Fibrotic Remodeling and Stiffening of Mitral Valve Leaflets After Undersizing Ring Annuloplasty to Correct Ischemic Mitral Regurgitation

Introduction: Systolic leaflet coaptation after undersizing ring annuloplasty (URA) to repair ischemic mitral regurgitation (IMR) is highly non-physiological, with a hyper-extending anterior leaflet and restricted posterior leaflet. Such a leaflet configuration elevates leaflet stresses and could trigger pathological leaflet remodeling. Hypothesis: Abnormal leaflet stresses after URA can trigger fibrotic leaflet remodeling(Fig 1A). Adding a sub-valvular repair, such as papillary muscle approximation (PMA), that restores physiological coaptation and leaflet kinematics may inhibit this process. Methods: Eighteen swine with chronic IMR were randomized to four groups: (G1, n=3) sham/control; (G2, n=3) URA; (G3, n=6) URA+PMA; and (G4, n=6) PMA only. At 3 months post-repair, cardiac MRI was performed to assess leaflet kinematics, and valve leaflets were explanted and analyzed for fibrotic remodeling with immunoblotting. Results: Anterior leaflet hyper-extension was consistently observed in all the repair groups...