Frequency-dependent electrophysiological effects of flecainide, nifekalantand d,l-sotalol on the human atrium

To compare the effects of class Ic and III antiarrhythmic agents on the ter mination and prevention of atrial fibrillation, the present study investiga ted the use-dependent electrophysiological effects of flecainide, nifekalan t and d,l-sotalol on the human atrium. Flecainide significantly prolonged e ffective refractory period (ERP), intra-atrial conduction time (IACT) and m onophasic action potential duration (MAPD), and its effects on ERP and IACT were use-dependent. Nifekalalant significantly prolonged ERP and MAPD, and these effects were reverse use-dependent; however, there was no significan t change in IACT. ci,l-Sotalol significantly prolonged MAPD and the effect was reverse use-dependent. It significantly prolonged ERP, but the effect w as not reverse use-dependent. d,l-Sotalol increased IACT in a use-dependent manner. Thus, for atrial fibrillation, class Ic antiarrhythmic agents migh t be more effective in termination and class III antiarrhythmic agents migh t be more effective in prevention.