THE EFFECTS OF METOPROLOL GIVEN EARLY IN ACUTE MYOCARDIAL-INFARCTION ON VENTRICULAR ARRHYTHMIAS

The effects of metroprolol, administered in the early stages of acute myocardial infarction was studied in 126 patients. Patients were treated in a double-blind randomized fashion, with metoprolol -15 mg, intravenously followed by 100 mg twice daily for 15 days or placebo, with a mean delay of 8.1 hours from onset of symptoms. All patients underwent 24 hours Holter monitoring on days 1, 5 and 15 after randomization. Although there was no antiarrhythmic effect on day 1, metoprolol reduced the number of hours with warning arrhythmias (> 30 ventricular ectopics/hour, any R/T ectopics or ventricular tachycardia) on both days 5 (35 .+-. 16% vs 8 .+-. 11%; P < 0.05) and day 15 (13 .+-. 37% vs 4 .+-. 13%; P < 0.05). Metoprolol also reduced the incidence of ventricular fibrillation and ventricular tachycardia requiring cardioversion -6% vs 0%; P = 0.058. Metoprolol, administered in the early stages of acute myocardial infarction, had an antiarrhythmic effect which was evident only in the later phase of the study.