Risk of Thromboembolism With Short-term Interruption of Warfarin Therapy

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Abstract
Health care professionals face a dilemma when a warfarin sodium–treated patient needs to undergo an elective procedure or minor surgery. In these circumstances, the risk of bleeding, if the procedure is performed without stopping warfarin therapy, must be weighed against the risk of thrombosis associated with warfarin therapy interruption. The patient and physician have 3 options: (1) continue warfarin therapy, (2) withhold warfarin therapy for some time before (and after) the procedure, or (3) temporarily withhold warfarin therapy while also providing a short-acting (bridging) anticoagulant (such as unfractionated heparin or low-molecular-weight heparin) during the perioperative period. Current guidelines from the American College of Chest Physicians suggest that if the annual risk of thromboembolism is low, warfarin therapy may be held for 4 to 5 days before the procedure and restarted shortly thereafter.1 The 2006 guidelines for the treatment of patients with atrial fibrillation from the American College of Cardiology, American Heart Association, and European Society of Cardiology suggest an interval of up to 1 week without substituting heparin. The authors acknowledge that this level C recommendation is “based on extrapolation from the annual rate of thromboembolism”2(p298) and is not evidence based because no studies are available to inform this question.2 For patients at higher risk for thromboembolism, several studies3-6 have described outcomes in patients treated with periprocedural low-molecular-weight heparin. However, since none of these studies included a control arm (ie, patients for whom bridging therapy was not prescribed), the risk of thromboembolism associated with short-term warfarin therapy interruption> remains unknown. This represents a critical gap in current knowledge because the increased risk of hemorrhage associated with perioperative heparin is justified by the theory that such bridging therapy will prevent potentially devastating thromboembolic events (eg, stroke) that would otherwise occur. Without knowing the risk of thromboembolism associated with warfarin therapy interruption alone, an informed risk-benefit examination of bridging therapy cannot be performed. Three small observational studies7-9 of patients with mechanical heart valves (n = 28, n = 16, and n = 25) have reported successful warfarin therapy interruption without bridging therapy around the time of a procedure; however, the small size of these studies prohibits definitive conclusion.

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