The Wolff-Parkinson-White syndrome has held an unusual fascination for cardiologists ever since its original description in 1930. Over 60 different theories have been postulated to describe the mechanism of pre-excitation. The recent development of epicardial mapping techniques to define the sequence of ventricular activation, and the introduction of His bundle electrocardiography have provided valuable procedures for studying pre-excitation. This presentation will discuss some of the insights into the mechanism of pre-excitation that have been derived from these two electrophysiological procedures
