Beta-blocker therapy in the cardiac arrhythmia suppression trial

Abstract

The Cardiac Arrhythmia Suppression Trial (CAST) showed antiarrhythmic drug suppression of asymptomatic or mildly symptomatic ventricular arrhythmias in survivors of myocardial infarction to be harmful. This study retrospectively searched the CAST results for evidence of mortality and morbidity reduction in patients receiving optional β-blocker therapy. All enrolled (n = 2,611) and suppressed main study (n = 1,735) CAST patients with an ejection fraction of ≤40% were examined using univariate analysis, Kaplan-Meier curves, and a Cox proportional-hazards multivariate analysis with respect to optional β-blocker therapy prescribed at baseline. CAST patients receiving β-blocker therapy had significantly enhanced survival at 30 days, and at 1 and 2 years of follow-up against all-cause and arrhythmic death or nonfatal cardiac arrest. Multivariate analysis showed β-blocker therapy to be independently associated with a one-third reduction in arrhythmic death or cardiac arrest (p = 0.036). In CAST patients with a history of congestive heart failure, β-blocker therapy was independently associated with longer time to occurrence of new or worsened congestive heart failure (p = 0.015). This study supports the secondary preventive benefit of β-blocker therapy in high-risk post-myocardial infarction patients, and calls attention to the possible preventive benefit of β-blocker therapy against proarrhythmic events experienced in the CAST.