Fluid Stresses in the Vicinity of Disk, Ball, and Tilting Disk Prosthetic Heart Valves From In-Vitro Measurements

Experiments were conducted in a steady flow test apparatus with an axisymmetric aortic shaped test chamber using hot-wire anemometry to obtain local momentum transfer and turbulence data in the vicinity of the model disk, Kay-Shiley disk, Starr-Edwards ball and Bjork-Shiley tilting disk prosthetic heart valve configurations. These data for Reynolds numbers of 2000, 4000, and 6000 were used to locate regions of high stress where erythrocytes may be lysed or severely strained. Nondimensionalized velocity profiles downstream of the valves indicated a similarity of behavior for all Reynolds numbers at an axial location. Velocity gradients of magnitudes potentially damaging to erythrocytes were found. These gradients were largest for disk-type occluders. Large regions of separated flow were found to occur behind the valve sewing ring, distal to the valve occluder, and along the test chamber wall distal to the valve for all valves tested. Relatively high turbulence was found to exist distal to all valves tested. Turbulent stresses of magnitudes potentially hemolytic were measured.