Leakage Flow at Mechanical Heart Valve Prostheses:
Improved Washout or Increased Blood Damage?
A. Steegers, R. Paul, H. Reul, G. Rau

An essential problem of mechanical heart valve (MHV) prostheses is the risk of thromboembolic events and consequent need for lifetime anticoagulation. This is due to unnatural hemodynamics which result in traumatization of red blood cells and platelets. The precise spatial and tidal localization of blood-damaging events within the flow, however, is still poorly understood. The present investigation addressed the question of whether leakage flow at MHV, which is often claimed to improve washout in the hinge areas of microthrombi and platelet-activating agents, is responsible for significant blood damage. All valves analyzed showed characteristic and reproducible jet patterns, mainly emerging from the hinge areas. Damage indices for corpuscle destruction were calculated as a function of exposure time and shear stresses within the flow field. The investigated MHV revealed significant differences in the calculated blood damage index; this was validated by direct hemolysis measurements.