A 3-year, in-vitro investigation is proposed to study the mechanics of the natural mitral valve (MV). The normal fluid mechanics and leaflet mechanics of the natural MV will be studied. The effects of leaflet geometry, and papillary muscle position and tension on normal MV function will be established. The range over which these parameters can be varied with normal MV function is of interest. The influence of MV preservation techniques, used in porcine heterografts and human homografts, on valve mechanics (flow and structural mobility) will be studied. Since the transmitral flow field is partially dependent on leaflet structure, changes in valve mechanics, which may occur with common preservation techniques, can influence the transmitral flow fields. In each of these replacement techniques, the function of the substitute valve is dependent on resulting valve geometry and structure (papillary muscle position and tension) postoperatively. Furthermore, long term durability of tissue valve protheses has been shown to be strongly dependent on valve mechanics. A better understanding of how structural changes in the mitral apparatus influences overall MV function, and the range over which these structures can be modified without greatly affecting MV function would be of significant benefit to the cardiac surgeon. The significance and health relatedness of the proposed research is to address issues concerning the roles of the transmitral flow field mechanics of the MV components on normal MV function. The goal of this investigation is to improve our understanding of the MV complex, and to provide the cardiologist and surgeon with detailed scientific data on the normal mechanics of MV function. This may result in improved diagnosis and treatment of MV disease. The studies of the MV replacements will provide important data towards the understanding and potential refinement of some of the more promising valve replacement techniques. A comprehensive in-vitro study using both rigid and flexible sack left ventricular models is planned. This will provide excellent control over experimental conditions, the isolation of specific MV changes without the compounding difficulties of several changes affecting the results, and the use of state of art measurement techniques unavailable clinically. The major measurement tools to be used during this investigation are: flow visualization and high speed photography, multi-component laser Doppler anemometry, color Doppler flow mapping, and spectral Doppler ultrasound. The acquired data will be used for comparison of flow field changes resulting from variations in the mitral complex or from the MV replacement techniques. These results will provide the cardiac surgeon with basic scientific data on papillary muscle position and tension and the impact of variations on MV function and leaflet mechanics.
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