Anticoagulation Targets for Mechanical Valve Replacement

Introduction to Anticoagulation Targets

• The American College of Cardiology recommends a target INR of 2.5 (range 2.0-3.0) for mechanical aortic valve replacement (AVR) without additional risk factors, and a target INR of 3.0 (range 2.5-3.5) for mechanical mitral valve replacement (MVR) or mechanical AVR with risk factors 1, 2, 3

Mechanical Aortic Valve Replacement

• For standard risk patients with mechanical aortic valve replacement, the target INR is 2.5 (range 2.0-3.0), and aspirin 75-100 mg daily should be added to warfarin therapy 1, 2, 3, 5
• High risk patients with mechanical aortic valve replacement, such as those with atrial fibrillation, previous thromboembolism, left ventricular dysfunction, or hypercoagulable conditions, should target an INR of 3.0 (range 2.5-3.5) 1, 2, 3, 4

Mechanical Mitral Valve Replacement

• The target INR for mechanical mitral valve replacement is 3.0 (range 2.5-3.5), regardless of valve type, due to the higher thromboembolic risk associated with mitral position valves 1, 2, 3, 6
• Aspirin 75-100 mg daily should be added to warfarin therapy for mechanical mitral valve replacement 1, 3

Special Considerations

• For On-X mechanical aortic valve replacement without thromboembolic risk factors, a lower INR target of 1.5-2.0 may be reasonable starting ≥3 months after surgery, with continuation of aspirin 75-100 mg daily 2, 3
• If stroke or systemic embolism occurs while in therapeutic range, mechanical AVR patients should increase their INR goal from 2.5 (range 2.0-3.0) to 3.0 (range 2.5-3.5) or add aspirin 75-100 mg daily if not already prescribed 2, 7
• Mechanical MVR patients who experience stroke or systemic embolism while in therapeutic range should increase their INR goal from 3.0 (range 2.5-3.5) to 4.0 (range 3.5-4.0) or add aspirin 75-100 mg daily 2, 7, 8

Critical Pitfalls to Avoid

• Direct oral anticoagulants (DOACs) should not be used in mechanical valve patients, as dabigatran is contraindicated and anti-Xa DOACs are not recommended 2, 7, 3
• Excessive anticoagulation (INR >4.0) provides no additional benefit and significantly increases bleeding risk 2, 7, 3
• Mitral position valves always require higher INR targets than aortic position valves due to inherently higher thrombotic risk 6, 4