Anticoagulation Management for Bileaflet Mechanical Aortic Valve
Lifelong Warfarin is Mandatory
All patients with bileaflet mechanical aortic valves require lifelong warfarin anticoagulation with no acceptable alternatives—this is non-negotiable. 1, 2 Direct oral anticoagulants (DOACs) are contraindicated and have demonstrated harm in this population, including increased valve thrombosis and bleeding. 1
The mechanical valve creates inherently thrombogenic conditions through abnormal flow patterns, zones of low flow within valve components, and high-shear stress that activates platelets, leading to valve thrombosis and embolic events without anticoagulation. 1, 2
Target INR Based on Risk Stratification
Low-Risk Patients (No Additional Risk Factors)
For bileaflet mechanical aortic valves in patients without additional risk factors, target INR 2.5 (range 2.0-3.0). 1, 2, 3
Low-risk criteria include: 1
- Normal sinus rhythm
- Normal left atrial size
- No history of thromboembolism
- No hypercoagulable state
- No severe left ventricular dysfunction
This moderate-intensity anticoagulation provides optimal balance between thromboembolism prevention and bleeding risk, with studies demonstrating similar thromboembolic protection but significantly lower bleeding compared to higher INR targets. 1, 4
High-Risk Patients (Any Additional Risk Factor Present)
For patients with any thromboembolic risk factor, increase target INR to 3.0 (range 2.5-3.5). 1, 3
High-risk criteria include: 1
- Atrial fibrillation
- Previous thromboembolism
- Hypercoagulable state
- Severe left ventricular dysfunction
- Older-generation mechanical valves (ball-in-cage, caged disk)
Aspirin as Adjunctive Therapy
Add aspirin 75-100 mg daily to warfarin in all patients with mechanical aortic valves. 1 This combination provides additional thromboembolic protection beyond warfarin alone, though it modestly increases bleeding risk. 1, 5
If systemic embolism occurs despite therapeutic INR, escalate to INR 3.0 (range 2.5-3.5) and ensure aspirin 80-100 mg daily is added if not already prescribed. 1, 3
INR Monitoring Strategy
Specify a single INR target value (2.5 or 3.0) rather than just stating the range, as INR fluctuations are associated with increased complications. 1, 2
Monitoring frequency: 3
- Daily until stable therapeutic range achieved
- 2-3 times weekly for 1-2 weeks
- Weekly for 1 month
- Every 1-2 months once consistently stable
Anticoagulation clinic management or home INR monitoring for motivated patients both result in lower complication rates compared to standard care. 1, 2
Perioperative Management
Minor Procedures (Dental Extractions, Cataract Surgery)
Continue warfarin at therapeutic INR for minor procedures where bleeding is easily controlled. 1 Do not interrupt anticoagulation for dental cleaning, simple dental caries treatment, or most eye surgeries. 1
Major Procedures in Low-Risk Patients
For bileaflet mechanical aortic valve patients without additional risk factors, temporarily interrupt warfarin without bridging anticoagulation. 1
Protocol: 1
- Stop warfarin 2-4 days before procedure (allow INR to fall to <1.5)
- Restart warfarin 12-24 hours after surgery when bleeding risk allows
- No bridging with heparin or LMWH needed in this low-risk group
Major Procedures in High-Risk Patients
For patients with any thromboembolic risk factor, older-generation valves, or mechanical mitral valves, use bridging anticoagulation. 1
- Stop warfarin 2-4 days preoperatively
- Start intravenous unfractionated heparin (UFH) or subcutaneous LMWH when INR falls below 2.0
- Continue bridging until INR returns to therapeutic range postoperatively
- Maintain both warfarin and heparin together for at least 24 hours with therapeutic INR before discontinuing heparin
Emergency Surgery
For emergency procedures requiring immediate reversal: 1
- Administer fresh frozen plasma or intravenous prothrombin complex concentrate
- Add low-dose oral vitamin K 1-2 mg (avoid higher doses that complicate re-anticoagulation)
Postoperative Initiation
Initiate bridging anticoagulation with heparin or LMWH early after valve surgery once postoperative bleeding is no longer an issue. 1, 2
Start intravenous UFH or subcutaneous LMWH and continue until INR reaches therapeutic range on warfarin. 1, 6 Many centers begin this within 24-48 hours post-surgery. 6
Pregnancy Considerations
Warfarin crosses the placenta and causes embryopathy, particularly during weeks 6-12 of gestation. 1 Management requires specialized consultation, but general principles include:
- First trimester: Consider switching to UFH or LMWH to avoid warfarin embryopathy
- Second and third trimesters: Warfarin may be resumed
- Peripartum: Switch to UFH for delivery
This represents one of the most challenging clinical scenarios requiring maternal-fetal medicine and cardiology co-management. 1
Bleeding Management
If major bleeding occurs on therapeutic warfarin: 1
- Administer fresh frozen plasma or prothrombin complex concentrate for immediate reversal
- Add vitamin K 1-2 mg orally
- Identify and treat bleeding source
- Resume anticoagulation as soon as bleeding controlled (mechanical valves cannot tolerate prolonged interruption)
The risk of valve thrombosis from withholding anticoagulation often exceeds bleeding risk, making this a critical balance. 2, 6
Activity and Lifestyle
No specific activity restrictions are mandated by valve type alone. 1 However, counsel patients on:
- Avoiding contact sports with high trauma risk due to bleeding concerns on anticoagulation
- Maintaining consistent vitamin K intake (avoid dramatic dietary changes)
- Avoiding NSAIDs and other medications that increase bleeding risk
- Reporting any signs of bleeding or thromboembolism immediately
Infective Endocarditis Prophylaxis
While not specific to anticoagulation, patients with mechanical valves require antibiotic prophylaxis before dental procedures involving gingival manipulation or oral mucosal perforation. 1 This is separate from anticoagulation management but represents another critical aspect of care.
Common Pitfalls to Avoid
Never use DOACs (dabigatran, rivaroxaban, apixaban, edoxaban) in patients with mechanical valves—this is FDA contraindicated and associated with increased valve thrombosis and bleeding. 1, 3
Never allow prolonged subtherapeutic INR, as valve thrombosis can develop within days. 6 If INR drops below therapeutic range, immediately increase monitoring frequency and adjust warfarin dosing.
Never prescribe antiplatelet agents alone without warfarin—this provides inadequate protection and is associated with unacceptably high thromboembolic rates. 2, 5
Never use excessively high vitamin K doses (>2 mg) for INR reversal, as this makes re-anticoagulation extremely difficult. 1