Implantable Cardioverter-Defibrillator for Nonischemic Cardiomyopathy
Authors: Harsh Golwala, Navkaranbir Singh Bajaj, Garima Arora, Pankaj Arora
Journal: Circulation (2016)

T he use of implantable cardioverter-defibrillators (ICDs) has been a major advancement in patients with ischemic cardiomyopathy with reduced ejection fraction <35%. 1 Although the data supporting the use of ICDs are robust in patients with ischemic cardiomyopathy, limited randomized controlled clinical trial (RCT) data exist for similar benefit in patients with nonischemic cardiomyopathy (NICM). 2 A prior metaanalysis that included both primary and secondary prevention ICD trials in 2004 by Desai et al 2 demonstrated a 31% reduction in all-cause mortality with ICD use in patients with NICM.The data became the back bone of the current American College of Cardiology/ American Heart Association guidelines for ICD implantation in patients with NICM. 3 However, recently, the DANISH trial (Defibrillator Implantation in Patients with Nonischemic Systolic Heart Failure), which randomly assigned >1100 patients with NICM on optimal medical therapy (OMT) and cardiac resynchronization therapy (CRT) to ICD versus no ICD for primary prevention of sudden cardiac death, revealed no difference in all-cause mortality between the 2 groups at 5-year follow-up. 4Although the primary results of DAN-ISH were neutral, the ICD group showed reduction in incidence of sudden cardiac death by half, and there was an interaction of survival benefit with ICD use in younger patients with NICM.In light of the recent data, we sought to update the meta-analysis of RCTs assessing the utility of ICD for primary prevention in patients with NICM.We searched the MEDLINE, PUBMED, and SCOPUS databases using the following keywords: implantable cardioverter defibrillator, ICD, cardiac resynchronization therapy, CRT, heart failure, cardiomyopathy, and randomized controlled trials from their inception to October 20, 2016.After examining 773 relevant studies, we included 6 RCTs that assessed the efficacy of ICD for primary prevention in patients with NICM.Two authors (H.G., N.B.) independently extracted data from each individual study.We calculated risk ratios/hazard ratios and 95% confidence intervals (CIs) using the available event rate data from individual trials when these measures were not reported in the individual trial.The risk measures and 95% CIs were log transformed and combined using random-effects models.Data were analyzed for heterogeneity using the I 2 statistic.We also performed a separate analysis of trials with/without CRT use to assess the differential effect of CRT on the efficacy of ICDs.Analyses were performed using Stata V14.1 statistical software.We identified 6 RCTs enrolling 2970 patients with NICM to study the efficacy of ICDs for primary prevention.Pooled analysis of the 6 RCTs (including those with CRT defibrillator) demonstrated a statistically significant 23% risk reduction in all-cause mortality in favor of ICD therapy (hazard ratio, 0.77; 95% CI, 0.64-0.91)(Figure).In addition, when we performed separate analysis of trials that assessed ICD plus OMT versus OMT alone (after exclusion of trials that involved patients with CRT defibrillator), we found a statistically significant 24% reduction in all-cause mortality with ICD (hazard ratio, 0.76; 95% CI, 0.62-0.94).When we compared the 2 trials (COMPANION [Comparison of Medical Therapy, Pacing, and