Objectives: To evaluate atrial fibrillation (AF) recurrence and Sarcoplasmic Endoplasmic Reticulum Calcium ATPase (SERCA) levels in patients treated by epicardial thoracoscopic ablation for persistent AF. Background: Reduced levels of SERCA have been reported in the peripheral blood cells of patients with AF. We hypothesize that SERCA levels can predict the response to epicardial ablation. Methods: We designed a prospective, multicenter observational study to recruit, from October 2014 to June 2016, patients with persistent AF receiving an epicardial thoracoscopic pulmonary vein isolation. Results: We enrolled 27 patients; responders patients (n=15) did not present AF recurrence after epicardial ablation at 1-year follow-up. These patients displayed a marked remodeling of the left atrium, with a significant reduction of inflammatory cytokines, B type Natriuretic Peptide (BNP), and over expression of SERCA as compared to baseline and to non-responders (p<0.05). Furthermore, mean AF duration (HR 1.235 [1.037-1.471], p<0.05), LAV (HR 1.755 [1.126-2.738], p<0.05), BNP (HR 1.945 [1.895-1.999], p<0.05), and SERCA (HR 1.763 [1.167-2.663], p<0.05) were predictive of AF recurrence. Conclusions: Our data indicate that baseline values of SERCA in patients with persistent AF might be predictive of failure to epicardial ablative approach. Intriguingly, epicardial ablation was associated with increased levels of SERCA in responders. Therefore, SERCA might be an innovative therapeutic target to improve the response to epicardial ablative treatments.