The Electrocardiogram in Wolff-ParkinsonWhite Syndrome

Abstract

In its most common form, the Wolff-Parkinson-White (WPW) syndrome is caused by the presence of an embryonic remnant consisting of an accessory atrioventricular pathway. When the pathway bypasses the AV node and connects the atria directly to the ventricles, it is referred to as the bundle of Kent. Less frequently, the anomalous connection is between the AV node or bundle of His and the ventricles, and it is referred to as the bundle of Mahaim. The bundle of Kent is by far the more common variant. In this case, the excitation wavefront travels simultaneously through the usual pathway (the AV node, which normally slows conduction) and much more rapidly through the accessory pathway, thereby activating the ventricles earlier than usual. As a result, the P-R interval is shortened, and the initial part of the ventricular complex is slurred or notched. This distortion is referred to as a delta wave, and it is pathognomonic for the WPW syndrome. The QRS complex in this case is actually a fusion of the complexes resulting from the two pathways of ventricular activation (Figs. 7.1 and 7.2).