The efficacy of cibenzoline in preventing PES induction of ventricular tachycardia in the dog.

The electrophysiologic effects of cibenzoline were studied using programmed electrical stimulation (PES) techniques and were compared to those of quinidine. Cibenzoline, like the conventional class 1 agent quinidine, was effective in preventing arrhythmia induction. Twelve dogs were given 0.02 mg/kg digoxin intravenously for seven days to achieve a steady-state digoxin level. On the eighth day, cibenzoline was administered in incremental doses (0.5 to 10.5 mg/kg) and PES was performed at 30-minute intervals. A mean dose of 2.6 +/- 0.8 mg/kg cibenzoline prevented ventricular tachycardia induction. At this dose, cibenzoline had no significant effect on mean arterial blood pressure, but PR interval increased by 17 +/- 9 per cent, QRS duration by 27 +/- 14 per cent, and the ventricular refractory period (ERP) for the first extra stimulus increased by 35 +/- 9 per cent. A gradual decrease in heart rate and an increase in PR interval and QRS duration was caused by incremental doses of cibenzoline. In six additional animals, quinidine was administered in incremental doses (1 to 30 mg/kg) and PES performed at 30-minute intervals. A mean of 15 +/- 5 mg/kg prevented induction of ventricular tachycardia in five animals. No significant change in heart rate, PR, QRS, and ERP was found at the effective dose.