Optimal Valve Orientation of Tilting Disc Valve Prostheses in the Aortic Position and in-vitro Evaluation of Their Hydraulic Characteristics

The effect of valve orientation on the hydraulic characteristics of aortic valve prostheses was studied by using a total mock system of human left heart and aorta. The system replicated the geometry of left heart and aortic arch having a pertinent hydraulic load of the systemic circulation so that the flow process simulated a physiological pulsatile condition. Simultaneous flow visualization study was carried out to investigate the dependence of valve orientation on the flow development in the aortic arch. Five different tilting disc valves, Björk-Shiley spherical, Beörk-Shiley convexo-concave, Björk-Shiley monostrut, Medtronic-Hall, and Omni-Science valves, each having an annulus diameter of 25 mm, were evaluated as to how the valve insertion should be oriented. Total hydraulic evaluations regarding systolic energy loss, resistive coefficient as well as the turbulent flow formation suggested that the major orifice of these valves should be oriented towards the aortic outer curvature. The outer curve orientation provided low systolic energy loss and low resistive coefficient. These findings were found to be in good agreement with the clinically and empirically arrived approvals of valve orientation.