Retrograde flow through bileaflet mechanical heart valves

In vitro experiments were conducted to investigate the time-varying retrograde flow characteristics of 27 mm bileaflet aortic valves. The retrograde flow fields of bileaflet valves range from uniform squeeze flow and regurgitant jet flow fields to flow fields involving complex secondary flows. Stress levels are sufficiently high to cause cell damage or activation in both the squeeze and jet flows. The squeeze occur over a shorter time span but encompass a larger area of flow and potential exposure to more cells. It is speculated that valves exhibiting complex flow patterns have lower incidence of thrombus due to increased washing of the hinge region and valve perimeter by these flow patterns. These results, and the test protocol developed in this study, may improve future capabilities for predicting thrombus potential in new valve designs.