What is the recommended anticoagulation therapy after valve replacement?

Anticoagulation After Valve Replacement

For mechanical mitral valves, warfarin targeting INR 3.0 (range 2.5-3.5) is mandatory lifelong; for mechanical aortic valves, target INR 2.5 (range 2.0-3.0); for bioprosthetic valves in either position, warfarin targeting INR 2.5 (range 2.0-3.0) for 3-6 months followed by aspirin 75-100 mg daily is recommended. 1, 2, 3

Mechanical Valve Replacement

Mitral Position

• Warfarin is the only acceptable anticoagulant, targeting INR 3.0 (range 2.5-3.5) indefinitely 1, 3, 4
• The higher INR target compared to aortic valves reflects the substantially greater thrombotic risk in the mitral position 1, 3
• Adding aspirin 75-100 mg daily to warfarin is recommended for patients at low bleeding risk (no history of GI bleeding or other bleeding risk factors) 1, 3
• Direct oral anticoagulants (DOACs) like dabigatran, rivaroxaban, or apixaban are absolutely contraindicated due to increased thrombotic and bleeding complications 3, 5
• A recent 2023 randomized trial attempted lower-intensity warfarin (INR 2.0-2.5) for On-X mechanical mitral valves but failed to demonstrate noninferiority, reinforcing the need for standard INR 2.5-3.5 targets 6

Aortic Position

• Warfarin targeting INR 2.5 (range 2.0-3.0) is recommended for bileaflet mechanical valves (St. Jude Medical) and Medtronic Hall prostheses 1, 4
• For older valve types (Starr-Edwards, mechanical disk valves), target INR 2.5-3.5 1
• During the first 3 months post-operatively, a higher target of INR 2.5-3.5 is reasonable until the valve is fully endothelialized 1
• For On-X aortic valves specifically, after 3 months of standard anticoagulation, a lower INR target of 1.5-2.0 (with aspirin 81 mg daily) may be considered, though this is based on a single trial with an unusually high bleeding rate in the control group 1
• Adding aspirin 75-100 mg daily is recommended for low bleeding risk patients 1

Critical Implementation Points

• VKAs (warfarin) are the only proven anticoagulants for mechanical valves 3, 7
• Bridge with prophylactic-dose unfractionated heparin or LMWH (prophylactic or therapeutic dose) until therapeutic INR is achieved 1
• Start warfarin at 2-5 mg daily (lower doses for elderly, debilitated, or those with CYP2C9/VKORC1 genetic variations) 4
• Most patients maintain therapeutic anticoagulation on 2-10 mg daily 4

Bioprosthetic Valve Replacement

Initial 3-6 Month Period

• Warfarin targeting INR 2.5 (range 2.0-3.0) for at least 3 months and up to 6 months is recommended for both mitral and aortic positions in patients at low bleeding risk 1, 2, 3
• This early period carries substantially elevated stroke risk (4.6% within 30 days for bioprosthetic valves versus 1.3% for mechanical valves), justifying aggressive initial anticoagulation 1, 2
• For mitral bioprosthetic valves specifically, warfarin for the first 3 months is more strongly recommended than for aortic position 1
• Aspirin 50-100 mg daily is an alternative for the first 3 months in aortic bioprosthetic valves for patients in sinus rhythm without other indications 1

Long-Term Management (After 3-6 Months)

• Transition to aspirin 75-100 mg daily alone for patients without additional risk factors 2, 3
• Continue warfarin indefinitely (INR 2.0-3.0) plus aspirin 75-100 mg daily if any of these risk factors exist: 2, 3
  • Atrial fibrillation
  • Previous thromboembolism
  • Left ventricular dysfunction
  • Hypercoagulable state
  • Enlarged left atrium

Special Considerations

• For transcatheter aortic valve replacement (TAVR), aspirin 50-100 mg plus clopidogrel 75 mg daily for 3 months may be reasonable, though warfarin INR 2.5 for 3 months is also reasonable in low bleeding risk patients 1
• Valve thrombosis can occur in bioprosthetic valves and may be warfarin-responsive, supporting the rationale for early anticoagulation 1
• DOACs have not been adequately studied for bioprosthetic valves and are not recommended 2, 7

Right-Sided Valve Replacement

Pulmonary Position

• For bioprosthetic pulmonary valves, forgoing anticoagulation is reasonable 1
• For mechanical pulmonary valves, higher INR targets (2.5-4.0 or 3.0-4.5) appear necessary based on limited data, though specific recommendations cannot be made due to inadequate evidence 1

Tricuspid Position

• For bioprosthetic tricuspid valves, warfarin (INR 2.0-3.0) plus aspirin for 3-6 months is recommended, particularly with decreased right ventricular function 1
• For mechanical tricuspid valves, warfarin targeting INR 2.0-3.0 is used, though valve thrombosis risk remains elevated (2.9% per patient-year) 1

Common Pitfalls and Caveats

• Never use DOACs for mechanical valves under any circumstances - this is associated with increased thrombotic complications and mortality 3, 5
• Bleeding risk increases 2-3 fold when combining dual antiplatelet therapy with warfarin; use aspirin addition judiciously 1
• Patients unable to maintain consistent INR levels require more frequent monitoring, not a switch to DOACs 7
• The benefit of aspirin addition to warfarin in pediatric patients is less established than in adults 1
• For patients who cannot take warfarin, aspirin alone represents suboptimal but acceptable protection for bioprosthetic valves 1, 2
• Large loading doses of warfarin increase hemorrhagic complications without providing faster protection and should be avoided 4