Evaluation of antiarrhythmic effect of metoprolol treatment after acute myocardial infarction: relationship between treatment responses and survival during a 3-year follow-up

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Abstract
Three hundred and one patients were randomized to 3 years double-blind postinfarction treatment with metoprolol(N = 154) 100 mg b.i.d. or matching placebo (N = 147). Repeated 6 h electrocardiograms were performedpretreatment and after 3 days, 1 month, 6, 12, 24 and 36 months treatment. There were no significant differences in pretreatment ventricular arrhythmia in the two groups. In the placebo group there was an increase both in complexity of the arrhythmia (P−1 was evaluated. In metoprolol treated patients in whom the arrhythmia frequency was reduced by >75% after three days of treatment, mortality was lower as compared to those metoprolol treated patients who did not show this treatment response (3% vs 28%, P = 0.013). Mortality in placebo treated patients with frequent PVCs was 24%. In conclusion, chronic metoprolol treatment after acute myocardial infarction blunts the naturally occurring increase of PVC frequency and PVC complexity by time. Patients with frequent PVCs in the early postinfarction phase who respond to metoprolol with > 75% reduction of the arrhythmias may have an excellent prognosis. However, this latter hypothesis has to be further tested in a prospective study.