Evaluation of arterial prostheses in a baboon ex vivo shunt: the effect of graft material and flow on platelet deposition.

Surface thrombogenicity is recognized as an important factor in the failure of small caliber vascular prostheses. The baboon ex vivo shunt was developed to study small caliber grafts under controlled conditions at different flow rates. The shunt was created by percutaneous insertion of catheters into the baboon femoral artery and vein. Platelet-graft interactions were studied using autogenous indium 111 labeled platelets. Two graft materials were placed in series and exposed to blood flow for 2 1/2 hours at flow rates of 25 and 200 ml/min. At the end of this period, the grafts were removed for morphologic examination. Platelet adhesion to the grafts, especially with the less thrombogenic materials (PTFE and HUV), was found to be independent of flow rate. PTFE was found to be the least platelet-reactive material, HUV was intermediate, and knitted Dacron was the most thrombogenic surface. Platelet deposition on the flow surface was confirmed by light microscopy and scanning electron microscopy.