INR Goals for Onyx Mitral and Aortic Valves
Critical Note on "Onyx" Valves
There is no established mechanical heart valve brand called "Onyx" in the major cardiovascular guidelines or FDA-approved valve literature. You may be referring to the On-X valve (manufactured by CryoLife), which is a modern bileaflet mechanical valve with specific anticoagulation recommendations that differ from traditional mechanical valves.
INR Goals for On-X Mechanical Valves
On-X Aortic Valve Position
For On-X aortic valves, target INR 1.8 (range 1.5-2.0) plus aspirin 75-100 mg daily is safe and effective after the first 3 months post-implantation. 1
- Recent prospective registry data (2024) with 510 patients demonstrates that low-dose warfarin (INR 1.8, range 1.5-2.0) plus aspirin results in a 57% reduction in the composite endpoint of thromboembolism, valve thrombosis, and major bleeding compared to standard-dose warfarin (INR 2.0-3.0) 1
- Major bleeding decreased by 85% with the lower INR target, with no valve thrombosis events reported 1
- This lower INR target is specific to the On-X valve and should not be extrapolated to other mechanical valve types 1
On-X Mitral Valve Position
For On-X mitral valves, target INR 2.5 (range 2.5-3.5) plus aspirin 75-100 mg daily is recommended. 2
- The American College of Cardiology recommends INR 3.0 (range 2.5-3.5) for all mechanical mitral valve replacements, which applies to On-X valves in the mitral position 2
- Some data suggest INR 2.5-3.5 may be acceptable for On-X mitral valves specifically, but this is less established than the aortic position data 3
On-X Double Valve Replacement (Aortic + Mitral)
For patients with On-X valves in both positions, target INR 3.0 (range 2.5-3.5) plus aspirin 75-100 mg daily. 4, 2
- When mechanical valves are present in both aortic and mitral positions, the higher INR target for mitral valves takes precedence 4
Standard Mechanical Valve INR Goals (If NOT On-X)
If you are referring to a different valve or standard mechanical valves:
Aortic Position
- Bileaflet or current-generation single tilting disc valves without risk factors: INR 2.5 (range 2.0-3.0) 4, 5
- With additional risk factors (AF, prior thromboembolism, LV dysfunction, hypercoagulable state): INR 3.0 (range 2.5-3.5) 4, 2
- Older-generation valves (caged ball/disk): INR 3.0 (range 2.5-3.5) plus aspirin 75-100 mg daily 4, 5
Mitral Position
Double Valve Replacement
Aspirin Addition
Add aspirin 75-100 mg daily to warfarin therapy for all mechanical valves in patients at low bleeding risk. 4, 2
- The combination reduces mortality (2.8% vs 7.4% per year) and stroke (1.3% vs 4.2% per year) compared to warfarin alone 4
- Minor bleeding increases slightly (epistaxis, bruising), but major bleeding risk does not significantly increase when INR is maintained at 2.0-3.5 4
- Caution: Do not add aspirin if INR target is 3.0-4.5 or higher, as bleeding risk becomes excessive 6
Management After Thromboembolic Events
If Stroke/Embolism Occurs While in Therapeutic Range
Aortic valve: Increase INR from 2.5 (range 2.0-3.0) to 3.0 (range 2.5-3.5) OR add aspirin 75-100 mg daily 4, 2
Mitral valve: Increase INR from 3.0 (range 2.5-3.5) to 4.0 (range 3.5-4.0) OR add aspirin 75-100 mg daily 4, 2
Critical Pitfalls
- Direct oral anticoagulants (DOACs) are absolutely contraindicated for mechanical valves—dabigatran increases thrombotic and bleeding complications 4, 2
- Patient compliance is challenging with higher INR goals: patients with target INR 2.0-3.5 achieve therapeutic range 74.5% of the time, while those with target 3.0-4.5 achieve it only 44.5% of the time 4
- The On-X valve is unique—do not apply its lower INR targets to other mechanical valve brands 1
- INR fluctuations increase complications—consistent monitoring and patient education are essential 2