Electrophysiological effects of intravenous disopyramide phosphate on the Wolff-Parkinson-White syndrome.

The effects of a single intravenous infusion of 2mg/kg body weight disopyramide phosphate (DP) on the mode of initiation of reentrant supraventricular tachycardia were assessed in seven patients with Wolff-Parkinson-White (WPW) syndrome using bundle of His electrograms and the ventricular extrastimulus method. The delta wave disappeared in three patients after DP. However, retrograde conduction via the accessory pathway persisted even after DP administration in all patients. These effects contributed to the induction of reciprocating tachycardia after DP. The retrograde functional refractory period of the His-Purkinje system (HPS) and the effective refractory period of the accessory pathway were increased in all cases and contributed to the development of reentry HPS. After DP, the zone of reentry HPS widened in four cases (including a newly developed case) and remained unchanged in three cases. Reentrant supraventricular tachycardia zones widened in three cases; these widened reentrant supraventricular tachycardia zones were induced by the widened reentry HPS, that is, reentry HPS was followed by the reentrant supraventricular tachycardia. This study demonstrates that persistence of retrograde accessory pathway conduction and widened reentry HPS which might be dose-related after DP could be the retrograde determinants affecting the reentrant supraventricular tachycardia zone.