Protective effect of propranolol in threatened myocardial infarction.

Propranolol 0.1 mg/kg intravenously followed by 320 mg orally over 27 h was given to 20 randomly selected patients within 4 h of the onset of suspected myocardial infarction unaccompanied by diagnostic electrocardiographic changes. Patients given propranolol had fewer completed infarcts as assessed by serial electrocardiograms, a lower frequency of serum-creatine-kinase levels above the normal range, and lower peak serum-creatine-kinase levels than 23 control subjects. This evidence suggests that threatened myocardial infarction can in some cases be prevented by early beta-adrenoceptor blockade.