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Background: The clinical benefit of primary prevention implantable cardioverter-defibrillator (ICD) therapy in asymptomatic patients (New York Heart Association [NYHA] functional class I) with ischemic cardiomyopathy and left ventricular dysfunction is continually disputed., Objective: The purpose of this study was to evaluate the incidence of ventricular arrhythmias, mortality rates, and appropriate device therapies by NYHA class in a prospective national ICD registry., Methods: The study comprised 1670 consecutive patients with ischemic cardiomyopathy who were implanted with a primary prevention ICD and enrolled in the prospective national Israeli ICD Registry from 2010. The risk for clinical and arrhythmic events was assessed by NYHA class., Results: Asymptomatic patients (NYHA I) composed 19% of the study cohort. Comparison according to NYHA class showed that the highest mortality rate was in the NYHA III-IV group vs NYHA I and NYHA II (10.5% vs 5.4% and 5.8%, respectively; log rank P = .003). Conversely, cumulative incidence of appropriate ICD therapies, corrected for death as a competing risk, were higher among patients with NYHA I (11% vs 7%; P = .021). In a multivariate model, NYHA I vs ≥II remained independently associated with a significant 2-fold risk for appropriate ICD therapy (hazard ratio 2.03; 95% confidence interval 1.28-3.24)., Conclusion: Our findings indicate that patients with ischemic cardiomyopathy without heart failure symptoms have a higher risk of appropriate ICD therapy compared with symptomatic patients after adjustment for the competing risk of death, suggesting possible incremental benefit of primary ICD implantation in this population., (Copyright © 2019. Published by Elsevier Inc.)

Background: Implantable cardioverter-defibrillators (ICDs) have become the mainstay of preventive measures for sudden cardiac death (SCD). However, there are limited data on rates of appropriate life-saving ICD shock therapies in contemporary real-life settings., Objective: The purpose of the study was to evaluate the rate of appropriate life-saving ICD shock therapies in a contemporary registry., Methods: The Israeli ICD Registry includes all implants and other ICD operative procedures nationwide. The present study comprises 2349 consecutive cases who were enrolled in the Registry and prospectively followed up for information regarding survival, hospitalizations, and ICD therapies since 2010., Results: Kaplan-Meier survival analysis showed that the rate of appropriate ICD shock therapy at 30-month follow-up was 2.6% among patients who received an ICD for primary prevention compared with 7.4% among those who received a device for secondary prevention (log-rank P < .001). Rates of appropriate ICD shocks among primary prevention patients were 1.1% at 1-year of follow-up and 2.6% at 30 months, whereas the corresponding rates in the secondary prevention group were 3.8% at 1 year and 7.4% at 30 months (log-rank P < .001). A total of 253 patients (4.8%) died during follow-up, 65% of noncardiac causes., Conclusion: Rates of life-saving appropriate ICD shock therapies among patients implanted with a defibrillator for the primary prevention of SCD in a contemporary real-world setting are lower than reported previously. These findings suggest a need for improved risk stratification and patient selection in this population., (Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Defibrillation threshold (DFT) testing during placement of an implantable cardioverter-defibrillator (ICD) has been considered mandatory. Accumulating data suggest a more limited role for DFT., Objective: The purpose of this study was to compare the outcome of ICD recipients who underwent DFT testing compared with those who did not., Methods: In this prospective cohort analysis of patients who received an ICD between July 2010 and March 2013, we compared patients who underwent DFT testing and those who did not. Primary end-points were death and malignant ventricular arrhythmias. Secondary end-points included the composite end-points and inappropriate ICD discharges., Results: Of the 3596 patients in the registry, 614 patients (17%) underwent DFT testing during ICD placement vs 2982 (83%) who did not. Variables associated with ICD testing were implantation for secondary prevention (relative risk [RR] 1.87), prior ventricular arrhythmias (RR 1.81), use of antiarrhythmic medication (RR 1.59), and sinus rhythm (RR 2.05). Factors predisposing against testing were cardiac resynchronization therapy defibrillator implantation (RR 0.56) and concomitant diuretic use (RR 0.71). ICD testing was not associated with 1-year mortality (5.3% vs 5.1%, P = .74), delivery of appropriate shocks (8.6% vs 5.6%, P = .16), combined outcomes of ventricular arrhythmias and death (12.9% vs 11.3%, P = .45), or inappropriate ICD discharges (3.9% vs 2.1%, P = .2) compared to no DFT testing., Conclusion: No significant differences in the incidence of mortality, malignant ventricular arrhythmias, or inappropriate ICD discharges were observed between patients who underwent DFT testing compared to those who did not. Our results may support avoiding DFT testing during ICD placement, but this requires confirmation by additional prospective studies., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Elderly patients are underrepresented in clinical trials of device therapy., Objective: To provide real-world data regarding outcomes associated with device-based therapy in a large cohort of elderly patients enrolled in the Israeli ICD Registry., Methods: Between July 2010 and June 2012, a total of 2807 consecutive patients undergoing implanted cardioverter-defibrillator/cardiac resynchronization therapy-defibrillator (ICD/CRT-D) implantation were prospectively enrolled in the Israeli ICD Registry. For the present analysis, patients were categorized into 3 age groups: ≤60 years (n = 1378 [49%]), 61-75 years (n = 863 [31%]), and >75 years (n = 566 [20%])., Results: Elderly patients (>75 years of age) had more comorbid conditions and were more likely to undergo CRT-D implantation (all P < .01). However, the rate of device-related complications associated with surgical reinterventions at 1 year was <3% regardless of age (P = .70 for the comparison among the 3 age groups). Multivariate analysis showed that the risk of heart failure or death and of appropriate ICD therapy for ventricular arrhythmias was significantly increased with increasing age among patients who received an ICD. In contrast, the age-related increase in the risk of all end points was attenuated among patients who received CRT-D devices (all P values for age-by-device-type interactions are <.05)., Conclusions: In a real-world scenario, elderly patients (>75 years of age) comprise approximately 20% of the ICD/CRT-D recipients and experience a device reintervention rate similar to that of their younger counterparts. Our data suggest that the association between advanced age and adverse clinical outcomes is attenuated in elderly patients implanted with CRT-D devices., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Calsequestrin-associated catecholaminergic polymorphic ventricular tachycardia (CPVT2) can cause sudden death in young individuals in response to stress. Beta-blockers are the mainstay medical treatment for patients with CPVT2. However, they do not prevent syncope and sudden death in all patients. Flecainide was reported to reduce exercise-induced ventricular arrhythmias (EIVA) in patients with ryanodine receptor-associated CPVT. The role of flecainide in CPVT2 is not known., Objective: To summarize our experience in combining flecainide and beta-blockers in high-risk patients with CPVT2., Methods: All patients with CPVT2 (10 patients) who have high-risk features (syncope, EIVA, or appropriate implantable cardioverter-defibrillator [ICD] shocks) despite beta-blockers with or without calcium channel blockers were treated with a combination of flecainide and beta-blockers. Exercise test was done before and after beginning treatment with flecainide., Results: All patients had EIVA and 4 had appropriate ICD shocks before flecainide treatment. EIVA-included frequent ventricular premature beats and or ventricular tachycardia during the exercise test while on high dose of beta-blockers with or without calcium channel blockers before treatment with flecainide. After combination therapy with flecainide and beta-blockers, EIVA were suppressed completely in all patients. During follow-up of 15.5 ± 10.4 months (range 2-29 months), 8 patients were free of symptoms and free of arrhythmias. Two patients had 1 VT storm episode with recurrent ICD shocks despite repeated normal stress test., Conclusions: Flecainide can completely prevent ventricular arrhythmia during exercise and partially prevent recurrent ICD shocks in high-risk patients with CPVT2., (© 2013 Heart Rhythm Society. All rights reserved.)

Background: It is known that statins are effective in preventing atrial fibrillation (AF) in patients undergoing cardiac surgery., Objective: The purpose of this study was to evaluate the efficacy of statins in preventing AF recurrence following left atrial ablation., Methods: One hundred twenty-five patients who had no statin indication undergoing catheter ablation due to drug-refractory paroxysmal (n = 90) or persistent (n = 35) AF were randomized in a prospective, double-blind, placebo-controlled trial to receive 80 mg atorvastatin (n = 62) or placebo (n = 63) for 3 months. The primary endpoint was freedom from symptomatic AF at 3 months. Secondary endpoints included freedom from any atrial arrhythmia recurrence irrespective of symptoms, quality of life (QoL), and reduction in C-reactive protein (CRP)., Results: At 3 months, 95% of patients in the atorvastatin group were free of symptomatic AF compared with 93.5% in the placebo group (P = .75). Similarly, 85% of patients treated in the atorvastatin group remained free of any recurrent atrial arrhythmia vs 88% of patients in the placebo group (P = .37). Mean CRP levels decreased in the atorvastatin group (mean change -0.75 ± 3, P = .02) and increased in the placebo group (mean change 2.1 ± 19.9, P = .48). Mean QoL score improved significantly in both groups (mean change 13.14 ± 18.2 in the atorvastatin group and 11.10 ± 17.7 in the placebo group, P = .53)., Conclusion: In patients with no standard indication for statin therapy, treatment with atorvastatin 80 mg/day following AF ablation does not decrease the risk of AF recurrence in the first 3 months and should not be routinely administered to prevent periprocedural arrhythmias., (Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Sleep-disordered breathing (SDB) has been associated with various benign cardiac arrhythmias occurring during sleep., Objective: The purpose of this study was to demonstrate that SDB contributes to the development of life-threatening ventricular arrhythmias in patients with an established arrhythmic substrate., Methods: We prospectively studied the association between SDB and timing of life-threatening ventricular arrhythmic events in 45 patients with an implantable cardioverter-defibrillator (ICD). SDB was defined as an apnea-hypopnea index (AHI) >10 events/hour based on an overnight sleep study. The primary outcome measure was appropriate ICD therapy, defined as antitachycardia pacing or shock for ventricular tachycardia or ventricular fibrillation during 1-year follow-up., Results: SDB was present in 26 (57.8%) patients. Appropriate ICD therapies were higher among patients with SDB (73% vs 47%, P = .02). Logistic regression identified SDB as a predictor of any appropriate ICD therapy (odds ratio 4.4, 95% confidence interval 1.4-15.3, P = .01). The risk for ventricular arrhythmias was higher in patients with SDB solely due to an increase in events occurring between midnight and 6 AM (odds ratio 5.6, 95% confidence interval 2.0-15.6, P = .001) with no discernible effect on appropriate ICD therapy during nonsleeping hours (odds ratio 0.7, 95% confidence interval 0.2-2.3, P = .61)., Conclusion: Patients with an ICD and SDB have a striking increase in the onset of life-threatening ventricular arrhythmic events during sleeping hours. These findings provide a rationale for SDB screening in patients with appropriate ICD therapy if device interrogation reveals a predominance of nocturnal onset of arrhythmias., (Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: With the increased number of implantable cardioverter-defibrillator (ICD) recipients and the frequent need for device upgrading, lead malfunction is a concern, but the optimal approach to managing nonfunctioning leads is unknown., Objective: The purpose of this study was to determine the rate and characteristics of complications related to abandoned ICD leads., Methods: Patients with abandoned leads were identified by retrospective review of the Mayo Clinic ICD database from August 1993 to May 2002. We reviewed the medical records to assess long-term follow-up for venous thromboembolic complications, device sensing malfunction, appropriateness of delivered shocks, defibrillation threshold (DFT) values before and after lead abandonment, and subsequent surgical procedures related to devices or leads., Results: We identified 78 ICD patients (81% males; mean age 63 +/- 14 years) with 101 abandoned leads (69 in the right ventricle, 31 in the right atrium or superior vena cava, 1 in the coronary sinus). During a mean follow-up of 3.1 +/- 2.0 years, neither sensing malfunction nor venous thromboembolic complications were detected. DFT values were high in 13 patients (17%), but there was no significant increase in mean DFT values before and after lead abandonment in 43 patients for whom both values were available (16.2 +/- 9.2 J before abandonment vs 14.1 +/- 5.5 J after; P = .24). Fourteen patients (18%) required further ICD-related surgery; none of these operations were attributed to abandoned leads. Five-year rates of appropriate and inappropriate shocks were 25.9% and 20.5%, respectively., Conclusion: Abandoning a nonfunctioning lead appears to be safe and does not pose a clinically significant additional risk of future complications.

In this two-part series, we discuss the anatomical basis for arrhythmias arising above the semilunar valves. In this part (part I), we describe the relevant anatomy and technique for mapping and ablation of ventricular arrhythmias arising above either the pulmonic or the aortic valve. After an initial discussion of the underlying anatomy and characteristics of the substrate targeted for ablation above the semilunar valve, an approach for safe and effective ablation of supravalvar ventricular arrhythmias is presented.