MULTIPLE ATRIOVENTRICULAR NODAL PATHWAYS IN HUMANS - ELECTROPHYSIOLOGIC DEMONSTRATION AND CHARACTERIZATION

Multiple AV Nodal Pathways. Introduction: Multiple AV nodal pathway ph ysiology can be demonstrated in certain patients with clinical AV reen trant tachycardia. Methods and Results: Evidence suggesting multiple A V nodal pathway conduction was present in seven (two males; age range 15 to 75 years) of 78 patients (9%) who underwent electrophysiologic s tudies for AV nodal tachycardia. The presence of two discrete disconti nuities in the AV nodal conduction curves suggested triple AV nodal pa thway conduction. Detailed mapping of their retrograde atrial activati on sequence was performed along the tricuspid annulus from the coronar y sinus ostium to the His-bundle electrogram recording site. Three zon es (anterior, middle, and posterior) correspond to the upper, middle, and lower third of the triangle of Koch, respectively. The fast pathwa y exits were determined as anterior (4/7) or middle (3/7), the interme diate pathway exits as middle (4/7) or posterior (3/7), and the slow p athway exits as middle (1/7) or posterior (6/7). Other evidence sugges ting multiple AV nodal pathway conduction includes: (1) triple ventric ular depolarizations from a single atrial impulse; (2) sequential dual ventricular echoes; (3) spontaneous transformation between the slow-f ast and fast-slow forms of AV nodal reentrant tachycardia; and (4) per sistent cycle length alternans during AV nodal reentrant tachycardia. In four patients, all three pathways were shown to be involved in AV n odal echoes or reentrant tachycardia. Conclusion: Multiple AV nodal pa thways are not uncommon and can be identified by careful electrophysio logic elucidation and mapping technique.