Implantable Cardioverter Defibrillators for Primary Prevention of Mortality in Patients With Nonischemic Cardiomyopathy: A Meta‐Analysis of Randomized Controlled Trials

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Sudden cardiac death (SCD) accounts for about 50% of the mortality from cardiovascular disease in the United States and other developed countries.1 In patients with left ventricular (LV) systolic dysfunction, approximately one‐half to two‐thirds of the total annual death rate is attributed to SCD.2 Several randomized clinical trials have established the role of implantable cardioverter defibrillator (ICD) therapy in primary prevention of SCD in patients with LV systolic dysfunction due to ischemic cardiomyopathy.3 However, in patients with nonischemic cardiomyopathy (NICM), individual trials failed to show a reduction in total mortality associated with the use of an ICD.6 As such, the benefit of ICD in patients with NICM has been recently questioned.10 In the most recent and largest to‐date trial, there was a group by age interaction where the survival benefit of ICD was observed only in the younger age group.8 Moreover, it has been suggested that the high prevalence of cardiac resynchronization therapy (CRT) in the aforementioned trial accounted for the lack of benefit of the ICD, even though the study did not find a difference in the relative effect of ICD between patients who received CRT versus those who did not.8
Individual trials are often underpowered to detect an effect in subgroups.11 In order to increase the sample size, and thus improve the power and precision of the estimates, we undertook a meta‐analysis of randomized controlled trials examining the effect of ICD on total mortality and arrhythmic death in patients with NICM. In addition, we examined the impact of age and CRT, as well as other risk factors, including gender, severity of heart failure, and history of atrial fibrillation, on the relative effect of ICD compared to control in this patient population.
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