What is the protocol for bridging warfarin (International Normalized Ratio (INR) anticoagulant) before surgery for patients with mechanical heart valves?

From the Guidelines

Patients with mechanical heart valves who require surgery should undergo a highly individualized warfarin bridging protocol, prioritizing those with high thrombotic risk, such as mitral mechanical valves, while carefully considering bleeding risk, as evidenced by the most recent guidelines 1.

Key Considerations

• The decision to bridge should be based on the patient's specific risk factors for thromboembolism and bleeding, with a focus on minimizing both risks.
• For high-risk patients, bridging with low molecular weight heparin (LMWH) such as enoxaparin may be recommended, starting when the INR falls below 2.0, typically 3 days before surgery, at a therapeutic dose of 1 mg/kg subcutaneously twice daily.
• The last preoperative dose should be given 24 hours before surgery at half the therapeutic dose.
• After surgery, LMWH can be resumed 24 hours after minor procedures or 48-72 hours after major surgery with significant bleeding risk, once hemostasis is established.
• Warfarin should be restarted within 24 hours post-operation when oral intake is possible, and LMWH should be continued until the INR returns to the therapeutic range (typically 2.5-3.5 for mechanical valves).

Evidence-Based Recommendations

• The 2024 AHA/ACC/ACS/ASNC/HRS/SCA/SCCT/SCMR/SVM guideline for perioperative cardiovascular management for noncardiac surgery suggests limiting the use of bridging to very high thrombotic risk patients on VKA, with careful consideration of bleeding risk 1.
• The PERIOP-2 trial found that bridging increased overall bleeding without lowering thromboembolism risk in patients with mechanical heart valves, highlighting the need for individualized decision-making 1.

Monitoring and Management

• Patients should be monitored closely during the transition period with regular INR checks to ensure timely restart of warfarin and discontinuation of LMWH.
• The use of bridging anticoagulation should be carefully weighed against the risk of bleeding, particularly in patients with high bleeding risk, such as those with a history of bleeding or high HAS-BLED scores.

From the Research

Bridging Warfarin for Mechanical Heart Valve Patients

• The protocol for bridging warfarin before surgery for patients with mechanical heart valves typically involves temporarily discontinuing anticoagulant therapy and using either intravenous unfractionated heparin (UFH) or subcutaneous low-molecular-weight heparin (LMWH) as a bridging strategy 2.
• A study comparing UFH and LMWH as bridging strategies in left-sided mechanical heart valve patients found that both strategies had similar rates of major bleeding, thromboembolism, and mortality, with more than 50% of bleeding complications categorized as major bleeding 2.
• Another study compared the safety of subcutaneous enoxaparin as an outpatient anticoagulation bridging therapy in patients with mechanical heart valves versus those with nonvalvular atrial fibrillation, and found that the rates of major and minor bleeding were similar between the two groups 3.

Anticoagulation Management

• The American College of Chest Physicians recommends anticoagulation with warfarin at an INR range of 2-3 for patients with a bileaflet mechanical valve in the aortic position, and an INR of 2.5-3.5 for those with a mechanical valve in the mitral position 4.
• Rapid anticoagulation can be achieved with either unfractionated heparin or low-molecular-weight heparin (LMWH), with heparin initiated with an intravenous bolus and an infusion, and LMWH prescribed in a mg/kg dose 4.
• Treatment quality with warfarin is crucial for patients with mechanical valve prostheses, and a time in therapeutic range (TTR) of 83% or higher is recommended for best outcome 5.

Alternative Anticoagulation Therapies

• A case study reported successful long-term anticoagulation with enoxaparin in a patient with a mechanical aortic valve who had a contraindication to warfarin, with meticulous monitoring of anti-factor Xa levels and dosage adjustments crucial to treatment success 6.
• This case provides promising evidence of the potential role of enoxaparin in patients with mechanical heart valves in whom warfarin thromboprophylaxis is not possible 6.