Atrial Functional Mitral Regurgitation- A Review with Emphasis on Therapeutic Strategies

Atrial functional mitral regurgitation (AFMR) may account for a substantial proportion of functional MR, although its prevalence varies by population and diagnostic definition. AFMR increases mortality risk regardless of left ventricular (LV) function. The mechanism involves mitral annular dilation and "atriogenic leaflet tethering." Key echocardiographic features include preserved left ventricular ejection fraction (LVEF; typically >50%), significant left atrial (LA) enlargement, mitral annular dilation, and minimal leaflet tethering. Medical therapy, including renin-angiotensin system inhibition/ angiotensin receptor-neprilysin inhibition (ARNI) and sodium-glucose co-transporter 2 (SGLT2) inhibitors, may favorably influence LA remodeling and AFMR severity, although AFMR-specific evidence remains limited. In patients with concomitant atrial fibrillation/flutter, restoration of sinus rhythm with cardioversion or catheter ablation may improve LA function and reduce AFMR severity. Surgical mitral annuloplasty is an also an option for low-risk patients with concomitant procedures. Mitral transcatheter edge-to-edge repair (M-TEER) in AFMR has had outcomes comparable to ventricular functional MR (VFMR). Maintaining a low post-procedural mean pressure gradient (MPG < 5 mmHg) is crucial. Preliminary experience with transcatheter indirect mitral valve annuloplasty (Carillon device) has also shown feasibility. Mitral replacement platforms face challenges due to high risk of LV outflow tract obstruction and atrial migration.