INR Goals for Mechanical Heart Valves
For mechanical aortic valves without risk factors, target an INR of 2.5 (range 2.0-3.0); for mechanical mitral valves or aortic valves with risk factors, target an INR of 3.0 (range 2.5-3.5). 1, 2
Mechanical Aortic Valve Replacement
Low-Risk Patients
- Target INR of 2.5 (range 2.0-3.0) for bileaflet or current-generation single tilting disc mechanical aortic valves in patients without additional risk factors 1, 2, 3
- Add low-dose aspirin 75-100 mg daily to warfarin therapy, though this must be balanced against increased bleeding risk 1, 2
High-Risk Patients
- Target INR of 3.0 (range 2.5-3.5) when any of the following risk factors are present 1, 2:
- Add low-dose aspirin 75-100 mg daily, weighing bleeding risk 1, 2
Important caveat: Recent research challenges the higher INR goal for high-risk aortic valve patients, showing that standard-intensity anticoagulation (INR 2.5) was associated with fewer bleeding events without increased thromboembolism compared to higher-intensity (INR 3.0) in patients with additional risk factors 4. However, current guidelines still recommend the higher target 1, 2.
Mechanical Mitral Valve Replacement
- Target INR of 3.0 (range 2.5-3.5) for ALL mechanical mitral valve replacements, regardless of risk factors 1, 2, 3
- Add low-dose aspirin 75-100 mg daily to warfarin therapy 1, 2
- The higher INR target reflects the inherently higher thrombotic risk associated with the mitral position 5
Management After Thromboembolic Events on Therapeutic Anticoagulation
For Mechanical Aortic Valves
- Increase INR goal from 2.5 (range 2.0-3.0) to 3.0 (range 2.5-3.5) if stroke or systemic embolism occurs while patient is in therapeutic range 1, 2
- Add low-dose aspirin 75-100 mg daily if not already prescribed 1, 2
For Mechanical Mitral Valves
- Increase INR goal from 3.0 (range 2.5-3.5) to 4.0 (range 3.5-4.5) if stroke or systemic embolism occurs while patient is in therapeutic range 1, 2
- Add low-dose aspirin 75-100 mg daily if not already prescribed, after assessing bleeding risk 1, 2
Critical Pitfalls to Avoid
- Never use direct oral anticoagulants (DOACs) in patients with mechanical heart valves—dabigatran is contraindicated and anti-Xa DOACs have not been adequately assessed 1, 2
- Specify a single target INR value, not just a range, to prevent patients from consistently running at the upper or lower boundary 1
- INR fluctuations significantly increase complications—patients should strive for consistent values within the target range, with studies showing only 44.5% time in range when targeting INR 3.0-4.5 versus 74.5% when targeting 2.0-3.5 2, 6
- Anticoagulation clinics with dedicated pharmacists or nurses achieve lower complication rates than standard care 1
- INR values greater than 4.0 provide no additional therapeutic benefit and are associated with higher bleeding risk 3
- Older-generation mechanical valves (caged ball, caged disk) require higher INR targets of 2.5-3.5 even in the aortic position 2, 5
Adjunctive Aspirin Therapy
- Low-dose aspirin (75-100 mg daily) is recommended in addition to warfarin for all mechanical valve patients 1, 2
- Aspirin reduces thromboembolic events but increases bleeding risk, particularly when INR is maintained at 3.0-4.5 7
- The addition of aspirin should be individualized based on bleeding risk assessment 2