Antiplatelet therapy and vascular grafts. Studies in a baboon ex vivo shunt.

Antiplatelet therapy is currently recommended in an effort to improve patency rates of small-caliber vascular grafts. The effect of aspirin and heparin on acute platelet deposition was studied in a baboon ex vivo shunt. Two grafts, expanded polytetrafluoroethylene and knitted Dacron, were exposed to a flow rate of 25 mL/min after administration of aspirin or heparin. Indium 111-labeled platelet uptake by the grafts was determined over 2 1/2 hours. The amount of platelet deposition in the treated groups was significantly less than that of controls after 2 1/2 hours. There was no difference between the aspirin and heparin groups. The finding that heparin inhibited platelet deposition to a degree comparable with aspirin suggests that it may not be necessary to start antiplatelet therapy preoperatively. Intraoperative systemic heparinization will provide sufficient inhibition of platelet deposition. A protocol for perioperative antiplatelet therapy is outlined.