The effects of bileaflet prosthesis pivot geometry on turbulence and blood damage potential

Bileaflet mechanical heart valves are often chosen for replacement of diseased heart valves due to the minimal resistance that they impose to forward flow and their superior durability. However, patients bearing these prostheses are prone to thromboembolic disorders, and must undergo lifelong anticoagulation therapy. The turbulence generated by leakage flow through the pivots of bileaflet mechanical valves could cause disruption or activation of blood corpuscles, and is a therefore a potential means of thrombosis initiation.;These studies tested the hypotheses that bileaflet valve pivot geometry influences blood damage and that the turbulence created by forward flow through a common bileaflet prosthesis, the St. Jude Medical design, has a greater potential to initiate blood damage than Reynolds stresses created by leakage flow through the valve. To test these hypotheses, sensitive biochemical markers of valve induced blood damage were identified. These markers were used to test the effects of pivot design, pivot gap width, and valve size on damage to whole human blood within a steady leakage flow circuit. Preliminary tests were performed in a more physiologic pulsatile flow circuit. Forward and leakage flow turbulence through St. Jude Medical aortic valves were quantified both experimentally and analytically. This turbulence was related to blood damage potential by mathematical models and magnitude thresholds developed by previous researchers.