Enhanced atrioventricular nodal conduction in a patient with dual extranodal pathways.

A patient was admitted to the hospital with wide complex tachycardia and a history of recurrent palpitations. Electrophysiologic studies showed evidence of dual atrioventricular (AV) accessory pathways. One proved to be an anteroseptal (possible right anterior) pathway probably capable of only unidirectional conduction. The other pathway was in the posterior septum and conducted only in the retrograde direction. The tachycardia circuit involved anterograde conduction via either the AV node-His axis or the anteroseptal pathway and retroconduction over the posteroseptal accessory pathway. In addition, enhanced AV nodal conduction coupled with two accessory AV nodal pathways has rarely been described in English medical literature. Previous reports have carefully described anatomic, electrocardiographic, and electrophysiologic evidence of more than one accessory pathway in patients with the Wolff-Parkinson-White syndrome. The introduction of surgical techniques for ablation of an accessory pathway demands precision in the electrophysiologic evaluation of patients with ventricular preexcitation. Reported herein is a patient with the unique finding of two extranodal accessory pathways and enhanced atrioventricular (AV) nodal conduction (or AV nodal bypass).