Abstract 18607: Intra-ventricular Papillary Muscle Banding vs. Undersized Mitral Annuloplasty to Treat Ischemic Mitral Regurgitation in a Chronic Swine Model

Abstract

Introduction: Intra-ventricular papillary muscle banding (PMB), is a new mitral repair technique for ischemic mitral regurgitation (IMR), which reduces lateral distance between the two muscles to relieve leaflet tethering (Fig A). In this study, we compared the hemodynamic efficacy of PMB against undersized mitral annuloplasty (UMA) and the combination of PMB and UMA, in a chronic swine IMR model. Methods: Six swine were induced with chronic IMR via percutaneous infarction of the postero-lateral wall of the left ventricle(LV), and followed to 6 weeks to develop >3+ IMR. At 6 weeks, via a left atriotomy an adjustable PMB externalized through the LV wall, and an adjustable UMA suture externalized through the anterior annulus were implanted (Fig B1,B2). The animals were weaned from bypass, and physiological swine hemodynamics of 90/65 mm Hg were achieved at 75 bpm. PMB was done such that 50% reduction in the lateral distance between the muscles was achieved, and UMA reduced septal-lateral annular dimension to 24mm. Epicardial echocardiography was performed to assess mitral valve function, with IMR severity and tenting area recorded. Computational valve modeling was performed to quantify leaflet stresses and chordal forces, to assess and compare repair durability. Results: Table 1 summarizes valve function after each repair, with PMB reducing MR grade from 3.67±0.52 to 0.33±0.52 (p<0.05), which was significantly better than the persistent MR grade of 1.5±0.55 after UMA (p<0.05). PMB+UMA achieved the best results overall. Similar trends in tenting area were seen, with PMB reducing the tenting area better than UMA, but the combination demonstrating the best results. Table 2 summarizes the valve and chordal stresses, with PMB alone or with UMA reducing the overall leaflet peak stress and chordal peak forces. Conclusions: PMB alone or concomitant with UMA is an effective technique to repair IMR in this model, with good hemodynamic efficacy and better mechanics compared to UMA.