Metoprolol treatment after acute myocardial infarction. Effects on ventricular arrhythmias and exercise tests during 6 months.

One hundred and six patients on double-blind treatment with placebo or metoprolol, 100 mg b.i.d., during the first 6 months after an acute myocardial infarction were investigated. The patients were stratified and randomized to treatment according to type of ventricular arrhythmias on a six-hour ECG registration, size of infarct estimated by enzyme maximum and age. During the follow-up period, a further three six-hour ECG recordings and three exercise tests were performed. In the metoprolol group the incidence of malignant ventricular ectopic beats decreased significantly (p less than 0.05) after three days' treatment. This decrease lasted for one month but was not observed at the six-month registration. No difference in working capacity was seen between the two groups, nor were there any differences in ischemic ST depressions on ECG during exercise. The proportion of patients terminating exercise because of angina pectoris was similar, but significantly more patients in the metoprolol group (p less than 0.05) discontinued exercise at six months because of fatigue. Large heart volumes were observed somewhat more often in the metoprolol group but there was no extended need of treatment for cardiac failure.