[Electrophysiological effects of the new antiarrhythmic drug flecainide (R 818) in man (author's transl)].

The electrophysiological effects of the new antiarrhythmic drug Flecainide (R 818) was tested in altogether 27 patients with and without disturbances of sinus node function and intraventricular conduction. Flecainide was given intravenously in a dose of 1 mg/kg and 2 mg/kg. Constant "therapeutic" plasma levels were reached by application of 1 mg/kg as a bolus and an additional infusion of 1 mg/kg during the test period of 20 min. The drug had no significant effects on sinus node function even in patients with sinus node dysfunction tested so far. Intracardiac conduction time was prolonged within all compartments of the heart in a dose-dependent manner. After bolus injection of 1 mg/kg, the HRA-A interval lengthened by 10.4%, the A-H interval by 13.5%, the H-V time by 15.7% and the V-RVA interval by 29.1% of the control value. In addition, the QRS complex widened by 8.1%. After 2 mg/kg Flecainide the HRA-A interval was prolonged by 9.0%, the A-H interval by 24.4%, the H-V time by 40.2%, and the V-RVA interval by 16.5% of the control value. The QRS complex widened by 24.2%. In contrast, there was only a small and often insignificant increase in the refractoriness of the different compartments of the heart (5-15% increase of the control value). In two patients with bundle branch block, a higher degree A-V block distal the H potential occurred after 2 mg/kg Flecainide. These electrophysiological effects may explain some antiarrhythmic actions of Flecainide. In addition, possible side effects of the drug can be assessed. In patients with intraventricular conduction defects the drug should be used with caution especially when given iv in higher doses.