The nodoventricular Mahaim pathway: an endangered concept?

It is unusual, if not unprecedented, to have three articles on the same topic in two consecutive issues of Circulation, especially relating to a relatively obscure and infrequently observed electrophysiological problem. This can only be a reflection of the intense interest and passion that students of arrhythmias have always had for the preexcitation syndromes and their variants. Our understanding of clinical arrhythmias has been greatly enhanced by both anatomic-pathological observations and electrophysiological observations. Nonetheless, the correlation between anatomic and electrophysiological observations is frequently problematic. The electrophysiologist will speculate on the variable anatomic structures that could be invoked to explain the observed phenomena, whereas the anatomist ponders the function of the structures observed under the microscope. Mahaim et all,2 initially described anatomic connections between the normal atrioventricular (AV) conduction system and the ventricles, and others subsequently verified and expanded on these observations.3-7 Wellens8 was the first to invoke the concept of the nodoventricular fiber to explain intracardiac electrophysiological phenomena, and others subsequently followed suit.9-'9 The essence of this issue was as follows. The "typical" accessory AV pathway has a relatively short conduction time and exhibits "all or none" conduction when stressed by progressively premature extrastimuli or rapid rates. Some accessory pathways, however, have impressively long conduction times and exhibit rate-dependent prolongation ("decremental") conduction that greatly resembles conduction observed