INR Goal for Aortic Mechanical Valve
For patients with a mechanical aortic valve, target an INR of 2.5 (range 2.0-3.0) if they have no additional risk factors, or an INR of 3.0 (range 2.5-3.5) if they have atrial fibrillation, prior thromboembolism, left ventricular dysfunction, hypercoagulable conditions, or an older-generation valve. 1
Standard Risk Patients (No Additional Risk Factors)
Target INR of 2.5 with a therapeutic range of 2.0-3.0 for bileaflet mechanical valves (such as St. Jude Medical) or current-generation single tilting disc valves in the aortic position 1, 2, 3
This lower intensity anticoagulation applies specifically to patients in normal sinus rhythm with normal left atrial size and no history of thromboembolism 2, 4
Add low-dose aspirin 75-100 mg daily to warfarin therapy, which reduces major embolism or death from 8.5% to 1.9% per year 1, 2
High Risk Patients (With Additional Risk Factors)
Increase the target INR to 3.0 with a therapeutic range of 2.5-3.5 for patients with any of the following risk factors: 1, 2
- Atrial fibrillation
- Previous thromboembolism
- Left ventricular dysfunction
- Hypercoagulable conditions
- Older-generation mechanical valves (ball-in-cage, caged disc, or Starr-Edwards valves)
Continue aspirin 75-100 mg daily in addition to the higher intensity warfarin 1, 5
Evidence Challenging Higher Intensity in High-Risk Patients
A 2021 study found that standard-intensity anticoagulation (INR goal 2.5) in high-risk mechanical AVR patients was associated with significantly fewer bleeding events compared to higher-intensity (INR goal 3.0), with few thromboembolic events in either group 6. However, current guidelines still recommend the higher target of 3.0 for high-risk patients 1, and this should be followed until guidelines are updated with stronger evidence.
Special Consideration: On-X Valve
For the On-X aortic valve specifically, a lower INR target of 1.8 (range 1.5-2.0) plus aspirin 75-100 mg daily may be considered after 3 months post-implantation 7, 8
Recent 2024 data showed this lower intensity regimen reduced the composite endpoint by 57% compared to standard therapy, with 85% reduction in major bleeding and no valve thrombosis 8
Critical Management Principles
Specify a single INR target value (2.5 or 3.0) rather than just providing a range, as this reduces the likelihood of patients consistently running at the boundaries 2, 5
Avoid INR >4.0, as adverse events increase significantly above this threshold without additional therapeutic benefit 2
All mechanical valve patients require vitamin K antagonist (VKA) anticoagulation with INR monitoring—never use direct oral anticoagulants (DOACs), as they are contraindicated 5
Anticoagulation clinics with dedicated monitoring result in lower complication rates than standard care 5