[Comparative study of the electrophysiological properties of class iii medicinals (cardiocyclide, nibentan, sotalol) and evaluation of their efficacy in atrial fibrillation produced by auricular and vagal stimulation].

: The electrophysiological properties of cardiocyclide, nibentan and sotalol and their efficacy on a model of atrial fibrillation were compared in experiments in anaesthetized dogs. The electrophysiological parameters of drugs were investigated using the method of programmed electrical stimulation of myocardium on the background of excitation of the peripheral segment of the right vagus nerve with current pulses of increasing frequency. The atrial fibrillation was produced by short stimulation (10 pulses) of the right auriculum (10 Hz, 4 thresholds). Cardiocyclide was injected in a dose of 2.5-5.0 mg/kg; nibentan, 0.25 mg/kg; and sotalol, 2.5 mg/kg. Cardiocyclide was found to prevent vagotonic atrial fibrillation in 80% of cases; under vagal stimulation this drug maintained the electrophysiological attributes and exhibited the frequency-independent action inherent in this agent. Nibentan completely retained its ability to prolong the ventricular repolarization under vagal stimulation conditions, increased the effective atrial and ventricular refractory periods, and showed the ability to prevent and eliminate the vagotonic atrial fibrillation in 80-90% of cases. Under vagal stimulation, sotalol increased the repolarization and prolonged the effective refractory atrial and ventricular periods, reduced the heart rate, and suppressed the sinus node function. The action of sotalol was frequency-dependent. Sotalol was found to prevent the vagotonic atrial fibrillation in 60% of cases.