New Pacing Method for Estimating the Entrance of the Antegrade Fast Pathway

Abstract

Backgrounds: Catheter ablation of the slow pathway in patients with the inferiorly dislocated fast pathway (IDF) showed high rate of procedure failure and high risk of atrioventricular block. Objective: The purpose of this study is to test the effectiveness of the new pacing method for estimating the antegrade fast pathway entrance (AF). Methods: 30 consecutive patients with PSVT (25 AVNRT, 4 AVRT, 1 AT) were entered this study. Using the electroanatomical mapping system, the AF was detected and divided into 4 groups; outside and posterior to the triangle of Koch (TOK) (group F: n=8) and inside and the upper (group S: n=3), the middle (group M: n=7), and the lower (group I: n=12) third of the TOK. Group M and I were defined as the IDF. During the constant pacing from the Halo catheter at the inferolateral right atrium (Lat) and the coronary sinus ostium (CS), Atrial-His interval at the His bundle recording catheter was measured (A-HLat and A-HCS, respectively). The difference between A-HLat and A-HCS was calculated (δLat-CS) and compared with the AF. Results: The dimension of the TOK was not different in all groups. δLat-CS was significantly larger in the IDF (group F: 2.4±2.3 ms, group S: 2.3±2.1 ms, group M: 11.6±4.8 ms, group I: 25.3±7.4 ms (P<0.0001)). Conclusion: Using new pacing method, we could easily estimate the AF before radiofrequency energy application to the slow pathway.