INR Goal for Valvular Atrial Fibrillation
For patients with valvular atrial fibrillation, the recommended INR target is 2.5 (range 2.0-3.0), with higher targets of 2.5-3.5 for mechanical heart valves. 1, 2
Definition and Classification
Valvular atrial fibrillation refers to AF associated with:
- Rheumatic mitral stenosis
- Mechanical prosthetic heart valves
- Mitral valve repair
INR Targets by Specific Valve Type
Mechanical Heart Valves
- St. Jude Medical bileaflet valve in aortic position: Target INR 2.5 (range 2.0-3.0) 2
- Tilting disk valves and bileaflet valves in mitral position: Target INR 3.0 (range 2.5-3.5) 2
- Caged ball or caged disk valves: Target INR 3.0 (range 2.5-3.5) plus aspirin 75-100 mg/day 2
Bioprosthetic Valves
- Mitral position: Target INR 2.5 (range 2.0-3.0) for first 3 months after insertion 2
- Aortic position: Target INR 2.5 (range 2.0-3.0) suggested for first 3 months after insertion 2
Rheumatic Mitral Stenosis
- Target INR 2.5 (range 2.0-3.0) 1
Evidence Supporting These Recommendations
The American College of Cardiology/American Heart Association guidelines strongly recommend warfarin for patients with AF who have valvular heart disease, particularly those with mechanical heart valves (Class I, Level of Evidence A) 1. This is supported by the FDA labeling for warfarin, which specifies target INR ranges based on valve type and position 2.
Studies have demonstrated that lower INR targets (≤1.6) are associated with significantly higher risk of thromboembolism compared to standard INR targets (2.0-3.0), with a relative risk of 1.50 (95% CI 1.29-1.74) 3. A meta-analysis showed that adjusted-dose warfarin with standard INR targets reduced the risk of thrombosis by 50% compared to lower-dose regimens 4.
Monitoring Recommendations
- INR should be determined at least weekly during initiation of therapy 1
- Once stable, INR should be monitored at least monthly 1
- Time in therapeutic range (TTR) should ideally be ≥70% 1
Special Considerations
Elderly Patients
While some experts have suggested lower INR targets (1.6-2.5) for elderly patients (≥75 years) to reduce bleeding risk 1, the most recent guidelines still recommend standard INR targets of 2.0-3.0 even in elderly patients if their risk of ischemic stroke without warfarin outweighs their risk of bleeding 1.
Bleeding Risk
- Major bleeding risk increases exponentially when INR exceeds 5.0 5
- Poorly controlled hypertension and concomitant use of aspirin or NSAIDs increase bleeding risk during anticoagulation 1
Common Pitfalls
Inadequate monitoring: Failure to check INR at least monthly once stable can lead to poor anticoagulation control 1
Inappropriate lowering of INR target: Using lower INR targets (1.5-2.0) significantly increases thromboembolic risk without substantial reduction in major bleeding 4, 3
Assuming INR history predicts future INR control: Historic time in therapeutic range has only weak association with future TTR (R² = 0.212) 6
Using DOACs instead of warfarin: Direct oral anticoagulants are contraindicated in patients with mechanical heart valves 1, 7
For patients with valvular AF, warfarin remains the gold standard with appropriate INR monitoring and dose adjustment to maintain the target range specific to their valve type and clinical situation.