Early Mitral Valve Surgery and Survival in Asymptomatic Severe Primary Mitral Regurgitation

Importance The optimal timing of mitral valve (MV) surgery in patients with asymptomatic severe primary mitral regurgitation (MR) remains uncertain because randomized clinical trials are lacking. Objective To evaluate the association of early MV surgery with long-term survival in patients with asymptomatic severe primary MR using a target trial emulation framework. Design, Setting, and Participants This cohort study used a clinical valve registry from 3 tertiary hospitals in South Korea between 2000 and 2022. Patients with asymptomatic severe primary MR were analyzed using a clone-censor-weight approach to emulate a target trial. A 6-month grace period after diagnosis was used to define treatment strategies. This analysis was conducted from September 2024 to January 2025. Exposure Early MV surgery (within 6 months of diagnosis) vs watchful waiting. Main Outcomes and Measures The primary outcome was all-cause mortality and the secondary outcome, a composite of all-cause mortality or heart failure hospitalization. Inverse probability of censoring-weighted estimates of the per-protocol effect size included restricted mean survival time (RMST) differences as the primary measure and hazard ratios (HRs) as secondary measures. Results Among 802 patients (mean [SD] age, 55 [16] years; 476 men [59%]), 344 underwent early surgery, and 458 received watchful waiting. During a median (IQR) follow-up of 7.4 (4.1-11.6) years, 27 deaths occurred in the early surgery group and 103 in the watchful waiting group. At 5 years, early surgery was associated with an RMST gain of 66 days (95% CI, 19-129 days). The survival benefit persisted up to 15 years. Early surgery was also associated with a lower risk of all-cause mortality compared with watchful waiting (HR, 0.69; 95% CI, 0.41-0.94; P = .02). Similar associations were observed in patients without left ventricular decompensation (HR, 0.61; 95% CI, 0.31-0.96; P = .04) and in those with degenerative MR (HR, 0.66; 95% CI, 0.36-0.98; P = .04). Conclusions and Relevance In this multicenter cohort study with a target trial framework, early surgery was associated with improved long-term survival among patients with asymptomatic severe primary MR. These findings support consideration of earlier surgical intervention in contemporary clinical practice.