Abstract 2343: Analysis of the Tachycardia Circuit in Patients With Slow-Fast Form of Atrioventricular Nodal Reentrant Tachycardia Using the Right and Left Atrial Single Extrastimulation
Background: Radiofrequency catheter ablation of the slow pathway is an establish treatment for slow-fast form of atrioventricular nodal reentrant tachycardia (AVNRT). However, rare cases of the slow-fast form of AVNRT (SF-AVNRT) were resistant to the standard right-sided slow pathway ablation and required a left-sided ablation.
Objectives: The purpose of this study was to elucidate whether the left septal atrium is involved in the tachycardia circuit of the SF-AVNRT.
Methods: In 7 patients with the SF-AVNRT, single extrastimuli were delivered during tachycardia at 7 sites along the right interatrial septum; the His-bundle (HB) site, 3 arbitrarily divided sites of the atrioventricular junction extending from HB site to the coronary sinus ostium (CSOS) (sites S, M and I), inferior and posterior portions of the CSOS (I-CSOS and P-CSOS) and CSOS, and at 4 sites along the mitral annulus; 9, 8, 7 and 6 o’clock position (MV 9, 8, 7 and 6) in the left anterior oblique view.
Results: The mean tachycardia cycle length (TCL) was 367±52 ms. The longest coupling interval (LCI) of single extrastimuli that reset the tachycardia at HB, site S, M, I and I-CSOS were longer than those at P-CSOS and CSOS (p<0.01). The following return cycle (RC) at HB, sites S, M, I and I-CSOS did not differ from the TCL, whereas those at P-CSOS and CSOS were longer than the TCL (p<0.01). The LCI at MV 9 did not differ from those at HB, sites S, M, I and I-CSOS. At MV 6, LCI was shorter than those at HB, sites S, M, I and I-CSOS (p<0.005) and RC was longer than TCL (p<0.0001). These suggest that MV 9, located opposite to HB, is involved in the tachycardia circuit but MV 6 is not. Regarding MV 7 and 8, the difference between TCL and LCI and the that between RC and TCL at MV 8 and 7 were short in 3 patients (MV 8; 15±5 and 5±5 ms, MV 7; 15±5 and 5±5 ms, respectively), whereas those were relatively long in remaining 4 patients (MV 8; 23±3 and 13±3 ms, MV 7; 25±6 and 15±5 ms, respectively).
Conclusions: The right perinodal atrium extending from the HB site to I-CSOS and left septal atrium, opposite to HB, is involved in the tachycardia circuit of the SF-AVNRT. In addition, the left side of the septum extending from MV 7 to 9 is involved in the tachycardia circuit of SF-AVNRT in some cases.