Antithrombotic agents for preventing thrombosis after infrainguinal arterial bypass surgery

 

Abstract

Background

Peripheral arterial disease (PAD) is frequently treated by either an infrainguinal autologous (using the patient's own veins) or artificial graft. The rate of occlusion after one year is between 15 and 75%. To prevent occlusion, patients are treated with an antiplatelet or antithrombotic drug, or a combination of both. Little is known about which drug is optimal to prevent infrainguinal graft occlusion.

Objectives

To evaluate whether antithrombotic treatment improves graft patency, limb salvage and survival in patients with chronic PAD undergoing infrainguinal bypass surgery.

Search strategy

The search strategy was that adopted by the Cochrane Review Group on Peripheral Vascular Diseases. Reference lists of papers resulting from the searches were also reviewed.

Selection criteria

Two reviewers independently assessed methodological quality of each trial using a standardised checklist, with emphasis on concealment of randomisation.

Data collection and analysis

An 'intention to treat' analysis was performed. Data collected included patient details, inclusion and exclusion criteria, type of graft, antithrombotic therapy, outcomes, and side effects. Treatment and control groups were compared for important prognostic factors and differences described. Missing data were sought from trial authors. Heterogeneity between trials could not be tested due to inaccessible data. Data were synthesized by comparing group results.

Main results

Four trials evaluating vitamin K antagonists (VKA) versus no VKA indicated that oral anticoagulation may favour venous but not artificial graft patency, as well as limb salvage and survival. Two other studies comparing VKA with aspirin or aspirin/dipyridamole supported evidence for a positive effect of VKA on the patency of venous but not artificial grafts. Subgroup analysis for artificial grafts as performed in one trial showed a favourable effect of antiplatelet agents on synthetic bypasses. In two trials, a small number of patients treated with low molecular weight heparin showed a lower incidence of early postoperative graft thrombosis compared to unfractionated heparin. In one trial, infusion of antithrombin concentrate was reported to have a negative effect on intraoperative graft thrombosis requiring the study to be stopped before completion. Perioperative administration of ancrod showed no greater benefit when compared to unfractionated heparin.

Authors' conclusions

Patients undergoing infrainguinal venous graft might benefit from treatment with VKA, whereas patients receiving an artificial graft might profit more from platelet inhibitors (aspirin). However, the evidence is not conclusive. Randomised controlled trials with larger patient numbers comparing antithrombotic therapies with either placebo or antiplatelet therapies are needed in the future.

 

Plain language summary

Antithrombotics drugs to prevent blood vessel blockage after bypass surgery of the legs with autologous vein grafts or artifical grafts

Poor blood supply from blocked blood vessels in the legs can cause muscle pain or sores in the calf or foot. Surgery to bypass the blockage using a piece of vein from somewhere else in the body (autologous vein) or an artificial graft may help. However, the bypass can also become blocked. To help prevent this, people are given aspirin (antiplatelet) or vitamin K antagonists (antithrombotic) to try to stop blood clotting. The review of trials found that antithrombotic drugs may be more effective than antiplatelets for autologous grafts. More research is needed on the optimal treatment for artificial grafts.