A common method of assessing the thrombogenicity of prosthetic arterial grafts is to determine the amount of platelets and
fibrin that accumulates on their surfaces. This study was designed to compare
thrombus formation in cylindrical and tapered vascular grafts (angle of taper 0.5 deg) made from the same
biomaterial. Turbulence was generated upstream of the grafts by means of a 75% axi-symmetric
stenosis. In general, turbulence is dissipated by the effect of blood viscosity, whereas in a tapered graft, there is an additional reduction in the intensity of turbulence owing to the effect of converging flow through the taper. The aim of this study was to assess the effect of turbulence on
thrombus formation in cylindrical and tapered grafts. After blood had circulated for 2 and 4 h through the cylindrical and tapered grafts, which formed part of two parallel ex vivo circuits, platelet deposition and
fibrinogen uptake were measured by means of a
radioisotope technique. Although the flow disturbances were less in the tapered grafts, no significant difference in platelet and
fibrin deposition in the two types of graft was observed at 2 h. For the longer perfusion time, however, increased platelet and
fibrin activity was recorded in the annular vortex region in the tapered grafts. In general, neither platelets nor
fibrin accumulated in areas of high turbulence intensity.