The 2026 American Association for Thoracic Surgery (AATS) Expert Consensus Document: Management of Atrial Functional Mitral Regurgitation.

Objective Atrial functional mitral regurgitation (AFMR) represents a distinct pathophysiologic entity characterized by mitral regurgitation secondary to left atrial dilation and annular remodeling, in the absence of significant left ventricular disease. With the increasing prevalence of atrial fibrillation and heart failure with preserved ejection fraction, AFMR has emerged as an important and potentially underrecognized etiology of mitral regurgitation. This expert consensus statement provides an evidence- and experience-based framework for the evaluation and management of AFMR, encompassing diagnosis, medical and rhythm therapy, surgical and transcatheter interventions, and postoperative management.Methods The American Association for Thoracic Surgery convened an international multidisciplinary panel of cardiac surgeons, cardiologists, and electrophysiologists with expertise in atrial and mitral valve disease. The panel conducted a systematic literature review and iterative Delphi consensus process to develop recommendations, graded according to class of recommendation (CoR) and level of evidence (LoE).Results Consensus was achieved on 18 statements, organized into five sections: (1) Definition, pathophysiology, and diagnostic evaluation of AFMR. (2) Medical and rhythm management strategies. (3) Surgical treatment and concomitant procedures. (4) Transcatheter and hybrid interventions. (5) Postoperative rhythm and anticoagulation management CONCLUSIONS: AFMR represents a distinct form of secondary mitral regurgitation driven by atrial remodeling. This document summarizes current expert consensus to guide diagnosis, timing, and choice of intervention, and highlights the need for multidisciplinary collaboration and prospective research to optimize outcomes.