Distal end of the atrioventricular nodal artery predicts the risk of atrioventricular block during slow pathway catheter ablation of atrioventricularnodal re-entrant tachycardia

Objective-To search for a reliable anatomical landmark within Koch's triang le to predict the risk of atrioventricular (AV) block during radiofrequency slow pathway catheter ablation of AV nodal re-entrant tachycardia (AVNRT). Patients and methods-To test the hypothesis that the distal end of the AV n odal artery represents the anatomical location of the AV node, and thus cou ld be a useful landmark for predicting the risk of AV block, 128 consecutiv e patients with AVNRT receiving slow pathway catheter ablation were prospec tively studied in two phases. In phase I (77 patients), angiographic demons tration of the AV nodal artery and its ending was performed at the end of t he ablation procedure, whereas in the subsequent phase II study (51 patient s), the angiography was performed immediately before catheter ablation to a ssess the value of identifying this new landmark in reducing the risk of AV block. Multiple electrophysiologic and anatomical parameters were analysed . The former included the atrial activation sequence between the His bundle recording site (HBE) and the coronary sinus orifice or the catheter ablati on site, either during AVNRT or during sinus rhythm. The latter included th e spatial distances between the distal end of the AV nodal artery and the H BE and the final catheter ablation site, and the distance between the HBE a nd the tricuspid border at the coronary sinus orifice floor. Results-In phase I, nine of the 77 patients had complications of transient (seven patients) or permanent (two patients) complete AV block during stepw ise, anatomy guided slow pathway catheter ablation. These nine patients had a wider distance between the HBE and the distal end of the AV nodal artery , and a closer approximation of the catheter ablation site to the distal en d of the AV nodal artery, which independently predicted the risk of AV bloc k. In contrast, none of the available electrophysiologic parameters were sh own to be reliable. When the distance between the distal end of the AV noda l artery and the ablation target site was more than 2 mm, the complication of AV block virtually never occurred. In phase II, all 51 patients had succ essful elimination of the slow pathways without complication when the ablat ion procedure was guided by preceding angiography with identification of th e distal end of the AV nodal artery. Conclusions-The distal end of the AV nodal artery shown by angiography serv es as a useful landmark for the prediction of the risk of AV block during s low pathway catheter ablation of AVNRT.