Interactive Effects Between Papillary Muscle Approximation and Ring Annuloplasty to Repair Functional Mitral...

In this study, we used computational modeling to investigate the benefit of the addition of annuloplasty to papillary muscle approximation (PMA) and the effects of ring sizing on functional mitral regurgitation (FMR) repair in enlarged left ventricles. 3D echo images were obtained in three pigs with heart failure, enlarged ventricles, and FMR. Each echo dataset was segmented, and computational model of the mitral valve was created. 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. Both PMA alone and in combination with annuloplasty improved valve geometry and biomechanics. On average, compared to pre-repair, PMA increased A2-P2 coaptation length by 56.1±10.4%, while the addition of annuloplasty increased this length by 35.2±42.8% with 40 mm, 80.1±38% with 38 mm, and 97.7±37.6% with 36 mm ring. Peak leaflet stress was observed on the P2 cusp, and PMA reduced it by 26.9±3.9%. Adding true-sized ring reduced peak stress by 10.7±16.4%, while the addition of 38 mm ring reduced it by 29.9±2.2%, and 36 mm by 43.7±8.8%. Overall, the addition of true-sized ring to PMA slightly 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.