Natural History and Outcomes of Patients With Moderate and Moderate-Severe Mitral Regurgitation

BACKGROUND: The natural history of mitral regurgitation (MR) in contemporary practice remains poorly defined. OBJECTIVES: The purpose of this study was to quantify clinical outcomes of patients with moderate and moderate-severe MR. METHODS: We conducted a retrospective cohort study of consecutive patients with moderate or moderate-severe MR who underwent echocardiography at Mayo Clinic between 2010 and 2023. MR was classified as degenerative or functional. The primary outcome was all-cause mortality. Secondary outcomes included heart failure (HF) hospitalization, MR progression to severe MR, and mitral valve intervention. RESULTS: Of 8,687 patients (mean age 70.7 ± 13.7 years; 45.1% female), 21.4% had degenerative MR and 78.6% had functional MR, and median follow-up was 4.1 years (Q1-Q3: 2.3-7.9). At 4 years, overall survival was 68.5% (95% CI: 67.4%-69.7%), with higher survival in patients with degenerative MR (84.1%; 95% CI: 81.9%-86.3%) compared to functional MR (65.0%; 95% CI: 63.7%-66.3%), and the cumulative incidence of HF hospitalization was higher in functional MR (36.8%; 95% CI: 35.6%-38.1%) than degenerative MR (17.9%; 95% CI: 15.7%-20%). However, the risk of death and HF hospitalization was similar after multivariable adjustments. MR progression occurred in 32.7% (95% CI: 31.0%-34.4%), less commonly in functional MR (adjusted HR: 0.65; 95% CI: 0.54-0.79; P < 0.001). Mitral valve intervention was infrequent (11.4%; 95% CI: 10.6%-12.1%) and significantly less common in functional MR (adjusted HR: 0.45; 95% CI: 0.37-0.56; P < 0.001). CONCLUSIONS: Patients with moderate or moderate-severe MR accrue significant mortality and morbidity over follow-up. Further trials are needed to ascertain the indication, optimal timing and method of procedural intervention.