Anticoagulation Therapy for Atrial Fibrillation
For patients with atrial fibrillation, oral anticoagulation is recommended for those with one or more non-sex CHA₂DS₂-VASc stroke risk factors, with direct oral anticoagulants (DOACs) preferred over warfarin in eligible patients. 1, 2
Risk Assessment for Anticoagulation
Risk stratification should be performed using the CHA₂DS₂-VASc score, which includes:
- Congestive heart failure (1 point) 2
- Hypertension (1 point) 2
- Age ≥75 years (2 points) 2
- Diabetes mellitus (1 point) 2
- Prior stroke/TIA (2 points) 2
- Vascular disease (1 point) 2
- Age 65-74 years (1 point) 2
- Sex category (female) (1 point) 2
Anticoagulation Recommendations Based on Risk
Low Risk (CHA₂DS₂-VASc score = 0 in males, 1 in females)
- No antithrombotic therapy is recommended 1
- If patient chooses antithrombotic therapy, aspirin (75-325 mg daily) is suggested rather than oral anticoagulation 1
Intermediate Risk (CHA₂DS₂-VASc score = 1 in males)
- Oral anticoagulation is recommended rather than no therapy (Grade 1B) 1
- Oral anticoagulation is suggested over aspirin or aspirin plus clopidogrel combination 1
- For patients unable to take oral anticoagulants (for reasons other than bleeding concerns), combination therapy with aspirin and clopidogrel is suggested 1
High Risk (CHA₂DS₂-VASc score ≥ 2)
- Oral anticoagulation is strongly recommended rather than no therapy, aspirin, or combination therapy with aspirin and clopidogrel 1, 2
Choice of Anticoagulant
Direct Oral Anticoagulants (DOACs)
- DOACs (apixaban, dabigatran, rivaroxaban, edoxaban) are preferred over warfarin for non-valvular atrial fibrillation 2
- Dabigatran 150 mg twice daily is suggested over adjusted-dose vitamin K antagonist therapy (Grade 2B) 1
- DOACs have demonstrated lower risk of intracranial hemorrhage compared to warfarin 2, 3
Vitamin K Antagonists (Warfarin)
- Target INR of 2.0-3.0 is recommended for patients on warfarin 4
- Warfarin is specifically indicated for patients with:
Special Considerations
Valvular vs. Non-valvular Atrial Fibrillation
- For patients with AF and mitral stenosis, adjusted-dose warfarin (target INR 2.0-3.0) is recommended rather than no therapy, aspirin, or combination therapy 1, 4
- For patients with mechanical prosthetic heart valves, warfarin is recommended with target INR based on valve type and position 4
Renal Function
- DOACs require dose adjustment based on renal function 2
- Dabigatran is contraindicated in patients with severe renal impairment (creatinine clearance ≤30 mL/min) 1
- Warfarin is preferred for patients on dialysis 2
Bleeding Risk
- Bleeding risk assessment should be performed for all patients with AF at every patient contact 1
- Focus initially on potentially modifiable bleeding risk factors such as:
Common Pitfalls and Caveats
- Underutilization of anticoagulation in elderly patients despite their higher stroke risk 5
- Inappropriate use of aspirin alone in high-risk patients when oral anticoagulation would provide greater benefit 5, 3
- Failure to maintain therapeutic INR range (2.0-3.0) in patients on warfarin, increasing risk of thromboembolism or bleeding 4
- Discontinuing anticoagulation after cardioversion or ablation in patients with ongoing stroke risk factors 2
- Overestimation of bleeding risk leading to inappropriate withholding of anticoagulation 2, 3
Recent Developments
Recent clinical trials have explored factor XIa inhibitors like asundexian as potential alternatives to current anticoagulants, but a recent study showed higher rates of stroke or systemic embolism compared to apixaban despite lower bleeding rates, leading to premature trial termination 6. This reinforces the current recommendation for DOACs as first-line therapy for eligible patients with AF.