What is the recommended anticoagulant (Anti-Coagulant) or antiplatelet therapy for patients with a prosthetic aortic valve replacement?

Antithrombotic Therapy for Prosthetic Aortic Valve Replacement

For prosthetic aortic valve replacement, vitamin K antagonist (VKA) therapy is recommended for mechanical valves, while aspirin 75-100 mg daily is recommended for bioprosthetic valves beyond the initial 3-month period. 1

Mechanical Aortic Valve Replacement

Standard Anticoagulation Regimen

• Mechanical valves require lifelong VKA therapy 1
• Target INR depends on valve type and patient risk factors:
  • Bileaflet or current-generation single-tilting disk mechanical aortic valve with no risk factors: Target INR 2.5 (range 2.0-3.0) 1, 2
  • Mechanical aortic valve with additional risk factors (AF, previous thromboembolism, LV dysfunction, hypercoagulable state) or older-generation prosthesis: Target INR 3.0 (range 2.5-3.5) 1

Special Considerations

• For patients with a mechanical On-X AVR and no thromboembolic risk factors, a lower INR target (1.5-2.0) may be reasonable starting ≥3 months after surgery, with continuation of aspirin 75-100 mg daily 1
  • However, the PROACT trial showed that dual antiplatelet therapy alone (without anticoagulation) resulted in excess cerebral thromboembolic events compared to standard warfarin therapy 3

Addition of Antiplatelet Therapy

• For patients with mechanical valves at low risk of bleeding, adding aspirin 75-100 mg daily to VKA therapy is recommended 1
• This combination reduces thromboembolic events but increases bleeding risk 4
• Use caution in patients with increased bleeding risk (e.g., history of GI bleeding) 1

Bioprosthetic Aortic Valve Replacement

Initial 3-Month Period

• For surgical bioprosthetic aortic valves:

  • Aspirin 75-100 mg daily is recommended 1
  • Alternatively, VKA therapy (target INR 2.5, range 2.0-3.0) may be reasonable for at least 3 months and up to 6 months after surgical replacement, particularly in patients at low bleeding risk 1

• For transcatheter aortic bioprosthetic valves:

  • Aspirin 75-100 mg plus clopidogrel 75 mg daily is recommended for the first 3 months 1

Beyond 3 Months

• Lifelong aspirin 75-100 mg daily is recommended for all bioprosthetic aortic valves in the absence of other indications for oral anticoagulants 1

Bridging Therapy

• When initiating VKA therapy in patients with mechanical heart valves, bridging with unfractionated heparin (prophylactic dose) or LMWH (prophylactic or therapeutic dose) is recommended until stable on VKA therapy 1

Management of Valve Thrombosis

• For prosthetic valve thrombosis:
  • Right-sided thrombosis: Fibrinolytic therapy is preferred over surgery 1
  • Left-sided thrombosis with large thrombus (≥0.8 cm²): Early surgery is preferred 1
  • Left-sided thrombosis with small thrombus (<0.8 cm²): Fibrinolytic therapy may be considered 1

Common Pitfalls and Caveats

1. Never use direct oral anticoagulants (DOACs) for patients with mechanical valves - they are contraindicated due to increased risk of thrombotic complications 1

2. Bleeding risk assessment is crucial when considering combination therapy with VKA and antiplatelet agents

3. INR monitoring frequency should be more frequent during the initial period of anticoagulation and can be extended to longer intervals once stability is achieved

4. Anticoagulation interruption for procedures should be carefully managed, with appropriate bridging strategies for mechanical valves

5. Lower-dose aspirin (<100 mg) may be associated with lower bleeding risk than higher doses when combined with anticoagulation 4

The evidence clearly demonstrates that the type of prosthetic valve (mechanical vs. bioprosthetic) is the primary determinant of antithrombotic therapy strategy, with mechanical valves requiring lifelong anticoagulation to prevent potentially fatal valve thrombosis and thromboembolic events.