Propranolol and the morning increase in sudden cardiac death: (the beta-blocker heart attack trial experience).

To provide insight into the protective effect of propranolol on mortality after myocardial infarction observed in the beta-Blocker Heart Attack Trial, the time of occurrence of sudden cardiac death was examined in this population. Between 5 A.M. and 11 A.M., 25 of the 56 total deaths (38%) occurred in the placebo patients compared with 11 of 45 (24%) in the propranolol patients. Excluding this period, there were nearly equal numbers of sudden cardiac deaths in the propranolol and placebo groups. This retrospective analysis suggests that beta blockade is protective during the morning hours when a surge of sympathetic activity may increase the risk of sudden cardiac death.