Estimation of shear stress-related blood damage in heart valve prostheses--in vitro comparison of 25 aortic valves.

The hemodynamics of heart valve prostheses can be reproducibly investigated in vitro within circulatory mock loops. By measuring the downstream velocity and shear stress fields the shear stresses which are clinically responsible for damage to platelets and red blood cells can be determined. The mechanisms of damage and the effects of shear stresses on blood corpuscles were investigated by Wurzinger et al. at the Aerodynamics Institute of the RWTH Aachen. In the present study, the above data are incorporated into a mathematical correlation, which serves as a basic model for the estimation of blood damage. This mathematical model was applied to in vitro investigations of 25 different aortic valve prostheses. The results were compared to clinical findings. In most cases agreement was good, indicating that this model may be directly applied to the clinical situation. This new method facilitates the estimation of clinically expected blood damage from in vitro measurements. It may be useful for the development and evaluation of new valve prostheses. By comparative evaluation of different valve types it also provides additional information to help the implanting surgeon select the optimum valve for his patient.