What is the recommended anticoagulation treatment for patients with valve replacements, including mechanical and bioprosthetic valves?

Anticoagulation Treatment of Valve Replacement

For mechanical valve replacements, lifelong warfarin anticoagulation is mandatory with target INR 2.5 for aortic valves without risk factors and INR 3.0 for mitral valves or those with risk factors; bioprosthetic valves require warfarin (INR 2.5) for 3-6 months post-operatively, then transition to aspirin 75-100 mg daily unless risk factors are present. 1

Mechanical Valve Anticoagulation

Aortic Position

• Bileaflet or current-generation single-tilting disk valves without risk factors: Target INR 2.5 (range 2.0-3.0) 1, 2
• With risk factors (atrial fibrillation, prior thromboembolism, LV dysfunction, hypercoagulable state) or older-generation valves (ball-in-cage, Starr-Edwards): Target INR 3.0 (range 2.5-3.5) 1, 2
• First 3 months post-operatively: Consider higher INR target of 2.5-3.5 regardless of valve type 1

Mitral Position

• All mechanical mitral valves: Target INR 3.0 (range 2.5-3.5) regardless of valve type or risk factors 1, 2
• This higher target reflects the substantially greater thrombotic risk in the mitral position compared to aortic 1

Aspirin Addition

• Add aspirin 75-100 mg daily to warfarin for all mechanical valve patients at low bleeding risk 1
• The combination reduces thromboembolic events beyond warfarin alone, though it increases bleeding risk 1, 2

Special Consideration: On-X Valves

• For On-X aortic valves in patients without thromboembolic risk factors, lower INR target of 1.5-2.0 may be reasonable starting ≥3 months post-surgery with aspirin 75-100 mg daily 1
• Critical caveat: Recent PROACT trial data showed dual antiplatelet therapy (aspirin + clopidogrel) without warfarin resulted in excess cerebral thromboembolic events (3.12% vs 0.29% per patient-year, p=0.02) and is contraindicated 3
• For On-X mitral valves, low-dose warfarin (INR 2.0-2.5) did not achieve noninferiority compared to standard dosing (INR 2.5-3.5), so standard targets should be maintained 4

Bioprosthetic Valve Anticoagulation

Initial Period (First 3-6 Months)

• Mitral position: Warfarin targeting INR 2.5 (range 2.0-3.0) for at least 3 months, may extend to 6 months in low bleeding risk patients 1, 5, 2
• Aortic position (surgical): Warfarin targeting INR 2.5 for 3-6 months is reasonable in low bleeding risk patients, though aspirin alone is also acceptable 1, 2
• Transcatheter aortic valves (TAVI): Aspirin 75-100 mg daily is the standard approach 1
  • Dual antiplatelet therapy (aspirin + clopidogrel 75 mg) for 3-6 months may be reasonable in low bleeding risk patients 1
  • Avoid rivaroxaban 10 mg + aspirin: This combination is contraindicated due to increased bleeding without benefit 1

Long-Term Management (After 3-6 Months)

• Without risk factors: Transition to aspirin 75-100 mg daily alone 1, 5
• With risk factors (atrial fibrillation, prior thromboembolism, LV dysfunction, hypercoagulable state, enlarged left atrium): Continue warfarin indefinitely at INR 2.0-3.0 plus aspirin 75-100 mg daily 1, 5

Right-Sided Valves

• Pulmonary bioprosthetic valves: No anticoagulation required; thromboembolic risk is essentially nonexistent 1
• Tricuspid bioprosthetic valves: Warfarin targeting INR 2.0-3.0 for 3-6 months post-implantation, then transition to lifelong aspirin 1
  • If decreased right ventricular function or other risk factors present, consider long-term warfarin (INR 2.0-3.0) 1

Critical Contraindications and Warnings

Direct Oral Anticoagulants (DOACs)

• Dabigatran is absolutely contraindicated in mechanical valve patients due to increased thromboembolic and bleeding events 1
• Anti-Xa DOACs (rivaroxaban, apixaban, edoxaban) have not been assessed and are not recommended for mechanical valves 1
• DOACs are also not recommended for bioprosthetic valves outside of independent indications like atrial fibrillation 5

Bridging Therapy

• When initiating warfarin post-operatively, bridge with unfractionated heparin (DVT dosing) or low-molecular-weight heparin until therapeutic INR achieved 1
• For perioperative interruption of warfarin, bridging with heparin is indicated for mechanical mitral valves, older-generation mechanical aortic valves, or any mechanical aortic valve with thromboembolic risk factors 6

Pediatric Considerations

The pediatric recommendations mirror adult guidelines but warrant specific mention 1:

• Mechanical aortic valves: INR 2.0-3.0 without risk factors; INR 2.5-3.5 with risk factors
• Mechanical mitral valves: INR 2.5-3.5 in all cases
• Bioprosthetic valves: Aspirin alone if no risk factors; warfarin (INR 2.0-3.0) if risk factors present
• Addition of low-dose aspirin to warfarin is recommended based on adult data, though pediatric-specific evidence is limited 1

Common Pitfalls to Avoid

• Never use DOACs for mechanical valves regardless of patient preference or monitoring challenges 1
• Do not undertarget INR in mitral mechanical valves: The 3.0 target is non-negotiable due to higher thrombotic risk 1
• Avoid assuming all bioprosthetic valves are the same: Mitral bioprosthetics require more aggressive initial anticoagulation than aortic 1, 5
• Do not continue dual antiplatelet therapy long-term in TAVI patients without other indications; transition to aspirin alone after 3-6 months 1
• Remember that "low bleeding risk" is a prerequisite for many of these recommendations; patients with bleeding history require individualized assessment 1, 5