HEART-RATE AND BETA-ADRENERGIC MECHANISMS IN ACUTE MYOCARDIAL-INFARCTION

Increased heart rate is an independent predictor of mortality in patients with acute myocardial infarction. Elevated heart rate is due to increased sympathetic activity and/or decreased parasympathetic activity. In placebo-controlled trials beta-blockers are known to reduce mortality as well as morbidity and these effects are most evident among patients with elevated heart rate. Studies on circadian variation have demonstrated that there is an increased sympathetic activity in the morning as well as a more frequent onset of ischemic attacked including acute myocardial infarction and sudden death. there seems to be a close relationship between increased sympathetic activity and the onset of ischemic events which can be prevented by prophylactic institution of a beta-blocker.