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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 performed pretreatment 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 less than 0.001) and frequency of premature ventricular complexes (PVCs) (P less than 0.001) by time. These increases were blunted by metoprolol treatment. Treatment effect on mortality was similar in patients both with and without complex PVCs before treatment. In a retrospective analysis, the outcome of patients with an initial PVC frequency of greater than 1 PVC h-1 was evaluated. In metoprolol treated patients in whom the arrhythmia frequency was reduced by greater than 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 greater than 75% reduction of the arrhythmias may have an excellent prognosis. However, this latter hypothesis has to be further tested in a prospective study.
Olsson et al. (Tue,) studied this question.