A comparative study of the effects of antiarrhythmic class III drugs cardiocyclide and sotalol on the atrioventricular fibrillation caused by vagus nerve excitation in narcotized dogs

摘要

The new class III antiarrhythmic agent cardiocyclide effectively prevents the atrioventricular fibrillations caused by the vagus nerve excitation in narcotized dogs. The electrophysiological effect of cardiocyclide was studied by method of programmed electric stimulation of myocardium on the background of excitation of a peripheral segment of the right vagus nerve by current pulses of increasing frequency. On this background, cardiocyclide exhibited characteristic effects manifested primarily by elongation of the QT and QTc intervals (corrected in accordance with the heart rate) and the effective refractory periods of both atrium and ventricles. The ability of cardiocyclide to increase the effective refractory period was retained irrespective of the drive signal frequency. A specific feature of the cardiocyclide effect on the model of vagus nerve excitation is a greater increase in the effective refractory auricular period as compared to that observed under normal conditions. Sotalol is less effective than cardiocyclide in the case of vagotonic atrial stimulation and does not prevent the bradycardia induced by the vagus nerve excitation. However, sotalol still retains its effects on the repolarization, the effective refractory auricular and ventricular periods, and the AV node under these conditions.