Atrial fibrillation: choosing anticoagulation by CHA2DS2-VASc
The case
A 68-year-old man with treated hypertension (perindopril) and type 2 diabetes (metformin and sitagliptin) presents after a routine ECG showed persistent non-valvular atrial fibrillation (heart rate 84/min, irregularly irregular). He has no history of heart failure, myocardial infarction, peripheral arterial disease, stroke or transient ischaemic attack. Creatinine clearance is 75 mL/min. Echocardiogram shows an ejection fraction of 62% with mild left atrial enlargement. His CHA2DS2-VASc score is 3 (age 65–74 = 1, hypertension = 1, diabetes = 1). His HAS-BLED score is 1. What is the most appropriate long-term stroke prevention strategy?
Options
- AOral apixaban 5 mg twice daily
- BNo antithrombotic therapy
- CAspirin 100 mg once daily
- DClopidogrel 75 mg once daily
- EWarfarin titrated to INR 2 to 3
Think it through before you read on. Which single option is best, and why are the other four wrong?
Show the answer and explanation
Answer
A. Oral apixaban 5 mg twice daily
Why this is the right answer
This man has non-valvular atrial fibrillation with a CHA2DS2-VASc score of 3. In a man, a score of 2 or more means the yearly stroke risk is high enough that anticoagulation is recommended. His bleeding risk is low (HAS-BLED 1), so there is no reason to withhold treatment.
The Australian atrial fibrillation guideline (NHFA/CSANZ, 2018) recommends a direct oral anticoagulant (DOAC) in preference to warfarin for non-valvular AF [VERIFY]. DOACs are at least as effective as warfarin for preventing stroke and cause fewer intracranial bleeds. They also need no INR monitoring and have fewer food and drug interactions.
Apixaban 5 mg twice daily is the standard dose. The dose is reduced to 2.5 mg twice daily only when the patient has at least two of: age 80 years or older, weight 60 kg or less, or serum creatinine 133 micromol/L or more [VERIFY]. This man meets none of these, so the full dose is correct.
Warfarin is still the right choice when a DOAC cannot be used: a mechanical heart valve, moderate to severe mitral stenosis, or severe kidney impairment. None of these apply here.
Antiplatelet drugs are not a substitute for anticoagulation in AF. Aspirin gives little stroke protection but still causes bleeding, so guidelines now advise against it for this purpose.
Why the other options are wrong
- B
A score of 3 carries a stroke risk of roughly 3–4% per year, so doing nothing is unsafe.
- C
Aspirin is much less effective than anticoagulation for AF-related stroke and has a similar bleeding risk.
- D
Clopidogrel alone has no meaningful evidence for stroke prevention in AF.
- E
Warfarin works but is second choice: more intracranial bleeding, INR monitoring, and more interactions than a DOAC.
High-yield takeaway
Men with CHA2DS2-VASc 2 or more (women 3 or more) need anticoagulation, and a DOAC is first choice unless there is a mechanical valve, mitral stenosis or severe renal failure.
Reference: NHFA/CSANZ Australian Clinical Guidelines for the Diagnosis and Management of Atrial Fibrillation (2018)
Common questions
Does a woman with the same history score differently?
Yes. Female sex adds one point, so she would score 4. In women, anticoagulation is recommended at a score of 3 or more; in men at 2 or more.
When is warfarin still the right anticoagulant in AF?
With a mechanical heart valve, moderate to severe mitral stenosis, or kidney function too poor for a DOAC. Everyone else is usually better served by a DOAC.
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