What is the therapeutic range for International Normalized Ratio (INR) in patients with mechanical aortic valve replacement?

Therapeutic Range for INR in Mechanical Aortic Valve Replacement

For patients with mechanical aortic valve replacement, the recommended therapeutic INR range is 2.0-3.0 (target 2.5) for bileaflet or current-generation single tilting disc valves without risk factors for thromboembolism, and 2.5-3.5 (target 3.0) for those with additional risk factors.

Standard INR Targets Based on Valve Type and Position

Mechanical Aortic Valve

• Without risk factors:

  • INR target: 2.5 (range 2.0-3.0) 1, 2, 3
  • This applies to bileaflet mechanical valves or current-generation single tilting disc valves in the aortic position

• With risk factors for thromboembolism:

  • INR target: 3.0 (range 2.5-3.5) 1, 2, 1
  • Risk factors include: atrial fibrillation, previous thromboembolism, left ventricular dysfunction, or hypercoagulable conditions

• Older-generation mechanical valves (ball-in-cage):

  • INR target: 3.0 (range 2.5-3.5) 1, 3

Adjunctive Therapy

• Aspirin 75-100 mg daily is recommended in addition to warfarin for all patients with mechanical heart valves 1, 2
• The addition of aspirin decreases the incidence of major embolism or death (1.9% versus 8.5% per year) 1

Special Considerations

On-X Mechanical Aortic Valves

• For On-X mechanical aortic valves without risk factors, a lower INR of 1.5-2.0 plus aspirin (75-100 mg daily) may be reasonable starting 3 months after surgery 2, 4
• The PROACT trial showed a 57% reduction in the primary composite endpoint with this lower INR target compared to standard anticoagulation 4

Initial Post-Operative Period

• During the first 3 months after aortic valve replacement with a mechanical prosthesis, it is reasonable to maintain a higher INR target of 2.5-3.5 1
• After this initial period, the INR can be adjusted to the standard target based on valve type and risk factors

Monitoring Considerations

• Regular INR monitoring is essential to maintain therapeutic levels
• Patients with a target INR between 2.0-3.5 typically maintain therapeutic range approximately 74.5% of the time 2
• Patients with higher INR targets (3.0-4.5) tend to stay in range only about 44.5% of the time, highlighting the challenges of maintaining higher targets 1

Contraindications and Warnings

• Direct oral anticoagulants (DOACs) are contraindicated for mechanical valves 2
• Antiplatelet therapy alone is insufficient for mechanical valves and carries unacceptable thrombosis risk 2

Comparative Thrombotic Risk

• Mechanical aortic valves have a lower thrombotic risk compared to mechanical mitral valves (0.5%/year vs 0.9%/year) 2
• Among patients with mechanical aortic valves anticoagulated with warfarin (target INR 2.5-3.5), the risk of thromboembolic complications ranges from 0% to 1.3% per patient-year 1

The evidence strongly supports that maintaining the appropriate INR range significantly reduces both thromboembolic and bleeding complications in patients with mechanical aortic valves, with the specific target depending on valve type and patient risk factors.