Abstract
The effect of valve orientation on the flow development and the hydrodynamic characteristics of prosthetic mitral valves has been studied by using a total mock system of human left heart and aorta. The system replicated the geometry of human left heart and aortic arch having a pertinent hydraulic load of the systemic circulation so that the flow process simulated physiological pulsatile conditions. Simultaneous flow visualization study was carried out to investigate the dependence of valve orientation on the flow development in the left ventricle. Five different mitral valves, Björk-Shiley spherical disc, Hall-Raster pivoting disc, St. Jude Medical, Carpentier-Edwards porcine xenograft and Ionescu-Shiley pericardial xenograft, each having an annulus diameter of 29mm, were assessed as to how the valve insertion should be oriented.
Total hydrodynamic evaluations regarding effective orifice area, diastolic energy loss and turbulent formation suggested that the major orifices of Björk-Shiley as well as Hall-Kaster valves should be oriented towards the parietal wall of left ventricle. As for the St. Jude Medical valve, it was found advisable to direct the two pivot guards towards the septal and parietal walls of left ventricle respectively. Regarding the two bioprostheses, the orientation placing one of the three leaflets on the anterior side of mitral position was also found advisable. These findings have been found to be in good agreement with the clinically and empirically arrived approvals of valve orientation.
