Isolated and combined effects of papillary muscle approximation and mitral annuloplasty in dilated left ventricles

Functional mitral regurgitation (FMR) remains challenging to repair surgically, as highlighted by the Cardiothoracic Surgical Trials Network (CTSN) trial, which showed limited durability of mitral annuloplasty. We previously demonstrated in vivo and experimentally that papillary muscle approximation (PMA) can improve mitral valve (MV) function, with or without annuloplasty. In this study, we assessed valve biomechanics after PMA, mitral annuloplasty, and their combination in imaging-derived computational models.

3D echo images were obtained in three pigs with heart failure, dilated ventricles, and FMR. Each echo dataset was segmented, and a subject-specific computational model of the MV was created. Virtual FMR repair was performed on each valve using PMA, annuloplasty with true-sized (40 mm) and downsized (38 mm and 36 mm) rings, and a combination of both techniques. For each repair strategy, leaflet closure was simulated, and MV geometry and biomechanics at peak systole were evaluated.

Isolated PMA improved valve coaptation, reduced leaflet stresses and chordal tension forces, but failed to completely eliminate FMR. Isolated mitral annuloplasty also improved coaptation, but overall provided only limited geometric and biomechanical benefits. Combining annuloplasty and PMA resulted in the most favorable outcomes, eliminating FMR, increasing coaptation length (up to 97.7%), and reducing leaflet stresses (up to 43.7%) and chordal forces (up to 43.0%).

While both PMA and annuloplasty independently improved MV function, neither technique fully resolved FMR on its own. Their combination yielded the most favorable repair outcomes, eliminating FMR and significantly improving valve geometry and biomechanics without the need for excessive annular downsizing.