The effect of a selective beta adrenergic blocking agent on ventricular arrhythmias in the first year following myocardial infarction.

Fifty-five patients with recent acute myocardial infarction entered a single-blind cross-over trial to assess the effect of oral practolol 200 mg twice daily on the incidence and nature of ventricular arrhythmias in the first year following myocardial infarction. Patients had 24-hour Holter electrocardiogram tape monitoring at two weeks following infarction and at three-monthly intervals for one year. Twenty-six patients completed the full year of the trial with 12% of tape recordings technically unsatisfactory. A total of 46 periods of comparison of the action of practolol versus placebo therapy were available in thirty patients. Whilst receiving the selective beta adrenergic blocking agent, practolol, there was a significant reduction in the percentage of studied hours during which salvos of ventricular premature beats occurred (P < 0.025), however the percentage of patients in whom salvos were recorded was unchanged. The incidence of all other ventricular arrhythmias was not reduced in the practolol group. When the effect of practolol was related to the site of infarction, anterior or inferior, there was no significant reduction in the incidence of ventricular arrhythmias.