388 Induced Atrial Tachycardia After Circumferential Pulmonary Vein Isolation of Paroxysmal Atrial Fibrillation: Electrophysiological Characteristics and Impact of Catheter Ablation on the Follow-Up Results SHIH-LIN CHANG, M.D., ∗ ,†,‡ YENN-JIANG LIN, M.D., ∗ ,† CHING-TAI TAI, M.D.,† LI-WEI LO, M.D.,† TA-CHUAN TUAN, M.D.,† AMEYA R. UDYAVAR, M.D.,† YU-FENG HU, M.D.,† SHUO-JU CHIANG,† WANWARANG WONGCHAROEN, M.D.,† HSUAN-MING TSAO, M.D.,§ KWO-CHANG UENG, M.D.,¶ SATOSHI HIGA, M.D. Ph.D.,# PI-CHANG LEE, M.D., ∗ ,† and SHIH-ANN CHEN, M.D., ∗ ,† From the ∗ Department of Medicine and Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine, †Taipei Veterans General Hospital, ‡Yuanshan Veterans Hospital, §National Yang-Ming University Hospital, ¶Institute of Medicine, Chung Shan Medical University Hospital, Taiwan; and #Second Department of Internal Medicine, University of the Ryukyus, Okinawa, Japan Induced AT after AF ablation. Introduction: Atrial tachycardia (AT), including focal and reentrant AT, can occur after circumferential pulmonary vein isolation (CPVI). The aim of this study was to investigate the electrophysiological characteristics of induced AT and its clinical outcome. Methods and Results: In our series of 160 patients with paroxysmal atrial fibrillation (AF), 45 ATs were induced by high-current burst pacing after CPVI in 26 patients. All induced ATs were mapped using a three-dimensional (3D) mapping system. Noninducibility was the endpoint of the ablation of the AT. Gap- related AT was considered if the AT was related to the CPVI lesions. A 16-slice multidetector computed tomography scan was performed in all patients to correlate the anatomical structure with electroanatomical mapping. Thirty-five (78%) reentrant ATs and 10 (22%) focal ATs were identified. Of those, 34 were gap- related ATs (24 reentrant and 10 focal ATs). Reentrant AT had more gaps in the left atrial appendage ridge than did focal AT (39.6% vs 0%, P = 0.02). Focal AT had a higher incidence of gap in the PV carina compared with reentrant AT (80% vs 10%, P < 0.001). Reentrant ATs were mostly terminated during the ablation creating the mitral and roof lines with crossing of the gaps. During a mean follow-up of 21 ± 8 months, only one patient (0.6%) with induced mitral reentry had a recurrent AT. Conclusion: The location of the AT gap may be related with the complex anatomy of the LA. The induced ATs after CPVI can be eliminated by catheter ablation. (J Cardiovasc Electrophysiol, Vol. 20, pp. 388-394, April 2009) atrial fibrillation, atrial tachycardia, catheter ablation, inducibility, mapping Introduction The postablation atrial tachycardia (AT) has been reported in patients who have undergone catheter ablation of atrial fib- rillation (AF). 1-3 ATs, including focal and reentrant AT, can occur immediately after circumferential pulmonary vein iso- lation (CPVI) or during the follow-up; however, a variant prevalence has been reported in previous studies and was associated with the ablation technique. 2,4 A gap in prior ab- lation lesions has been thought to be the main mechanism of the postablation AT. However, the optimal strategy to prevent This work was supported by Taipei Veterans General Hospital (V96C1-049, V97C1-059), NSC95-2314-B-010-017, NSC95-2314-B-010-025, NSC96- 2314-B-010-006, NSC96-2628-B-010-036. Address for correspondence: Shih-Ann Chen, M.D., Division of Cardio- logy, Veterans General Hospital-Taipei, 201 Sec. 2, Shih-Pai Road, Taipei, Taiwan. Fax: 886-2-2873-5656; E-mail: epsachen@ms41.hinet.net Manuscript received 11 August 2008; Revised manuscript received 10 September 2008; Accepted for publication 12 September 2008. doi: 10.1111/j.1540-8167.2008.01358.x the AT after CPVI has not been demonstrated. The aim of this study was to investigate the electrophysiological characteris- tics of induced AT after CPVI and provide better management in order to avoid the occurrence of AT. Methods One hundred and sixty consecutive patients with drug re- fractory paroxysmal AF were included in this study. The clinical characteristics of the patients are shown in Table 1. In those patients, 45 sustained ATs were induced by high- current burst pacing after the CPVI in 26 patients with parox- ysmal AF. Induced cavotricuspid isthmus (CTI)-dependent atrial flutter caused by incomplete block after routine CTI ablation was excluded from this study. All the induced ATs were mapped using a three-dimensional (3D) mapping sys- tem (NavX, St. Jude Medical, Inc., Minnetonka, MN, USA). The study patients underwent a 16-slice multidetector com- puted tomography (MDCT) scan 1 to 14 days before the ablation procedure.