What are the indications for bridging heparin (unfractionated heparin)-warfarin in patients with a mechanical aortic valve?

From the Guidelines

Bridging with unfractionated heparin is recommended for patients with mechanical aortic valves when warfarin must be temporarily discontinued for procedures or when INR falls below therapeutic range, particularly in those with high risk of thromboembolism, such as older-generation mechanical valves, recent stroke or TIA, or multiple risk factors. The decision to use bridging anticoagulation should be individualized, taking into account the trade-offs between thrombosis and bleeding, as there are no randomized comparative-effectiveness trials evaluating a strategy of bridging versus no bridging in adequate numbers of patients with prosthetic heart valves needing temporary interruption of oral anticoagulant therapy 1.

For perioperative management, warfarin is typically stopped 3 to 4 days before surgery, with heparin bridging started when INR falls below the therapeutic threshold, usually 36 to 48 hours before surgery, and is stopped 4 to 6 hours (for intravenous unfractionated heparin) or 12 hours (for subcutaneous low-molecular-weight heparin) before the procedure 1.

• Key considerations for bridging therapy include:
  • Patient risk factors for thromboembolism, such as atrial fibrillation, previous thromboembolism, left ventricular dysfunction, or hypercoagulable conditions
  • Type of mechanical valve, with older-generation valves (caged-ball, tilting-disc) posing a higher risk
  • Recent stroke or TIA (within 6 months)
  • Multiple mechanical valves
• The goal of bridging therapy is to minimize the risk of thromboembolism while avoiding excessive bleeding risk, and the choice of bridging agent (unfractionated heparin or low-molecular-weight heparin) should be based on individual patient factors and clinical context 1.

In patients with mechanical valves on long-term warfarin therapy who require emergency surgery or invasive procedures, anticoagulation can be reversed by administration of fresh frozen plasma or intravenous prothrombin complex concentrate, with the addition of low-dose oral vitamin K in some cases 1.

• The most recent guidelines from the American College of Cardiology/American Heart Association recommend an individualized approach to bridging anticoagulation, taking into account the specific clinical context and patient risk factors 1.
• The evidence cited to support bridging therapy derives from cohort studies with poor or no comparator groups, highlighting the need for further research in this area 1.

Overall, the decision to use bridging anticoagulation in patients with mechanical aortic valves should be based on a careful assessment of the individual patient's risk factors and clinical context, with the goal of minimizing the risk of thromboembolism while avoiding excessive bleeding risk 1.

From the Research

Indications for Bridging Heparin-Warfarin in Mechanical Aortic Valve Patients

The decision to use bridging heparin (unfractionated heparin) in patients with a mechanical aortic valve is based on the individual's risk of thromboembolism and bleeding. Key points to consider include:

• The risk of thromboembolism is higher in patients with mechanical heart valves, particularly those with mitral valves, multiple valves, or a history of stroke or atrial fibrillation 2.
• Bridging anticoagulation with heparin is typically reserved for patients at high risk of thromboembolism, such as those with mitral mechanical heart valves, multiple mechanical heart valves, or a history of stroke or atrial fibrillation 2.
• The use of low molecular weight heparin (LMWH) as a bridging agent has been shown to be safe and effective in patients with mechanical heart valves, with similar rates of thromboembolic and hemorrhagic events compared to patients with nonvalvular atrial fibrillation 3.
• Long-term use of LMWH is not recommended for patients with mechanical aortic valves, as it may increase the risk of valve dysfunction and thromboembolic events 4.
• Alternative anticoagulants, such as dabigatran etexilate, have been shown to be effective for thromboprophylaxis in mechanical heart valves, but more research is needed to determine their safety and efficacy in this population 5.
• The use of low-dose warfarin and aspirin has been shown to be safe and effective in patients with On-X aortic mechanical valves, with reduced rates of thromboembolism and major bleeding 6.

Key Considerations

• The decision to use bridging heparin should be individualized based on the patient's risk factors and medical history.
• The choice of anticoagulant and dosing regimen should be carefully considered to minimize the risk of thromboembolism and bleeding.
• Regular monitoring of international normalized ratio (INR) and anti-Xa factor levels may be necessary to ensure effective anticoagulation and minimize the risk of adverse events.