Efficacy of Implantable Cardioverter-Defibrillator Therapy in Patients With Nonischemic Cardiomyopathy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Objectives This study sought to evaluate the efficacy of implantable cardioverter-defibrillator (ICD) therapy with or without cardiac resynchronization therapy (CRT) in patients with nonischemic cardiomyopathy (NICM). Background The effect of ICD on mortality of patients with NICM and left ventricular ejection fraction ≤35% has recently been questioned. Prior randomized controlled trials (RCTs) evaluating ICD efficacy in patients with NICM have yielded conflicting results. Furthermore, whether ICD therapy benefits NICM patients with concomitant CRT is unknown. Methods Relevant RCTs published between 2000 and 2016 were identified. Patients with ischemic cardiomyopathy were excluded. Study sample was stratified into CRT and non-CRT groups. The efficacy of having a defibrillator in each group was compared using random effects meta-analysis techniques. Results Six RCTs (N = 3,544) were included. Among the 2,347 patients who did not have CRT, ICD use was associated with a 24% reduction in mortality (relative risk [RR]: 0.76; 95% confidence interval [CI]: 0.63 to 0.91; p = 0.003). However, among the 1,197 patients with CRT, having a CRT defibrillator was not associated with a statistically significant reduction in mortality (RR: 0.74; 95% CI: 0.46 to 1.16; p = 0.19) compared to CRT-pacemaker. Subgroup analysis in non-CRT patients showed that ICD use reduced sudden cardiac death by 73% (RR: 0.27; 95% CI: 0.15 to 0.50; p < 0.001) compared to medical therapy. Conclusions Compared to medical therapy, ICD use significantly improved survival among patients with NICM and ejection fraction ≤35%. Although CRT-defibrillator was not associated with a statistically significant mortality benefit compared to CRT-pacemaker, the apparent lack of power in this analysis warrants further investigation.