Abstract 16801: Papillary Muscle Tip Approximation in Repair of Ischemic Mitral Regurgitation in a Chronic Swine Model

Abstract

Introduction: Mitral valve (MV) repair with undersized annuloplasty (UMA) for ischemic mitral regurgitation (IMR) is being abandoned in favor of valve replacement (MVR) following CTSN trial results. However, in patients with durable repair, survival and left ventricular function (LVF) were significantly better than MVR. Achieving a durable repair with UMA is challenging as it draws leaflets away from papillary muscle (PM) insertions, causing unphysiological tethering and unicuspid configuration that fails (FigA-B). Hypothesis: Drawing PM tips together with an approximating stitch (PMT-A) can relieve leaflet tethering and enable better repair (FigC). A chronic swine model of IMR was used to compare effects of isolated PMT-A, UMA and PMT-A+UMA on MV and LV at 3 months post surgery. Methods: Twenty-five farm swine underwent catheterization and occlusion of left circumflex artery, resulting in postero-lateral myocardial infarction (MI). Two months after MI, IMR severity of >2+ was confirmed on echo, and animals underwent one of the 3 repairs: PMT-A (n=6), UMA (n=8), PMT-A+UMA (n=11). Echo was performed postoperatively and repeated with MRI at 3 months (FigD). MV kinematics, coaptation geometry, and LVF were assessed. Results: IMR was eliminated after all repairs and did not recur through the study. Annulus continued to grow after PMT-A, but not in UMA or PMT-A+UMA group (FigE1) without increasing severity of IMR. Compared to prerepair, tenting depth was significantly reduced only in PMT-A and PMT-A+UMA groups (FigE2). Both leaflet excursion angles (diastolic minus systolic angles) increased after PMT-A, but not in other groups (FigE3-4). LV size and LVF was similar between groups, confirming that PMT-A did not perturb diastolic filling. Conclusions: In this model of IMR, PMT-A improved leaflet mobility, compared to isolated UMA or PMT-A+UMA. PMT-A is a simple technique that can potentially improve durability of MV repair by restoring valvular kinematics.