Encainide in lethal ventricular arrhythmias evaluated by electrophysiologic testing and decrease in symptoms

Abstract

Encainide hydrochloride has distinct electrophysiologic properties that suggest active antiarrhythmic properties. Encainide has been administered both intravenously (0.5 to 1.7 mg/kg) and orally (100 to 300 mg/day) to patients with lethal ventricular arrhythmias—ventricular tachycardia (VT) and ventricular fibrillation—and evaluated by electrophysiologic testing. In 62 patients with inducible sustained VT, intravenous encainide prevented initiation in 13 (21%). In 57 patients with refractory sustained VT, oral encainide prevented initiation of VT by programmed stimulation in 17 (30%). The results obtained with intravenous and oral encainide in the same patient were usually concordant (93%). Encainide may worsen ventricular arrhythmia, most typically by converting nonsustained VT into sustained VT during electrophysiologic testing. In patients with lethal ventricular arrhythmia, analysis of symptoms before and during chronic encainide therapy showed that the number and severity of arrhythmia-related symptoms were reduced. Encainide appears to be a useful antiarrhythmic agent.