The occurrence of atrioventricular nodal reentrant tachycardia requires not only the electrophysiological substrate but also the electro-anatomical characteristics in the triangle of Koch

Abstract Background Some patients do not develop atrioventricular nodal reentrant tachycardia (AVNRT) clinically despite having the electrophysiological substrate for AVNRT; however, the cause remains unclear. Recently, the conduction to the slow pathway has been reported to be visualized using high-density mapping in the triangle of Koch (ToK) during sinus rhythm. Purpose To investigate whether the conduction to the slow pathway is associated with the occurrence of AVNRT. Methods We studied 83 patients (55 males, 67 ± 13 years, 10 with typical AVNRT, 66 atrial fibrillation; AF, 5 atrioventricular reentrant tachycardia; AVRT, and 2 Atrial Flitter) who received electrophysiological test and high-density mapping in the ToK during sinus rhythm. The conduction pattern to the slow pathway, rotating around the end (pivot point: PP) of the functional block line (FBL), was evaluated using the Advisor HD Grid mapping catheter. Results 10 out of 10 AVNRT (100%), 17 of 66 AF (26%), and 1 of 4 AVRT showed PP and FBL (p<0.0001). 21 out of 21 (10 AVNRT and 11 AF) with the jump-up phenomenon in atrioventricular conduction indicated PP and FBL (100%), meanwhile 7 of 62 without jump-up phenomenon showed PP and FBL (11%) (p<0.0001). Among patients (10 AVNRT and 9 AF) who had the electrophysiological substrate for AVNRT (jump-up phenomenon and retrograde ventriculoarterial conduction), patients with AVNRT had a longer distance from PP to the tricuspid annulus; TA (16.9mm vs, 13.4mm, p=0.0116) than patients with non-AVNRT. There were no differences in the length of FBI, distance and conduction time from His to PP, distance and conduction time from PP to CS ostial, and the area size of ToK. All AVNRT patients underwent linear ablation from PP to TA and showed loss of atrial potential in the region between PP, TA, and His, AVNRT was no longer provoked, and in 8 out of 10 patients, a jump-up phenomenon disappeared. Conclusion Patients with AVNRT showed a functional block line and a longer distance from the pivot point to the tricuspid annulus. The occurrence of AVNRT requires not only the electrophysiological substrate but also the electro-anatomical characteristics, especially in the triangle of Koch.