Efficacy of catheter ablation from the noncoronary aortic cusp of verapamil-sensitive atrial tachycardia arising near the atrioventricular node

BACKGROUND The efficacy of catheter ablation from the noncoro-nary aortic cusp (NCC) of verapamil-sensitive atrial tachycardia arising near the atrioventricular node (AVN-AT) has yet to be fully clarified. OBJECTIVE We elucidated the determinant of an effective AVN-AT ablation from the NCC.& nbsp;METHODS After identifying the earliest atrial activation site (EAAS) during tachycardia, the direction of the slow conduction zone (SCZ) of the reentry circuit was identified by demonstrating manifest entrainment in 26 patients with AVN-AT. Catheter ablation was initially performed from the NCC irrespective of the local activation time. If NCC ablation was ineffective, catheter ablation was per -formed targeting the SCZ entrance. Then the anatomical relationship between the SCZ and the successful ablation site was elucidated.& nbsp;RESULTS NCC catheter ablation terminated AVN-AT in 14 patients (NCC group) but not in 12 (non-NCC group). Catheter ablation targeting the SCZ entrance terminated all non-NCC group ATs. The local activation time at the NCC relative to the EAAS did not differ between the NCC and non-NCC groups (10.1 +/- 6.5 ms vs 11.2 +/- 4.8 ms; P = .6333). The direction of the SCZ was posterior to the EAAS in all NCC group patients; however, it was posterolateral (n = 5) and lateral (n = 7) to the EAAS in the non-NCC group, suggest -ing that the SCZ existed in the direction of the NCC in the NCC group but was away from the NCC in the non-NCC group.& nbsp;CONCLUSION A close proximity between the NCC and the SCZ of the reentry circuit, but not the local activation time at the NCC, deter-mined the efficacy of NCC catheter ablation in AVN-ATs.& nbsp;