Efficacy of acebutolol after acute myocardial infarction (the APSI trial). The APSI Investigators. A randomized, placebo-controlled trial was carried out to determine the effectiveness of acebutolol in preventing late death in high-risk patients surviving an acute myocardial infarction (MI). The average 1-year mortality rate in placebo groups of 9 trials of beta blockers in post-MI patients was 7.2% compared with 17% in a nonselected cohort of patients who had survived at least 7 days after an MI. The mandate for this trial was based on the fact that high-risk patients whose mortality rate exceeds 20% have not been enrolled in significant numbers in previous trials. It remains to be proved whether beta-blocking therapy in this patient population is beneficial. Selection of high-risk patients for inclusion in the trial was based on an algorithm set up from the Essai de Prevention Secondaire de l'Infarctus du Myocarde Registry. At the time of the second interim analysis, the mortality rate in the placebo group was 12%, lower than expected (greater than or equal to 20%). The trial was stopped; at that time, 309 patients had been allocated to placebo and 298 patients to acebutolol therapy. After 318 days, there were 17 deaths in the acebutolol-treated group and 34 in the placebo group, a reduction in total mortality of 48% (p = 0.019). There were 30 vascular deaths in the placebo group and 12 in the acebutolol group. Thus, cardiovascular mortality with acebutolol was reduced by 58% (p = 0.006). The incidence of all cardiovascular-related deaths was lower in the acebutolol-treated group. The total reduction in mortality did not appear to be correlated with secondary risk factors. 