Electrocardiographic clues for multiple accessory pathways in patients with pre-excitation syndromes.

Background. Wolff, Parkinson and White (I) in 1930 reported an electrophysiologic syndrome based on their observation of 11 "healthy young" people who had "bundle branch block with short PR interval" and who were "prone to paroxysmal tachycardia." However, substantial progress in understanding the pathophysiology and in devising therapy for the various complex arrhythmias in patients with this syndrome had to wait for the development of clinical electrophysiologic testing, antiarrhythmic drugs and open heart surgery. Electrophysiologic tests have their origin in the recording of the bundle of His electrogram, first documented in the dog by Alanis et al. (2) in 1958. The first successful termination of atrioventricular (AV) reentrant tachycardia (circus movement, AV tachycardia) in a patient with WolffParkinson-White syndrome was accomplished in 1968 by Ryan et al. (3) by asynchronous ventricular capture by an implanted permanent ventricular pacemaker. Most of our current approaches employed for patients with this syndrome are based on the remarkable progress made in the 1970s, as summarized in the now classic review article by Gallagher et al. (4). This syndrome is relatively common (occurring in about 1 in every 1,000 people) and its clinical manifestations vary greatly, ranging from a totally asymptomatic benign course in some patients to a malignant course in others who die of ventricular fibrillation as a result of an extremely rapid ventricular response in the presence of atrial fibrillation. The rapid ventricular response during atrial fibrillation results from rapid conduction over the accessory pathway and is related to its extremely short anterograde refractory period (5). Because routine use of clinical electrophysiologic tests in all patients with this syndrome is prohibitively costly,