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ICD Efficacy in Nonischemic Cardiomyopathy
Study Questions:
What is the efficacy of implantable cardioverter-defibrillator (ICD) therapy with or without cardiac resynchronization therapy (CRT) in patients with nonischemic cardiomyopathy (NICM)?
Methods:
The authors identified randomized clinical trials (RCTs) on ICD use in NICM published between 2000 and 2016. 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], 0.63-0.91; 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, 0.46-1.16; p = 0.19) compared with CRT-pacemaker. Subgroup analysis in non-CRT patients showed that ICD use reduced sudden cardiac death by 73% (RR, 0.27; 95% CI, 0.15-0.50; p < 0.001) compared with medical therapy.
Conclusions:
Compared with 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.
Perspective:
The recent DANISH trial has raised questions about whether ICD therapy in patients with NICM results in reduction of total mortality. The present meta-analysis suggests that there is indeed a significant risk reduction in total mortality with ICDs in NICM patients without concomitant CRT. Those tend to be heathier patients with less advanced heart failure. There did not appear to be a significant impact of ICDs on mortality among patients with CRT. It would be interesting to see if additional risk stratification tools beyond left ventricular ejection fraction, such as the presence of delayed enhancement on cardiac magnetic resonance imaging or biochemical assays might help in further defining a group of patients with definite benefit from ICDs.
Keywords: Arrhythmias, Cardiac, Cardiac Resynchronization Therapy, Cardiomyopathies, Death, Sudden, Cardiac, Defibrillators, Implantable, Heart Defects, Congenital, Heart Failure, Magnetic Resonance Imaging, Pacemaker, Artificial, Risk, Risk Reduction Behavior, Secondary Prevention, Stroke Volume
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