BackgroundDespite prospective randomized evidence supporting concomitant treatment of atrial fibrillation (AF) during mitral valve (MV) surgery, variation in surgical management of AF remains. We assessed longitudinal outcomes after surgical treatment of persistent or paroxysmal AF during MV surgery in Medicare beneficiaries. MethodsAll Medicare beneficiaries with a diagnosis of AF undergoing MV surgery (2018-2020) were evaluated. Patients were stratified by no AF treatment, left atrial appendage obliteration (LAAO) alone, or surgical ablation and LAAO (SA+LAAO). Doubly robust risk adjustment and subgroup analysis by persistent or paroxysmal AF were performed. ResultsA total of 7517 patients with preoperative AF underwent MV surgery (32.1% no AF treatment, 23.1% LAAO alone, 44.7% SA+LAAO). After doubly robust risk adjustment, AF treatment with SA+LAAO or LAAO alone were associated with lower 3-year readmission for stroke or bleeding. However, SA+LAAO was associated with reduced 3-year mortality and readmission for AF or heart failure compared with no AF treatment or LAAO alone. Compared with no AF treatment or LAAO alone, SA+LAAO was associated with lower composite end point of stroke (hazard ratio, 0.75) or death (hazard ratio, 0.83) at 3 years. Subgroup analysis identified similar longitudinal benefits of SA+LAAO in patients with persistent or paroxysmal AF. ConclusionsIn Medicare beneficiaries with AF undergoing MV surgery, SA+LAAO was associated with improved longitudinal outcomes compared with LAAO alone or no AF treatment in patients with paroxysmal or persistent AF. These contemporary real-world data further clarify the benefit of SA+LAAO during MV surgery across all types of AF.