Implantable cardioverter defibrillator in non-ischemic cardiomyopathy: a meta-analysis of randomized controlled trials

Background: Sudden cardiac death (SCD) is a significant cause of mortality in patients with non-ischemic cardiomyopathy (NICM). Implantable cardioverter defibrillators (ICDs) are currently indicated for the primary prevention of SCD in these patients. Conflicting results from published randomized controlled trials (RCTs) have recently questioned the protective role of ICD in NICM patients to perform an updated meta-analysis of the effect of ICDs on outcomes of NICM patients. Methods: We performed a search of PubMed, EMBASE, and Cochrane databases for RCTs comparing ICD to medical therapy in patients with NICM. Outcomes were all-cause mortality, SCD, and cardiac mortality. Mantel-Haenszel (MH) risk ratios (RR) were calculated using random-effects meta-analysis for the outcomes mentioned. Heterogeneity was assessed using I2 statistics and Q-statistic. Results: A total of five RCTs met the inclusion criteria, with a total of 1,503 patients in the ICD group and 1,364 patients in the medical therapy. Compared to medical therapy, ICD use resulted in a 24% relative risk reduction (RRR) of all-cause mortality (RR 0.76, 95% CI 0.64-0.91, P=0.002), and 60% RRR of SCD (RR 0.40, 95% CI 0.18-0.90, P=0.03), but was not associated with a statistically significant benefit in the prevention of cardiac mortality (RR 0.75, 95% CI 0.39-1.44, P=0.39). Limiting the analysis to patients who received an ICD only without cardiac resynchronization therapy (CRT) pacemakers (4 trials, 1,825 patients) showed similar all-cause mortality results with 24% RRR in ICD group (RR 0.76, 95% CI 0.61-0.94, P=0.01). Conclusions: ICD therapy reduces all-cause mortality and SCD in patients with NICM.