro. NTC-801 potently inhibited carbachol-induced I(K,ACh) in guinea pig atrial cells and the GIRK1/4 current in Xenopus oocytes with IC(50) values of 5.7 and 0.70 nmol/L, respectively. NTC-801 selectively inhibited I(K,ACh) >1000-fold over other cardiac ionic currents. NTC-801 (10 to 100 nmol/L) reversed the action potential duration (APD(90)) shortened by carbachol or adenosine in atrial cells, whereas it did not affect APD(90) at 100 nmol/L in ventricular cells. Antiarrhythmic effects of NTC-801 were evaluated in 3 AF models in vivo. NTC-801 significantly prolonged atrial effective refractory period without affecting ventricular effective refractory period under vagal nerve stimulation. NTC-801 dose-dependently converted AF to normal sinus rhythm in both vagal nerve stimulation-induced (0.3 to 3 μg · kg(-1) · min(-1) IV) and aconitine-induced (0.01 to 0.1 mg/kg IV) models. In a rapid atrial pacing model, NTC-801 (3 μg · kg(-1) · min(-1) IV) significantly decreased AF inducibility with a prolonged atrial effective refractory period that was frequency-independent.</AbstractText>A selective I(K,ACh) blockade induced by NTC-801 exerted anti-AF effects mediated by atrial-selective effective refractory period prolongation. These findings suggest that I(K,ACh) may be important in the development and maintenance of AF.</AbstractText>
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5,005
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Predictors of electrical storm recurrences in patients with implantable cardioverter-defibrillators.
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To determine prevalence and predictors of electrical storm recurrences (ES-Rs) in patients with implantable cardioverter-defibrillators (ICDs) as electrical storms (ESs) represent serious clinical events carrying a high risk of mortality.</AbstractText>Single-centre study analysing data of consecutive patients receiving an ICD between 1993 and 2008. Electrical storm was defined as ≥ 3 separate ventricular tachyarrhythmic (VT/VF) episodes ≤ 24 h. Nine hundred and fifty-five patients [mean left ventricular ejection fraction (LVEF) 35.7 ± 15.6%] were prospectively followed for 54.2 ± 35.5 months. In 274 of 955 patients (28.7%), 2871 VT/VF episodes were observed. One hundred and fifty-three ES episodes occurred in 63 of 955 patients (6.6%). Thirty-two of 63 patients (50.8%) experienced ≥ 2 ES episodes. Twenty-six of 32 patients (81.2%) with ES-Rs experienced the second ES episode within 1 year after the initial event. Cox regression analysis identified an LVEF ≤ 30% (OR 2.2; 95% CI 1.021-4.856; P = 0.044) and a patient's age >65 years (OR 3.5; 95% CI 1.207-10.176; P = 0.021) to be predictive for ES-Rs. Patients with angiotensin-converting enzyme (ACE) inhibitor therapy were less likely to experience ES-Rs (OR 0.39; 95% CI 0.187-0.817; P = 0.013).</AbstractText>Electrical storm events are not rare in a 'real-world' patient population with ICDs (6.6% in 4.5 years). The risk for ES-Rs, especially within the first year after the initial event, is high. Left ventricular ejection fraction ≤ 30%, age >65 years, and a lack of ACE inhibitor therapy are independent predictors of ES-R.</AbstractText>
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5,006
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Noninvasive computational imaging of cardiac electrophysiology for 3-D infarct.
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Myocardial infarction (MI) creates electrophysiologically altered substrates that are responsible for ventricular arrhythmias, such as tachycardia and fibrillation. The presence, size, location, and composition of infarct scar bear significant prognostic and therapeutic implications for individual subjects. We have developed a statistical physiological model-constrained framework that uses noninvasive body-surface-potential data and tomographic images to estimate subject-specific transmembrane-potential (TMP) dynamics inside the 3-D myocardium. In this paper, we adapt this framework for the purpose of noninvasive imaging, detection, and quantification of 3-D scar mass for postMI patients: the framework requires no prior knowledge of MI and converges to final subject-specific TMP estimates after several passes of estimation with intermediate feedback; based on the primary features of the estimated spatiotemporal TMP dynamics, we provide 3-D imaging of scar tissue and quantitative evaluation of scar location and extent. Phantom experiments were performed on a computational model of realistic heart-torso geometry, considering 87 transmural infarct scars of different sizes and locations inside the myocardium, and 12 compact infarct scars (extent between 10% and 30%) at different transmural depths. Real-data experiments were carried out on BSP and magnetic resonance imaging (MRI) data from four postMI patients, validated by gold standards and existing results. This framework shows unique advantage of noninvasive, quantitative, computational imaging of subject-specific TMP dynamics and infarct mass of the 3-D myocardium, with the potential to reflect details in the spatial structure and tissue composition/heterogeneity of 3-D infarct scar.
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5,007
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Atrial Tachycardia Successfully Ablated from the Left Coronary Sinus Cusp of the Aorta: An Unusual Site of Origin.
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It has been recognized in the last decade that atrial and ventricular tachycardias may arise from the myocardium around the aorta. These tachycardias can be ablated from the coronary sinus cusps of the aorta (ASCs) . In some of those tachycardias, the site of origin may be epicardial and thus can be ablated only through the thin structure of the ASCs. It is important to know how to make a diagnosis, map and ablate tachycardias arising from this region.
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5,008
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Poor tolerance of beta-blockers by elderly patients with heart failure.
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Despite the well-understood importance of beta-blocker therapy in heart failure, it is sometimes not possible to use beta-blockers in elderly patients due to poor tolerance. In this report, we describe the case of an 83-year-old patient with severe systolic heart failure complicated by aortic valve stenosis and atrial fibrillation. A simple therapeutic approach involving discontinuation of beta-blockers remarkably alleviated the symptoms such as left ventricular ejection fraction, and improved the chest radiography and laboratory findings; further, atrial fibrillation converted to sinus rhythm. It is important to carefully administer beta-blocker therapy to elderly patients with heart failure, especially after considering cardiac output.
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5,009
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A comparison of long-standing implantable cardioverter-defibrillator patients with and without appropriate therapy for ventricular arrhythmias: impact of a widening QRS.
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The comparison of patients with long-standing implantable cardioverter-defibrillators (ICDs) who have had or never have had appropriate therapy for ventricular arrhythmias may offer insight into potential risk factors that may improve patient selection.</AbstractText>Records from patients in the Columbia Presbyterian device clinic whose original ICD was implanted before 31 December 2004 were analysed. The patients were divided into those who had never received appropriate therapy for ventricular arrhythmias (Group A, n = 188), and those who had received appropriate therapy (Group B, n = 173). The subset of patients with consistent follow-up greater than 5 years was then analysed (Group A, n = 140; Group B, n = 158). Demographic, clinical, echocardiographic, and electrocardiographic data were collected. There were no significant differences in age, sex, or type of heart disease between the groups. There were more patients in Group B vs. A who had ICDs implanted for secondary prevention (70.3 vs. 55.7%, P < 0.05). The mean QRS width was similar at implant but increased significantly in Group B vs. A on pre-ICD discharge electrocardiograms (134.1 ± 35.0 vs. 125.1 ± 36.2 ms, P < 0.05). Congestive heart failure class, comorbidities, use of antiarrhythmic agents, or left ventricular ejection fraction were not discriminators between Groups A and B.</AbstractText>In this study of patients with long-standing ICDs, the only discriminating factors for appropriate shocks were implant for secondary prevention or increasing QRS width, suggesting electrical factors are the best predictors of ultimate ICD discharges.</AbstractText>
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5,010
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Rate-dependent shortening of action potential duration increases ventricular vulnerability in failing rabbit heart.
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Congestive heart failure (CHF) predisposes to ventricular fibrillation (VF) in association with electrical remodeling of the ventricle. However, much remains unknown about the rate-dependent electrophysiological properties in a failing heart. Action potential properties in the left ventricular subepicardial muscles during dynamic pacing were examined with optical mapping in pacing-induced CHF (n=18) and control (n=17) rabbit hearts perfused in vitro. Action potential durations (APDs) in CHF were significantly longer than those observed for controls at basic cycle lengths (BCLs)>1,000 ms but significantly shorter at BCLs<400 ms. Spatial APD dispersions were significantly increased in CHF versus control (by 17-81%), and conduction velocity was significantly decreased in CHF (by 6-20%). In both groups, high-frequency stimulation (BCLs<150 ms) always caused spatial APD alternans; spatially concordant alternans and spatially discordant alternans (SDA) were induced at 60% and 40% in control, respectively, whereas 18% and 82% in CHF. SDA in CHF caused wavebreaks followed by reentrant excitations, giving rise to VF. Incidence of ventricular tachycardia/VFs elicited by high-frequency dynamic pacing (BCLs<150 ms) was significantly higher in CHF versus control (93% vs. 20%). In CHF, left ventricular subepicardial muscles show significant APD shortenings at short BCLs favoring reentry formations following wavebreaks in association with SDA. High-frequency excitation itself may increase the vulnerability to VF in CHF.
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5,011
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Ajmaline challenge for the diagnosis of Brugada syndrome: which protocol?
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Ajmaline challenge is commonly used for the diagnosis of Brugada syndrome. A slow infusion rate has been recommended in view of the proarrhythmic risk, but the diagnostic value of various infusion rates has not been investigated.</AbstractText>To compare rapid and slow ajmaline infusion rates and to assess the proarrhythmic risk.</AbstractText>The first part of this study prospectively compared rapid and slow infusion rates in terms of results and ventricular arrhythmias. Thirty-two patients (mean age 41±12 years; 26 men) received the two ajmaline challenges on different days. According to randomization, ajmaline (1 mg/kg) was infused at 1 mg/sec or over 10 minutes. The second part of the study retrospectively assessed the prevalence of ventricular arrhythmia during 386 challenges performed at a rapid infusion rate.</AbstractText>No differences were observed between rapid and slow tests. All patients diagnosed as positive or negative with one test obtained the same result with the other test. Ventricular premature beats were observed in five of 32 patients during the slow challenge and in four of 32 patients during the rapid challenge. No sustained ventricular arrhythmias were observed. Analysis of the 386 tests revealed four episodes of ventricular arrhythmia (two complex ventricular premature beats, one non-sustained ventricular tachycardia and one ventricular fibrillation).</AbstractText>Slow and rapid infusions of ajmaline have identical diagnostic performances on suspected Brugada electrocardiograms. Owing to the risk of severe proarrhythmia, a slow infusion rate, allowing early discontinuation, should be recommended.</AbstractText>Copyright © 2010 Elsevier Masson SAS. All rights reserved.</CopyrightInformation>
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5,012
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Acquired long QT syndrome from stress cardiomyopathy is associated with ventricular arrhythmias and torsades de pointes.
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Stress cardiomyopathy (SCM) is a syndrome of transient ventricular dysfunction triggered by severe emotional or physical stress, likely resulting from catecholamine-mediated myocardial toxicity. Repolarization abnormalities associated with other hyperadrenergic states can cause QT prolongation and lethal arrhythmia including torsades de pointes (TdP). Despite the development of repolarization abnormalities and QT prolongation in SCM, little is known about the risk of ventricular fibrillation (VF) and TdP.</AbstractText>The aim of this study was to assess the prevalence and clinical predictors of ventricular arrhythmias in a cohort of patients with SCM.</AbstractText>Data from a registry of consecutive patients with SCM from 2 institutions were reviewed. Patients who developed VF or TdP were identified. Clinical characteristics and outcomes were analyzed and compared with a control group of patients with SCM without VF/TdP.</AbstractText>Of 93 patients with SCM, 8 (8.6%) experienced VF/TdP. Of these 8 patients, 2 presented with VF and were subsequently diagnosed with SCM. Six other patients experienced pause-dependent TdP or VF after SCM diagnosis in the setting of substantial QT prolongation. Prolongation of the corrected QT interval (QTc) was significantly associated with the occurrence of ventricular arrhythmia (odds ratio 1.28 for each 10 ms increase in QTc, 95% confidence interval 1.10 to 1.50).</AbstractText>SCM can be associated with life-threatening ventricular arrhythmia in over 8% of cases. SCM should be recognized among the causes of acquired long QT syndrome and can be associated with a risk of TdP.</AbstractText>Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.</CopyrightInformation>
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5,013
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Alternans of action potential duration and amplitude in rabbits with left ventricular dysfunction following myocardial infarction.
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T-wave alternans may predict the occurrence of ventricular arrhythmias in patients with left ventricular dysfunction and experimental work has linked discordant repolarization alternans to the induction of re-entry. The aim of this study was to examine the occurrence of transmural repolarization alternans and to investigate the link between alternans and ventricular arrhythmia in rabbits with left ventricular dysfunction following myocardial infarction. Optical mapping was used to record action potentials from the transmural surface of left ventricular wedge preparations from normal and post-infarction hearts during a progressive reduction in pacing cycle length at 30 and 37°C. Data were analyzed using custom software, including spectral analysis. There were no significant differences in baseline transmural electrophysiology between the groups. Post-infarction hearts had a lower threshold for both repolarization alternans (286 vs. 333 bpm, p<0.05) and ventricular arrhythmias (79 vs. 19%, p<0.01) during rapid pacing, which was not accounted for by increased transmural discordant alternans. In VF-prone hearts, alternans in optical action potential amplitude was observed and increased until 2:1 block occurred. The degree of optical action potential amplitude alternans (12.0 ± 7.0 vs. 1.8 ± 0.3, p<0.05), but not APD(90) alternans (1.4 ± 0.6 vs. 1.1 ± 0.1, p>0.05) was associated with VF inducibility during rapid pacing. Post-infarction hearts are more vulnerable to transmural alternans and ventricular arrhythmias at rapid rates. Alternans in optical action potential amplitude was associated with conduction block and VF. The data suggest that changes in optical action potential amplitude may underlie a mechanism for alternans-associated ventricular arrhythmia in left ventricular dysfunction.
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5,014
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Atrial protective effects of n-3 polyunsaturated fatty acids: a long-term study in ovine chronic heart failure.
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It has been suggested that omega-3 polyunsaturated fatty acids (n-3 PUFAs) may prevent the development of atrial fibrillation (AF).</AbstractText>The purpose of this study was to evaluate the impact of these agents on development of the AF substrate in heart failure (HF).</AbstractText>In this study, HF was induced by intracoronary doxorubicin infusions. Twenty-one sheep [7 with n-3 PUFAs treated HF (HF-PUFA), 7 with olive oil-treated HF controls (HF-CTL), 7 controls (CTL)] were studied. Open chest electrophysiologic study was performed with assessment of biatrial effective refractory period (ERP) and conduction. Cardiac function was monitored by magnetic resonance imaging. Atrial n-3 PUFAs levels were quantified using chromatography. Structural analysis was also performed.</AbstractText>Atrial n-3 PUFAs levels were twofold to threefold higher in the HF-PUFA group. n-3 PUFAs prevented the development of HF-related left atrial enlargement (P = .001) but not left ventricular/atrial dysfunction. Atrial ERP was significantly lower in the HF-PUFA group (P <.001), but ERP heterogeneity was unchanged. In addition, n-3 PUFAs suppressed atrial conduction abnormalities seen in HF of prolonged P-wave duration (P = .01) and slowed (P <.001) and heterogeneous (P <.05) conduction. The duration of induced AF episodes in HF-PUFA was shorter (P = .02), although AF inducibility was unaltered (P = NS). A 20% reduction of atrial interstitial fibrosis was seen in the HF-PUFA group (P <.05).</AbstractText>In this ovine HF study, chronic n-3 PUFAs use protected against adverse atrial remodeling by preventing atrial enlargement, fibrosis, and conduction abnormalities leading to shorter AF episodes despite lower ERP.</AbstractText>Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.</CopyrightInformation>
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5,015
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Detection of ventricular ectopy by a novel miniature electrocardiogram recorder.
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The ability of a miniaturized, skin-attached, 3-channel electrocardiogram (ECG) recorder prototype to detect ventricular ectopic beats (VEBs) and ventricular fibrillation (VF) was compared with that of standard Holter ECG.</AbstractText>Concurrent 15-hour ECG recordings were made in 143 patients using an experimental device provided by Philips Healthcare (Seattle, WA) and a commercially available Holter recorder. In a consensus review process, 3 physicians (M.L., A.J., and A.G.), blinded for the recording device, analyzed 1804 seven-second strips for total number of VEBs, total number of their QRS configurations, and presence of VF. Agreement between the experimental and standard devices was calculated using Spearman correlation coefficients.</AbstractText>There was 100% agreement regarding VF recognition. Spearman correlation coefficients were 0.98 (P < .001) for the total number of VEBs and 0.91 (P < .001) for the total number of QRS configurations.</AbstractText>The accuracy of the experimental miniaturized ECG recorder for detecting ventricular activity was found to be high. This finding could be of clinical importance.</AbstractText>Copyright © 2011 Elsevier Inc. All rights reserved.</CopyrightInformation>
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5,016
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Crossing over to the other side.
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What happened when a doctor on duty in the emergency department suddenly made the transition to "patient in Resus 2"?
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5,017
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Use of implantable cardioverter-defibrillators.
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The implantable cardioverter-defibrillator (ICD) is the most effective treatment for patients with life-threatening ventricular tachycardia or ventricular fibrillation not due to reversible causes. The American College of Cardiology/American Heart Association class I and IIa indications for an ICD are discussed. Patients with ICDs who need pacing should be treated with biventricular pacing, not with dual-chamber rate-responsive pacing, at a rate of 70/min. Patients with ICDs should be treated with β-blockers, statins and angiotensin-converting enzyme inhibitors or angiotensin receptor blockers.
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5,018
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Heart failure with preserved left ventricular ejection fraction: concepts, misconceptions and future directions.
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Heart failure with preserved left ventricular ejection fraction (HFPEF) represents a huge medical problem, especially in light of an increasing elderly population. Dysfunction of both left ventricular filling and ejection, combined with adverse loading conditions related to advanced age, arterial hypertension, diabetes mellitus, obesity and atrial fibrillation are fundamental pathophysiological mechanisms. Hypertension is probably the most important modifiable risk factor. The diagnosis has largely been based on signs of increased left ventricular filling pressure. Additional matters of debate are the interpretation of left ventricular ejection fraction in concentric remodelling and the cut-off used for the definition of HFPEF, as well as inconsistencies related to prevalence and prognosis, and lack of benefit of drugs in randomized trials.
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5,019
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Intracoronary administration of bone marrow-derived mononuclear cells and arrhythmic events in patients with chronic heart failure.
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There are continued debates on potential proarrhythmic effects of intracoronary bone marrow-derived progenitor cell (BMC) therapy for treatment of chronic heart failure. Implantable cardioverter-defibrillators (ICDs), a mainstay of heart failure therapy, provide the possibility of validly assessing arrhythmias in patients with chronic heart failure. The aim of this analysis was to assess the arrhythmogenic potential of intracoronary BMC therapy, continuously documented by ICD-stored intracardiac electrograms.</AbstractText>Matched cohort study of 112 patients receiving intracoronary administration of autologous BMC and 224 heart failure patients, matched for age, gender, and left ventricular ejection fraction fitted with an ICD. Within a follow-up period of 2 years (total patient-years at risk: 595 years), no significant difference was detected for ICD-stored episodes of ventricular tachycardia (VT; 25.0 vs. 27.1%; P = 0.779), VT/ventricular fibrillation treated by antitachycardia pacing or ICD shock (15.6 vs. 15.5%; P = 0.956), or death from arrhythmic cause (4.2 vs. 1.0%; P = 0.667). Predictors of occurrence of major arrhythmic events were parameters of advanced heart failure and implantation of ICD for secondary prevention; no influence could be detected for BMC administration (odds ratio = 1.198; P = 0.440).</AbstractText>There is no evidence that intracoronary administration of BMC aggravates life-threatening arrhythmias in patients with chronic heart failure.</AbstractText>
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5,020
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Twenty-five years in the making: flecainide is safe and effective for the management of atrial fibrillation.
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Atrial fibrillation (AF) is the most common arrhythmia in clinical practise and its prevalence is increasing. Over the last 25 years, flecainide has been used extensively worldwide, and its capacity to reduce AF symptoms and provide long-term restoration of sinus rhythm (SR) has been well documented. The increased mortality seen in patients treated with flecainide in the Cardiac Arrhythmia Suppression Trial (CAST) study, published in 1991, still deters many clinicians from using flecainide, denying many new AF patients a valuable treatment option. There is now a body of evidence that clearly demonstrates that flecainide has a favourable safety profile in AF patients without significant left ventricular disease or coronary heart disease. As a result of this evidence, flecainide is now recommended as one of the first-line treatment options for restoring and maintaining SR in patients with AF under current treatment guidelines. The objective of this article is to review the literature pertaining to the pharmacological characteristics, safety and efficacy of flecainide, and to place this drug in the context of current therapeutic management strategies for AF.
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5,021
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Cardiac resynchronization therapy: current trends and future directions.
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Despite the clear cut indications for cardiac resynchronization therapy (CRT) laid down by guideline forming bodies, there are numerous unresolved issues. This review article primarily focuses on the current trends in CRT and the challenges encountered in patient selection, procedure related and postimplantation patient management issues. The high rate of non-response to CRT warrants a critical appraisal of the patient selection criteria, with the role of QRS duration and use of imaging to quantify ventricular dyssynchrony being the major points of discussion. Likewise the role of CRT in relatively asymptomatic heart failure patients, those with atrial fibrillation and the benefits of providing an implantable cardioverter defibrillator backup to all CRT devices has yet to be clearly defined. The development of effective and minimally invasive surgical techniques, dependable and reproducible means for optimal pacing site localization and comparative trials on superior mode of lead positioning, pacing sites and optimized CRT programming encompassing diverse patient populations would further advance current standards of CRT. Innovative approaches to resolve these controversies and future goal directed research is needed. Development of novel, comprehensive prediction tools to identify responders to CRT and the possibility of 'leadless' pacing would be interesting futuristic prospects.
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5,022
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Management of ventricular arrhythmias.
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Underlying causes of ventricular tachycardia (VT) or complex ventricular arrhythmias (VA) should be treated if possible. Anti-arrhythmic drugs should not be used to treat asymptomatic patients with complex VA and no heart disease. Beta blockers are the only antiarrhythmic drugs that have been documented to reduce mortality in patients with VT or complex VA. Radiofrequency catheter ablation of VT has been beneficial in treating selected patients with arrhythmogenic foci of monomorphic VT. The automatic implantable cardioverter-defibrillator (AICD) is the most effective treatment for patients with life-threatening VT or ventricular fibrillation. The American College of Cardiology/American Heart Association class I indications for an AICD are discussed. Other indications for an AICD are discussed. Patients with AICDs should be treated with biventricular pacing, not with dual-chamber rate-responsive pacing at a rate of 70/minute. Patients with AICDs should be treated with beta blockers, statins, and angiotensin-converting enzyme inhibitors or angiotensin blockers.
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5,023
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Value of robotic navigation and ablation.
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Catheter ablation has been established as a potentially curative treatment modality for various arrhythmias. Over the past years, catheter ablation has progressed from focal ablation to complex ablations within a three-dimensional anatomy for the treatment of ventricular tachycardia or atrial fibrillation. Complex ablation relies on reproducible catheter navigation in conjunction with stable catheter position and contact force, which depends on the operators´ individual experience and manual skills. Therefore, it would be desirable that technical innovations pursue the goal to minimize the physician's physical demands and exposure to scattered fluoroscopy, to improve catheter stability and, most importantly, to increase procedural safety. This review will discuss the role of remote controlled robotic navigation systems in catheter ablation with particular focus on safety, efficacy and novel applications.
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5,024
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Advances in the treatment of atrial fibrillation.
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Management of atrial fibrillation (AF) has changed greatly in the past 10 years. The advent of a greater understanding of the pathophysiology of AF has resulted in major therapeutic breakthroughs, both in invasive and non-invasive strategies. New antiarrhythmic agents with fewer side effects, new anticoagulants and technical advances in ablation have changed the treatment of this condition. Molecular modification of the highly effective amiodarone, to improve safety and tolerability, has produced promising analogues such as Dronedarone. Although this drug seems less effective than amiodarone in preventing AF recurrence, the drug presented an interesting data on reduction of stroke and cardiovascular death, a novel effect that needs further investigation. New antiarrhythmics with atria selectiveness such Vernakalant, might be useful for cardioversion in AF without ventricular proarrhythmia. Dabigatran, a prodrug that directly inhibits thrombin, represents an alternative to warfarin for anticoagulant treatment in selected patients. In AF ablation, technological advances are sure to result in the necessary improvements in the safety and procedures efficacy. These technologies include ablation catheters designed to electrically isolate the pulmonary veins with improved safety, efficacy, speed, and precision and improved imaging and electrical mapping systems. Although pulmonary vein isolation remains essential for most ablation procedures, the role of substrate modification has taken on increasing importance. In this article, we review the advances in the treatment of AF, focus on the new medications and advances in invasive procedures.
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5,025
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Autonomic denervation with magnetic nanoparticles.
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prior studies indicated that ablation of the 4 major atrial ganglionated plexi (GP) suppressed atrial fibrillation.</AbstractText>superparamagnetic nanoparticles (MNPs) made of Fe(3)O(4) (core), thermoresponsive polymeric hydrogel (shell), and neurotoxic agent (N-isopropylacrylamide monomer [NIPA-M]) were synthesized. In 23 dogs, a right thoracotomy exposed the anterior right GP (ARGP) and inferior right GP (IRGP). The sinus rate and ventricular rate slowing responses to high-frequency stimulation (20 Hz, 0.1 ms) were used as the surrogate for the ARGP and IRGP functions, respectively. In 6 dogs, MNPs carrying 0.4 mg NIPA-M were injected into the ARGP. In 4 other dogs, a cylindrical magnet (2600 G) was placed epicardially on the IRGP. MNPs carrying 0.8 mg NIPA-M were then infused into the circumflex artery supplying the IRGP. The hydrogel shell reliably contracted in vitro at temperatures ≥ 37°C, releasing NIPA-M. MNPs injected into the ARGP suppressed high-frequency stimulation-induced sinus rate slowing response (40 ± 8% at baseline; 21 ± 9% at 2 hours; P=0.006). The lowest voltage of ARGP high-frequency stimulation inducing atrial fibrillation was increased from 5.9 ± 0.8 V (baseline) to 10.2 ± 0.9 V (2 hours; P=0.009). Intracoronary infusion of MNPs suppressed the IRGP but not ARGP function (ventricular rate slowing: 57 ± 8% at baseline, 20 ± 8% at 2 hours; P=0.002; sinus rate slowing: 31 ± 7% at baseline, 33 ± 8 % at 2 hours; P=0.604). Prussian Blue staining revealed MNP aggregates only in the IRGP, not the ARGP.</AbstractText>intravascularly administered MNPs carrying NIPA-M can be magnetically targeted to the IRGP and reduce GP activity presumably by the subsequent release of NIPA-M. This novel targeted drug delivery system can be used intravascularly for targeted autonomic denervation.</AbstractText>
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5,026
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Differences in myocardial structure and coronary microvasculature between men and women with coronary artery disease.
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Women younger than 75 years with stable angina or acute coronary syndrome have higher cardiac mortality than similarly aged men, despite less obstructive coronary artery disease. To determine whether the myocardial structure and coronary microvasculature of women differs from that of men, we performed histological analysis of biopsies from nonischemic left ventricular myocardium from 46 men and 11 women undergoing coronary artery bypass graft surgery who did not have previous cardiac surgery, myocardial infarction, heart failure, atrial fibrillation, or furosemide therapy. The 2 patient groups had similar clinical characteristics, apart from a lower body surface area (BSA) in women (P = 0.0015). Women had less interstitial fibrosis than men (P = 0.019) but similar perivascular fibrosis. Arteriolar wall area/circumference ratio, a measure of arteriolar wall thickness, was 47% greater in women than men (P = 0.012). Cardiomyocyte width and diffusion radius were positively correlated, and capillary length density was negatively correlated with BSA (P < 0.05). Whereas cardiomyocyte width, capillary length density, diffusion radius, and cardiomyocyte width/BSA ratio were similar for men and women, women had a greater diffusion radius/BSA ratio (P = 0.0038) and a greater diffusion radius/cardiomyocyte width ratio (P = 0.027). Women also had lower vascular endothelial growth factor (VEGF) receptor-1 levels (P = 0.048) and VEGF receptor-1/VEGF-A ratio (P = 0.024) in plasma. We conclude that women with extensive coronary artery disease have greater arteriolar wall thickness and diffusion radius relative to BSA and to cardiomyocyte width than men, which may predispose to myocardial ischemia. Additional studies of larger numbers of women with less extensive coronary artery disease are required to confirm these findings.
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5,027
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Mitral valve prolapse and out-of-hospital sudden death: a case report and literature review.
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The emergency medical services were called to the workplace of a 25-year-old woman who appeared to be dead. The alarm was raised by employees who had found her unconscious at her desk. There was no semi-automatic defibrillator on the premises and no member of staff had received specific training in management of cardiac arrest. External cardiac massage was immediately started as advised by telephone by the emergency physician and ventricular fibrillation was diagnosed on arrival of the medical team. Despite continuous resuscitation, the victim did not revive. The death certificate was signed with a medicolegal objection to burial, leading to an inquiry. Several causes were suggested by the emergency physician who had been called to the patient, and who was unable to account for the death. Autopsy established the diagnosis of mitral valve prolapse. The authors stress that autopsy is imperative and detail the implications of such a procedure.
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5,028
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Comparison of effectiveness of carvedilol versus bisoprolol for prevention of postdischarge atrial fibrillation after coronary artery bypass grafting in patients with heart failure.
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Atrial fibrillation (AF) occurs frequently soon after coronary artery bypass grafting (CABG) and often results in increased mortality and morbidity, particularly in patients with heart failure. New-onset AF is also a common event in the early period after discharge from a cardiac surgery clinic. Current guidelines recommend β blockers as first-line medication for the prevention of AF after CABG. In this prospective study, we investigated the effectiveness of the highly selective β1 receptor antagonist bisoprolol compared to the less selective β blocker carvedilol in preventing postdischarge AF after CABG in patients with decreased left ventricular function. Three hundred twenty patients (231 men, 89 women, mean age 66 ± 10 years) with ejection fraction <40% who underwent CABG and were then referred to an in-hospital cardiac rehabilitation program were randomized to receive bisoprolol (n = 160) or carvedilol (n = 160) starting 4 to 5 days after surgery. Bisoprolol was started at 1.25 mg 1 time/day and carvedilol was started 3.125 mg 2 times/day. All patients underwent continuous telemetric electrocardiographic monitoring for 5 days after entry in the study and thereafter 2 times/day routinely up to hospital discharge. During follow-up, 23 patients (14.6%) in the bisoprolol group and 37 patients (23%) in the carvedilol group developed AF (relative risk 0.6, confidence interval 0.4 to 0.9, p = 0.032). Twenty-six percent of all AF episodes were asymptomatic. At the 4-week outpatient visit, those in the bisoprolol group showed a significantly greater decrease in heart rate, being in sinus rhythm or AF (-15.6 ± 3 vs -9.4 ± 3 beats/min, p = 0.021), whereas changes in systolic and diastolic blood pressures did not differ significantly. In conclusion, bisoprolol is more effective than carvedilol in decreasing the incidence of postdischarge AF after CABG in patients with decreased left ventricular function.
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5,029
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Efficacy of fluid assessment based on intrathoracic impedance monitoring in patients with systolic heart failure.
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Previous studies have demonstrated that intrathoracic impedance monitoring (IIM) is associated with fluid overload. However, it remains unclear whether this new technology can predict heart failure (HF) before deterioration. Whether fluid status based on IIM predicts HF in patients with left ventricular (LV) systolic dysfunction was investigated.</AbstractText>A prospective clinical observational study of 123 patients implanted with IIM-capable cardiac devices was carried out. The primary endpoint was the positive predictive value (PPV) at 12 months. Secondary endpoints were a correlation between onset of HF and IIM, optimal threshold of fluid index and duration between the alert and HF. Complete follow-up clinical data were obtained from 111 patients. During the observational period, 168 alerts were confirmed from 68 patients. In patient-based analysis (alert-based analysis), PPV was 33.8% (33.9%). Sensitivity, specificity and false positive was 67.6% (83.8%), 49.4% (28.4%) and 50.6% (71.6%), respectively. Mean duration between the alert and HF event was 21.4 ± 6.1 days. On multivariate logistic analysis, maximum fluid index, LV ejection fraction and atrial fibrillation were independent predictors of HF events. The optimal cut-off value determined by receiver operating characteristic curve was 114-ohm·day with sensitivity and specificity of 89.5% and 73.0%, respectively.</AbstractText>IIM-based fluid index in patients with HF due to LV systolic dysfunction was effective in predicting worsening HF.</AbstractText>
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5,030
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Marked variability in susceptibility to ventricular fibrillation in an experimental commotio cordis model.
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Precordial blows in sports and daily activities can trigger ventricular fibrillation (VF) (commotio cordis). Whereas chest wall blows are common, commotio cordis is rare. Although factors such as timing, location, orientation, and energy of impact are critically important, we also hypothesize that there is individual susceptibility to commotio cordis. Using our model of commotio cordis, we evaluated individual animal susceptibility to VF induction and assessed animal characteristics that might be involved.</AbstractText>This retrospective analysis included 139 juvenile swine (weight, 8 to 54 kg) that were anesthetized and placed prone in a sling to receive chest wall strikes with a ball propelled at 30 to 40 mph. Each animal received a minimum of 4 impacts directly over the cardiac silhouette, all timed to a narrow vulnerable window during cardiac repolarization. Of 1274 total impacts, 360 impacts (28%) resulted in VF. There was wide variability in individual animal susceptibility to VF. In 38 animals, none of the impacts resulted in VF (range, 4 to 18 impacts per animal). The majority of animals (91; 65%) were induced into VF with <30% of the strikes. In fact, only 19 animals (14%) had >50% occurrence of VF with chest wall impacts, and only 7 (5%) had >80% occurrence of chest impacts that induced VF. In the animal-based analysis, individual correlates of VF included animal weight, mean impact velocity, mean left ventricular pressure generated by the blow, mean QRS duration, mean QTc, and QTc variability. In multivariable analysis, mean left ventricular pressure generated by the blow, mean QRS duration, and QTc variability remained significant correlates of risk, and number of impacts gained statistical significance such that animals with more impacts were less susceptible to VF.</AbstractText>Swine display a wide range of individual vulnerability to VF triggered by chest wall impact, with a distinct minority being uniquely susceptible. Mild abnormalities in cardiac depolarization and repolarization might underlie this susceptibility. Such individual susceptibility may also be present in humans and contribute to the rarity of commotio cordis.</AbstractText>
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5,031
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Congestive heart failure and atrial fibrillation in a cat with myocardial fibro-fatty infiltration.
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Congestive heart failure and atrial fibrillation were diagnosed in a 4-year-old castrated Birman cat with progressive signs of dyspnea, tachypnea, and lethargy. Echocardiography revealed massive right-sided heart dilatation with ascites and hydrothorax. Electrocardiogram recording showed atrial fibrillation. Medical therapy with diuretics, benazepril, and antithrombotic agents was unsuccessful. The owner requested euthanasia. In post-mortem examination, changes associated with myocardial fibro-fatty infiltration were confirmed. Changes were most marked in the right ventricular wall but with left ventricular involvement was detected.
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5,032
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The persistent sodium current blocker riluzole is antiarrhythmic and anti-ischaemic in a pig model of acute myocardial infarction.
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The potential of the cardiac persistent sodium current as a target for protection of the myocardium from ischaemia and reperfusion injury is gaining increasing interest. We have investigated the anti-ischaemic and antiarrhythmic effects of riluzole, a selective INaP blocker, in an open chest pig model of infarction.</AbstractText>The left anterior descending coronary artery (LAD) was ligated in 27 anesthetised pigs (landrace or large white, either sex, 20-35 kg) which had received riluzole (8 mg/kg IP; n = 6), lidocaine (2.5-12 mg/kg bolus plus 0.05-0.24 mg/kg/min; n = 11) or vehicle (n = 10) 50 min prior. Arrhythmias could be delineated into phase 1a (0 to 20 min), phase 1b (20 to 50 min) and phase 2 (from 50 min to termination at 180 min) and were classified as premature ventricular contractions (PVCs), non-sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) (spontaneously reverting within 15 s) or sustained VT or VF (ie. requiring cardioversion at 15 s). Riluzole reduced the average number of all arrhythmias in Phase 2 (PVCs from 484+/-119 to 32+/-13; non sustained arrhythmias from 8.9+/-4.4 to 0.7+/-0.5; sustained arrhythmias from 3.9+/-2.2 to 0.5+/-0.4); lidocaine reduced the average number of non-sustained and sustained arrhythmias (to 0.4+/-0.3 and 0.4+/-0.3 respectively) but not PVCs (to 390+/-234). Riluzole and lidocaine reduced the average number of sustained arrhythmias in phase 1b (from 1.8+/-0.4 to 0.17+/-0.13 (p<0.02) and to 0.55+/-0.26 (p = ns) respectively). Neither lidocaine or riluzole changed the ECG intervals: there was no statistical significance between groups at time zero (just before ligation) for any ECG measure. During the course of the 3 hour period of the ischaemia R-R, and P-R intervals shortened slightly in control and riluzole groups (not significantly different from each other) but not in the lidocaine group (significantly different from control). QRS and QTc did not change appreciably in any group Riluzole reduced the degree of histopathological tissue damage across the infarct zone considerably more than did lidocaine.</AbstractText>At the doses used, riluzole was at least as effective as lidocaine at reducing the number of episodes of ischaemic VT or VF in pigs, and much more effective at reducing the number of PVCs. We propose that this is related to the ability of riluzole to block cardiac persistent sodium current.</AbstractText>
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5,033
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Tetralogy of fallot repair in patients 40 years or older.
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To report the outcomes of patients with tetralogy of Fallot (TOF) undergoing surgical repair at age 40 years or older.</AbstractText>We reviewed records of patients (age, ≥40 years) who underwent TOF repair from January 1, 1970, through December 31, 2007. Symptoms, palliative procedures, surgical reports, and long-term outcomes were analyzed.</AbstractText>Fifty-two patients (30 men [58%]) had surgery at a mean ± SD age of 50±8 years; 27 (52%) had prior palliative surgery at a mean ± SD age of 17±11 years. Procedures for TOF repair included pulmonary valve replacement (n=10), transannular patch (n=10), and native pulmonary valve preservation (n=32). The 30-day mortality rate was 6% (stroke, n=2; ventricular fibrillation, n=1). A mean ± SD follow-up of 14.9±9.3 years was feasible in 48 of 49 survivors; improvement in functional class was observed in 42 patients. Reoperation was performed in 7 patients (4 for pulmonary regurgitation). Twenty-nine patients died (mean ± SD age, 65±12 years); causes of death were cardiac (n=7), noncardiac (n=4), and unknown (n=18). Mean ± SD age at death was younger in patients with previous palliation (59±11 years vs 70±12 years; P=.03). The 10-year survival rate was lower than expected compared with an age- and sex-matched population (73% vs 91%; P<.001).</AbstractText>Complete repair of TOF in patients 40 years or older is feasible but carries increased operative risk. Surgical survivors have improvement in functional class; however, survival remains lower than expected. Reduced survival and need for reoperation emphasize the importance of pulmonary valve replacement at the time of initial repair and long-term follow-up.</AbstractText>
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5,034
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[The effects on brain function and ultrastructure changes by elevating mean arterial pressure after cardio-pulmonary resuscitation in pigs].
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To investigate the effects on brain function and ultrastructure changes by elevating mean arterial pressure (MAP) with norepinephrine after cardiopulmonary resuscitation (CPR) in pigs.</AbstractText>After 4 minutes of untreated ventricular fibrillation, CPR was begun in 10 piglets, followed by defibrillation. Following the restoration of spontaneous circulation (ROSC), the animals were randomly assigned to two treatment groups: the hypertension group (HT, n=5), in which animals were given an infusion of norepinephrine to maintain the MAP to 130% above that before ventricular fibrillation, and the normal perfusion group (NP, n=5) who received an infusion of norepinephrine to maintain the MAP to that obtained right after ROSC. Sham-operation group of 2 animals were treated identically, with the exception that neither cardiac arrest was induced nor CPR was performed, to serve as control group. Variables of hemodynamics were measured at baseline and also 4 hours after ROSC. The overall performance categories (OPC) was evaluated 24 hours after ROSC. Then, animals were sacrificed and the brains were removed for histopathological examination of cerebral cortex, CA1 region of hippocampus, cerebellar cortex, and corpus striatum for the assay of histological damage score (HDS), and apoptosis of cerebral neurons were evaluated [terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)] 24 hours after ROSC. The ultrastructure of neurons was characterized, using transmission electron microscopy.</AbstractText>Five animals in the HT group showed good OPC (OPC 1-2), while 3 animals in the NP group showed good OPC (OPC 1-3). Brain tissue from different regions was normal in sham-operation group. The HDS in the cerebral cortex and CA1 region of hippocampus in the HT group was lower than that in the NP group (cerebral cortex: 1.6±0.5 vs. 2.2±0.8, hippocampus: 1.8±0.8 vs. 2.8±0.5, both P<0.05). The TUNEL- positive cells in the cerebella and the CA1 region of hippocampus were significantly reduced in the HT group compared with the NP group (cerebella:21.2±3.2 vs. 38.6±3.8, hippocampus: 22.7±7.6 vs. 35.0±6.8, both P<0.05). With transmission electron microscopy, necrotic neurons were found in the cerebral cortex, striatum and the CA1 region of hippocampus, while in cerebella only granular cells and glial cells in the CA1 region of hippocampus showed apoptosis. The damages to neurons were significantly reduced in HT group.</AbstractText>Hypertension induced by norepinephrine is a safe and effective method to reduce brain damages and prevent apoptosis of neurons.</AbstractText>
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5,035
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Short QT Syndromes.
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The short QT syndrome is a recently described genetic arrhythmogenic disorder, characterized by abnormally short QT intervals and a high incidence of sudden death and atrial fibrillation. Clinical manifestations may also be present in infants; a family history of cardiac sudden death is often present. Gain-of-function mutations in 3 genes encoding potassium channels and loss-of-function mutations in 2 genes encoding the cardiac L-type calcium channel have been identified. Today, the first choice therapy is implantable cardioverter-defibrillator implantation; however, pharmacologic treatment with hydroquinidine, which prolongs QT and reduces the inducibility of ventricular arrhythmias, may be proposed for children and probably for elderly asymptomatic patients.
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5,036
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Brugada Syndrome 2010.
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The Brugada syndrome is a genetically determined cardiac disorder, presenting with characteristic electrocardiogram features and high risk of sudden cardiac death from polymorphic ventricular tachycardia/ventricular fibrillation in young individuals with a structurally normal heart. Scientific knowledge about the disease has grown exponentially in recent years. Two consensus reports on the disease were published (in 2002 and 2005) in an effort to state diagnostic criteria, risk stratification, and treatment indications. However, substantial controversies remain, especially considering risk stratification of asymptomatic patients. Given the enormous amount of valuable information collected by many groups since the consensus reports, current diagnostic criteria, recommended prognostic tools, and treatment must be reviewed. This article briefly reviews recent advances in understanding of Brugada syndrome and its genetic and molecular basis, arrhythmogenic mechanisms, and clinical course. An update of tools for risk stratification and treatment of the condition is also included.
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5,037
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Hemodynamic support with TandemHeart in tako-tsubo cardiomyopathy - a case report.
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Tako-tsubo cardiomyopathy is characterized by chest pain, electrocardiographic abnormalities mimicking acute myocardial infarction, akinesis or dyskinesis of apical or mid left ventricular segments, and the absence of obstructive coronary artery disease. Tako-tsubo cardiomyopathy is usually a potentially reversible form of cardiac dysfunction. A careful literature search revealed no previous report of a patient requiring mechanical circulatory support in tako-tsubo cardiomyopathy. We report a patient with tako-tsubo cardiomyopathy, ventricular fibrillation, and hemodynamic instability requiring a left ventricular assist device (TandemHeart(™)) followed by improvement of left ventricular ejection fraction to 45%.
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5,038
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Persistent atrial fibrillation is not associated with thrombomodulin level increase in efficiently anticoagulated patients.
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Atrial fibrillation (AF) is the most common arrhythmia and leads to a five-fold increased risk of stroke compared to persons with sinus rhythm. A soluble form of thrombomodulin (sTM) is a recognized marker of endothelial dysfunction and may contribute to the hypercoagulable state in AF. The aim of the study was to evaluate plasma concentration of sTM in persistent AF patients before and after sinus rhythm recovery following direct current cardioversion (CV).</AbstractText>In 45 effectively anticoagulated consecutive patients, with persistent non-valvular AF, and normal left ventricular function, CV was performed. Blood samples for sTM assessment were collected twice: 24 hours before and 24 hours after CV.</AbstractText>In 43 patients sinus rhythm was obtained. The mean plasma sTM level was significantly lower in AF patients compared to the control group with sinus rhythm and without anticoagulation (38.5 ±9.9 ng/ml vs. 44.1 ±9.1 ng/ml, p = 0.04). Plasma sTM levels did not change 24 hours after successful CV (36.7 ±9.5 ng/ml vs. 38.5 ±9.9 ng/ml, p = 0.16).</AbstractText>Plasma sTM concentration was lower in patients with persistent AF and normal left ventricle systolic function than in patients with sinus rhythm, presumably due to chronic oral anticoagulant therapy in the AF group. CV has no impact on sTM plasma level evaluated 24 hours after sinus rhythm restoration.</AbstractText>
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5,039
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Tachycardia transition during ablation of persistent atrial fibrillation.
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The "sequential ablation" strategy for persistent AF is aimed at progressive organization of AF until the rhythm converts to sinus rhythm or atrial tachycardia (AT). During ablation of an AT, apparently seamless transitions from one organized AT to another occur. The purpose of our study was to quantify the occurrence and the mechanism of this transition.</AbstractText>Twenty-nine of 90 patients undergoing ablation for persistent AF had multiple AT during the procedure and constitute the study group. Thirty-nine direct transitions from one AT to another during ablation were observed classified in four types: type I (79.4%), i.e., a direct transition of a faster to a slower tachycardia without significant intervening pause; type II (7.69%)--transition after intervening ectopy or longer pause; type III (10.26%)--A slower AT accelerated; type IV (2.56%)--alteration of activation sequence but with no change on CL.</AbstractText>Transition to a second AT occurs frequently in the midst of ablation of AT in persistent AF patients. This transition occurs most commonly abruptly within the range of a single cycle length of the original AT. This is best explained by a continuation of AT that was "present" simultaneously with the pretransition tachycardia, being "entrained" (for a reentrant tachycardia) or "overdriven" for an automatic focal tachycardia. The presence of multiple tachycardia mechanisms active simultaneously would be consistent with the eclectic pathophysiology of persistent AF.</AbstractText>© 2010 Wiley Periodicals, Inc.</CopyrightInformation>
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5,040
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A review of the appropriate and inappropriate use of dronedarone: lessons learned from controlled studies and regulatory submission.
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Dronedarone is a multichannel blocker with electrophysiologic effects similar to amiodarone. Dronedarone has been documented to prevent atrial fibrillation recurrences and also has efficacy in slowing the ventricular response during episodes of atrial fibrillation. However, in the ANDROMEDA trial, dronedarone was associated with increased mortality when tested in New York Heart Association (NYHA) III/IV patients with left ventricular ejection fractions of less than 35%, who also had a recent hospitalization for decompensated heart failure. When such high-risk patients with heart failure were excluded in the ATHENA trial, dronedarone treatment resulted in a statistical reduction in the composite primary end point of all-cause mortality or cardiovascular hospitalization. In ATHENA, dronedarone reduced cardiovascular hospitalizations even though in the DIONY-SOS trial dronedarone had less effect than amiodarone on suppressing atrial fibrillation recurrences. The most appropriate patients for treatment with dronedarone would be patients with a recent history of paroxysmal or persistent atrial fibrillation/atrial flutter (AF/AFL) that have associated risk factors per the inclusion criteria of ATHENA. Inappropriate patients would be those with class IV heart failure or recently hospitalized for heart failure within the last month from an acute decompensation, the main inclusion criteria in ANDROMEDA. Dronedarone is a novel, multichannel blocking antiarrhythmic agent that may have some pleiotropic effects in addition to its ability to suppress and maintain sinus rhythm and control the rate during AF/AFL recurrences.
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5,041
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A new agent for atrial fibrillation: electrophysiological properties of dronedarone.
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Although originally synthesized as an antianginal compound, amiodarone has emerged as an effective antiarrhythmic for both supraventricular and ventricular arrhythmias. Over the decades, the properties, the effectiveness, the merits as well as the shortcomings of the compound have been well established. The major limitations of this agent are mainly due to the systemic side effects seen with prolonged therapy. Many of the toxic effects observed are primarily caused by the high iodine content present in the amiodarone molecule. Dronedarone, the first noniodinated amiodarone congener, has been developed largely to obtain the antiarrhythmic efficacy in the control of atrial fibrillation without the known adverse side effects of dronedarone. In this part of the supplement, the focus is the electrophysiological effects of dronedarone with the characterization in normal cardiac cells, in animal models of disease, as well as in human studies.
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5,042
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Prompt prediction of successful defibrillation from 1-s ventricular fibrillation waveform in patients with out-of-hospital sudden cardiac arrest.
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Ventricular fibrillation (VF) is a common cardiac arrest rhythm that can be terminated by electrical defibrillation. During cardiopulmonary resuscitation, there is a strong need for a prompt and reliable predictor of successful defibrillation because myocardial damage can result from repeated futile defibrillation attempts. Continuous wavelet transform (CWT) provides excellent time and frequency resolution of signals. The purpose of this study was to evaluate whether features based on CWT could predict successful defibrillation.</AbstractText>VF electrocardiogram (ECG) waveforms stored in ambulance-located defibrillators were collected. Predefibrillation waveforms were divided into 1.0- or 5.12-s VF waveforms. Indices in frequency domain or nonlinear analysis were calculated on the 5.12-s waveform. Simultaneously, CWT was performed on the 1.0-s waveform, and total low-band (1-3 Hz), mid-band (3-10 Hz), and high-band (10-32 Hz) energy were calculated.</AbstractText>In 152 patients with out-of-hospital cardiac arrest, a total of 233 ECG predefibrillation recordings, consisting of 164 unsuccessful and 69 successful episodes, were analyzed. Indices of frequency domain analysis (peak frequency, centroid frequency, and amplitude spectral area), nonlinear analysis (approximate entropy and Hurst exponent, detrended fluctuation analysis), and CWT analysis (mid-band and high-band energy) were significantly different between unsuccessful and successful episodes (P < 0.01 for all). However, logistic regression analysis showed that centroid frequency and total mid-band energy were effective predictors (P < 0.01 for both).</AbstractText>Energy spectrum analysis based on CWT as short as a 1.0-s VF ECG waveform enables prompt and reliable prediction of successful defibrillation.</AbstractText>
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5,043
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[Class I antiarrhythmic drugs: mechanisms, contraindications, and current indications].
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Class I antiarrhythmic drugs are sodium channel inhibitors that act by slowing myocardial conduction and, thus, interrupting or preventing reentrant arrhythmia. Due to proarrhythmic effects and the risk of ventricular tachyarrhythmia, class I antiarrhythmics should not be administered in patients with structural heart disease. Nevertheless, there remains a broad spectrum of arrhythmias--among the most common being atrial fibrillation--that can successfully be treated with class I antiarrhythmic drugs. This review gives an overview on the classification, antiarrhythmic mechanisms, indications, side effects, and application modes of class I antiarrhythmic drugs.
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5,044
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Long-term follow-up of patients with myotonic dystrophy: an electrocardiogram every year is not necessary.
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A high risk of arrhythmias was reported in myotonic dystrophy (MD). The purpose of the study was to evaluate the value of non-invasive and invasive investigations for the arrhythmias detection and when to repeat the investigations. 129 patients, mean age 41 ± 14 years, with MD, were asymptomatic, except 4. Electrocardiogram (ECG), left ventricular ejection fraction determination, Holter monitoring, signal-averaged ECG, electrophysiological study (51) were obtained and repeated each year in patients without conduction abnormalities. Electrocardiogram and Holter monitoring were normal in 72 and 89 patients, respectively. Standard deviation of the mean RR intervals (SDNN) was <100 ms in 30 patients. Late potentials were present in 32 patients, without ventricular tachycardia (VT) correlation. Ejection fraction was normal in all but six patients (60±10.5%). HV interval was prolonged in 0 of 8 patients with normal ECG, 1 of 9 with isolated first degree atrioventricular block, 9 of 16 with hemiblock, and 10 of 15 with bundle branch block. Atrial fibrillation (AF) was induced in 22 patients, non-sustained VT in 6 patients, and sick sinus syndrome noted in 10 patients. The mean time for the ECG change was 5±1 years. After 10±7.5 years, AF occurred in 15 patients; 12 patients died. Multivariate analysis indicated that both AF at ECG and SDNN lower than 100 ms were independent predictors of death. HV increase was noted only in patients with abnormal ECG. The most frequent arrhythmia was AF and was associated with a high risk of death. The repetition of ECG every year is probably not useful.
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5,045
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Adverse experiences with implantable defibrillators in Oregon hospices.
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Implantable cardioverter-defibrillators (ICDs) improve survival in patients at risk for recurrent, sustained ventricular tachycardia or fibrillation. Unless deactivated, ICDs may deliver unwanted shocks to terminally ill patients near the time of death. This study sought to determine the frequency and nature of adverse experiences with ICDs in hospice programs and what preventative measures the programs had taken.</AbstractText>A mailed survey to all 50 Oregon Hospice Programs in August 2008.</AbstractText>42 (84%) of 50 programs participated. In all 36 (86%) of 42 programs reported having taken care of a patient with an ICD in the preceding 4 years. The average number of patients with ICDs per program increased from 2.2 (SD 2.5) in 2005 and 2006 to 3.6 (SD 3.7) in 2007 and 2008. Of the 36 programs who had cared for a patient with an ICD, 31 (86%) reported having some kind of adverse experience. These ranged from unwanted shocks delivered (64%), patient/family distress related to the decision to deactivate the ICD (47%), and time delay in ICD deactivation (42%). Only 16 (38%) programs had policies for managing ICDs and only 19 (43%) routinely screened new patients for ICDs.</AbstractText>As patients near the end of their lives, receiving defibrillating shocks may no longer be consistent with their goals of care. Based on the high frequencies of potentially preventable adverse outcomes documented by this study, we propose that hospices routinely screen patients for ICDs and proactively adopt policies to manage them, rather than in response to an adverse event.</AbstractText>
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5,046
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Equitable improvement for women and men in the use of guideline-recommended therapies for heart failure: findings from IMPROVE HF.
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Although sex-based disparities in use of guideline-recommended heart failure (HF) therapies have been described, little is known about whether performance improvement (PI) initiatives produce equitable improvements in guideline-recommended therapies.</AbstractText>IMPROVE HF is a prospective study of a practice-based PI intervention in patients with systolic HF or post-myocardial infarction left ventricular dysfunction. Mean changes from baseline to 24 months after intervention were compared between women and men for treatment with angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, β-blockers, aldosterone antagonists, anticoagulation for atrial fibrillation, cardiac resynchronization therapy (CRT), implantable cardioverter-defibrillator (ICD), and HF education. This analysis included 15,170 patients at 167 cardiology practices (4,383 [28.9%] women, 10,787 [71.1%] men). At baseline, women were less likely than men to be treated with anticoagulation and ICD. Significant improvements in 6 of 7 quality measures were evident at 24 months for both sexes. The absolute magnitude of improvement was similar for 5 measures and significantly better in women for CRT, ICD, and composite care.</AbstractText>This PI intervention was associated with similar or greater increases in use of guideline-recommended HF therapies for eligible women compared with men. Clinical decision support and performance feedback may help to ensure improved, equitable care for men and women with HF.</AbstractText>Copyright © 2010 Elsevier Inc. All rights reserved.</CopyrightInformation>
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5,047
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Comparative validation of a novel risk score for predicting bleeding risk in anticoagulated patients with atrial fibrillation: the HAS-BLED (Hypertension, Abnormal Renal/Liver Function, Stroke, Bleeding History or Predisposition, Labile INR, Elderly, Drugs/Alcohol Concomitantly) score.
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The purpose of this study was to investigate predictors of bleeding in a cohort of anticoagulated patients and to evaluate the predictive value of several bleeding risk stratification schemas.</AbstractText>The risk of bleeding during antithrombotic therapy in patients with atrial fibrillation (AF) is not homogeneous, and several clinical risk factors have been incorporated into clinical bleeding risk stratification schemas. Current risk stratification schemas for bleeding during anticoagulation therapy have been based on complex scoring systems that are difficult to apply in clinical practice, and few have been derived and validated in AF cohorts.</AbstractText>We investigated predictors of bleeding in a cohort of 7,329 patients with AF participating in the SPORTIF (Stroke Prevention Using an ORal Thrombin Inhibitor in Atrial Fibrillation) III and V clinical trials and evaluated the predictive value of several risk stratification schemas by multivariate analysis. Patients were anticoagulated orally with either adjusted-dose warfarin (target international normalized ratio 2 to 3) or fixed-dose ximelagatran 36 mg twice daily. Major bleeding was centrally adjudicated, and concurrent aspirin therapy was allowed in patients with clinical atherosclerosis.</AbstractText>By multivariate analyses, significant predictors of bleeding were concurrent aspirin use (hazard ratio [HR]: 2.10; 95% confidence interval [CI]: 1.59 to 2.77; p < 0.001); renal impairment (HR: 1.98; 95% CI: 1.42 to 2.76; p < 0.001); age 75 years or older (HR: 1.63; 95% CI: 1.23 to 2.17; p = 0.0008); diabetes (HR: 1.47; 95% CI: 1.10 to 1.97; p = 0.009), and heart failure or left ventricular dysfunction (HR: 1.32; 95% CI: 1.01 to 1.73; p = 0.041). Of the tested schemas, the new HAS-BLED (Hypertension, Abnormal Renal/Liver Function, Stroke, Bleeding History or Predisposition, Labile INR, Elderly, Drugs/Alcohol Concomitantly) score performed best, with a stepwise increase in rates of major bleeding with increasing HAS-BLED score (p(trend) <0.0001). The c statistic for bleeding varied between 0.50 and 0.67 in the overall entire cohort and 0.68 among patients naive to warfarin at baseline (n = 769).</AbstractText>This analysis identifies diabetes and heart failure or left ventricular dysfunction as potential risk factors for bleeding in AF beyond those previously recognized. Of the contemporary bleeding risk stratification schemas, the new HAS-BLED scheme offers useful predictive capacity for bleeding over previously published schemas and may be simpler to apply.</AbstractText>Copyright © 2011 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.</CopyrightInformation>
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5,048
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A slightly elevated level of N-terminal pro-brain natriuretic peptide can predict coronary artery disease in a population with normal left ventricular function.
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The prognostic and diagnostic values of N-terminal pro-brain natriuretic peptide (NT-pro-BNP) in ischemic heart disease have already been investigated in many previous studies. Although NT-pro-BNP is affected by many factors, these previous studies did not strictly exclude them. This study included 110 patients who received coronary arteriography between November 2007 and September 2009. Excluded from the study were those patients who had clinical symptoms of heart failure, asynergy by echocardiography or left ventriculography (LVG), atrial fibrillation, prior myocardial infarction, valvular disease, lung disease, anemia or renal dysfunction. We compared the laboratory data, LVG and early transmitral-to-early diastolic annular velocity ratio (E/E (a)) in echocardiography between the group with coronary stenosis and the group without it. NT-pro-BNP and the low-density lipoprotein/high-density lipoprotein ratio (LDL/HDL) independently associated with the presence of coronary artery stenosis (odds ratio of NT-pro-BNP, each 50 pg/ml 2.367, 95% confidence interval 1.302-4.303, p = 0.005). The area under the curve of the receiver-operating characteristic (ROC) curve of NT-pro-BNP, used to predict coronary artery stenosis, was 0.801 (0.719-0.883, p < 0.001). According to the ROC curve, the optimal cut-off level for predicting coronary stenosis was 64.3 pg/ml (sensitivity 82.5%, false-positive 34%). NT-pro-BNP is an attractive supplemental marker to predict the presence of coronary artery stenosis in a population that strictly excluded any affecting factors. In the population without factors affecting NT-pro-BNP, a slight increase suggests the presence of ischemic heart disease. The normal criteria for NT-pro-BNP in the patients undergoing coronary angiography may be much lower than the one currently used.
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5,049
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Shortening of paced QRS complex and clinical improvement following upgrading from apical right ventricular pacing to bifocal right ventricular or biventricular pacing in patients with permanent atrial fibrillation.
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Cardiac resynchronisation therapy (CRT) using biventricular pacing (BVP) has been shown to improve survival in patients with chronic heart failure (CHF). However, BVP cannot be achieved in all patients because of technical problems. In such patients, bifocal right ventricular pacing (BFP) may be an alternative.</AbstractText>To analyse the relationship between changes in paced QRS complex width and clinical responses in previously conventionally paced patients, who underwent upgrading to BFP or BVP.</AbstractText>A total of 34 patients (26 male, eight female) aged 53.4 to 84 years (mean age 70.3) with CHF, permanent atrial fibrillation and previous right ventricular apical pacing lasting 35.4-184.2 months (mean duration 92.2 months) due to primary or post-ablation (12 patients) atrioventricular block, were included in the study. The patients were split into two subgroups: in the first (ten patients), the cardiac pacing system was changed to BFP, whereas in the second (24 patients), BVP was performed. Over a 12-month period, the following changes were studied: NYHA classification, brain natriuretic peptide levels (BNP), distance covered in a six-minute walk test (6MWT) and left ventricular ejection fraction (LVEF). The observation period was divided into two stages: the first six months after the pacing system was changed, and the six months following that. All 34 patients finished the first observation period, and 27 of them completed the second period.</AbstractText>Clinical improvement was observed in all the patients following the change of pacing system. The greatest clinical improvement occurred during the first stage of observation. At that time, a significant amelioration of HF, according to NYHA classification and improvement in LVEF and 6MWT were noted in both groups. Additionally, a significant improvement (reduction) of BNP level in the BVP subgroup was reported. In the second observation period, a further improvement in the LVEF value was observed in the BVP subgroup. A significant negative correlation between the relative shortening of QRS complex and relative change in LVEF was observed in the whole group, and in the BVP subgroup.</AbstractText>In patients with permanent AF the change of pacing site from right ventricular apex to BFP or BVP results in significant improvement in CHF symptoms. During long-term follow-up these changes are more prehounced in BVP than BFP patients. There is a correlation between shortened QRS complex duration and improvement of LVEF in BVP patients.</AbstractText>
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5,050
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[New developments in the antiarrhythmic therapy of atrial fibrillation].
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Atrial fibrillation, which is associated with a worsening of congestive heart failure symptoms, an increased rate of stoke, and increased mortality, is still difficult to treat. New therapies must not only increase effectiveness, but also have to have an improved safety profile, in order to avoid sodium channel block in the ventricle of older patients with atrial fibrillation, and also prevent electrical and morphological remodeling. Dronedarone is less effective compared to amiodarone, but has a better side effect profile which leads to fewer discontinuations of treatment. The atrial ion channels are specifically blocked by a number of prospective antiarrhythmic substances. The most advanced is the testing of vernakalant (RSD1235), which primarily suppresses the I(Kur) current. Ranolazine is a new antianginal substance which influences the atrial ion channels and leads to a significant reduction of atrial and more specifically ventricular tachyarrhythmias. A number of other drugs are in development. They will lead to a better understanding of which form of atrial fibrillation can be best treated with which antiarrhythmic agent.
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5,051
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Changes in cytokine concentrations following successful ablation of atrial fibrillation.
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Atrial fibrillation is associated with the activation of inflammatory processes [e.g. higher concentrations of pro-inflammatory cytokines interleukin-6 (IL-6), C-reactive protein (CRP)], as well as a pro-thrombotic state [e.g. increased concentration of serum pro-thrombotic markers P-selectin and CD40 ligand (CD40L)]. The aim of the present study was to establish, whether successful epicardial ablation of AF leads to decreased concentrations of traditional inflammatory and thrombotic markers.</AbstractText>Twenty-five patients with symptomatic paroxysmal or persistent AF were prospectively studied. All underwent epicardial isolation of pulmonary veins. The success of the ablation was assessed clinically and with three Holter recordings. Blood samples were drawn before, three and six months after surgery. Serum concentrations of IL-6, interleukin-10 (IL-10), CRP, CD40L and P-selectin were measured using ELISA.</AbstractText>AF was successfully ablated in 15 patients (SR group). In the other 10 patients (AF group), AF re-occurred during follow-up. Neither group differed with respect to age, gender, left ventricular ejection fraction, or preoperative concentrations of measured molecules. The concentrations of IL-6, CRP and CD40L decreased in successfully ablated patients; however, there was no change in the concentrations of these molecules in the AF group. The concentrations of IL-10 and P-selectin were unchanged in both groups during follow-up.</AbstractText>Successful ablation of AF, with sinus rhythm restoration and maintenance, is associated with decreased serum levels of markers of inflammation.</AbstractText>
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5,052
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[Antiarrhythmic therapy with β-receptor antagonists].
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β-Blockers are an essential component of medical therapy in patients with ischemic heart disease or cardiac dysfunction of any genesis. They have an effect at the level of the sinus and the atrioventricular node, as well as on the atrial and ventricular refractory period of the myocardium. Overall, there are complicated antifibrillatory effects which are involved in the reduction of morbidity and mortality of this the therapy. According to the guidelines, it is important to uptitrate to highest tolerated dose. In patients with atrial fibrillation, antiadrenergic therapy should be the first line treatment; if well tolerated, then β-blockers alone or as a combination with an antiarrhythmic drug is preferable. Future prospective studies on the antiarrhythmic effects in this therapeutic area should include comparisons of different α - and β-selective active substances. Increasing knowledge of the differential therapy with the available active substances including intravenously applicable short-acting β-blockers, e.g., in intensive care therapy - should distinguish the different therapeutic effects.
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5,053
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[Current role of amiodarone in antiarrhythmic therapy].
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Decades after its registration, amiodarone is still regarded as the most effective antiarrhythmic drug available for the treatment of tachyarrhythmias. Amiodarone is classified as a class III antiarrhythmic drug. In addition to the prolongation of cardiac repolarization, its leading pharmacologic features are sodium and calcium channel block, nonselective β-adrenergic inhibition as well as high lipophilicity and a very long plasma half-life. In patients with paroxysmal atrial fibrillation, amiodarone is the most effective antiarrhythmic drug in maintaining sinus rhythm. Furthermore, it prevents ventricular arrhythmias, such as frequent ventricular extrasystoles or nonsustained runs of ventricular tachycardia, as well as sustained ventricular tachycardia and ventricular fibrillation. In patients with increased risk for sudden cardiac death, e.g., with severely depressed left ventricular function, amiodarone is a highly effective and safe antiarrhythmic drug. In addition, amiodarone has been shown to reduce the number of appropriate and inappropriate shocks in patients with an implantable cardioverter-defibrillator. During long-term amiodarone treatment, typical side effects including corneal microdeposits, blue-gray skin discoloration, photosensitivity, hypothyroidism, hyperthyroidism, peripheral neuropathy, optical neuritis and hepatotoxicity accrue. Upon cessation of medication, these are almost always reversible. Irreversible, severe adverse effects, such as pulmonary toxicity, are very rare under the currently used maintenance dose of 200 mg/day. With regard to its side effect profile, an adequate follow-up of patients including laboratory values, lung function tests, and visual acuity is necessary.
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5,054
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Cardiovascular implications in the treatment of obstructive sleep apnea.
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Epidemiological studies provide strong evidence that obstructive sleep apnea (OSA) is associated with cardiovascular complications such as systemic hypertension, congestive heart failure, and atrial fibrillation. Successful OSA treatment with continuous positive airway pressure (CPAP) has resulted in coincident reductions in systemic hypertension, improvements in left ventricular systolic function, and reductions in sympathetic nervous activity. These data suggest that successful treatment of OSA may reduce cardiovascular morbidity in such patients. Although CPAP is the more successful treatment for OSA when used properly and consistently, its clinical success is often limited by poor patient and partner acceptance, which leads to suboptimal compliance. Oral appliances or upper airway surgeries are considered a second line of treatment for patients with mild to moderate OSA who do not comply with or refuse long-term CPAP treatment. Oral devices such as mandibular repositioning appliances were recently shown to improve arterial hypertension in OSA patients. Electrical stimulation of the hypoglossal nerve is a new investigational therapy for patients with moderate to severe OSA. This new treatment option, if proven effective, may provide cardiovascular benefits secondary to treating OSA.
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5,055
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Coronary-artery spasm after coronary artery bypass graft surgery without extracorporeal circulation: diagnostic and management.
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Coronary artery spasm in perioperative of coronary artery bypass graft surgery is a serious complication, with high rate mortality. Patient 51 years-old submitted to coronary artery bypass graft surgery without Extracorporeal Circulation. The patient evolved in 1st post operative (PO) day with enzymatic alteration and ST-elevation, developing soon afterwards in ventricular fibrillation, defibrillation with success. Cardiac catheterization showed important spasm of all coronary arteries and anastomosis between the left internal thoracic artery and the left anterior interventricular artery. Intracoronary Vasodilators and intra-graft, with re-establishment of their usual and immediate calibers to improve clinic and Hemodynamic stability was used. Satisfactory evolution, discharged at 13rd PO day.
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5,056
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Transmural dispersion of repolarization determines scroll wave behavior during ventricular tachyarrhythmias.
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Ventricular tachyarrhythmia is the leading cause of sudden cardiac death, and scroll wave re-entry is known to underlie this condition. Class III antiarrhythmic drugs are commonly used worldwide to treat ventricular tachyarrhythmias; however, these drugs have a proarrhythmic adverse effect and can cause Torsade de Pointes or ventricular fibrillation. Transmural dispersion of repolarization (TDR) has been suggested to be a strong indicator of ventricular tachyarrhythmia induction. However, the role of TDR during sustained scroll wave re-entry is poorly understood. The purpose of the present study was to investigate how TDR affects scroll wave behavior and to provide a novel analysis of the mechanisms that sustain tachyarrhythmias, using computer simulations.</AbstractText>Computer simulations were carried out to quantify the TDR and QT interval under a variety of I(Ks) and I(Kr) during transmural conduction. Simulated scroll wave re-entries were done under a variety of I(Ks) and I(Kr) in a ventricular wall slab model, and the scroll wave behavior and the filament dynamics (3-dimensional organizing center) were analyzed. A slight increase in TDR, but not in the QT interval, reflected antiarrhythmic properties resulting from the restraint of scroll wave breakup, whereas a marked increase in TDR was proarrhythmic, as a result of scroll wave breakup.</AbstractText>The TDR determines the sustainment of ventricular tachyarrhythmias, through control of the scroll wave filament dynamics.</AbstractText>
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5,057
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Long-term results of catheter ablation in paroxysmal atrial fibrillation: lessons from a 5-year follow-up.
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Paroxysmal atrial fibrillation (AF) naturally progresses toward chronic AF at an estimated rate of 15% to 30% over a 1- to 3-year period. Pulmonary vein (PV) isolation is increasingly performed for the treatment of drug-refractory paroxysmal AF. The long-term data on clinical outcome after circumferential PV isolation are limited.</AbstractText>From 2003 to late 2004, 161 patients (121 men; age, 59.8±9.7 years) with symptomatic paroxysmal AF and normal left ventricular function underwent circumferential PV isolation guided by 3-dimensional mapping and double Lasso technique. Right-sided and left-sided continuous circular lesions encircling the ipsilateral PVs were placed with irrigated radiofrequency energy. The procedure end point was the absence of all PV spikes for at least 30 minutes after PV isolation verified by 2 Lasso catheters placed within the ipsilateral PVs. Sinus rhythm was present in 75 patients (46.6%) after the initial procedure during a median follow-up period of 4.8 years (0.33 to 5.5 years). A second procedure was performed in 66 and a third procedure in 12 patients. Recovered PV isolation conduction was observed in 62 of 66 patients (94.0%) during the second and in 8 of 12 patients (66.7%) during the third procedure. After a median of 1 (1 to 3) procedure, stable sinus rhythm was achieved in 128 of 161 patients (79.5%), whereas clinical improvement occurred in an additional 21 of 161 patients (13.0%) during a median follow-up of 4.6 years (0.33 to 5.5 years). Four patients in stable sinus rhythm died during follow-up. Progression toward chronic AF was observed in 4 patients (2.4%); however, only 2 patients reported symptoms.</AbstractText>In patients with paroxysmal AF and normal left ventricular function, circumferential PV isolation results in stable sinus rhythm in the majority of patients, and low incidence of chronic AF was observed after ablation during up to 5 years of follow-up.</AbstractText>
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5,058
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MicroRNA-328 contributes to adverse electrical remodeling in atrial fibrillation.
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A characteristic of both clinical and experimental atrial fibrillation (AF) is atrial electric remodeling associated with profound reduction of L-type Ca(2+) current and shortening of the action potential duration. The possibility that microRNAs (miRNAs) may be involved in this process has not been tested. Accordingly, we assessed the potential role of miRNAs in regulating experimental AF.</AbstractText>The miRNA transcriptome was analyzed by microarray and verified by real-time reverse-transcription polymerase chain reaction with left atrial samples from dogs with AF established by right atrial tachypacing for 8 weeks and from human atrial samples from AF patients with rheumatic heart disease. miR-223, miR-328, and miR-664 were found to be upregulated by >2 fold, whereas miR-101, miR-320, and miR-499 were downregulated by at least 50%. In particular, miR-328 level was elevated by 3.9-fold in AF dogs and 3.5-fold in AF patients relative to non-AF subjects. Computational prediction identified CACNA1C and CACNB1, which encode cardiac L-type Ca(2+) channel α1c- and β1 subunits, respectively, as potential targets for miR-328. Forced expression of miR-328 through adenovirus infection in canine atrium and transgenic approach in mice recapitulated the phenotypes of AF, exemplified by enhanced AF vulnerability, diminished L-type Ca(2+) current, and shortened atrial action potential duration. Normalization of miR-328 level with antagomiR reversed the conditions, and genetic knockdown of endogenous miR-328 dampened AF vulnerability. CACNA1C and CACNB1 as the cognate target genes for miR-328 were confirmed by Western blot and luciferase activity assay showing the reciprocal relationship between the levels of miR-328 and L-type Ca(2+) channel protein subunits.</AbstractText>miR-328 contributes to the adverse atrial electric remodeling in AF through targeting L-type Ca(2+) channel genes. The study therefore uncovered a novel molecular mechanism for AF and indicated miR-328 as a potential therapeutic target for AF.</AbstractText>
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5,059
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Diagnosis of cardiovascular abnormalities from compressed ECG: a data mining-based approach.
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Usage of compressed ECG for fast and efficient telecardiology application is crucial, as ECG signals are enormously large in size. However, conventional ECG diagnosis algorithms require the compressed ECG packets to be decompressed before diagnosis can be performed. This added step of decompression before performing diagnosis for every ECG packet introduces unnecessary delay, which is undesirable for cardiovascular diseased (CVD) patients. In this paper, we are demonstrating an innovative technique that performs real-time classification of CVD. With the help of this real-time classification of CVD, the emergency personnel or the hospital can automatically be notified via SMS/MMS/e-mail when a life-threatening cardiac abnormality of the CVD affected patient is detected. Our proposed system initially uses data mining techniques, such as attribute selection (i.e., selects only a few features from the compressed ECG) and expectation maximization (EM)-based clustering. These data mining techniques running on a hospital server generate a set of constraints for representing each of the abnormalities. Then, the patient's mobile phone receives these set of constraints and employs a rule-based system that can identify each of abnormal beats in real time. Our experimentation results on 50 MIT-BIH ECG entries reveal that the proposed approach can successfully detect cardiac abnormalities (e.g., ventricular flutter/fibrillation, premature ventricular contraction, atrial fibrillation, etc.) with 97% accuracy on average. This innovative data mining technique on compressed ECG packets enables faster identification of cardiac abnormality directly from the compressed ECG, helping to build an efficient telecardiology diagnosis system.
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5,060
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Distinguishing between ventricular tachycardia and ventricular fibrillation from compressed ECG signal in wireless Body Sensor Networks.
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Since ECG is huge in size sending large volume data over resource constrained wireless networks is power consuming and will reduce the energy of nodes in Body Sensor Networks (BSN). Therefore, compression of ECGs and diagnosis of diseases from compressed ECGs will play key roles in enhancing the life-time of body sensor networks. Moreover, discrimination between ventricular Tachycardia and Ventricular Fibrillation is of crucial importance to save human life. Existing algorithms work only on plain text ECGs to distinguish between the two, and therefore, not suitable in BSN. VT and VF are often similar in patterns and in filtration of noise and improper attribute selection in compressed ECGs will make it even harder to classify them properly. In this paper, a supervised attribute selection algorithm called Correlation Based Feature Selection (CFS) [4] is used to filter the unwanted attributes and select the most relevant attributes. We then use the selected attributes to train and classify VT and VF using Radial Basis Function (RBF) Neural Network and k-nearest neighbour techniques. We experimented with 103 ECG samples taken from MIT-BIH Malignant Ventricular Ectopy Database. Results showed that accuracy can be as high as 93.3% when attribute selection is used and large number of training samples are provided.
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5,061
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Prediction of ventricular fibrillation based on the ST-segment deviation: allometric model.
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Based on some reported clinical data, we attempt to apply the allometric law for evaluating the probability of ventricular fibrillation when electrocardiographic ST-segment deviations are determined. The deviation is measured in millimeters at the standard calibration of 1mV = 10mm and the probability in percent. Using the equation VF(P) = δ + β (ST) in log-log representation, the fitting procedure produced the following overall coefficients: Average β = 1.11, with a maximum = 1.65 and a minimum = 0.78; Average δ = 0.83, with a maximum = 1.39 and a minimum = 0.41. For a 2mm ST-deviation, the full range of predicted ventricular fibrillation probability extended from about 6% at 1 month up to 47% at 4 years after the original cardiac event. These results, at least preliminarily, appear acceptable and still call for full clinical test. The model seems promising if other parameters were taken into account, such as cardiac enzyme concentration, ischemic or infarcted epicardial areas or ejection fraction. It is concluded, considering these results and a few references found in the literature, that the allometric model shows promising features in cardiology.
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5,062
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Influences of sites and protocols on inducing ventricular fibrillation: A computer simulation study.
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In cardiac electrophysiological study, several electrical stimulation protocols have been employed to induce ventricular fibrillations (VF). In addition, sites of inducing may have different impacts on inducing results as well as different inducing protocols. To study whether VF inducing method is determinant of induced outcome, we simulated VFs induced with different protocols at different sites based on the Wei-Harumi whole heart model. Simulations showed that only certain combinations of pacing protocols and sites could induce sustainable VFs, which had similar frequency distributions. This result suggested that the interactions between protocols and sites determine the odds of successful inducing but once the VF was induced, the pattern was solely determined by inner cardiac properties.
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5,063
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Wavelet-based markers of ventricular fibrillation in optimizing human cardiac resuscitation.
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During cardiac resuscitation from ventricular fibrillation (VF) it would be helpful if we could monitor and predict the optimal state of the heart to be shocked into a perfusing rhythm. Real-time feedback of this state to the emergency medical staff (EMS) could improve the survival rate after resuscitation. In this paper, using real world out-of-the-hospital human VF data obtained during resuscitation by EMS personnel, we present the results of applying wavelet markers in predicting the shock outcomes. We also performed comparative analysis of 5 existing techniques (spectral and correlation based approaches) against the proposed wavelet markers. A database of 29 human VF tracings was extracted from the defibrillator recordings collected by the EMS personnel and was used to validate the waveform markers. The results obtained by the comparison of the wavelet based features with other spectral, and correlation-based features indicates that the proposed wavelet features perform well with an overall accuracy of 79.3% in predicting the shock outcomes and hence demonstrate potential to provide near real-time feedback to EMS personnel in optimizing resuscitation outcomes.
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5,064
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A fast critical arrhythmic ECG waveform identification method using cross-correlation and multiple template matching.
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Critical Arrhythmic ECG such as Ventricular Tachycardia (VT) and Ventricular Fibrillation (VF) are both distinguishable by its waveform characteristics. A VF waveform is often described as disorganized and has an irregular rhythm while a VT waveform exhibits abnormal signatures and presents a regular rhythm pattern. This paper presents a fast cross-correlation algorithm using multiple waveform templates for automatic detection of life threatening arrhythmias such as VT and VF from the Normal Sinus Rhythm (NSR) waveforms. A sliding-window template cross-correlation technique is applied to an ECG signal to generate an array of correlation coefficients. Then a correlation coefficient curve is used to detect high coefficient values for a type of template that will quantify the similarity between an examined ECG signal and a template. The method presented in this paper is able to detect all three different types of ECG signals from a total 21 testing signal set with a satisfied correct rate.
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5,065
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A novel mechanism for electrical currents inducing ventricular fibrillation: The three-fold way to fibrillation.
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It has been long recognized that there are 2 methods for inducing VF (ventricular fibrillation) with electrical currents‥ These are: (1) delivering a high-charge shock into the cardiac T-wave, and (2) delivering lower level currents for 1-5 seconds. Present electrical safety standards are based on this understanding. We present new data showing a 3(rd) mechanism of inducing VF which involves the steps of delivering sufficient current to cause high-rate cardiac capture, causing cardiac output collapse, leading to ischemia, for sufficiently long duration, which then lowers the VFT (VF threshold) to the level of the current, which finally results in VF. This requires about 40% of the normal VF-induction current but requires a duration of minutes instead of seconds for the VF to be induced. Anesthetized and ventilated swine (n=6) had current delivered from a probe tip 10 mm from the epicardium sufficient to cause hypotensive capture but not directly induce VF within 5 s. After a median time of 90 s, VF was induced. This 3(rd) mechanism of VF induction should be studied further and considered for electrical safety standards and is relevant to long-duration TASER Electronic Control Device applications.
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5,066
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Wireless transmission of cardiac action potentials with ultrasonically guided insertion of silicon probes.
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This paper reports on the coupling of ultrasonically guided cardiac probes with wireless transmission of cardiac action potentials for applications in monitoring the 3D electrical onset of ventricular fibrillation. An application specific integrated circuit has been designed with a 40 dB amplifying stage and a frequency modulating oscillator to wirelessly transmit the recorded action potentials. Combined with the ultrasonically inserted cardiac probe that reduces penetration force, this system demonstrates the initial results in wireless monitoring of 3D action potential propagation.
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5,067
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ECG Data-Acquisition and classification system by using wavelet-domain Hidden Markov Models.
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This article is concerned with the classification of ECG pulses by using state of the art Continuous Density Hidden Markov Models (CDHMM's). The ECG signal is simultaneously observed at three different level of focus by means of the Wavelet Transform (WT). The types of beat being selected are normal (N), premature ventricular contraction (V) which is often precursor of ventricular arrhythmia, two of the most common class of supra-ventricular arrhythmia (S), named atrial fibrillation (AF), atrial flutter (AFL), and normal rhythm (N). Both MLII and V1 derivations are used. Run time classification errors can be detected at the decoding stage if the classification of each derivation is different. These pulses are selected for a posterior physician analysis. Experimental results were obtained in real data from MIT-BIH Arrhythmia Database and also in data acquired from a developed low-cost Data-Acquisition System.
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5,068
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Functional model of dual AV nodal pathway physiology.
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Role of dual AV nodal pathway physiology in the atrioventricular nodal (AVN) conduction during atrial arrhythmias remains unclear. By using His electrogram alternans (HEA), we have developed a functional model of the atrioventricular conduction that incorporates the dual AV nodal pathway physiology. Experiments performed on 5 rabbit atrial-AVN preparations were used to develop and test the presented AV nodal functional model. HEAs from the inferior margin of the His bundle were used to identify fast and slow wavefront propagations (FP and SP). Conduction curves were calculated by using the model and compared with the real experiments, the root mean square error of the FP and SP were 7 ± 4ms and 3 ± 3 ms respectively. In addition, the model has been used for illustrating the effects of the atrioventricular node modification, which has emerged as one of the alternatives for ventricular rate control during atrial fibrillation. The presented model can help in understanding some of the unclear AV node conduction mechanisms and should be considered as a step forward in understanding the AV node and specifically its dual pathway physiology.
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5,069
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Shock-induced arrhythmogenesis in the human heart: A computational modelling study.
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Electrical defibrillation by application of a strong shock to the heart is the only effective treatment against lethal cardiac arrhythmias such as ventricular fibrillation. A large body of experimental and computational research has been devoted to understanding shock-induced effects on the heart in an attempt to improve defibrillation efficacy. However, most of the research has been performed in small animal hearts, and in particular rabbits. The difference in size between rabbits and humans might limit the extrapolation of the results to the clinical setting. In this paper, we present, for the first time, computer simulations of shock-induced effects on a human ventricular model with realistic ion channel dynamics and fibre architecture. Bidomain simulations using the human ventricular model were performed using the Chaste open source simulation package. The parallel performance of the software package was highly improved in order to meet the computational requirements of these kind of studies.
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5,070
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Echocardiographic left atrial reverse remodeling after catheter ablation of atrial fibrillation is predicted by preablation delayed enhancement of left atrium by magnetic resonance imaging.
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Atrial fibrosis is a hallmark of atrial structural remodeling (SRM) and leads to structural and functional impairment of left atrial (LA) and persistence of atrial fibrillation (AF). This study was conducted to assess LA reverse remodeling after catheter ablation of AF in mild and moderate-severe LA SRM.</AbstractText>Catheter ablation was performed in 68 patients (age 62 ± 14 years, 68% males) with paroxysmal (n = 26) and persistent (n = 42) AF. The patients were divided into group 1 with mild LA SRM (<10%, n = 31) and group 2 with moderate-severe LA SRM (>10%, n = 37) by delayed enhancement magnetic resonance imaging (DEMRI). Two-dimensional echocardiography, LA strain, and strain rate during left ventricular systole by velocity vector imaging were performed pre and at 6 ± 3 months postablation. The long-term outcome was monitored for 12 months.</AbstractText>Patients in group 1 were younger (57 ± 15 vs 66 ± 13 years, P = .009) with a male predominance (80% vs 57%, P < .05) as compared to group 2. Postablation, group 1 had significant increase in average LA strain (Δ↑: 14% vs 4%, P < .05) and strain rate (Δ↑: 0.5 vs 0.1 cm/s, P < .05) as compared to group 2. There was a trend toward more patients with persistent AF in group 2 (68% vs 55%, P = .2), but it was not statistically significant. Group 2 had more AF recurrences (41% vs 16%, P = .02) at 12 months after ablation.</AbstractText>Mild preablation LA SRM by DEMRI predicts favorable LA structural and functional reverse remodeling and long-term success after catheter ablation of AF, irrespective of the paroxysmal or persistent nature of AF.</AbstractText>Copyright © 2010 Mosby, Inc. All rights reserved.</CopyrightInformation>
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5,071
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Can an elderly woman's heart be too strong? Increased mortality with high versus normal ejection fraction after an acute coronary syndrome. The Global Registry of Acute Coronary Events.
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Coronary artery disease is the leading cause of death in women. We sought to validate previous clinical experience in which we have observed that elderly women with a very high left ventricular ejection fraction (LVEF) are at increased risk of death compared with elderly women with acute coronary syndromes with a normal LVEF.</AbstractText>Data from 5,127 elderly female patients (age >65 years) enrolled in the Global Registry of Acute Coronary Events were collected. Patients were divided into 3 groups based on their LVEF: group I had a low ejection fraction (<55%), group II had a normal ejection fraction (55%-65%), and group III had a high ejection fraction (>65%). χ² test and multiple logistic regression analysis were performed. The main outcome measures were death in-hospital and death, stroke, rehospitalization, and myocardial infarction at 6-month follow-up.</AbstractText>Hospital mortality was 12% in group I. Patients in group III were more likely to die in-hospital than those in group II (P = .003). Multivariable logistic regression showed that high ejection fraction was an independent predictor of hospital death (odds ratio [OR] 2.5, 95% CI [CI] 1.2-5.2, P = .01), 6-month death (OR 2.0, 95% CI 1.1-3.4, P = .01), and cardiac arrest/ventricular fibrillation (OR 2.5, 95% CI 1.2-5.0, P = .01) compared with the normal ejection fraction group.</AbstractText>Having a very high LVEF (> 65%) is associated with worse survival and higher rates of sudden cardiac death than an LVEF considered to be in the reference range.</AbstractText>Copyright © 2010 Mosby, Inc. All rights reserved.</CopyrightInformation>
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5,072
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Onset dynamics of ventricular tachyarrhythmias as measured by dominant frequency.
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Differences in dominant frequency (DF), a measure of electrical activation rate, were used to characterize and classify ventricular tachyarrhythmias (VTA) at onset.</AbstractText>In canine 3- to 5-day-old infarct border zone, monomorphic re-entrant ventricular tachycardia (MVT) was repeatedly induced by programmed electrical stimulation (14 experiments, total of 23 instances used for analysis). Ventricular fibrillation (VF) and polymorphic ventricular tachycardia (PVT) occasionally occurred (total of 23 and 4 episodes, respectively, for all experiments). For each of 196 to 312 border zone bipolar electrode recordings, the DF and DF spatial derivative (DFD) were calculated to assess electrical activity organization and were used to classify VTAs at onset. For classification, measurements were made at 1.5 and 3 seconds from last stimulus for all recording sites, and at 2.25 and 3 seconds for 3- to 7-site subsets as a test with limited data.</AbstractText>At 1.5 seconds after stimulus end, the DF/DFD magnitudes were ordered: MVT < PVT < VF (P < .001). DF/DFD trended upward in VF, downward in MVT, and lacked trend in PVT (P < .001). Based on DF/DFD magnitudes/trends, the MVT/VF classifier accuracy was 94.6% (all sites/1.5 s), 97.9% (all sites/3 s), 82.6% (subset sites/2.25 s), and 86.3% (subset sites/3 s).</AbstractText>VTAs are distinguishable at early onset by degree and trend in organization of electrical activity as estimated by DF and DFD. VF becomes increasingly disorganized, MVT becomes increasingly organized, and PVT remains intermediate. It may be possible to apply this technique for analysis and classification in a clinical setting using currently available special mapping catheters.</AbstractText>Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.</CopyrightInformation>
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5,073
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Antifibrillatory effect of ranolazine during severe coronary stenosis in the intact porcine model.
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Clinical evidence suggests that the antianginal agent ranolazine has antiarrhythmic properties, but its effects on vulnerability to ventricular fibrillation (VF) and T-wave alternans (TWA) during coronary artery stenosis have not been measured.</AbstractText>We investigated whether the antiarrhythmic effect of ranolazine during acute coronary stenosis could be quantified by measuring VF threshold and TWA magnitude.</AbstractText>Electrode catheters placed in the left ventricular apex were used to determine VF threshold during ventricular pacing at 130 beats/min, and TWA was quantified from epicardial electrograms using modified moving average method (N = 18). Left anterior descending coronary flow was reduced with a balloon occluder by 75% for 10 minutes. The I(Kr) blocker E-4031 was used to distinguish effects of late I(Na) and I(Kr) inhibition by ranolazine.</AbstractText>Before stenosis, ranolazine and E-4031 increased VF threshold from 32 ± 4 mA to 46 ± 4 mA (mean ± SEM), P = .02, and from 33 ± 5 mA to 40 ± 9 mA, P = .02, respectively. During stenosis, ranolazine increased VF threshold from 19 ± 2 mA to 33 ± 3 mA (P = .02), whereas E-4031 decreased VF threshold from 21 ± 3 mA to 15 ± 3 mA (P = .02). The ischemia-induced increase in TWA was suppressed by ranolazine but not by E-4031, consistent with effects of these agents on VF threshold.</AbstractText>Ranolazine exerts significant antifibrillatory effects during coronary stenosis through direct effects on cardiac electrical properties independent of coronary flow. Ranolazine's antifibrillatory action during myocardial ischemia does not appear to be mediated by blockade of I(Kr) but rather by inhibition of late I(Na). TWA changes paralleled vulnerability to VF as indicated by VF threshold testing.</AbstractText>Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.</CopyrightInformation>
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5,074
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Effect of amiodarone-induced hyperthyroidism on left ventricular outflow obstruction after septal myectomy for hypertrophic cardiomyopathy.
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Patients with obstructive hypertrophic cardiomyopathy who undergo septal myectomy are at risk for developing postoperative atrial fibrillation. Amiodarone is effective in treating this arrhythmia but is associated with multiple adverse effects, often with delayed onset. A novel case is described of a patient who developed type 2 amiodarone-induced hyperthyroidism that presented as recurrence of outflow obstruction after septal myectomy. The patient's symptoms and echocardiographic findings of outflow obstruction resolved substantially with the treatment of the amiodarone-induced hyperthyroidism. Amiodarone-induced hyperthyroidism of delayed onset can be a subtle diagnosis, requiring a high index of suspicion. In conclusion, recognition of this diagnosis in patients with recurrence of outflow obstruction by symptoms and cardiac imaging after septal myectomy may avoid unnecessary repeat surgical intervention.
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5,075
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Effect of combined spironolactone-β-blocker ± enalapril treatment on occurrence of symptomatic atrial fibrillation episodes in patients with a history of paroxysmal atrial fibrillation (SPIR-AF study).
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Angiotensin II and aldosterone are key factors responsible for the structural and neurohormonal remodeling of the atria and ventricles in patients with atrial fibrillation (AF). The aim of the present study was to evaluate the antiarrhythmic effects of spironolactone compared to angiotensin-converting enzyme inhibitors in patients with recurrent AF. A cohort of 164 consecutive patients (mean age 66 years, 87 men), with an average 4-year history of recurrent AF episodes, was enrolled in a prospective, randomized, 12-month trial with 4 treatment arms: group A, spironolactone, enalapril, and a β blocker; group B, spironolactone and a β blocker; group C, enalapril plus a β blocker; and group D, a β blocker alone. The primary end point of the trial was the presence of symptomatic AF episodes documented on the electrocardiogram. At 3-, 6-, 9-, and 12 months, a significant (p < 0.001) reduction had occurred in the incidence of AF episodes in both spironolactone-treated groups (group A, spironolactone, enalapril, and a β blocker; and group B, spironolactone plus a β blocker) compared to the incidence in patients treated with enalapril and a β blocker (group C) or a β blocker alone (group D). No significant difference was seen in AF recurrences between patients taking spironolactone and a β blocker with (group A) and without (group B) enalapril. No significant differences were found in the systolic or diastolic blood pressure or heart rate among the groups before and after 1 year of follow-up. In conclusion, combined spironolactone plus β-blocker treatment might be a simple and valuable option in preventing AF episodes in patients with normal left ventricular function and a history of refractory paroxysmal AF.
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5,076
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A new electrocardiogram marker to identify patients at low risk for ventricular tachyarrhythmias: sum magnitude of the absolute QRST integral.
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We proposed and tested a novel electrocardiogram marker of risk of ventricular arrhythmias (VAs).</AbstractText>Digital orthogonal electrocardiograms were recorded at rest before implantable cardioverter-defibrillator (ICD) implantation in 508 participants of a primary prevention ICDs prospective cohort study (mean ± SD age, 60 ± 12 years; 377 male [74%]). The sum magnitude of the absolute QRST integral in 3 orthogonal leads (SAI QRST) was calculated. A derivation cohort of 128 patients was used to define a cutoff; a validation cohort (n = 380) was used to test a predictive value.</AbstractText>During a mean follow-up of 18 months, 58 patients received appropriate ICD therapies. The SAI QRST was lower in patients with VA (105.2 ± 60.1 vs 138.4 ± 85.7 mV ms, P = .002). In the Cox proportional hazards analysis, patients with SAI QRST not exceeding 145 mV ms had about 4-fold higher risk of VA (hazard ratio, 3.6; 95% confidence interval, 1.96-6.71; P < .0001) and a 6-fold higher risk of monomorphic ventricular tachycardia (hazard ratio, 6.58; 95% confidence interval, 1.46-29.69; P = .014), whereas prediction of polymorphic ventricular tachycardia or ventricular fibrillation did not reach statistical significance.</AbstractText>High SAI QRST is associated with low risk of sustained VA in patients with structural heart disease.</AbstractText>Copyright © 2011 Elsevier Inc. All rights reserved.</CopyrightInformation>
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5,077
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The incidence and prognostic significance of new-onset atrial fibrillation in patients with acute myocardial infarction and left ventricular systolic dysfunction: a CARISMA substudy.
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The incidence and risk associated with new-onset atrial fibrillation (AF) occurring after discharge in patients with acute myocardial infarction (MI) remains unknown.</AbstractText>This study sought to describe the incidence and clinical risk associated with postdischarge new-onset AF in post-MI patients with left ventricular systolic dysfunction.</AbstractText>The population included 271 post-MI patients with left ventricular ejection fraction ≤ 40% and no history of previous AF from the Cardiac Arrhythmias and Risk Stratification after Acute Myocardial Infarction (CARISMA) study. All patients were implanted with an implantable cardiac monitor and followed up every 3 months for 2 years. Major cardiovascular events were defined as reinfarction, stroke, hospitalization for heart failure, or death.</AbstractText>The risk of new-onset AF is highest during the first 2 months after the acute MI (16% event rate) and decreases until month 12 post-MI, after which the risk for new-onset AF is stable. The risk of major cardiovascular events was increased in patients with AF events ≥ 30 seconds (hazard ratio [95% CI] = 2.73 [1.35 to 5.50], P = .005), but not in patients with AF events lasting <30 seconds (hazard ratio [95% CI] = 1.17 [0.35 to 3.92], P = .80). More than 90% of all recorded AF events were asymptomatic.</AbstractText>Using an implantable cardiac monitor, the incidence of new-onset AF was found to be 4-fold higher than earlier reported. In the study population, in which treatment with beta-blockers was optimized, the vast majority of AF events were asymptomatic, emphasizing the importance of using continuous monitoring for studies concerning AF in heart failure patients. A duration of 30 seconds or more identified clinically important AF episodes documented by an implantable cardiac monitor.</AbstractText>Copyright © 2011. Published by Elsevier Inc.</CopyrightInformation>
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5,078
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Mechanical chest compressions with trapezoidal waveform improve haemodynamics during cardiac arrest.
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During manual chest compressions for cardiac arrest the waveforms of chest compressions are generally sinusoidal, whereas mechanical chest compression devices can have different waveforms, including trapezoidal. We studied the haemodynamic differences of such waveforms in a porcine model of cardiac arrest.</AbstractText>Eight domestic pigs (weight 31±3kg) were anaesthetised and instrumented to continuously monitor aortic (AP) and right atrial pressure (RAP), carotid (CF) and cerebral cortical microcirculation blood flow (CCF). Coronary perfusion pressure (CPP) was calculated as the maximal difference between AP and RAP during diastole or decompression phase. After 4 min of electrically induced ventricular fibrillation, mechanical chest compressions were performed with four different waveforms in a factorial design, and in randomized sequence for 3 min each. Resulting differences are presented as mean with 95% confidence intervals.</AbstractText>Mean AP and RAP were higher with trapezoid than sinusoid chest compressions, difference 5.7 (0.7, 11) and 6.3 (2.1, 11)mmHg, respectively. Flow measured as CF and CCF was also improved with trapezoidal waveform, difference 14 (2.8, 26)ml/min and 11 (5.6, 17)% of baseline, respectively, with a parallel, non-significant (P=0.08) trend for CPP. Active vs. passive decompression to zero level improved CF, but without even a trend for CPP.</AbstractText>Trapezoid chest compressions and active decompression to zero level improved blood flow to the brain. The compression waveform is an additional factor to consider when comparing mechanical and manual chest compressions and when comparing different compression devices.</AbstractText>Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.</CopyrightInformation>
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5,079
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[Early repolarization syndrome and recurrent syncope in two Chinese pedigrees].
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to investigate the clinical characteristics in two families with early repolarization syndrome (ERS) and recurrent syncope.</AbstractText>all family members including the probands were screened with routine clinical examination, electrocardiography, echocardiography, Holter recording, chest x-ray, head-up tilt test and blood biochemistry.</AbstractText>there was no clinical evidence of organic heart disease in all members from the two families. Proband 1 showed recurrent syncope, ERS and repeated torsade de pointes ventricular tachycardia and ventricular fibrillation were documented with resting ECG. ERS was detected in one brother, one nephew and one son from him and all were free of cardiac events including syncope, cardiac arrest and sudden cardiac death. Proband 2 showed recurrent syncope, ERS and ST segment arched upward elevation in V(1)-V(3) were documented by ECG. His father suffered sudden cardiac death at the age of 65 and asymptomatic ERS was detected in one of his nephew.</AbstractText>ERS is not always linked with benign clinical course and can sometimes lead to repeated syncope, torsade de pointes ventricular tachycardia and ventricular fibrillation. Pedigree research is of importance for ERS.</AbstractText>
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5,080
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A case of aborted sudden cardiac death and consequent extreme electrical storm secondary to a metastatic cardiac tumor.
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We report a 43-year-old man with an implantable cardioverter defibrillator for aborted sudden cardiac death. He represents in extreme electrical storm with 111 different ventricular fibrillation episodes. Successful treatment was achieved with multiple antiarrhythmic agents, mechanical ventilation, external shocks, and ultimately overdrive pacing. A cardiac magnetic resonance scan revealed two cardiac lesions that were later diagnosed as metastatic fibrosarcoma. This case highlights two very important and increasingly common cardiological dilemmas: the management of extreme electrical storm and the role of magnetic resonance imaging in aborted cardiac death patients with an apparent "normal" heart.
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5,081
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Chronic heart disease and severe obstetric morbidity among hospitalisations for pregnancy in the USA: 1995-2006.
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to describe changes in characteristics of delivery and postpartum hospitalisations with chronic heart disease from 1995 to 2006.</AbstractText>cross-sectional study.</AbstractText>USA, nationwide hospital discharge data.</AbstractText>a total of 47 882 817 delivery hospitalisations and 660 038 postpartum hospitalisations.</AbstractText>adjusted odds ratios describing the associations between chronic maternal heart disease and severe obstetric complications were obtained from multivariable logistic models. The contribution of chronic heart disease to severe morbidity was estimated using adjusted population-attributable fractions.</AbstractText>prevalence and trends in chronic heart disease, rate and risk of severe obstetric complications.</AbstractText>in 2004-2006, about 1.4% of delivery hospitalisations were complicated with chronic heart disease. No substantial changes in the overall prevalence of chronic heart disease among hospitalisations for delivery were observed from 1995-1997 to 2004-2006. Even so, a linear increase was found for specific congenital heart disease, cardiac dysrhythmias, and cardiomyopathy and congestive heart failure (P < 0.01). During this same period the rate of postpartum hospitalisations with chronic heart disease tripled (P < 0.01). Severe complications during hospitalisations for delivery among women with chronic heart disease were more common in 2004-2006 than in 1995-1997. In 2004-2006, 64.5% of the cases of acute myocardial infarction, 57.5% of the instances of cardiac arrest/ventricular fibrillation, 27.8% of in-hospital mortality and 26.0% of the cases of adult respiratory distress syndrome were associated with hospitalisations with chronic heart disease.</AbstractText>in the USA chronic heart disease among women hospitalised during pregnancy may have increased in severity from 1995 to 2006.</AbstractText>
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5,082
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Left ventricular hypertrophy determines the severity of diastolic dysfunction in patients with nonvalvular atrial fibrillation and preserved left ventricular systolic function.
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Regression of left ventricular (LV) hypertrophy (LVH) is known to be related to a lower incidence of stroke in hypertensive patients with nonvalvular atrial fibrillation (NV-AF). However, its mechanism remains controversial. Recently, diastolic dysfunction (DD) was reported to be correlated with ischemic stroke in NV-AF. We hypothesized that hypertension (HTN) and resultant LVH might be associated with the severity of DD in NV-AF. Two hundred and ninety-four patients (204 males, age 66 ± 12 y) with NV-AF with preserved LV systolic function were included. Clinical and echocardiographic data were compared between patients with enlarged left atrial (LA) volume (n = 237) and patients with normal LA. Age (60 ± 12 vs. 67 ± 11 years), sex (male; 81 vs. 62%), duration of NV-AF (4.1 ± 7.8 vs. 45.7 ± 49.0 months), brain natriuretic peptide (108.3 ± 129.3 vs. 236.1 ± 197.0 pg/mL), right ventricular systolic pressure (24.5 ± 5.5 vs. 33.1 ± 11.1 mmHg), mitral inflow velocity (E [77.4 ± 22.2 vs. 88.3 ± 22.0 cm/s]), LV mass index (LVMI [87.6 ± 22.2 vs. 105.1 ± 23.2 g/m(2)]), peak systolic mitral annular velocity (S' [7.2 ± 2.0 vs. 5.8 ± 1.8 cm/s]), and mitral inflow velocity to diastolic mitral annular velocity (E/E' [9.8 ± 3.4 vs. 12.1 ± 4.4]) were significantly different between the two groups, respectively (P < 0.05). In multivariate analysis, LVMI was independently correlated with increased LA volume (OR: 1.037 [95% CI: 1.011-1.063], P < 0.05), whereas HTN was not. LA enlargement, which reflects the severity and chronicity of DD, is independently associated with LVH in patients with NV-AF. Therefore, regression of LVH with anti-hypertensive treatment may lead to improvement of diastolic function and favorable clinical outcomes in hypertensive patients with NV-AF.
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5,083
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A child with influenza A (H1N1)-associated myocarditis rescued by extracorporeal membrane oxygenation.
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A 6-year-old boy had cold-like symptoms and was diagnosed with influenza A at a clinic. Administration of oseltamivir and azithromycin did not improve the symptoms. He was referred to our hospital and was diagnosed with H1N1 pneumonia. The patient required ventilator support. However, hypoxia and hypercapnia were uncontrollable. To oxygenate and reduce the carbon dioxide concentration, veno-venous extracorporeal membrane oxygenation (ECMO) was applied 24 h after admission. We established outflow via the right internal jugular vein and inflow via the right femoral vein. Six hours later, an electrical storm of ventricular fibrillation occurred, probably due to influenza myocarditis. Chest compression was started immediately. Both cardioversion and medication were ineffective in treating the electrical storm. Therefore, we decided to switch the veno-venous ECMO to veno-arterial ECMO to maintain systemic flow. During chest compression, a 6-mm graft was anastomosed to the left common femoral artery, and an outflow tube was connected to the graft. Consequently, veno-arterial ECMO was established via outflow through the left common femoral artery and inflow through both the right jugular vein and right femoral vein. Veno-arterial ECMO terminated the electrical storm, and cardiac output improved. Veno-arterial ECMO was provided for 107 h, and was then replaced by veno-venous ECMO. Forty-three hours later, veno-venous ECMO was discontinued. The patient was successfully weaned from the mechanical ventilator on the 9th day after admission. Unfortunately, spinal infarction appeared as a complication. The patient was discharged from the hospital on the 86th day, and has now returned to primary school.
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5,084
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Gigantic coronary sinus associated with concurrent persistent left superior vena cava and right ventricular volume overload.
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A 76-year-old women with known atrial fibrillation and congestive heart failure presented with increasing shortness of breath. A 2-dimensional (2-D) transthoracic echocardiogram was performed to assess left ventricular function. An incidental finding of a very large coronary sinus with a diameter of 4.8 cm was seen, raising a suspicion for the possibility of a persistent left superior vena cava (PLSVC) (Figure 1). Additional pertinent positive findings included a massively dilated right atrium (estimated volume: 538 mL), dilated tricuspid annulus with poor leaflet coaptation, severe tricuspid regurgitation, and pulmonary artery systolic pressure (PASP) of 50 mmHg with an estimated mean right atrial pressure (RAP) of 25 mmHg. After agitated saline administration into the left brachial vein, there was immediate and sequential opacification of the dilated coronary sinus, right atrium, and right ventricle, confirming the presence of a PLSVC (Figure 2). CT angiography provided detailed anatomical and morphological characterization demonstrating drainage of the PLSVC into the gigantic coronary sinus and right-sided cardiac chambers and absence of other vascular or congenital anomaly (Figures 3 and 4).
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5,085
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Appropriate and inappropriate electrical therapies delivered by an implantable cardioverter-defibrillator: effect on intracardiac electrogram.
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Local injury current (LIC) seen after induced ventricular fibrillation rescue implantable cardioverter-defibrillator (ICD) shock predicts heart failure progression. We sought to determine the frequency of LIC after spontaneous events in patients receiving ICD therapies.</AbstractText>Near-field (NF) right ventricular (RV) EGM during 10 seconds after delivered ICD therapy was compared with baseline EGM in 420 events that occurred in 134 patients (mean age 60.8 ± 14.8, 106 [79%] male). The magnitude of elevated or depressed potential immediately after the major fast EGM deflection was defined as LIC, and its ratio to the peak-to-peak EGM amplitude was defined as relative LIC. LIC of at least 1 mV or relative LIC of at least 15% was considered significant. LIC was observed in 121 events (28.8%) and was detected more frequently after appropriate (43 [60.6%] events) and inappropriate (56 [64.4%] events) ICD shocks, as compared with appropriate (8 [9.2%] events) and inappropriate (3 [4.7%] events) antitachycardia pacing (ATP) or nonsustained ventricular tachycardia (11 [9.9%] events) [ANOVA P < 0.0001]. Type of ICD therapy (ICD shock vs ATP) was the most significant predictor of LIC (ATP β coefficient -0.81; 95%CI-1.19 to 0.44); P < 0.0001), along with cycle length of tachycardia (β coefficient -0.0117; 95%CI -0.0167 to -0.0068, P < 0.00001) and shock energy (β coefficient 0.024; 95%CI 0.003-0.045, P = 0.025).</AbstractText>Appropriate and inappropriate ICD shocks are frequently characterized by the development of LIC in patients with structural heart disease. Type of electrical ICD therapy, shock energy and cycle length of ventricular arrhythmia are important determinants of LIC.</AbstractText>© 2010 Wiley Periodicals, Inc.</CopyrightInformation>
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5,086
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Ablation of right-sided accessory pathways with atrial insertion far from the tricuspid annulus using an electroanatomical mapping system.
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It is difficult to ablate a right-sided accessory pathway (AP) with atrial insertion far from the tricuspid annulus (TA). We report our initial experience of ablating this rare AP by a 3-dimensional electroanatomical mapping system (CARTO).</AbstractText>From January of 2006 to April of 2008, 18 patients with right-sided APs who failed previous outside ablations were enrolled in this study. Retrograde AP conduction was mapped during pacing at the right ventricular apex by activation-mapping the right atrium (RA) using a 3-dimensional electroanatomical mapping system. AP atrial insertion was defined as the earliest retrograde atrial activations and successful ablation of the APs at this site.</AbstractText>Among the 18 patients who had failed previous ablation, 10 patients (7 patients with right manifest APs and 3 patients with right conceal APs) had atrial insertions far from the TA. Of the 10 patients, the atrial insertions were found at the base of the RA appendage in 3 patients, at the high lateral RA in 5 patients, at the low lateral RA in other 2 patients. Ablation at the atrial insertions successfully abolished the AP conduction. The mean distance between the atrial insertion sites and the TA was 20.2 ± 2.7 mm. No patients reported recovered AP conduction or recurrent tachycardias after 6-month follow-up.</AbstractText>The right-sided APs may have atrial insertion far from the TA. These uncommon variation of APs can be reliably identified and ablated using CARTO system.</AbstractText>© 2010 Wiley Periodicals, Inc.</CopyrightInformation>
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5,087
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Intraprocedural imaging of left atrium and pulmonary veins: a comparison study between rotational angiography and cardiac computed tomography.
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Atrial fibrillation (AF) ablation is facilitated by anatomical visualization of the left atrium (LA) and the pulmonary veins (PVs). The purpose of this study was to compare accuracy, radiation exposure, and costs between three-dimensional atriography (3D-ATG) and cardiac computed tomography (CCT).</AbstractText>Seventy patients with an indication for AF ablation were included. Contrast-enhanced CCT was performed preoperatively for all patients. In addition, intraoperative 3D-ATG was performed with contrast medium injection either indirectly into the pulmonary arteries during a breath-hold (Ind.-RTA, n = 25) or directly into the LA, during adenosine-induced asystole (Ad.-RTA, n = 23), or rapid ventricular pacing (VP-RTA, n = 22). We evaluated vertical ostial PV diameters and LA volume, time needed to perform, radiation exposure, and procedural cost for each imaging method.</AbstractText>The correlation coefficient between 3D-ATG and CCT for the ostial PV diameters was r = 0.83 for Ind.-RTA, 0.91 for Ad.-RTA, and 0.88 for the VP-RTA method (P > 0.05). The volume correlations were r = 0.87 for Ind.-RTA, 0.82 for Ad.-RTA, and 0.8 for VP-RTA (P > 0.05). Time to perform was 13 ± 5 minutes for ATG and 46 ± 9 minutes for CCT (P < 0.05). Effective radiation dose was 2.2 ± 0.2 mSv for ATG and 20.4 ± 7.4 mSv for CCT (P < 0.05). The procedural cost was estimated at 91-95 € for ATG and at 126-151 € for CCT.</AbstractText>3D-ATG is an intraprocedural imaging modality that provides anatomical accuracy comparable to that of CCT with significantly lower radiation dose, in less time and at less financial expense (PACE 2011; 34:315-322).</AbstractText>©2010, The Authors. Journal compilation ©2010 Wiley Periodicals, Inc.</CopyrightInformation>
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5,088
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Key roles of endothelin-1 and p38 MAPK in the regulation of atrial stretch response.
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Mechanisms regulating stretch response in the left ventricle are investigated in detail but not well understood in atrial myocardium. Hypertrophic growth of atrial myocardium contributes to the pathogenesis of atrial fibrillation. In this study, we sought to elucidate mechanisms of stretch-induced activation of key signaling pathways and hypertrophy-associated genes in rat atria. Stretching of isolated atria induced a rapid increase in phosphorylation of p38 MAPK and ERK and induced a p38 MAPK-dependent increase in DNA binding activity of transcription factors Elk-1 and GATA-4. Inhibition of the ERK pathway had no effect on the cardiac transcription factors studied. Stretch-induced increase in atrial contractile function was substantially enhanced by inhibition of p38 MAPK. p38 MAPK also regulated stretch-induced increase in c-fos, β-myosin heavy chain, B-type natriuretic peptide mRNA levels, and atrial natriuretic peptide secretion in isolated atria. Various autocrine/paracrine factors are known to mediate the stretch response in the left ventricle. Stretching of isolated atria resulted in a robust increase in endothelin-1 (ET-1) mRNA levels, while apelin and adrenomedullin signaling cascades were downregulated. Administration of mixed ET(A/B) receptor antagonist bosentan attenuated the stretch-induced activation of GATA-4 in isolated atria, whereas ANG II receptor type-1 antagonist CV-11974 had no effect. Moreover, analysis of RNA from intact atrial and ventricular myocardium revealed significantly higher mRNA levels of ET(A) receptor and ET converting enzyme-1 in atrial compared with ventricular myocardium. In conclusion, our findings identify the local ET-1 system and p38 MAPK as key regulators of load-induced hypertrophic response in isolated rat atria.
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5,089
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Atrial-selective drugs for treatment of atrial fibrillation.
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Atrial fibrillation (AF) is accompanied by a high risk of thromboembolic complications necessitating anticoagulation therapy. Arrhythmias have a high tendency to become persistent. Catheter ablation techniques are highly effective in the treatment of AF; however, these procedures are far too costly and time-consuming for the routine treatment of large numbers of AF patients. Moreover, many patients prefer drug treatment although conventional antiarrhythmic drugs are moderately effective and are burdened with severe cardiac and noncardiac side effects. New antifibrillatory drugs developed for the treatment of AF include multichannel blockers with a high degree of atrial selectivity. The rationale of this approach is to induce antiarrhythmic actions only in the atria without conferring proarrhythmic effects in the ventricles.Atrial selective drug action is expected with ion channel blockers targeting ion channels that are expressed predominantly in the atria, i.e., Kv1.5 (I(Kur)), or Kir 3.1 and Kir 3.4 (I(K,ACh)). Na(+) channel blockers that dissociate rapidly may exert atrial selectivity because of subtle differences in atrial and ventricular action potentials. Finally, atrial-selective targets may evolve due to disease-specific processes (e.g., rate-dependent Na(+) channel blockers, selective drugs against constitutively active I(K,ACh) channels).
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5,090
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Therapeutic hypothermia protocol in a community emergency department.
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Therapeutic hypothermia (TH) has been shown to improve survival and neurological outcome in patients resuscitated after out of hospital cardiac arrest (OHCA) from ventricular fibrillation/ventricular tachycardia (VF/VT). We evaluated the effects of using a TH protocol in a large community hospital emergency department (ED) for all patients with neurological impairment after resuscitated OHCA regardless of presenting rhythm. We hypothesized improved mortality and neurological outcomes without increased complication rates.</AbstractText>Our TH protocol entails cooling to 33°C for 24 hours with an endovascular catheter. We studied patients treated with this protocol from November 2006 to November 2008. All non-pregnant, unresponsive adult patients resuscitated from any initial rhythm were included. Exclusion criteria were initial hypotension or temperature less than 30°C, trauma, primary intracranial event, and coagulopathy. Control patients treated during the 12 months before the institution of our TH protocol met the same inclusion and exclusion criteria. We recorded survival to hospital discharge, neurological status at discharge, and rates of bleeding, sepsis, pneumonia, renal failure, and dysrhythmias in the first 72 hours of treatment.</AbstractText>Mortality rates were 71.1% (95% CI, 56-86%) for 38 patients treated with TH and 72.3% (95% CI 59-86%) for 47 controls. In the TH group, 8% of patients (95% CI, 0-17%) had a good neurological outcome on discharge, compared to 0 (95% CI 0-8%) in the control group. In 17 patients with VF/VT treated with TH, mortality was 47% (95% CI 21-74%) and 18% (95% CI 0-38%) had good neurological outcome; in 9 control patients with VF/VT, mortality was 67% (95% CI 28-100%), and 0% (95% CI 0-30%) had good neurological outcome. The groups were well-matched with respect to sex and age. Complication rates were similar or favored the TH group.</AbstractText>Instituting a TH protocol for OHCA patients with any presenting rhythm appears safe in a community hospital ED. A trend towards improved neurological outcome in TH patients was seen, but did not reach significance. Patients with VF appeared to derive more benefit from TH than patients with other rhythms.</AbstractText>
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5,091
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Automated external defibrillators and survival after in-hospital cardiac arrest.
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Automated external defibrillators (AEDs) improve survival from out-of-hospital cardiac arrests, but data on their effectiveness in hospitalized patients are limited.</AbstractText>To evaluate the association between AED use and survival for in-hospital cardiac arrest.</AbstractText><AbstractText Label="DESIGN, SETTING, AND PATIENTS" NlmCategory="METHODS">Cohort study of 11,695 hospitalized patients with cardiac arrests between January 1, 2000, and August 26, 2008, at 204 US hospitals following the introduction of AEDs on general hospital wards.</AbstractText>Survival to hospital discharge by AED use, using multivariable hierarchical regression analyses to adjust for patient factors and hospital site.</AbstractText>Of 11,695 patients, 9616 (82.2%) had nonshockable rhythms (asystole and pulseless electrical activity) and 2079 (17.8%) had shockable rhythms (ventricular fibrillation and pulseless ventricular tachycardia). AEDs were used in 4515 patients (38.6%). Overall, 2117 patients (18.1%) survived to hospital discharge. Within the entire study population, AED use was associated with a lower rate of survival after in-hospital cardiac arrest compared with no AED use (16.3% vs 19.3%; adjusted rate ratio [RR], 0.85; 95% confidence interval [CI], 0.78-0.92; P < .001). Among cardiac arrests due to nonshockable rhythms, AED use was associated with lower survival (10.4% vs 15.4%; adjusted RR, 0.74; 95% CI, 0.65-0.83; P < .001). In contrast, for cardiac arrests due to shockable rhythms, AED use was not associated with survival (38.4% vs 39.8%; adjusted RR, 1.00; 95% CI, 0.88-1.13; P = .99). These patterns were consistently observed in both monitored and nonmonitored hospital units where AEDs were used, after matching patients to the individual units in each hospital where the cardiac arrest occurred, and with a propensity score analysis.</AbstractText>Among hospitalized patients with cardiac arrest, use of AEDs was not associated with improved survival.</AbstractText>
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5,092
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Chaos in the genesis and maintenance of cardiac arrhythmias.
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Dynamical chaos, an irregular behavior of deterministic systems, has been widely shown in nature. It also has been demonstrated in cardiac myocytes in many studies, including rapid pacing-induced irregular beat-to-beat action potential alterations and slow pacing-induced irregular early afterdepolarizations, etc. Here we review the roles of chaos in the genesis of cardiac arrhythmias, the transition to ventricular fibrillation, and the spontaneous termination of fibrillation, based on evidence from computer simulation of mathematical models and experiments of animal models.
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5,093
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Implantable cardioverter defibrillator: charge saver, not syncope saver!
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In patients with an implantable cardioverter defibrillator, empirical antitachycardia pacing/burst pacing (ATP) is associated with a significantly decreased rate of appropriate shocks. The use of ATP as first-line therapy in ventricular tachycardia promotes less pain and better quality of life because the number of shocks is reduced. Additionally, battery longevity is substantially increased with this strategy. Based on this, device manufacturers have developed new algorithms to optimize the use of ATP and shocks in patients with an implantable cardioverter defibrillator. The present report describes a case in which the use of one of these new algorithms was associated with a significant delay in tachycardia termination and, consequently, led to syncope.</Abstract><AuthorList CompleteYN="Y"><Author ValidYN="Y"><LastName>Chemello</LastName><ForeName>Diego</ForeName><Initials>D</Initials><AffiliationInfo><Affiliation>The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario.</Affiliation></AffiliationInfo></Author><Author ValidYN="Y"><LastName>Subramanian</LastName><ForeName>Anandaraja</ForeName><Initials>A</Initials></Author><Author ValidYN="Y"><LastName>Watkins</LastName><ForeName>Sheila</ForeName><Initials>S</Initials></Author><Author ValidYN="Y"><LastName>Nair</LastName><ForeName>Krishnakumar</ForeName><Initials>K</Initials></Author><Author ValidYN="Y"><LastName>Nanthakumar</LastName><ForeName>Kumaraswamy</ForeName><Initials>K</Initials></Author></AuthorList><Language>eng</Language><PublicationTypeList><PublicationType UI="D002363">Case Reports</PublicationType><PublicationType UI="D016428">Journal Article</PublicationType><PublicationType UI="D013485">Research Support, Non-U.S. Gov't</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="D000368" MajorTopicYN="N">Aged</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D001281" MajorTopicYN="N">Atrial Fibrillation</DescriptorName><QualifierName UI="Q000209" MajorTopicYN="N">etiology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D002304" MajorTopicYN="Y">Cardiac Pacing, Artificial</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D017147" MajorTopicYN="Y">Defibrillators, Implantable</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D006801" MajorTopicYN="N">Humans</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D008297" MajorTopicYN="N">Male</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D017202" MajorTopicYN="N">Myocardial Ischemia</DescriptorName><QualifierName UI="Q000150" MajorTopicYN="N">complications</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D011788" MajorTopicYN="N">Quality of Life</DescriptorName></MeshHeading><MeshHeading><DescriptorName UI="D013575" MajorTopicYN="N">Syncope</DescriptorName><QualifierName UI="Q000209" MajorTopicYN="Y">etiology</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D017180" MajorTopicYN="N">Tachycardia, Ventricular</DescriptorName><QualifierName UI="Q000209" MajorTopicYN="Y">etiology</QualifierName><QualifierName UI="Q000503" MajorTopicYN="N">physiopathology</QualifierName><QualifierName UI="Q000517" MajorTopicYN="Y">prevention & control</QualifierName></MeshHeading><MeshHeading><DescriptorName UI="D016896" MajorTopicYN="N">Treatment Outcome</DescriptorName></MeshHeading></MeshHeadingList><OtherAbstract Type="Publisher" Language="fre">Chez les patients munis d’un défibrillateur interne, la stimulation antitachycardique empirique ou la stimulation de l’activité électrique (SAT) s’associe à une diminution considérable du rythme de chocs administrés. Le recours à la SAT comme thérapie de premier recours en cas de tachycardie ventriculaire favorise une diminution de la douleur et l’amélioration de la qualité de vie puisque le nombre de chocs est moins élevé. De plus, la longévité de la pile augmente de manière significative grâce à cette stratégie. Compte tenu de ces observations, les fabricants d’appareils ont mis au point de nouveaux algorithmes afin d’optimiser le recours à la SAT et aux chocs chez les patients munis d’un défibrillateur interne. Le présent rapport décrit un cas où le recours à l’un de ces nouveaux algorithmes a entraîné un report important de l’arrêt de la tachycardie et, par conséquent, une syncope.
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5,094
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The dynamic nature of ventricular tachycardia initiation.
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Initiation of ventricular tachycardia (VT) or ventricular fibrillation (VF) requires heterogeneity of the substrate. This heterogeneity has a stable/fixed component (structural or functional) and a dynamic component. The latter explains the random and sudden destabilization of the substrate and the initiation of VT or VF by a ventricular extra stimulus trigger. The main mechanisms of dynamic heterogeneity are discussed at the cellular level (action potential duration alternans and restitution and intracellular calcium cycling instability) and at the tissue level (conduction velocity restitution and concordant and discordant alternans). Better knowledge of dynamic factors in arrhythmogenesis has an overwhelming impact on both predicting malignant arrhythmias and changing the antiarrhythmic drug paradigm from suppressing triggers to modifying dynamic instability factors.
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5,095
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Targeting atrioventricular differences in ion channel properties for terminating acute atrial fibrillation in pigs.
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The goal was to terminate atrial fibrillation (AF) by targeting atrioventricular differences in ionic properties.</AbstractText>Optical mapping was used to record electrical activity during carbachol (0.25-0.5 μM)-induced AF in pig hearts. The atrial-specific current, I(Kur), was blocked with 100 μM 4-aminopyridine (4-AP) or with 0.5 μM DPO-1. Hearts in AF and ventricular fibrillation (VF) were also subjected to increasing levels of extracellular K(+) ([K(+)](o): 6-12 mM), compared with controls (4 mM). We hypothesized that due to the more negative steady-state half inactivation voltage for the atrial Na(+) current, I(Na), compared with the ventricle, AF would terminate before VF in hyperkalaemia. Mathematical models were used to interpret experimental findings. The I(Kur) block did not terminate AF in a majority of experiments (6/9 with 4-AP and 3/4 with DPO-1). AF terminated in mild hyperkalaemia ([K(+)](o) ≤ 10.0 mM; N = 8). In contrast, only two of five VF episodes terminated at the maximum ([K(+)](o): 12 mM [K(+)](o)). The I(Kur) block did not terminate a simulated rotor in cholinergic AF because its contribution to repolarization was dwarfed by the large magnitude of the acetylcholine-activated K(+) current (I(K,ACh)). Simulations showed that the lower availability of the atrial Na(+) current at depolarized potentials, and a smaller atrial tissue size compared with the ventricle, could partly explain the earlier termination of AF compared with VF during hyperkalaemia.</AbstractText>I(Kur) is an ineffective anti-arrhythmic drug target in cholinergic AF. Manipulating Na(+) current 'availability' might represent a viable anti-arrhythmic strategy in AF.</AbstractText>
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5,096
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Quantitative troponin and death, cardiogenic shock, cardiac arrest and new heart failure in patients with non-ST-segment elevation acute coronary syndromes (NSTE ACS): insights from the Global Registry of Acute Coronary Events.
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The objective of this study was to determine if the extent of quantitative troponin elevation predicted mortality as well as in-hospital complications of cardiac arrest, new heart failure and cardiogenic shock.</AbstractText>16,318 patients with non-ST-segment elevation acute coronary syndromes (NSTE ACS) from the Global Registry of Acute Coronary Events (GRACE) were included. The maximum 24 h troponin value as a multiple of the local laboratory upper limit of normal was used. The population was divided into five groups based on the degree of troponin elevation, and outcomes were compared. An adjusted analysis was performed using quantitative troponin as a continuous variable with adjustment for known prognostic variables.</AbstractText>For each approximate 10-fold increase in the troponin ratio, there was an associated increase in cardiac arrest, sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) (1.0, 2.4, 3.4, 5.9 and 13.4%; p<0.001 for linear trend), cardiogenic shock (0.5, 1.4, 2.0, 4.4 and 12.7%; p<0.001), new heart failure (2.5, 5.1, 7.4, 11.6 and 15.8%; p<0.001) and mortality (0.8, 2.2, 3.0, 5.3 and 14.0%; p<0.001). These findings were replicated using the troponin ratio as a continuous variable and adjusting for covariates (cardiac arrest, sustained VT or VF, OR 1.56, 95% CI 1.39 to 1.74; cardiogenic shock, OR 1.87, 95% CI 1.61 to 2.18; and new heart failure, OR 1.57, 95% CI 1.45 to 1.71). The degree of troponin elevation was predictive of early mortality (HR 1.61, 95% CI 1.44 to 1.81; p<0.001 for days 0-14) and longer term mortality (HR 1.18, 95% CI 1.07 to 1.30, p=0.001 for days 15-180).</AbstractText>The extent of troponin elevation is an independent predictor of morbidity and mortality.</AbstractText>
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5,097
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Isoproterenol as an adjunct for treatment of idiopathic ventricular fibrillation storm in a pregnant woman.
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Idiopathic ventricular fibrillation is a rare entity seen in a very small subset of patients presenting to the emergency department. Management of ventricular arrhythmias in pregnant women is similar to that in nonpregnant women, but special consideration is given to avoid adverse fetal effects when selecting antiarrhythmic agents. Electrical defibrillation is the intervention of choice in both pregnant and nonpregnant patients with ventricular fibrillation of all etiologies. This was not associated with any significant adverse effects for mother or fetus. Although lidocaine and sotalol are Food and Drug Administration category B antiarrhythmics used in pregnancy, Food and Drug Administration category C antiarrhythmics such as β-blockers and category D drugs such as amiodarone can be used as pharmacologic adjuncts to facilitate termination of recurrent ventricular fibrillation where other agents have failed. Isoproterenol has been used to terminate recurrent ventricular fibrillation in patients with Brugada syndrome and torsades de pointes resistant to magnesium therapy. This case report describes a previously healthy 32-year-old pregnant woman with recurrent idiopathic ventricular fibrillation that failed to respond to standard therapy including electrical defibrillation, intravenous lidocaine, metoprolol, and amiodarone but eventually terminated with isoproterenol infusion.
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5,098
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Synephrine: from trace concentrations to massive consumption in weight-loss.
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Synephrine is cited as 'the active component' of plants and dietary supplements used in weight loss. It became one of the most popular stimulants present in weight-loss products after the US Food and Drug Administration had interdicted the use of ephedrine-containing dietary supplements. Synephrine is also a trace amine that can be found in vertebrates and invertebrates. Synephrine acts on several adrenergic and serotonergic receptors and its activity on trace-amine-associated receptors has long been discussed. Synephrine exists in three different positional isomers; however, only p- and m-synephrine have been described in weight-loss products. The alleged effectiveness of synephrine-containing supplements is attributed to the thermogenic effects arising from synephrine's adrenergic stimulation. The growing use of synephrine has raised concerns since it has been accompanied by reports of adverse effects. Cardiac adverse events, including hypertension, tachyarrhythmia, variant angina, cardiac arrest, QT prolongation, ventricular fibrillation, myocardial infarction, and sudden death, have been the most common adverse effects associated with synephrine intake. The mechanisms involved in synephrine-induced cardiotoxicity are still unknown since studies related to its safety are scarce. This review will address general aspects concerning the pharmacology of synephrine, but will focus on the efficacy and toxicity aspects related to the use of synephrine in weight-loss.
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5,099
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Transient pseudorestrictive pattern of transmitral flow velocity curve in patients with paroxysmal atrial fibrillation.
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Early diastolic velocity of the mitral annulus and transmitral flow propagation velocity are reported as more reliable determinants of left ventricular diastolic function in patients with atrial fibrillation than are transmitral Doppler indices. This study aimed to test the hypothesis that transmitral flow curve shows pseudorestrictive pattern during rate-controlled atrial fibrillation.</AbstractText>Thirteen paroxysmal atrial fibrillation patients were monitored for three phases: before atrial fibrillation, during atrial fibrillation, and after the recovery of atrial fibrillation to sinus rhythm. Standard two-dimensional, color flow, and tissue Doppler echocardiography were performed. We compared the indices of left ventricular diastolic function among the three phases.</AbstractText>The early diastolic velocity of transmitral flow increased significantly during atrial fibrillation (before, 0.76 ± 0.19 m/sec; during, 0.86 ± 0.20 m/sec; after recovery to sinus rhythm, 0.73 ± 0.16 m/sec; P < 0.01). The deceleration time of early transmitral diastolic wave decreased during atrial fibrillation (182.5 ± 39.6 ms; 149.1 ± 38.7 ms; 184.0 ± 44.5 ms, respectively, P < 0.01). The early diastolic velocity of the mitral annulus increased during atrial fibrillation (5.37 ± 1.31 cm/sec; 7.29 ± 1.25 cm/sec; 5.37 ± 1.32 cm/sec; respectively, P < 0.01). The transmitral propagation velocity did not change significantly during atrial fibrillation.</AbstractText>Although conventional Doppler indices showed abnormal relaxation pattern, left ventricular diastolic function was preserved during rate-controlled atrial fibrillation, as determined from early diastolic velocity of the mitral annulus and transmitral flow propagation velocity.</AbstractText>© 2011, Wiley Periodicals, Inc.</CopyrightInformation>
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