Posterior Leaflet Restoration for Secondary Mitral Regurgitation: EXPLORE MR Results

Secondary mitral regurgitation (MR) contributes to morbidity and mortality in patients with symptomatic valve disease. Although transcatheter edge-to-edge repair is beneficial, many patients remain suboptimal candidates. Posterior leaflet restoration (PLR) provides a prosthetic coaptation surface via an adaptive coaptation element that inflates during systole and deflates during diastole to facilitate leaflet coaptation.

This study aims to evaluate the safety and feasibility of PLR using the MRace implant (Polares Medical, Inc).

Early Feasibility Experience of Posterior Leaflet Restoration to Reduce Mitral Regurgitation Using the MRace Implant in Georgia and Brazil (EXPLORE MR) enrolled 78 symptomatic patients with severe secondary MR (≥3+), stratified post hoc by left ventricular end-diastolic volume: nonseverely enlarged left ventricle (NSELV) (N = 46) and severely enlarged left ventricle (SELV) (N = 32). The primary endpoint was 30-day mortality; secondary endpoints were MR reduction and functional outcomes.

The implant was successfully deployed in 96.2% of patients. All-cause mortality at 30 days was 6.4%. MR ≤2+ was achieved in 93.8% of patients at 30 days and was sustained in 90.6% at 1 year. Patients with NSELV showed better results in MR ≤1+ at every time point (94.4% at 30 days, 89.5% at 1 year) compared with the SELV group (79.3% and 69.2%, respectively). The NSELV subgroup demonstrated better functional recovery, with NYHA functional class I or II rising from 8.7% to 84.2%, vs a more attenuated response in the SELV group (15.6%-76.9%). The 6-minute walk test improved in the paired NSELV cohort (Δ +93.9 m), but not in paired patients with SELV (Δ -7.8 m). Kaplan-Meier 1-year all-cause mortality was 29.5% overall and was better in patients with NSELV (19.4%) than in SELV (41.7%).

PLR with the MRace implant achieves substantial MR reduction and meaningful functional improvement, most pronounced in patients without severely enlarged left ventricles. (XPLORE MRace [BR]: Early Feasibility Experience of Posterior Leaflet Restoration to Reduce Mitral Regurgitation Using the MRace Implant [EXPLORE MRace]; NCT06113354).