In vitro dynamic strain analysis on porcine mitral valve

Dual camera stereo photogrammetry was used to quantify the deformation of the central region of the anterior leaflet of the mitral valve operating in a flow loop under the physiological and pathological condition. Stretches and strains were measured and analyzed. The principal stretches demonstrated a rapid rise early in leaflet closure, followed by a plateau, suggesting that the collagen fibers "locked" in place. There is a big difference between the major principal stretch and minor principal stretch. Similar to in-vitro tissue mechanics studies, the transmitral pressure-areal strain relationship during loading and unloading clearly demonstrated hysteresis. Further, this relationship demonstrated a dramatic stiffening attributed to collagen fiber locking. When the data of 3 papillary muscle positions were compared, the leaflet in the slack papillary position showed the highest areal strain rate. The valve exhibited a strongly anisotropic behavior. Papillary muscle position had a small effect on strain measured in the region.