The effect of sotalol on exercise-induced ventricular arrhythmias

Sotalol is a non-selective beta-adrenergic blocking agent with class III antiarrhythmic properties. Our study was intended to assess the efficacy of sotalol on exercise-inducible arrhythmias by oral administration to out patients. Thirty patients with exercise-inducible arrhythmias (80% coronary artery disease, 20% congestive cardiomyopathy) were studied after two baseline bicycle ergometric stress tests performed in upright position. Twenty-five patients (including nine crossover cases of the lower dose protocol) were given sotalol in a daily dose of 320 mg (group 1) and 14 patients in a dose of 160 mg (group 2). After 2 and 8 weeks, respectively, group 1 showed a mean reduction of the total number of inducible ventricular premature beats (VPBs) of 50% (P = 0.0042) and 61% (P = 0.0107), respectively and a significantly improved Lown score (P = 0.0002 and 0.0006, respectively). A significant antiarrhythmic response was not demonstrable for group-2 patients. Because of inefficacy, nine patients were changed from group 2 to group 1. Reduction of arrhythmias on the higher dose was significant (P = 0.0147) in this group. There was the same significant reduction of the heart rate pressure product with the low and high dosage indicating that the beta-blocker effect is achieved with the lower dosage. We conclude that sotalol is a powerful drug for reducing the number and complexity of ventricular arrhythmias in a dose of 320 mg daily. As the beta-blocking effect in both groups was the same, we assume that the reduction of arrhythmias is mainly due to class III action.