From the Guidelines
The International Normalized Ratio (INR) target for anticoagulation in patients with atrial fibrillation is 2.0 to 3.0.
Key Considerations
- This target range is recommended for patients with nonvalvular atrial fibrillation who are at high risk of stroke, such as those with prior thromboembolism, rheumatic mitral stenosis, or more than one moderate risk factor (e.g., age 75 years or older, hypertension, heart failure, impaired left ventricular systolic function, or diabetes mellitus) 1.
- For patients with mechanical heart valves, the target INR range may be higher, typically 2.5 to 3.5 1.
- The INR target range may need to be adjusted based on individual patient factors, such as bleeding risk or renal function 1.
Evidence Summary
- The 2011 ACCF/AHA/HRS focused updates incorporated into the ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation recommend an INR target range of 2.0 to 3.0 for patients with nonvalvular atrial fibrillation at high risk of stroke 1.
- The 2006 ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation also recommend an INR target range of 2.0 to 3.0 for patients with nonvalvular atrial fibrillation at high risk of stroke 1.
- The 2018 Canadian Stroke Best Practice Recommendations support the use of an INR target range of 2.0 to 3.0 for patients with atrial fibrillation taking warfarin, with careful dosing and consistent INR monitoring to minimize adverse events 1.
From the Research
International Normalized Ratio (INR) Target for Anticoagulation in Atrial Fibrillation
- The recommended INR target for patients with atrial fibrillation (AF) and risk factors for thromboembolism is between 2 and 3 2, 3, 4, 5, 6.
- Studies have shown that an INR range of 2 to 3 provides the best balance between ischemic stroke and intracranial hemorrhage (ICH), as well as optimal protection against death in patients with AF 2.
- A systematic review and meta-analysis of randomized controlled trials found that lower INR targets reduce bleeding but increase thromboembolism in AF, and that an INR range of 2 to 3 should remain standard for thromboembolic prophylaxis in AF 3.
- Another study found that the odds of thromboembolism (TE) were low and stable above INR 1.8, and that the odds of ICH increased markedly at INR values >3.5, confirming that the current standard of INR 2.0 to 3.0 for atrial fibrillation falls in the optimal INR range 4.
- A meta-analysis of studies published between 1985 and 2002 found that an INR < 2 was associated with an increased risk of ischemic events, and that an INR > 3 was associated with an increased risk of bleeding events 5.
- Adjusted-dose anticoagulant therapy with warfarin, with an optimal INR of 2-3, dramatically decreases the risk of embolic events in patients with AF, but slightly increases the risk of bleeding 6.