Outcomes of Mitral Valve Surgery for Atrial Functional Mitral Regurgitation vs Ventricular Functional Mitral Regurgitation

Objectives Atrial functional mitral regurgitation (AFMR) is a unique category of functional mitral regurgitation (FMR), and surgical outcomes compared to traditional ventricular FMR (VFMR) are limited. This study compared long-term outcomes of mitral valve surgery (MVS) for patients with AFMR and VFMR, including AFMR subtypes. Methods Patients who underwent MVS for non-degenerative, moderate, or greater MR from 2000 to 2022 at our institution were included. AFMR and VFMR groups were 1:1 propensity matched based on 14 preoperative variables. Primary outcomes were cumulative survival and MVS failure, which was defined as recurrent moderate or greater MR or reoperation. Secondary analysis stratified patients by AFMR subtype: atrial fibrillation (AF) only, heart failure with preserved ejection fraction (HFpEF) only, or AF and HFpEF. Results We identified 115 AFMR and 260 VFMR patients. AFMR patients had lower rates of concomitant CABG (24% vs 48%, P < 0.001) and higher rates of concomitant ablation (39% vs 12%, P < 0.001). Rates of mitral repair were similar between groups (87.8% vs 87.3%, P = 0.89). Propensity matching identified 92 AFMR and VFMR pairs. AFMR group had lower operative mortality (3.3% vs 13%, P = 0.03), better cumulative survival (P = 0.039), and a trend towards higher rates of freedom from reoperation compared to the VFMR group (P = 0.062). Among patients with AFMR, the AF+HFpEF subtype trended towards lower survival (P = 0.084). Conclusions Compared to patients with VFMR, patients with AFMR have improved long-term survival after MVS. MVS may be beneficial in AFMR compared to VFMR, and future studies focusing on the subtypes are needed.