PREOPERATIVE VS POSTOPERATIVE PHARMACOLOGICAL INHIBITION OF PLATELETS- EFFECT ON INTIMAL HYPERPLASIA IN CANINE AUTOGENOUS VEIN GRAFTS

Several clinical studies have shown that pharmacologic inhibition of p latelets can increase the patency of vascular grafts, but only if plat elet-inhibition is initiated before surgery. This study was performed to compare the efficacy of pre. vs postoperative platelet-inhibition o n the development of intimal hyperplasia in canine autogenous vein gra fts. Reversed femoral veins were used to bypass the ligated femoral ar teries in 15 dogs. End-to-side anastomoses were constructed. Eleven do gs were treated with aspirin (325 mg QD) and dipyridamole (25 mg BID). In six dogs treatment was begun 48 hours preoperatively and continued for 3 months. In five other dogs treatment was begun 48 hours after s urgery and was continued for 3 months. In 4 control dogs no antiplatel et treatment was given. Excison of the vein grafts 3 months after surg ery disclosed reduced intimal hyperplasia (p<0.05) in the grafts excis ed from all of the treated animals as compared with those obtained fro m the control animals. However, there was no difference in intimal hyp erplasia observed in the dogs treated both pre- and postoperatively (1 1 grafts) as compared with those treated only postoperatively (9 graft s). These data demonstrate that it is not necessary to begin antiplate let therapy preoperatively in order to inhibit intimal hyperplasia. Th ey also suggest that preoperative antiplatelet therapy may improve ear ly graft patency by directly preventing thrombosis, not by inhibiting the development of intimal hyperplasia.