Role of Vitamin K Antagonists in the Prevention of Thrombotic Bypass Occlusion After Infrainguinal Venous Bypass.

CLINICAL VIGNETTE: Despite being the most common antithrombotic strategy in trials comparing venous with prosthetic grafts, the use of vitamin K antagonists (VKAs) to improve the outcome of venous bypass remains the subject of debate. In this systematic review, evidence supporting the use of VKAs for improving venous patency following infrainguinal venous bypass is provided.

CLINICAL QUESTION: A 67 year old man with lifestyle limiting claudication underwent a successful infrainguinal venous bypass. Can VKAs help preserve patency after venous bypass surgery?

METHODS: A systematic review of electronic databases, including MEDLINE and Embase, was conducted. Only randomized controlled studies comparing VKAs with aspirin (ASA) were included. The main outcome was bypass patency.

RESULTS: Four studies using different intensities of anticoagulation ± ASA were identified. All but one showed a benefit of VKAs over ASA with respect to primary patency. However, this benefit was also accompanied by an increased risk of bleeding. The Dutch Bypass Oral Anticoagulants, or ASA, study was the largest included and showed that VKAs (without concomitant ASA) were superior to ASA alone for the prevention of graft occlusion (hazard ratio 0.69, 95% confidence interval 0.54-0.88).

CONCLUSION: Current evidence suggests that VKAs are superior to ASA for the prevention of infrainguinal autologous venous graft thrombosis.