[Electrophysiological effects of encainide in man]

Encainide is an antiarrhythmic agent under evaluation; it is effective in ventricular and supraventricular arrhythmias. Its electrophysiological effects seem to differ according to the route of administration, oral or intravenous, probably because of the effects of active metabolites. Two electrophysiological studies were carried out in 20 patients, under basal conditions, and after 4 to 10 days oral administration at doses ranging from 75 to 300 mg/day. Encainide depressed intra-atrial conduction (prolongation of the P-A interval from 29,7 +/- 2,2 to 36 +/- 4,5 ms, p less than 0,01), slowed conduction in the atrioventricular mode (prolongation of the A-H interval from 74 +/- 14 to 98 +/- 15 ms, p less than 0,01) and the His-Purkinje system (lengthening of H-V from 50 +/- 3 to 70 +/- 6,2 ms, p less than 0,001). The sinus node function was depressed with lengthening of the corrected sinus node recovery time (297 +/- 64 to 387 +/- 71 ms, p less than 0,01) and of the sinoatrial conduction time (173 +/- 25 to 219 +/- 43, p less than 0,01). The atrial and ventricular refractory periods were significantly longer (245 +/- 16 ms to 273 +/- 10 ms, p less than 0,001, and 237 +/- 12 to 266 +/- 19 ms, p less than 0,01, respectively). This new antiarrhythmic agent therefore seems to act at all levels which suggests that it may have wide ranging antiarrhythmic effects.