BACKGROUNDThe subcutaneous implantable cardioverter-defibrillator (ICD) was designed to avoid complications related to the transvenous ICD lead by using an entirely extrathoracic placement. Evidence comparing these systems has been based primarily on observational studies. METHODSWe conducted a noninferiority trial in which patients with an indication for an ICD but no indication for pacing were assigned to receive a subcutaneous ICD or transvenous ICD. The primary end point was the composite of device-related complications and inappropriate shocks; the noninferiority margin for the upper boundary of the 95% confidence interval for the hazard ratio (subcutaneous ICD vs. transvenous ICD) was 1.45. A superiority analysis was prespecified if noninferiority was established. Secondary end points included death and appropriate shocks. RESULTSA total of 849 patients (426 in the subcutaneous ICD group and 423 in the transvenous ICD group) were included in the analyses. At a median follow-up of 49.1 months, a primary end-point event occurred in 68 patients in the subcutaneous ICD group and in 68 patients in the transvenous ICD group (48-month Kaplan-Meier estimated cumulative incidence, 15.1% and 15.7%, respectively; hazard ratio, 0.99; 95% confidence interval [CI], 0.71 to 1.39; P = 0.01 for noninferiority; P = 0.95 for superiority). Device-related complications occurred in 31 patients in the subcutaneous ICD group and in 44 in the transvenous ICD group (hazard ratio, 0.69; 95% CI, 0.44 to 1.09); inappropriate shocks occurred in 41 and 29 patients, respectively (hazard ratio, 1.43; 95% CI, 0.89 to 2.30). Death occurred in 83 patients in the subcutaneous ICD group and in 68 in the transvenous ICD group (hazard ratio, 1.23; 95% CI, 0.89 to 1.70); appropriate shocks occurred in 83 and 57 patients, respectively (hazard ratio, 1.52; 95% CI, 1.08 to 2.12). CONCLUSIONSIn patients with an indication for an ICD but no indication for pacing, the subcutaneous ICD was noninferior to the transvenous ICD with respect to devicerelated complications and inappropriate shocks. (Funded by Boston Scientific; PRAETORIAN ClinicalTrials.gov number, NCT01296022.

The complication rate in patients implanted with an S-ICD or TV-ICD was similar, but their nature differed. The S-ICD reduced lead-related complications significantly, at the cost of nonlead-related complications. Rates of appropriate and inappropriate shocks were similar between the 2 groups.

Background-Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a genetic disorder causing life-threatening arrhythmias whenever sympathetic activity increases. β-Βlockers are the mainstay of therapy; when they fail, implantable cardioverter-defibrillators (ICDs) are used but often cause multiple shocks. Preliminary results with flecainide appear encouraging.We proposed left cardiac sympathetic denervation (LCSD) as useful additional therapy, but evidence remains anecdotal. Methods and Results-We report 63 patients with CPVT who underwent LCSD as secondary (n=54) or primary (n=9) prevention. The median post-LCSD follow-up was 37 months. The 9 asymptomatic patients remained free of major cardiac events. Of the 54 patients with prior major cardiac events either on (n=38) or off (n=16) optimal medical therapy, 13 (24%) had at least 1 recurrence: 0 patients had an aborted cardiac arrest, 2 patients had syncope only, 10 patients had ≥1 appropriate ICD discharges, and 1 patient died suddenly. The 1-and 2-year cumulative event-free survival rates were 87% and 81%. The percentage of patients with major cardiac events despite optimal medical therapy (n=38) was reduced from 100% to 32% (P<0.001) after LCSD, and among 29 patients with a presurgical ICD, the rate of shocks dropped by 93% from 3.6 to 0.6 shocks per person per year (P<0.001). Patients with an incomplete LCSD (n=7) were more likely to experience major cardiac events after LCSD (71% versus 17%; P<0.01) than those with a complete LCSD. Conclusions-LCSD is an effective antifibrillatory intervention for patients with CPVT. Whenever syncope occurs despite optimal medical therapy, LCSD could be considered the next step rather than an ICD and could complement ICDs in patients with recurrent shocks.