Finite element analysis of the mitral valve

A finite element model was developed to examine deformation and stress patterns in the mitral valve under systolic loading conditions. This is the first three-dimensional finite element model of the mitral valve, incorporating all essential anatomic components, regional tissue thickness, collagen fiber orientation and related anisotropic material properties. A non-linear, transient, dynamic analysis was performed which included time-dependent loading, leaflet and chordal mass inertial effects and chordal element bi-linearity. The model was first analyzed without either annular or papillary muscle contraction and then with either or both. The hypothesis was that the combination of annular and papillary muscle contraction would have a beneficial effect on valve function. In all models, the computed anterior leaflet principal stresses were tensile and of greater magnitude than those in the posterior leaflet. The principal stress directions were observed to correlate well with collagen fiber orientation. Earlier leaflet coaptation was demonstrated with annular contraction, promoting valve closure, while papillary muscle contraction increased the stress on the chordae tendineae and both leaflets, tending to pull the latter apart. The combination of the two combined these effects, and showed the most even stress distribution. The effects of annular and papillary muscle contraction on valve function were shown to be beneficial by this model, and they can be further elucidated by varying the extent and timing of the individual contractions. This model can be used to examine the effects of pathologic changes, surgical manipulations and proposed material replacements. It can thus aid both the surgeon and the biomedical engineer in improving the materials and techniques available for the repair and/or replacement of mitral valve system components.