Using low molecular weight heparins as "bridging anticoagulant therapy"

The temporary interruption of oral anticoagulant therapy in patients undergoing surgery or other invasive procedures is a frequently encountered clinical problem. Few prospective studies have evaluated the use of low molecular weight heparins (LMWHs) in the perioperative or periprocedure setting and, consequently, there are no universally accepted management recommendations at present.^1,2

The use of perioperative anticoagulation, or "bridging anticoagulant therapy," refers to the administration of therapeutic doses of short-acting anticoagulants in the days preceding the surgery or procedure, during which time warfarin(Drug information on warfarin) therapy is interrupted or its anticoagulant effect is subtherapeutic. Bridging anticoagulant therapy is used to minimize the risk of thromboembolic complications, including stroke, mechanical valve thrombosis, and venous thromboembolism (VTE).

In this article, we will address the question, "What approach do you recommend for using LMWH in patients who require temporary interruption of warfarin therapy?" We will present an approach that is currently used at our institu- tion, which has been standardized and evaluated for its efficacy and safety.³

The decision to use bridging anticoagulant therapy depends on an assessment of 2 clinical features:

• The patient's risk of thromboembolic complications while he or she is not receiving anticoagulants.

• The risk of bleeding associated with the procedure.

The risk of thromboembolic complications depends on the presence of thromboembolic (stroke) risk factors and the indication for warfarin therapy. Risk factors for stroke include atrial fibrillation, left ventricular dysfunction, hypertension, age over 75 years, diabetes mellitus, and a previous history of stroke or transient ischemic attack (TIA).^4,5 The most common indications for long-term anticoagulation include the presence of mechanical heart valves, chronic atrial fibrillation, and VTE.

• Mechanical heart valves: For patients with mechanical heart valves, the following features indicate high risk: recent (within the previous month) stroke or TIA, a mechanical mitral valve, or a caged-ball or single-leaflet tilting disk aortic valve. Patients at moderate risk include those with a bileaflet aortic valve and 2 or more risk factors for stroke. Low-risk patients are those with a bileaflet aortic valve and fewer than 2 risk factors for stroke.

• Chronic atrial fibrillation: Patients at high risk for thromboembolic complications include those with recent (within 1 month) stroke or TIA and those with rheumatic mitral valvular disease. Moderate-risk patients include those with 2 or more stroke risk factors, while low-risk patients have fewer than 2 risk factors.

• VTE: Patients at high risk include those who have had a recent (within the previous month) episode of VTE or who have ongoing risk factors for VTE, including active cancer (they have received treatment within 6 months or are receiving palliative care) and antiphospholipid antibodies (anticardiolipin antibody or lupus anticoagulant/nonspecific inhibitor).^6,7 Moderate-risk patients include those who had VTE within the previous 6 months or who have had VTE in the perioperative setting. Low-risk patients are those with none of the above-mentioned features.