Low-Molecular-Weight Heparin as Bridging Anticoagulation During Interruption of Warfarin

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Abstract
The treatment of patients with a mechanical heart valve or chronic atrial fibrillation who require temporary interruption of warfarin sodium therapy because of surgery or another invasive procedure is a frequently encountered but underinvestigated clinical problem.1-4 A major gap in knowledge is a lack of reliable estimates as to the incidence of thromboembolic events associated with warfarin therapy interruption.1 It is well established, however, that such events can have devastating clinical consequences: thrombosis of a mechanical heart valve is fatal in 15% of patients,5,6 and embolic stroke results in a major neurologic deficit or death in 70% of patients.7 Consequently, despite disagreement on the optimal periprocedural anticoagulation strategy during interruption of warfarin therapy,8-12 several authorities1-4 and consensus groups13,14 advocate, for most patients, some form of bridging therapy with a short-acting anticoagulant. The rationale for bridging anticoagulation is to minimize the time before and after a procedure that patients are not receiving therapeutic anticoagulation and, thereby, minimize the risk of thromboembolism. The conventional periprocedural anticoagulation approach is to hospitalize patients 4 to 5 days before surgery to stop warfarin and administer intravenous unfractionated heparin while the anticoagulant effect of warfarin recedes.15,16 Intravenous heparin is stopped 3 to 4 hours before the procedure to avoid a residual anticoagulant effect at the time of the procedure. After the procedure, warfarin and intravenous heparin are resumed, the latter administered for 4 to 5 days until therapeutic anticoagulation with warfarin is reestablished. This approach is difficult to implement because of the current constraints on hospital bed availability and the increasing number of surgical and other invasive procedures that are being performed without hospitalization.