Impact of Pre-ablation Weight Loss on the Success of Catheter Ablation for Atrial FibrillationAbdul Hafiz Al Tannir BS, Marwan M. Refaat MDDepartment of Internal Medicine, Division of Cardiology, American University of Beirut Medical Center, Beirut, LebanonRunning Title: Pre-ablation Weight Loss and Success of AF AblationDisclosures: NoneFunding: NoneKeywords: Cardiac Arrhythmias, Cardiovascular Diseases, Heart Diseases, Weight Loss, Catheter Ablation, Atrial FibrillationWords: 621 (excluding references)Correspondence:Marwan M. Refaat, MD, FACC, FAHA, FHRS, FASE, FESC, FACP, FRCPAssociate Professor of MedicineDirector, Cardiovascular Fellowship ProgramDepartment of Internal Medicine, Cardiovascular Medicine/Cardiac ElectrophysiologyDepartment of Biochemistry and Molecular GeneticsAmerican University of Beirut Faculty of Medicine and Medical CenterPO Box 11-0236, Riad El-Solh 1107 2020- Beirut, LebanonFax: +961-1-370814Clinic: +961-1-759616 or +961-1-355500 or +961-1-350000/+961-1-374374 Extension 5800Office: +961-1-350000/+961-1-374374 Extension 5353 or Extension 5366 (Direct)Email: mr48@aub.edu.lbIn the United States, the prevalence of obese individuals has risen 3-fold since 1960, with 1 in every 3 persons being obese. The effect of weight changes on the progression on atrial fibrillation is well-established but the effect of pre-ablation weight loss on the recurrence of atrial fibrillation is not well-studied. Atrial fibrillation is the most frequently encountered cardiac arrhythmia [1]; it currently affects around 2.7 million people in the United States of America and is estimated that 6-12 million people will suffer from this condition by 2050 [2, 3]. Pulmonary vein isolation is the primary target for cardiac ablation; it can be achieved either by radiofrequency (RF) or cryoballoon ablation (CBA) [4, 5]. The FIRE and ICE trial conducted by Kuck et al showed that CBA therapy was associated with significantly fewer recurrence, rehospitalization, and cardioversion rates [6]. Several studies suggest the preferred use of CBA in treating atrial fibrillation in obese patients due to the increased surface area for ablation [4].Obesity has adverse effects on the structure and hemodynamics of the heart and it is a well-established risk factor for the development of atrial fibrillation [3]. A prospective cohort study performed by Pathak et al showed that progressive weight loss in obese and overweight patients resulted in dose-dependent effects on freedom from atrial fibrillation (FFAF) [7]. Similarly, Middeldrop et al, concluded that obesity is associated with the progression of the disease while weight loss is associated with reversal of the progression [8]. Limited data is available regarding the effect of weight loss on the recurrence of atrial fibrillation post-ablation. Current guidelines recommend lifestyle modifications, including a healthy diet and exercise, for overweight and obese patients before ablation [8, 9].The study of Peigh et al. is a retrospective cohort study from 2012-2017; 607 patients met the inclusion criteria. The aim of the study is to assess the impact of patient-directed weight loss 1 year before CBA on FFAP 15 months after ablation. The authors addressed an important topic that is poorly understood. Obese patients have a significantly lower FFAF rate 40-50% than the overall population 60-80%. The study selectively included patients undergoing CBA therapy. The follow-up time was 1-year post-ablation. The study concluded that, with the exception of non-obese patients with persistent atrial fibrillation, weight loss is associated with a significantly increased FFAF while weight gain led to a decrease in FFAF. A similar study assessed the impacted of physician-mediated risk control in patients undergoing RF ablation for atrial fibrillation [10]. A total of 149 patients were included in the prospective cohort study. The study showed a positive association between physician-directed weight loss (≥ 10%) and FFAF in symptomatic obese patients. The study performed by Peigh et al, included though a larger subject group (607) than LEGACY (141); however, the LEGACY is a prospective cohort study that is more suitable to monitor the fluctuation in patients’ variables before ablation.This study was well conducted but has the limitations of retrospective studies; a prospective cohort study would better monitor the variations in patients’ variables pre-ablation. In addition, as the authors stated, asymptomatic atrial fibrillation episodes may go unnoticed.Patients with atrial fibrillation, particularly those who are obese, should be advised to lose weight prior to catheter ablation. Lifestyle modifications should not be limited to patients undergoing ablation; the effect of weight loss on disease progression is well-established. Due to the overgrowing prevalence of atrial fibrillation and obesity worldwide, more studies are encouraged to better understand the ideal lifestyle management in patients. Larger prospective cohort studies should be conducted in order to validate the results. There is also an ongoing randomized clinical trial BAROS (Bariatric Atrial Return of Sinus Trial) [NCT 04050969] which will provide more data on this topic.