Quantification of platelet retention in aortocoronary femoral vein bypass graft in dogs treated with dipyridamole and aspirin.

Autologous femoral vein segments were implanted as aortocoronary bypass grafts in 50 dogs, 25 of which were treated with dipyridamole and aspirin to inhibit platelet deposition and 25 that were not. Autologous platelets labeled with indium-111 were injected into some dogs 48 hr before they were killed on the first day after surgery; other dogs were injected 24 hr before they were killed (3, 7, 30, and 90 days after surgery). Radioactivity on the grafts and on control specimens of contralateral femoral veins was converted to quantification of platelets adhering to the vessel wall (platelets/cm2). The treated group had fewer graft platelets per square centimeter than the untreated group on postoperative days 3, 7 (p less than .01), and 30 (p less than .05). Graft and control vein platelets per square centimeter were nearly equal by day 90. Comparison of graft and control specimens by scanning electron microscopy nearly equal by day 90. Comparison of graft and control specimens by scanning electron microscopy revealed deendothelialization at 1 and 7 days after grafting and reendothelialization at 30 and 90 days. The data suggest that indefinite prolongation of therapy to inhibit platelet deposition after bypass grafting may be unnecessary (although other atherosclerotic vessels may benefit from therapy).