Effect of left ventricular ejection fraction and QRS duration on the survival benefit of implantable cardioverter-defibrillators: meta-analysis of primary prevention trials.

Background: Implantable cardioverter-defibrillators (ICDs) are recommended for the primary prevention of sudden cardiac death in patients with left ventricular dysfunction, but it is unclear whether treatment benefits are diminished in patients with very low baseline left ventricular ejection fraction (LVEF) (<25%) or increased in those with prolonged QRS duration (>120 ms).

Objective: To study the effects of very low LVEF and prolonged QRS duration on the mortality benefits of ICD therapy.

Methods: We performed a meta-analysis of primary prevention randomized controlled trials comparing ICD and standard medical therapy. All-cause mortality hazard ratios (HRs) in subgroups according to thresholds of 25% for LVEF and 120 ms for QRS duration were extracted from published reports or contributed by trial investigators and synthesized.

Results: There was no significant difference of ICD effectiveness in LVEF subgroups of 25%-35% (random effects HR 0.81; 95% confidence interval [CI] 0.70-0.94) vs<25% (HR 0.71; 95% CI 0.55-0.93). Results were also similar in the narrow and wide QRS subgroups (HR 0.78; 95% CI 0.68-0.90 and HR 0.70; 95% CI 0.51-0.95, respectively). Within the LVEF<25% and wide QRS subgroups, there was large heterogeneity driven by the Defibrillator in Acute Myocardial Infarction Trial that included patients with early post-myocardial infarction and its results (HR 1.49; 95% CI 0.84-2.68 and HR 1.51; 95% CI 0.83-2.83, respectively) differed significantly from other trials (P = .008 and P = .01, respectively).

Conclusions: LVEF values and QRS duration do not appear to directly modify the survival benefit of ICD in patients with baseline LVEF<35%. However, patients with a recent myocardial infarction do not benefit from ICD, especially when they have LVEF<25% and/or wide QRS.