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Beta-blocker therapy in the Cardiac Arrhythmia Suppression Trial. CAST Investigators
H L Kennedy1, M M Brooks, A H Barker
1Cardiovascular Research Foundation, St. Anthony's Medical Center, St. Louis, Missouri.
Insights
Beta-blocker therapy significantly improved survival and reduced cardiac events in high-risk myocardial infarction survivors from the Cardiac Arrhythmia Suppression Trial (CAST). This suggests a protective role against proarrhythmic events.
Area of Science:
- Cardiology
- Clinical Trials
- Pharmacology
Background:
- The Cardiac Arrhythmia Suppression Trial (CAST) revealed harm from antiarrhythmic drug suppression of ventricular arrhythmias post-myocardial infarction.
- High-risk patients surviving myocardial infarction require effective secondary prevention strategies.
Purpose of the Study:
- To retrospectively analyze CAST data for the impact of optional beta-blocker therapy on mortality and morbidity.
- To evaluate the association between beta-blocker use and survival outcomes in post-myocardial infarction patients with reduced ejection fraction.
Main Methods:
- Retrospective analysis of 2,611 enrolled and 1,735 suppressed CAST patients with ejection fraction ≤ 40%.
- Utilized univariate analysis, Kaplan-Meier curves, and Cox proportional-hazards multivariate analysis.
- Examined outcomes related to optional baseline beta-blocker therapy.
Main Results:
- Beta-blocker therapy was associated with significantly enhanced survival at 30 days, 1 year, and 2 years.
- Multivariate analysis indicated beta-blockers independently reduced arrhythmic death or cardiac arrest by one-third (p=0.036).
- In patients with heart failure history, beta-blockers delayed new or worsened congestive heart failure (p=0.015).
Conclusions:
- Beta-blocker therapy provides secondary preventive benefits in high-risk post-myocardial infarction patients.
- Beta-blockers may offer protection against proarrhythmic events observed in the CAST study.
- Supports the use of beta-blockers for improved outcomes in specific post-MI populations.
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 beta-blocker therapy. All enrolled (n = 2,611) and suppressed main study (n = 1,735) CAST patients with an ejection fraction of < or = 40% were examined using univariate analysis, Kaplan-Meier curves, and a Cox proportional-hazards multivariate analysis with respect to optional beta-blocker therapy prescribed at baseline. CAST patients receiving beta-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 beta-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, beta-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 beta-blocker therapy in high-risk post-myocardial infarction patients, and calls attention to the possible preventive benefit of beta-blocker therapy against proarrhythmic events experienced in the CAST.