P-174 Detailed Electroanatomical Mapping of Slow and Intermediate Pathway in Atypical Atrioventricular Nodal Reentry Tachycardia

Background: Slow pathway is the target of successful ablation in a patient with atrioventricular node (AVN) reentry tachycardia (AVNRT). However, detailed mapping of the AVN electroanatomy has not been clarified in vivo. Methods: To investigate the 3-dimensional anatomy of slow or intermediate pathway of AVN extensions, we studied 4 patients (pts) of fast-slow (F/S), 2 pts of fast intermediate (F/I), and 2 pts of slow-intermediate (S/I) AVNRT by a duodecapolar electrode positioned along the tendon of Todaro, a decapolar electrode placed along the high septum of left ventricle, and a decapolar one in the coronary sinus. The right and the left His bundle electrograms were recorded. The earliest retrograde atrial activation sites (RAAs) were analyzed during AVNRT. Results: RAAs in F/I and S/I AVNRT were all at anterosepal area, with 2 pts (50%) at right, 1 pt (25%) at left, and simultaneous at right and left in 1 pt (25%). In F/S AVNRT,
RAAs were at right posteroseptum in 2 pts (50%), anterosepal (simultaneous right and left) in 2 pts (50%). RAA via intermediate pathway at the Koch’s triangle was usually focal (3/4 pts, 75%), while RAA via slow pathway showed more broad breakthrough (1/4 pts, 25%). Conclusion: This strategy using multiple decapolar catheters to surround AVN made the evaluation of AVN extensions possible. The left extension used as the retrograde pathway limb of atypical AVNRT was not uncommon.