Atrial pacing and atrioventricular conduction in anomalous atrioventricular excitation (Wolff-Parkinson-White syndrome)

Abstract

A comparative study of atrioventricular conduction was made by single atrial pacing in normal subjects and in patients with the Wolff-Parkinson-White phenomenon. In those with the WPW phenomenon the atrial impulse, by a functional bypass of the A–V node, is not subjected to a physiologic delay at the A–V nodal region. Data are presented which lead us to conclude that the WPW beat is not a fusion beat as postulated by others. We suggest that the delta wave represents conduction through the accessory pathway and depolarization of a portion of ventricular myocardium, and that the terminal (normal) portion of the QRS represents conduction through the normal pathways below the A–V node, probably by entry of the impulse in this region, and depolarization of the remainder of the ventricles. We further suggest that an atrial impulse traverses either the normal A–V nodal route or takes the accessory pathway, but it does not traverse both pathways simultaneously.