Abstract 14699: Effects of Papillary Muscle Approximation and Annuloplasty Ring Sizing for Functional Mitral Regurgitation Repair in Enlarged Ventricles

Abstract

Introduction: Our recent large animal study showed that papillary muscle approximation (PMA) repairs functional mitral regurgitation (FMR) and increases valve coaptation in enlarged left ventricles without negatively affecting ventricular function. However, since PMA does not reduce mitral annular dilation, addition of annuloplasty ring might be beneficial for such repair. In this study, we used computational modeling to investigate the benefit of the addition of annuloplasty to PMA and the effects of ring sizing on FMR repair in enlarged ventricles. Methods: 3D echo images were obtained in 3 pigs with heart failure, enlarged ventricles, and FMR. Each echo dataset was segmented, and computational model of the mitral valve was developed. To mimic PMA repair, the papillary muscles were drawn together in diastole. A true-sized annuloplasty ring of 40 mm and two downsized-rings of 38 mm and 36 mm were then added to each model. Leaflet closure was simulated and mitral valve geometry and biomechanics in peak systole were evaluated ( Fig A-B ). Results: On average, compared to pre-repair, PMA increased coaptation area by 30.6%, while the addition of annuloplasty increased this area by 85.1% with 40 mm, 138.1% with 38 mm, and 190.6% with 36 mm ring. Tenting area was reduced by 45.8% after PMA, 64.1% with the addition of 40 mm ring, 70.6% with 38 mm, and 76.5% with 36 mm ring. PMA reduced tension forces in chordae by 19.8%, while adding true-sized ring reduced forces by 16.4%. Annular downsizing allowed to reduce chordal forces by 31.2% with 38 mm, and 43.0% with 36 mm ring. Peak leaflet stress was observed on the P2 cusp, and PMA reduced it by 26.9%. True-sized ring reduced peak stress by only 10.7%, while 38 mm ring by 29.9%, and 36 mm by 43.7% ( Fig C ). Conclusions: Addition of true-sized ring to PMA further improved systolic valve geometry but not biomechanical parameters. Annular downsizing added to PMA was more beneficial for FMR repair, as it improved both mitral valve geometry and biomechanics.