ELECTROPHYSIOLOGICAL CHARACTERISTICS DURING SLOW PATHWAY ABLATION OF POSTERIOR ATRIOVENTRICULAR JUNCTIONAL REENTRANT TACHYCARDIA

The purpose of this study was to compare the electrophysiological char acteristics of posterior and anterior atrioventricular junction al ree ntrant tachycardia (AVJRT) during radiofrequency (RF) catheter ablatio n of a slow pathway. Twenty-four patients with common AVJRT, including 4 posterior IPI and 20 anterior AVJRT(A) were studied. We analyzed th e retrograde atrial activation sequence of functional rhythm and the p resence of transient HA block during slow pathway ablation. When HA bl ock developed, the AH interval before ablation and immediately after t he end of energy delivery was measured. Successful ablation sites were divided into three groups; high (H), middle (M), and low (L) from the His bundle to the floor of the coronary sinus orifice. The results we re: (1) the number of successful ablation sites were H 0, M 1, L, 3 in P and H 2, M 8, L 11 in A; (2) the HA interval during AVJRT in P was longer than that in A (109 +/- 48 ms vs 43 +/- 6 ms, P < 0.02); (3) th e retrograde atrial activation sequence during junctional rhythm was s trictly concordant with that during AVJRT in both groups, but HA block developed during slow pathway ablation more often in P than in A (100 % vs 30%, P < 0.01); and (4) The AH interval did not lengthen after HA block developed in P. These data suggest that another pathway does ex ist from the AV node to the atrium in addition to anterograde fast pat hway and slow pathway and that this pathway is used as the retrograde limb of P..