Original Article http://dx.doi.org/10.3349/ymj.2012.53.1.76 pISSN: 0513-5796, eISSN: 1976-2437 Yonsei Med J 53(1):76-82, 2012 The Effects of a Bidirectional Cavo-Tricuspid Isthmus Block in Persistent Atrial Fibrillation Jin-Bae Kim,1* Seonghoon Choi,2* Boyoung Joung,3 Moon-Hyoung Lee, 3 and Sung-Soon Kim3 1Cardiology Division, Department of Internal Medicine, Kyung Hee University College of Medicine, Seoul; 2Cardiology Division, Kang-Nam Sacred Heart Hospital, Hallym University College of Medicine, Seoul; 3Cardiology Division, Yonsei Cardiovascular Center and Cardiovascular Research Institute, Yonsei University College of Medicine, Seoul, Korea. Received: January 6, 2011 Revised: March 20, 2011 Accepted: March 28, 2011 Corresponding author: Dr. Moon-Hyoung Lee, Cardiology Division, Yonsei Cardiovascular Center and Cardiovascular Research Institute, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Korea. Tel: 82-2-2228-8460, Fax: 82-2-393-2041 E-mail: mhlee@yuhs.ac *Jin-Bae Kim and Seonghoon Choi contributed equally to this work. ∙ An abstract of this work was presented at Orlando, FL, the annual meeting of the American College of Cardiology 2009 ∙ The authors have no financial conflicts of interest. © Copyright: Yonsei University College of Medicine 2012 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non- Commercial License (http://creativecommons.org/ licenses/by-nc/3.0) which permits unrestricted non- commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Purpose: Hybrid therapy with catheter ablation of the cavo-tricuspid isthmus (CTI) and continuation of anti-arrhythmic drugs (AAD), or electrical cardioversion with AADs might be alternative treatments for patients with persistent atrial fibrillation (AF). The goal of study was to assess the long term success rate of hybrid therapy for persistent AF compared to antiarrhythmic medication therapy after electrical cardioversion and identify the independent risk factors associated with recurrence after hybrid therapy. Materials and Methods: A total of 32 patients with persistent AF who developed atrial flutter after the administration of a class Ic or III anti-ar- rhythmic drug were enrolled. This group was compared with a group (33 patients) who underwent cardioversion and received direct current cardioversion with AADs. Baseline data were collected, and electrocardiogram and symptom driven Holter monitoring were performed every 2-4 months. Results: There was no significant difference in the baseline characteristics between the groups. The 12 month atrial arrhythmia free survival was better in the hybrid group, 49.0% vs. 33.1%, p=0.048. However, during a mean 55.7+/- 43.0 months of follow up, the improved survival rate regressed (p=0.25). A larger left atrium size was an independent risk factor for the recurrence of AF after adjusting for confounding factors. Conclusion: Despite favorable outcome during 12 month, the CTI block with AADs showed outcomes similar to AAD therapy after electrical cardioversion over a 12 month follow up pe- riod. Minimal substrate modification with AADs might be an alternative treatment for persistent AF with minimal atrial remodeling. Key Words: Atrial fibrillation, atrial flutter, cavo-tricuspid isthmus, antiarrhyth- mic drug INTRODUCTION Catheter ablation is considered standard therapy by current treatment guidelines1 for patients with symptomatic paroxysmal atrial fibrillation (AF) who do not re- spond to single antiarrhythmic drug therapy (AAD). However, the effectiveness of catheter ablation is low in patients with persistent AF despite prolongation of the complex procedure.2-4 Therefore, the mainstay of therapy for these patients has 76 Yonsei Med J http://www.eymj.org Volume 53 Number 1 January 2012