Antiplatelet agents for preventing thrombosis after peripheral arterial bypass surgery

Brown J, Lethaby A, Maxwell H, Wawrzyniak AJ, Prins MH

Summary

Antiplatelet agents for preventing failure of peripheral arterial grafts

Symptomatic peripheral arterial disease in people with atherosclerosis can present as intermittent claudication, disabling pain on walking, or as critical limb ischaemia with pain at rest, ulceration, gangrene and the risk of losing a leg. One treatment option is to implant a graft or makeshift blood vessel to bypass a blockage in the main artery of the thigh. Using a section of the vein from the patient's calf is often better than artificial materials such as Dacron or polytetrafluoroethylene, which take up platelets. Other factors affecting the patency of the graft, how long the bypass remains open, include length of the bypass, site where the graft connects to the existing artery and blood flow out of the graft. Narrowing (stenosis) of the graft most frequently occurs at the surgical connections because of smooth muscle cells often followed by the formation of a thrombosis (clot) at the stenotic site. Fifteen randomised controlled studies were included in the review.
The long-term (6 weeks to 2 years) administration of antiplatelet agents, started prior to surgery, resulted in improved graft patency. People who received aspirin alone or with dipyridamol showed reduced occlusion of grafts at one year (odds ratio 0.6, range 0.45 to 0.8) compared with no treatment (6 trials, 966 participants). People receiving an artificial graft were more likely to benefit than those treated with a venous graft. There was no clear beneficial effect of aspirin on cardiovascular outcomes or survival (4 trials, 811 participants). Gastrointestinal side effects and major bleeding tended to be more frequent with aspirin. Aspirin alone or in combination with dipyridamol was no different than anticoagulant vitamin K antagonist coumarin drugs on overall graft patency (2 trials, 2741 participants). For venous graft patency (1637 participants) coumarins had a more favourable effect but not for artificial grafts (1 trial, 1104 participants) where the findings favoured low dose aspirin over coumarin (OR 1.33, range 1.02 to 1.74 at 12 months). Haemorrhage necessitating hospitalisation was more evident with coumarin (9% of people) than with aspirin (4.5% of people) in one of the trials.