Jin-Bae Kim, et al. 100 80 ) % ( ilva 60 v r u s free 40 F A 20 0 Electrical cardioversion group Hybrid group p=0.048 Electrical cardioversion group Hybrid group p=0.25 100 80 ) % ( ilva 60 v r u s free 40 F A 20 0 0 2 4 6 8 10 12 14 Follow up duration (months) Fig. 1. Comparision of 12 month event free survival curves between hybrid and electrical cardioversion group patients. AF, atrial fibrillation. 0 20 40 60 80 100 Follow up duration (months) Fig. 2. Comparision of long term event free survival curves between hybrid and electrical cardioversion group patients. AF, atrial fibrillation. sleeve extending from the left atrium into the pulmonary veins (PV). Therefore, the target of treatment is the elimina- tion of these triggers and drivers, such as PV isolation. How- ever, in patients with persistent AF, the triggers and drivers are located at unusual sites, and the fibrillatory activity is independent. The remodeled atria act as substrate and can perpetuate fibrillatory waves and independently maintain chaotic electrical activity. Therefore, for restoration of sinus rhythm, more prolonged and highly sophisticated proce- dures are required for the treatment of patients with chronic persistent AF, and the efficacy of catheter ablation is lower than in paroxysmal AF, with a significant increase in the as- sociated risk of procedural complications. Several alternative strategies have been considered for these patients. Hybrid therapy, a combined method of phar- macological and non- pharmacological therapy, is one of the alternatives; it can be used for certain patients with atri- al flutter that is transformed from atrial fibrillation after ini- tiation of drug treatment. A previous study indicates that the incidence of drug-related atrial flutter is up to 12.8% among patients that had received classic anti-arrhythmic drug ther- apy for atrial fibrillation.6,12 In these patients, hybrid therapy has a good outcome without significant complications. Dif- ferent studies have documented 7% up to 42% AF recur- rence rate during 12 month to 2 year follow up.13-15 Howev- er, these studies included more paroxysmal patients than persistent and detected AF recurrence with symptom driven ECG recording. In contrast to previous studies, the present study included only patients with chronic persistent AF which continued overall 50 months, and showed a higher recurrence rate of AF by regular ECG follow up and symp- tom-driven Holter monitoring. However, the 12 month AF free-survival rate was comparable to that of previous AF ablation studies in patients with chronic persistent AF.16 Furthermore, a worldwide survey revealed that the success rate of AF ablation, including patients with paroxysmal and persistent AF, varied according to the volume of cases un- dergoing the procedure per center, and that the major com- plication rate was 5.9%, including early deaths.17 The re- sults of this study and the evidence from previous studies7,8 suggest that hybrid treatment is a reasonable approach for patients with atrial flutter that evolved from persistent AF. In contrast to hybrid therapy, sole antiarrhythmic medica- tion therapy after direct current (DC) cardioversion had a poorer outcome over the 12 months of follow up. Previously, the PAFAC trial reported a 65-67% rate of AF recurrence af- ter DC cardioversion.18 In the trial, sotalol and quinidine were used as antiarrhythmic medications, and the clinical out- come was comparable with the use of flecainide, propafe- none or amiodarone in our present study. However, during a mean of 55.7+/-43.0 months of follow up, the benefit of hy- brid therapy regressed and was not significant compared to single drug therapy (p=0.25). Reithmann, et al.19 reported that the presence of pre-ablation episodes of atrial fibrilla- tion, in patients taking anti-arrhythmic medication, and a decreased left ventricular ejection fraction were significant and independent predictors of post-ablation atrial fibrilla- tion. In our study, the only independent risk factor for re- currence of AF was the pre-ablative LA size. The likely ex- planation for this result is atrial electrical and structural remodeling. Electrical remodeling accompanied by struc- tural remodeling acts as substrate, and more modification of the substrate is required to restore sinus rhythm. Stabile, et al.20 reported that single drug therapy in pa- tients with atrial flutter, after flecainide infusion, showed an 80% AF recurrence rate over 12 months period, suggesting 80 Yonsei Med J http://www.eymj.org Volume 53 Number 1 January 2012