Effects of encainide on the inducibility of ventricular arrhythmia in normal anesthetized dogs

Abstract

Effects of encainide on electrophysiologic variables and ventricular arrhythmia inducibility were studied in normal anesthetized dogs, using programmed electrical stimulation with unipolar cathodal (8 dogs) or bipolar (10 dogs) stimulation modes. Encainide produced significant concentration-dependent increases in ventricular refractory period, and diastolic current threshold with smaller but significant increases in QRS and Q-Tc. It decreased spontaneous heart rate and mean arterial pressure at high concentration. After administration of encainide, ventricular tachyarrhythmias could be induced by bipolar stimulation in half of the dogs (5/10 dogs,P < 0.05, compared to control). While unipolar cathodal stimulation could not cause reproducible ventricular arrhythmias. We conclude that encainide may facilitate the induction of ventricular arrhythmias in normal dogs and that bipolar stimulation may produce different results compared to unipolar stimulation in the presence of encainide.

Keywords

encainide / inducibility of ventricular arrhythmia / programmed electrical stimulation / blood sample assay