Atrial Secondary Mitral Regurgitation: Pathophysiology, Diagnosis, and Surgical Implications

Background and Objectives Atrial secondary mitral regurgitation (A-SMR), also referred to as atrial functional mitral regurgitation, has emerged as a distinct clinical phenotype characterized by left atrial enlargement, mitral annular dilatation, and preserved left ventricular geometry and systolic function [1]. Frequently associated with long-standing atrial fibrillation and heart failure with preserved ejection fraction, A-SMR challenges the traditional ventricular-centered classification of functional mitral regurgitation and is increasingly recognized as a clinically relevant condition [2,3]. Materials and Methods This narrative review provides an updated and critical overview of cur-rent evidence on atrial secondary mitral regurgitation. We summarize available data on pathophysiology, diagnostic imaging, natural history, and therapeutic strategies, with particular emphasis on implications for cardiac surgery and clinical decision-making. Evidence was derived from observational studies, registry analyses, interventional reports, and contemporary guideline documents [4,5]. Results A-SMR is primarily driven by atrial remodeling and annular dilatation, with minimal contribution from ventricular distortion or leaflet tethering [1,3]. Echocardiography and Magnetic Resonance Imaging (MRI) play a central role in diagnosis and phenotypic characterization, allowing differentiation from ventricular functional mitral regurgitation and identification of distinct A-SMR subtypes with potential therapeutic implications [4]. A-SMR is a progressive condition associated with worsening symptoms and adverse clinical outcomes [2,3]. Rhythm control strategies may reduce mitral regurgitation severity in selected patients by promo-ting atrial reverse remodeling [6]. Transcatheter edge-to-edge repair (TEER) represents a treatment option for selected high-risk patients, al-though concerns regarding long-term durability remain in this predominantly annular disease [7]. From a pathophysiological standpoint, surgical mitral valve repair based on annuloplasty directly targets the dominant mechanism of A-SMR and has been associated with favorable outcomes in appropriately selected patients [8]. Conclusions Atrial secondary mitral regurgitation is a distinct and increasingly re-cognized form of functional mitral regurgitation requiring a mechanism-oriented diagnostic and therapeutic approach. 2025 ESC/EACTS Guidelines for the management of valvular heart disease have acknowledged A-SMR as a specific clinical phenotype, although dedicated phenotype-specific management recommendations remain limited [5]. Surgical mitral valve repair, particularly when combined with atrial fibrillation ablation, represents a rational treatment strategy in selected patients and may improve long-term outcomes [6,8].