What is the recommended anticoagulation regimen for a patient with a tissue valve?

Anticoagulation for Tissue (Bioprosthetic) Valves

For patients with tissue valves, warfarin (INR 2.0-3.0) should be given for 3-6 months after surgery, followed by indefinite aspirin 75-100 mg daily, unless additional risk factors mandate continued anticoagulation. 1

Initial Post-Operative Period (First 3-6 Months)

Warfarin is the recommended anticoagulant for the early post-operative period because stroke risk is substantially elevated during the first 90-180 days after bioprosthetic valve implantation, with incidence rates reaching 4.6% within 30 days. 1, 2

Valve Position-Specific Recommendations:

Mitral Position (Strongest Evidence):

• Warfarin with target INR 2.5 (range 2.0-3.0) for 3-6 months is a Class IIa recommendation for all patients at low bleeding risk 1, 2
• This applies regardless of rhythm status 1
• The mitral position carries higher thromboembolic risk than aortic (up to 40 events per 100 patient-years in the first month) 1

Aortic Position (More Flexible):

• Warfarin with target INR 2.5 (range 2.0-3.0) for 3-6 months is reasonable (Class IIa) but has weaker evidence than mitral 1, 2
• Alternative approach: Aspirin 50-100 mg daily for first 3 months is acceptable for patients in sinus rhythm without other risk factors (Grade 2C) 1
• The 2017 ACC/AHA guidelines upgraded the evidence level to B-NR based on Danish registry data showing lower stroke and mortality with warfarin extending to 6 months 1, 2

Critical Timing Details:

• Start warfarin within 48 hours of surgery 1
• Bridge with prophylactic-dose LMWH starting postoperative day 1 until INR is therapeutic 1
• Continue for at least 3 months, with extension to 6 months reasonable in low bleeding risk patients 1, 2

Long-Term Management (After 3-6 Months)

Transition to aspirin 75-100 mg daily indefinitely for patients without additional risk factors (Class IIa recommendation). 1, 2

Patients Requiring Continued Warfarin:

Continue warfarin indefinitely (INR 2.0-3.0) PLUS aspirin 75-100 mg daily if ANY of these risk factors exist:

• Atrial fibrillation (paroxysmal or chronic) 1, 2
• History of thromboembolism 1, 2
• Left ventricular dysfunction or ejection fraction <25% 1, 2
• Hypercoagulable conditions 1, 2
• Left atrial diameter >5.5 cm 1
• Rheumatic mitral valve disease 1

Transcatheter Valves (TAVR)

For transcatheter aortic valves, aspirin 75-100 mg daily alone is now preferred based on recent evidence. 1

• Older recommendations suggested clopidogrel 75 mg plus aspirin for 3-6 months, but this was extrapolated from coronary stenting without valve-specific evidence 1
• The 2014 guidelines suggested clopidogrel may be reasonable for first 6 months (Class IIb), but this has evolved toward aspirin monotherapy 1

Absolute Contraindications

Direct oral anticoagulants (DOACs) including dabigatran, rivaroxaban, apixaban, and edoxaban are CONTRAINDICATED for any prosthetic valve (Class III: Harm). 1, 2, 3

• This is based on the GALILEO trial showing excessive thrombotic complications 2
• Only warfarin (vitamin K antagonist) should be used when anticoagulation is indicated 1

Common Pitfalls to Avoid

Do not use aspirin alone for mitral bioprostheses in the first 3 months - the evidence strongly favors warfarin for mitral position due to substantially higher thromboembolic risk. 1

Do not continue warfarin indefinitely without indication - after 3-6 months, patients without risk factors should transition to aspirin alone to minimize bleeding risk. 1, 2

Do not assume all tissue valves are the same - mitral position requires more aggressive anticoagulation than aortic position. 1

Ensure dedicated anticoagulation clinic management when warfarin is used, as this results in significantly lower complication rates than standard care. 1, 3

Monitor INR closely during initiation - daily until stable, then 2-3 times weekly for 1-2 weeks, then weekly for 1 month, then every 1-2 months once stable. 1