From the Guidelines
Bridging to warfarin is a temporary anticoagulation strategy used to minimize the risk of arterial thromboembolism in patients with high thrombotic risk, such as those with mechanical heart valves or atrial fibrillation, by providing immediate anticoagulation with a short-acting anticoagulant like low molecular weight heparin (LMWH) or unfractionated heparin (UFH) until warfarin reaches its therapeutic effect, as defined by an international normalized ratio (INR) within the target range 1. The purpose of bridging to warfarin is to provide effective anticoagulation during the initial period when warfarin is being started but has not yet reached its therapeutic effect, which can take several days.
- The bridging anticoagulant is typically administered concurrently with warfarin until the INR reaches the target therapeutic range, usually between 2.0 and 3.0 for most indications.
- The choice of bridging anticoagulant, such as LMWH or UFH, depends on the patient's individual risk factors and clinical circumstances.
- Recent studies, such as the BRIDGE study, have shown that bridging anticoagulation may not be necessary for all patients and that the decision to bridge should be based on the patient's individual risk of thromboembolism and bleeding 1.
- The 2019 AHA/ACC/HRS focused update on atrial fibrillation recommends that bridging anticoagulation may be appropriate only in patients with a very high thromboembolic risk 1.
- Careful monitoring of both the INR and signs of bleeding is essential during this transition period to ensure patient safety and effective anticoagulation.
- The most recent and highest quality study, the 2022 American College of Chest Physicians clinical practice guideline, defines heparin bridging as the administration of a short-acting anticoagulant for an 8- to 10-day perioperative period during interruption of a vitamin K antagonist (VKA) when the INR is below the therapeutic range 1.
From the FDA Drug Label
The duration of therapy in each patient should be individualized. In general, anticoagulant therapy should be continued until the danger of thrombosis and embolism has passed. CONVERSION FROM HEPARIN THERAPY Since the anticoagulant effect of warfarin sodium tablets is delayed, heparin is preferred initially for rapid anticoagulation Conversion to warfarin sodium tablets may begin concomitantly with heparin therapy or may be delayed 3 to 6 days.
The purpose of bridging to warfarin is to ensure continuous anticoagulation when converting from heparin therapy to warfarin therapy, as the anticoagulant effect of warfarin is delayed.
- Bridging allows for the overlap of heparin and warfarin therapies, typically for 4 to 5 days, until warfarin has produced the desired therapeutic response as determined by PT/INR 2. This approach helps to prevent thrombosis and embolism during the transition period.
From the Research
Purpose of Bridging to Warfarin
The purpose of bridging to warfarin is to manage anticoagulation therapy in patients who require temporary interruption of warfarin treatment due to invasive procedures or other reasons.
- The goal of bridging is to balance the risk of bleeding against the risk of thromboembolism 3.
- Low-molecular-weight heparin (LMWH) is often used as a bridging therapy during temporary interruptions of warfarin treatment 4, 5.
Indications for Bridging
Bridging therapy is typically considered for patients at high risk of thromboembolism, such as those with:
Management of Bridging Therapy
The management of bridging therapy involves:
- Stopping warfarin therapy 4-5 days before the procedure 3
- Starting LMWH or unfractionated heparin 2-3 days before the procedure 3
- Resuming warfarin therapy after the procedure and continuing LMWH until a therapeutic International Normalized Ratio (INR) is achieved 5
Efficacy and Safety of Bridging Therapy
Studies have shown that bridging therapy with LMWH is associated with a low risk of thromboembolic and major bleeding complications 5.