Electrophysiological characteristics during slow pathway ablation of posterior atrioventricular junctional reentrant tachycardia.

The purpose of this study was to compare the electrophysiological characteristics of posterior and anterior atrioventricular junctional reentrant tachycardia (AVJRT) during radiofrequency (RF) catheter ablation of a slow pathway. Twenty-four patients with common AVJRT, including 4 posterior (P) and 20 anterior AVJRT (A) were studied. We analyzed the retrograde atrial activation sequence of junctional rhythm and the presence of transient HA block during slow pathway ablation. When HA block developed, the AH interval before ablation and immediately after the 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 were: (1) the number of successful ablation sites were H 0, M 1, L 3 in P and H 1, 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 < 0.01); (3) the retrograde atrial activation sequence during junctional rhythm was strictly 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 exist from the AV node to the atrium in addition to anterograde fast pathway and slow pathway, and that this pathway is used as the retrograde limb of P.