EFFECT OF PAPILLARY MUSCLE DISPLACEMENT AND ANNULAR DILATION ON DEVELOPMENT OF FUNCTIONAL MITRAL REGURGITATION

Functional mitral regurgitation (FMR) occurs following left ventricle (LV) dysfunction with normal mitral valve (MV) leaflet. The progress and severity of FMR are closely related to LV dilatation, which often results in displacement of the papillary muscles (PMs) and enlargement of the mitral annulus. We investigated the effect of PM displacement and annular dilation on FMR development to better understand the complex intercorrelation between these pathologic alterations leading to FMR. Virtual MV modeling was performed to create a normal human MV, and several different types of PM displacement, annular dilation, and the combination of PM displacement and annular dilation mimicking the pathology of FMR were modeled. Dynamic finite element evaluation of MV function was performed across the complete cardiac cycle for the normal and FMR MV models. PM displacement to both lateral and apical directions revealed markedly reduced leaflet coaptation and large stress distribution in the P2 scallop. Annular dilation greater than 2% demonstrated the occurrence of leaflet malcoaptation and increased stresses near the anterior saddle-horn region. The pathologic MV model with annular dilation combined with PM displacement provides physiologically realistic biomechanical characteristics as the MVs having FMR. Simulation-based biomechanical evaluation of MV pathology related to LV chamber dilatation provides an excellent tool to better understand the pathophysiologic mechanism of FMR.