Henry Ford Hospital Medical Journal


Mechanical forces caused by the dynamics of blood flow in the region of porcine bioprosthetic valves may directly injure the valve as well as formed elements of the blood. Previous in vitro studies in our laboratory evaluated quantitatively the fluid dynamic stresses in the region of such valves. In this paper we discuss our results in relation to fluid dynamic stresses found in patients with normal and diseased natural aortic valves. The levels of fluid dynamic stresses that may produce mechanical injury to erythrocytes and platelets are reviewed. These may indicate the extent to which fluid dynamic stresses may activate platelets or damage blood cells and thereby contribute to the valve degenerative process. The levels of fluid stresses measured in the region of intact aortic porcine valves are higher than those recorded in patients with normal natural aortic valves. Near bioprosthetic valves, the fluid dynamic stresses were similar to values encountered in patients with aortic valvular disease. The measured stresses were of sufficient magnitude to initiate platelet activation and cause sublethal injury to erythrocytes. Whether mechanical injury to blood constituents can enhance the degenerative process in bioprosthetic valves is speculative.