Changing QRS Morphology in a Patient with Wolff-Parkinson-White Syndrome.

A case of Wolff-Parkinson-White syndrome with supraventricular tachycardia is presented in which 2 atrioventricular (AV) reentry circuits are identified. The first circuit used the AV node in the antegrade limb and a left lateral accessory pathway in the retrograde limb. The second circuit used an atriofascicular accessory pathway as the antegrade limb and the left lateral accessory pathway as the retrograde limb. The characteristics of these tachycardias are described, along with diagnostic maneuvers used in the electrophysiology laboratory. Mapping and ablation of both of these accessory pathways is also described. This article is aimed at clinical electrophysiologists interested in management of complex supraventricular tachycardias in the electrophysiology laboratory.