Turbulent Stresses in the Region of a Hancock Porcine Bioprosthetic Aortic Valve

The purpose of this study was to measure stresses associated with turbulence (Reynolds stresses), in the region of a 29-mm-dia porcine bioprosthetic valve (Hancock, Model 242). Studies were performed in an in vitro pulse duplicating system with the valve mounted in the aortic position. The Reynolds stresses were calculated from velocities obtained with a two channel laser Doppler anemometer. The largest Reynolds shear stress and normal stress occurred at the highest stroke volume used (80 mL). Averaged over ejection they were 38 dynes/cm² and 380 dynes/cm², respectively. The maximal instantaneous Reynolds shear stress was 2500 dynes/cm² and the maximal instantaneous Reynolds normal stress was 6800 dynes/cm². Stresses of these magnitudes are in the range reported to damage platelets.