A new method for evaluating the effect of antiarrhythmic drugs on atrioventricular nodal conduction.

Electrophysiological variables were studied in 19 patients before and after one of three commonly used antiarrhythmic agents. The pacing rate at which alternating Wenckebach periods appeared in eight patients was significantly reduced by intravenous digoxin (0.01 mg/kg body weight). The atrioventricular nodal conduction time (A-H interval) and Wenckebach point were not significantly altered by digoxin. Intravenous propranolol (0.1 mg/kg body weight) in four patients did not affect the A-H interval, but it reduced the pacing rates at which the Wenckebach point and alternating Wenckebach periods occurred. Intravenous disopyramide (2 mg/kg body weight) significantly increased the pacing rate required to produce alternating Wenckebach periods but did not significantly alter the other indicators of atrioventricular conduction in seven patients. It is concluded that the pacing rate required to produce alternating Wenckebach periodicity may be a useful and sensitive variable in the evaluation of the effect of antiarrhythmic agents on atrioventricular nodal conduction.