Aspirin or dipyridamole individually prevent lipid accumulation in primate vein bypass grafts

Although platelet inhibition with both aspirin and dipyridamole is widely prescribed for patients with coronary artery bypass grafts, data are lacking to prove that combined drug therapy has greater efficacy in preserving graft integrity than either drug given independently. Thus, the ability of combined vs single drug therapy to reduce cholesterol and apolipoprotein-B accumulation were compared in autologous cephalic veins grafted into femoral arteries of 23 stump-tailed macaque monkeys. Ten monkeys were studied in 2 phases. They were treated with aspirin (80 mg/day) during 1 phase and with dipyridamole (50 mg/day) during the other phase. Five monkeys received aspirin plus dipyridamole in combination and 8 received no medication and served as controls. When grafts were removed 3 months after insertion cholesterol and apolipoprotein-B concentrations in grafts were similar for groups treated with aspirin, with dipyridamole, and with the drugs combined, and in each of the treated groups these concentrations were significantly reduced compared with grafts from untreated control monkeys. Cholesterol and apolipoprotein-B concentrations in grafts from the treated groups were similar to concentrations in normal ungrafted veins, whereas cholesterol and apolipoprotein-B levels in grafts from control monkeys were significantly greater than those in ungrafted veins (250% and 925% of normal, respectively). Our findings reaffirm the ameliorative effect of anti-platelet drugs in reducing the accumulation of lipid in vein bypass grafts and indicate that the efficacy of aspirin or dipyridamole given individually equals that of the combination of these drugs in this subhuman primate model. The relation of the lipid-lowering effect of these agents to their antithrombotic effect is uncertain.