Clinical outcomes and impact of mitral valve surgery in atrial functional mitral regurgitation: the REVEAL-AFMR registry

Abstract Background The real-world impact and effective treatment strategies of atrial functional mitral regurgitation (AFMR) are poorly understood. The aim of this study was to investigate the prevalence, clinical characteristics, and the effectiveness of mitral valve surgery in AFMR. Methods The REal-world obserVational study for invEstigAting the prevaLence and therapeutic options for Atrial Functional Mitral Regurgitation (REVEAL-AFMR) was a retrospective cohort study conducted across 26 Japanese centers. All transthoracic echocardiography performed in 2019 were reviewed and patients with moderate or severe AFMR defined by preserved left ventricular function, dilated left atrium, and absence of degenerative valvular changes. The primary composite outcomes were heart failure hospitalization and all-cause mortality. Besides traditional multivariable regression analysis, propensity score-based time-zero matching was performed to account for immortal time bias. Results In 177,235 patients who underwent echocardiography, 8,867 had moderate or severe MR. Within this group, 1,007 were diagnosed with AFMR (mean age 78±10, 56% female, 80% atrial fibrillation). Of these, 113 underwent MV surgery, with 81% receiving concurrent tricuspid valve surgery. Patients who underwent surgery were younger but had more severe MR, larger left heart chambers, and a higher prevalence of heart failure than those who remained under medical therapy. During a median follow-up of 1050 days, 28% experienced the primary outcome, and 18% died. Despite a more severe disease status, only the surgical group showed a decrease in natriuretic peptide levels at follow-up and had significantly lower rate of the primary outcome (hazard ratio 0.43 [0.29-0.64], p<0.001 after adjustment for 25 covariates). Propensity score-based time-zero matching also indicated a lower risk of the primary outcome in the surgical group (hazard ratio 0.39 [0.20–0.78], p=0.007). Multiple sensitivity analyses yielded consistent results. Subgroup analysis suggested a significantly greater benefit of surgery for patients with severe MR than those with non-severe MR (p for interaction=0.044). Conclusions Our registry revealed that patients with AFMR are typically old with predominantly with atrial fibrillation, facing poor outcomes. MV surgery was associated with fewer adverse events, a finding that should be validated in future clinical trials.