Functional characteristics of the Wolff-Parkinson-White bypass: A study of six patients with His bundle electrograms

Six cases of the WPW Syndrome were studied using the technique of His bundle recording and artificial atrial pacing. Increasing atrial pacing rates resulted in varying degrees of WPW fusion complexes and varying degrees of bypass conduction disturbances. This indicated that: (1) the WPW Syndrome is due to the presence of an anomalous A-V bypass, most probably sited ectopically on the A-V ring, (2) the classic WPW complex is indeed a fusion complex, (3) the precise ECG manifestation is the result of a fortuitous association of the properties of the two pathways, (4) the conduction properties of the bypass are unrelated to those of the normal A-V pathway, and (5) different degrees of block, as well as interference can occur within the bypass. Possible explanations for the conduction disturbances in the bypass are discussed and are: decremental conduction at a cellular level, exit block, impedance mismatch, and local depression of conduction.