QT time in patients treated with alprenolol or placebo after myocardial infarction.

Studies were made on the effects of long-term beta-blockade on the QT interval in patients discharged alive from hospital after myocardial infarction. The patients (n = 230) in this study constituted all those who participated in the alprenolol study on postmyocardial patients in Göteborg, Sweden. The study was double-blind (alprenolol 200 mg b.i.d. or placebo) and randomised. The patients were divided into 4 risk groups (1-4) with different predicted mortality. The electrocardiograms before and after 8 weeks of treatment were analysed with respect to heart rate and QT time. There was a decrease in heart rate of about 10% in the alprenolol treated patients. The QT time was not significantly influenced by alprenolol. The rate corrected QT time (QTc) decreased in the subgroup of the most severely diseased patients (subgroup 4) treated with alprenolol.