Beta-Blocker Heart Attack Trial: impact of propranolol therapy on ventricular arrhythmias

The natural history of and the effect of propranolol on ventricular arrhythmias post-myocardial infarction were analyzed using data from the Beta-Blocker Heart Attack Trial (BHAT). The Beta-Blocker Heart Attack Trial was a multicenter, randomized, double-blind, placebo-controlled trial among 3,837 patients entered from 5 to 21 days after hospitalization for acute myocardial infarction. At baseline, prior to randomization, 3,290 (85.7%) patients underwent 24-hr ambulatory ECG monitoring which was repeated in approximately 25% of a randomly selected subset of the study population at 6 weeks. Ventricular arrhythmias were divided into eight different categories which defined the prevalence of ventricular arrhythmias in terms of frequency and/or complexity. Ventricular arrhythmias at baseline were associated with age, past history of myocardial infarction, and use of diuretics and digitalis. Paired data (baseline and 6-week) were available for 428 patients on propranolol and 412 on placebo. Propranolol markedly blunted the two- to threefold increase in ventricular arrhythmias that occurred from baseline to 6 weeks in the placebo group. Propranolol decreased the proportion of patients having ventricular arrhythmias during waking hours compared with sleep. These data show that propranolol has an antiarrhythmic effect and suggest that an antiarrhythmic mechanism may in part be responsible for the observed reduction in sudden cardiac death mortality in BHAT.