What is the target International Normalized Ratio (INR) for a patient with an On-X (mechanical) mitral valve?

From the Guidelines

For patients with an On-X mechanical mitral valve, the recommended INR target is 3.0, with a range of 2.5-3.5, as this provides a reasonable balance between the risks of thromboembolism and bleeding. This recommendation is based on the 2020 ACC/AHA guideline for the management of patients with valvular heart disease 1. The guideline suggests that the incidence of thromboembolism is higher with mitral than with aortic mechanical valves, and it is lower in mitral mechanical valve patients with a higher rather than a lower INR.

Key Considerations

• The On-X mechanical mitral valve requires more aggressive anticoagulation due to the higher risk of thrombosis compared to the aortic position.
• Patients should take warfarin to maintain the recommended INR range and should undergo regular INR monitoring, typically every 2-4 weeks once stable.
• It's essential to avoid wide fluctuations in the INR as these increase both bleeding and thrombotic risks.
• The guideline recommends an INR target of 3.0 (range, 2.5–3.5) for patients with a mechanical mitral valve, which is supported by studies showing that this range provides a reasonable balance between the risks of under- or over-anticoagulation 1.

Additional Recommendations

• Patients should be educated about bleeding risks, the importance of compliance, and the need to inform all healthcare providers about their mechanical valve and anticoagulation status before any procedures or when starting new medications.
• Diet should remain consistent regarding vitamin K intake, as significant changes can affect INR stability.
• The use of antiplatelet therapy, such as daily aspirin 81mg, may be considered in addition to warfarin, unless there are contraindications to aspirin therapy.

From the FDA Drug Label

For patients with tilting disk valves and bileaflet mechanical valves in the mitral position, the 7th ACCP recommends a target INR of 3.0 (range, 2.5 to 3.5). The target International Normalized Ratio (INR) for a patient with an On-X (mechanical) mitral valve is not explicitly stated in the provided drug label. However, based on the information provided for tilting disk valves and bileaflet mechanical valves in the mitral position, a target INR of 3.0 (range, 2.5 to 3.5) can be considered, but this may not be directly applicable to the On-X valve. 2

From the Research

Target International Normalized Ratio (INR) for On-X Mechanical Mitral Valve

• The target INR range for patients with a mechanical mitral prosthesis is generally recommended to be between 2.5 and 3.5 3.
• A study on the Prospective Randomized On-X Anticoagulation Clinical Trial (PROACT) Mitral found that low-dose warfarin (target INR, 2.0-2.5) did not achieve noninferiority for the composite primary end point compared to standard-dose warfarin (target INR, 2.5-3.5) 3.
• Another study suggested that a target INR of 2.0-2.5 may be acceptable for preventing thromboembolic events and safe in terms of bleeding complications in patients with mechanical mitral valve replacement 4.
• The Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy recommends a target INR of 3.0 (range, 2.5 to 3.5) for patients with tilting disk valves and bileaflet mechanical valves in the mitral position 5.
• However, other studies have suggested that lower target INR ranges may be effective and safe for patients with mechanical heart valves, including those with On-X valves 6, 7.
• It is essential to note that the optimal target INR range may vary depending on individual patient factors, such as the type of valve, thromboembolism risk, and bleeding risk.