What is the recommended therapeutic International Normalized Ratio (INR) range for an adult with a mechanical aortic or mitral heart valve?

Recommended INR for Mechanical Heart Valves

For mechanical aortic valves without additional risk factors, maintain an INR of 2.5 (range 2.0–3.0); for mechanical mitral valves or aortic valves with risk factors, maintain an INR of 3.0 (range 2.5–3.5). 1

Mechanical Aortic Valve

Target INR 2.5 (range 2.0–3.0) for low-risk patients with bileaflet or current-generation single tilting disc valves. 1

• This lower target applies specifically to patients without atrial fibrillation, prior thromboembolism, left ventricular dysfunction, hypercoagulable conditions, or older-generation valves (ball-in-cage). 1
• Add aspirin 75–100 mg daily to warfarin therapy for all patients with mechanical aortic valves. 1

Increase to INR 3.0 (range 2.5–3.5) for high-risk aortic valve patients. 1

• Risk factors requiring higher INR include atrial fibrillation, previous thromboembolism, severe left ventricular dysfunction, hypercoagulable states, or older-generation mechanical valves. 1
• The FDA label confirms this recommendation for tilting disk valves in the aortic position. 2

Mechanical Mitral Valve

Target INR 3.0 (range 2.5–3.5) for ALL mechanical mitral valves, regardless of valve design or patient risk factors. 1, 3

• Mechanical mitral prostheses carry significantly higher thromboembolic risk (0.9% per year) compared to aortic prostheses (0.5% per year), justifying more intensive anticoagulation. 3
• This higher target applies to all mitral valve types—bileaflet, tilting disk, and caged-ball/disk valves. 1, 2
• The GELIA study demonstrated that patients with mitral valves targeting INR 2.0–3.5 had lower survival compared to those targeting 2.5–4.5, supporting the need for higher intensity anticoagulation. 1
• Add aspirin 75–100 mg daily to warfarin for all mechanical mitral valve patients. 1

Double Valve Replacement (Aortic + Mitral)

Target INR 3.0 (range 2.5–3.5) when mechanical valves are present in both positions. 1

• The mitral position drives the anticoagulation intensity, given its higher thrombotic risk. 1

Critical Evidence Considerations

The combination of warfarin plus low-dose aspirin (75–100 mg daily) reduces major embolism or death from 8.5% to 1.9% per year (p<0.001) and stroke from 4.2% to 1.3% per year (p<0.027). 1

• This combination modestly increases bleeding risk but provides net benefit on mortality and embolic protection. 3
• Aspirin should be used cautiously in patients with history of gastrointestinal bleeding. 1

Patients targeting INR 3.0–4.5 remain within therapeutic range only 44.5% of the time, whereas those targeting 2.0–3.5 achieve therapeutic range 74.5% of the time. 1, 3

• The recommended target of 3.0 (range 2.5–3.5) for mitral valves balances efficacy against achievability. 1, 3

Common Pitfalls to Avoid

• Do NOT apply the lower aortic valve INR target (2.0–3.0) to mitral valves—all mitral positions require INR 2.5–3.5 regardless of valve design. 3, 4
• Do NOT use direct oral anticoagulants (DOACs)—dabigatran is contraindicated and other DOACs have not been adequately studied in mechanical valve patients. 5
• Do NOT assume newer bileaflet mitral valves permit lower INR—the 2023 PROACT Mitral trial failed to demonstrate noninferiority of low-dose warfarin (INR 2.0–2.5) versus standard-dose (INR 2.5–3.5) in On-X mitral valves. 6

Bridging Anticoagulation

Initiate prophylactic-dose unfractionated heparin or low-molecular-weight heparin postoperatively until INR reaches therapeutic range on two consecutive measurements. 1

• Continue bridging therapy for at least 24 hours after achieving therapeutic INR before discontinuing heparin. 4
• The first few months after valve implantation carry the highest thromboembolic risk before complete endothelialization occurs. 4