Tehran University of Medical Sciences The Research in Heart Yield and Translational Medicine (RHYTHM) 3115-7270 3 2 2008 04 15 83 88 Mohammad Hasan Namazi Modarres Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. Hassan Kamalzadeh Modarres Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. Morteza Safi Modarres Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. Reza Karbasi Afshar Modarres Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. Mohammad Reza Motamedi Modarres Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. Habibollah Saadat Modarres Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. Hossein Vakili Modarres Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. 2015 10 03 Background: Complete atrioventricular block (AV block) is a serious complication of slow pathway ablation therapy in the treatment of atrioventricular nodal re-entrant tachycardia (AVNRT).  The present study was aimed at determining whether the electroanatomical pace mapping of Koch’s triangle could significantly improve the safety, efficiency, and efficacy of selective slow pathway ablation in the treatment of AVNRT. Methods: A total number of 124 patients were selected to be studied consecutively for radiofrequency (RF) ablation therapy in the treatment of AVNRT.  The subjects were divided into two groups: one, designated Group 1, to serve as the control group, and the other, designated Group 2, to serve as the study group.  Conventional fluoroscopic slow pathway ablation was performed on the Group 1 subjects (n=66), with the Group 2 subjects receiving slow pathway ablation therapy guided by pace mapping of Koch’s triangle.  The slow pathway ablation in Group 2 (n=58) was performed with regard to the pace mapping data obtained on the basis of the St-H interval in the anteroseptal (AS), midseptal (MS), and posteroseptal (PS) regions of Koch’s triangle.  The anterograde fast pathway (AFP) location was determined based on the shortest St-H interval obtained by stimulating the anteroseptal (AS), midseptal (MS), and posteroseptal (PS) aspects of Koch’s triangle. Results: In the Group 2 subjects, AFP location was AS in 50 (86.2%) of the cases, MS in 7 (12%) of the cases, and PS in 1 case (1.7%).  One patient with posteroseptal AFP was administered retrograde fast pathway ablation therapy.  One patient in the control group (Group 1), representing 1.5% of the group, developed persistent AV block in the course of the treatment, but none of the subjects in the study group (Group 2) developed any complications.    Conclusion: It was concluded that an atypical fast pathway location is conducive to the development of atrioventricular block in the ablation therapy in AVNRT, with pace mapping of Koch’s triangle having the capacity to eliminate the risk of any such complication developing.  It follows that it helps to identify the AFP location before ablation therapy is administered in AVNRT, thereby improving the safety of the treatment.     https://rhythm.tums.ac.ir/index.php/jthc/article/view/87 https://rhythm.tums.ac.ir/index.php/jthc/article/download/87/85