Antiarrhythmic efficacy of encainide in patients with refractory recurrent ventricular tachycardia

Encainide is a new agent for treating ventricular arrhythmias. We attempted long-term oral therapy with encainide in 38 patients with recurrent, strikingly drug-refractory ventricular tachycardia. The usual daily dose of encainide ws 150-250 mg divided into four or six doses. The mean period until withdrawal of encainide or the date of follow-up was 4.2 months. Encainide completely eliminated recurrence of ventricular tachycardia in 54% of the patients for 6 months of therapy and in 29% of the patients for 18-30 months of therapy. Twelve patients (32%) had side effects possibly due to encainide; in four, the arrhythmia may have been worsened by encainide. During chronic therapy, encainide increased the PR interval by 18% and the QRS duration by 32%. There was no significant change in the corrected QT interval. The presence of QRS prolongation appeared to correlate with antiarrhythmic effect. We conclude that encainide is a safe, well-tolerated antiarrhythmic agent that is often effective against previously drug-refractory ventricular tachycardia.