Wide QRS supraventricular tachycardia due to coexisting Mahaim and Kent pathways.

In two patients with Wolff-Parkinson-White syndrome, we observed the unusual coexistence of functional Mahaim and accessory atrioventricular pathways. In the first patient, three types of reciprocating tachycardia were demonstrable: (1) anterograde conduction over the atrioventricular (AV) node with right bundle branch block (RBBB) and retrograde conduction via a right-sided atrioventricular accessory pathway; (2) anterograde conduction through the AV node with RBBB and retrograde conduction via two (right-sided and septal) anomalous pathways; and (3) anterograde conduction through nodoventricular fibers and retrograde conduction over a right-sided accessory pathway. In the second patient the reentry circuit was comprised of AV node fasciculoventricular fiber in an anterograde direction and a right-sided accessory pathway in a retrograde direction. We believe this to be the first report of triple accessory pathways, consisting of two atrioventricular and one nodoventricular connection, demonstrated by intracardiac electrophysiologic study.