Effects of long-acting propranolol on A.M. and P.M. peaks in silent myocardial ischemia

The frequency of episodes of silent myocardial ischemia and the adverse impact of these episodes on cardiovascular morbidity and mortality have been demonstrated in several studies involving both symptomatic and asymptomatic subjects. Previous reports using a variety of agents-nitrates,¹ β blockers² and calcium antagonists³-have shown the efficacy of these drugs in reducing ischemic activity, but have not resolved the issue of whether the circadian variation in ischemic events could be totally abolished. Beta blockers have been shown to be successful in blunting the a.m. peak, but there is little data concerning the P.M. peak. The present study was designed to test the hypothesis that β blockade with a long-acting propranolol preparation could abolish both a.m. and p.m. peaks in silent myocardial ischemic activity.