Bridging Anticoagulation for Prosthetic Mitral Valve on Warfarin
For patients with mechanical mitral valves requiring interruption of warfarin, therapeutic-dose intravenous unfractionated heparin (UFH) or subcutaneous low-molecular-weight heparin (LMWH) bridging is recommended, as these patients are at high risk of thrombosis. 1
Risk Stratification
Patients with mechanical mitral valves are classified as high-risk for thrombosis and require bridging anticoagulation when warfarin must be interrupted for procedures. 1 This high-risk designation applies to:
- Any mechanical valve in the mitral position (regardless of valve type) 1
- Mechanical aortic valve replacement with additional risk factors (atrial fibrillation, previous thromboembolism, LV dysfunction, hypercoagulable conditions) 1
The mitral position carries substantially higher thromboembolic risk than the aortic position, with thromboembolism rates of 1-2% per year even with optimal anticoagulation. 1
Bridging Protocol for High-Risk Patients
Pre-Procedure Management
Stop warfarin 48 hours before the procedure to allow INR to fall below 2.0. 1
Start therapeutic-dose UFH intravenously when INR falls below 2.0 (typically 48 hours before surgery):
- Continue UFH until 4-6 hours before the procedure 1
- This timing allows adequate clearance while minimizing thrombotic risk 1
Alternative: Therapeutic-dose subcutaneous UFH (15,000 units every 12 hours) or LMWH can be used, though many centers prefer intravenous UFH for more precise control. 1
Post-Procedure Management
Restart UFH as early after surgery as bleeding stability allows and continue until INR is therapeutic again with warfarin. 1
Resume warfarin within 24 hours after the procedure at the patient's usual maintenance dose. 1
Target INR of 3.0 (range 2.5-3.5) for all mechanical mitral valves, as this provides optimal balance between thrombosis and bleeding risk. 1, 2, 3
Long-Term Anticoagulation Management
Maintain warfarin with INR target of 3.0 (range 2.5-3.5) indefinitely for all mechanical mitral valves. 1, 2, 4, 3 This higher target compared to mechanical aortic valves (INR 2.5) reflects the substantially elevated thrombotic risk in the mitral position. 1
Add aspirin 75-100 mg daily to warfarin therapy in all patients with mechanical valves when bleeding risk is low. 1, 2 This combination reduces major embolism or death from 8.5% to 1.9% per year (P<0.001) and stroke from 4.2% to 1.3% per year (P<0.027). 1
Critical Pitfalls to Avoid
Never use DOACs in patients with mechanical valves - they have demonstrated harm and are contraindicated. 2, 4
Do not use the low-risk bridging approach (no heparin bridging) for mechanical mitral valves, even if the valve is a modern bileaflet design - the mitral position itself confers high risk. 1
Avoid fresh frozen plasma for routine bridging - reserve this for emergency situations requiring immediate reversal. 1 For planned procedures, the gradual INR decline with warfarin cessation is preferred. 1
Do not attempt lower INR targets - a recent randomized trial (PROACT Mitral, 2023) demonstrated that low-dose warfarin (INR 2.0-2.5) failed to achieve noninferiority compared to standard-dose (INR 2.5-3.5) in mechanical mitral valves, with similar rates of thromboembolism and bleeding. 5
Special Considerations
For minor procedures where bleeding is easily controlled (dental work, dermatologic procedures), continue warfarin without interruption at therapeutic INR. 2
If thromboembolism occurs despite therapeutic INR, either increase the INR target from 3.0 to 4.0 (range 3.5-4.0) or add aspirin 75-100 mg daily after assessing bleeding risk. 2
Monitor INR closely during bridging - check daily until stable, then 2-3 times weekly for 1-2 weeks after resuming warfarin. 4