Electrophysiological delineation of the tachycardia circuit in atrioventricular nodal reentrant tachycardia

Abstract

Background - The exact boundaries of the reentry circuit in atrioventricular nodal reentrant tachycardia (AVNRT) have not been convincingly defined. Methods and Results - To define the tachycardia circuit, single extrastimuli were delivered during AVNRT to 8 sites of the right intra-atrial septum: 3 arbitrarily divided sites of the AV junction extending from the His bundle (HB) site to the coronary sinus ostium (CSOS) (sites S, M, and I) and the superior (S-CSOS), inferior (I-CSOS), posterior (P-CSOS), and posteroinferior (PI-CSOS) portions of the CSOS and the CSOS in 18 patients. The mean tachycardia cycle length (TCL) was 368 ± 52 ms. Retrograde earliest atrial activation was observed at the HB site in all patients. The longest coupling intervals of single extrastimuli that reset AVNRT at sites S, M, I, I-CSOS, CSOS, S-CSOS, P-CSOS, and PI-CSOS were 356 ± 51, 356 ± 51, 355 ± 52, 357 ± 51, 318 ± 47, 305 ± 53, 311 ± 56, and 312 ± 56 ms, respectively, and the following return cycles at these sites were 368 ± 52, 368 ± 53, 367 ± 53, 367 ± 53, 407 ± 66, 431 ± 73, 415 ± 55, and 412 ± 56 ms, respectively. The longest coupling intervals at sites S, M, I, and I-CSOS did not differ from each other and were longer than those at CSOS and S-, P-, and PI-CSOS (P < 0.0001). The return cycles at sites S, M, I, and I-CSOS did not differ from the TCL, whereas those at CSOS and S-, P-, and PI-CSOS were longer than the TCL (P < 0.0001). Conclusions - The perinodal atrium extending from the HB site to I-CSOS was involved in the tachycardia circuit. I-CSOS was thought to be the entrance of the slow pathway.