Antiplatelet agents for preventing thrombosis after peripheral arterial bypass surgery.

BACKGROUND: Peripheral arterial disease (PAD) may cause occlusions (blockages) in the main arteries of the lower limbs. It is frequently treated by implantation of either an infrainguinal autologous (using the patient's own tissue) venous or artificial graft. A number of factors influence occlusion rates, including the material used. To prevent graft occlusion, patients are usually treated with either an antiplatelet or antithrombotic drug, or a combination of both.

OBJECTIVES: To evaluate whether antiplatelet treatment in patients with symptomatic PAD undergoing infrainguinal bypass surgery improves graft patency, limb salvage and survival.

SEARCH STRATEGY: The reviewers searched the Cochrane Peripheral Vascular Diseases Group Specialised Register, (last searched April 2003), and the Cochrane Central Register of Controlled Trials (CENTRAL) (last searched Issue 1, 2003). Additional trials were sought through reference lists of papers and by reviewing proceedings from the vascular surgical society meetings.

SELECTION CRITERIA: The methodological quality of each trial was assessed independently by two reviewers (JD, MMK), with emphasis on concealment of randomisation.

DATA COLLECTION AND ANALYSIS: Details of the studies selected were extracted independently by two reviewers (JD, MMK), and an 'intention-to-treat' analysis performed. The treatment and control groups were compared for important prognostic factors and differences described. If any data were not available, further information was sought from the author. Data were synthesized by comparing group results.

MAIN RESULTS: The administration of a variety of platelet-inhibitors resulted in improved venous and artificial graft patency compared to no treatment. However, analysing patients for graft-type indicated that patients receiving a prosthetic graft were more likely to profit from administration of platelet-inhibitors than those treated with a venous graft.

REVIEWER'S CONCLUSIONS: Antiplatelet therapy with aspirin had a slight beneficial effect on the patency of peripheral bypasses, but seemed to have an inferior effect on venous graft patency compared with artificial grafts. The effect of aspirin on cardiovascular outcomes and survival was mild and not statistically significant; this might be due to the fact that the majority of patients receiving a peripheral graft have an advanced stage of PAD with critical ischemia. These patients are usually seriously ill with respect to cardiovascular diseases with high mortality rates of 20% per year. Additionally, the number of patients included in this analysis might still be too small to reach a statistically significant effect for mortality and cardiovascular morbidity.