Effect of aspirin on intimal proliferation and tissue cholesterol in long-term experimental bypass grafts

A single daily dose of aspirin (ASA) reduces the incidence of early graft thrombosis after coronary bypass operations. Recent data indicate that aspirin may not prevent intimal proliferation and cholesterol uptake in experimental bypass grafts which suggests that aspirin may not improve long-term graft patency. To further clarify the effects of aspirin on intimal proliferation and cholesterol metabolism, we performed femoral interposition vein grafts in 12 dogs receiving a 2% cholesterol diet. Six controls (CON) received the diet alone while the remaining animals received the diet with 160 mg aspirin daily before and for 9 months following operation. A segment of each graft was removed at 3 months for measurement of intimal thickness and tissue cholesterol. The entire graft was then harvested at 9 months. Intimal thickness increased rapidly during the first 3 months. A slow and progressive increase in intimal thickness was observed between 3 and 9 months. There was, however, no difference in intimal thickness between the two groups. Tissue cholesterol increased similarly in both groups. Rapid cholesterol uptake occurred within the first 3 months and then decreased between 3 and 9 months.

(1) ASA failed to reduce intimal proliferation and cholesterol uptake in experimental bypass grafts suggesting that ASA may not prevent late graft failure, (2) Accelerated intimal proliferation and cholesterol uptake occurred within the first 3 months emphasizing the importance of developing and instituting anti-proliferative therapy immediately after aortocoronary bypass.