Triple Ventricular Fusion in Wolff-Parkinson-White Pattern

Abstract

The classic form of conduction in the Wolff-Parkinson-White syndrome is reflected by a typical preexcitation fusion complex. The supraventricular front is conducted down both the anomalous pathway (Kent bundle) and the normal atrioventricular nodal pathway. The front is conducted without delay through the Kent bundle, and hence the very short P-R interval; however, on reaching the ventricle, further onward conduction is through ordinary myocardial tissue, a poor conducting medium. Conduction is thus slow and bizarre and is reflected by the delta wave. That part of the activation front which is conducted through the normal atrioventricular nodal pathway is subject to the normal atrioventricular nodal delay and, upon reaching the ventricles, is conducted through the highly efficient intraventricular conducting system of the bundle of His, the bundle branches, and Purkinje's fibers. This activation front thus completes ventricular activation in a rapid and coordinated manner, and hence the normal terminal part of the QRS complex. The typical preexcitation complex is thus, in effect, a fusion complex resulting from activation fronts which are conducted through two atrioventricular pathways, and each of the so divided fronts contribute to partial activation of the ventricles. The following presentation reflects a classic preexcitation fusion complex which is further modified by fusion from a coincidental ectopic ventricular escape pacemaker.