Medical AICHA2DS2-VASc stroke risk calculator
A weighted score (0 to 9) that refines stroke risk in non-valvular atrial fibrillation beyond the older CHADS2 schema, adding vascular disease, age 65 to 74, and female sex. It identifies the low-risk patients who can safely avoid anticoagulation and stratifies everyone else.
How to measure each input
- Age
- Use chronological age. Age 75 or older is the single most weighted factor (2 points); 65 to 74 adds 1. Only one age band applies.
- Sex category
- Female sex adds 1 point but acts as a risk modifier rather than a stand-alone indication. The common thresholds (men >= 2, women >= 3) build this in.
- Heart failure / LV dysfunction
- Counts for recent decompensated heart failure or moderate-to-severe left ventricular systolic dysfunction on imaging, with or without symptoms.
- Hypertension
- A documented history or current antihypertensive treatment qualifies; a single normal clinic reading today does not remove the point.
- Prior stroke / TIA / thromboembolism
- Any previous ischaemic stroke, TIA, or systemic embolism scores 2 points, the strongest single predictor of recurrence.
- Vascular disease
- Prior myocardial infarction, peripheral arterial disease, or complex aortic plaque. Coronary disease without infarction is a grey area; follow local guidance.
Interpretation
| Band | Meaning |
|---|---|
| 0, low risk | Lowest category (a true score of 0 only occurs in a man, since female sex contributes a point). Annual stroke risk is roughly 0.2 to 0.3%. Oral anticoagulation is not recommended. |
| 1, low-to-intermediate risk | Annual stroke risk around 0.6 to 1.3%. In men a score of 1 is commonly an indication to consider anticoagulation; in women a score of 1 (female sex alone) is treated as low risk and usually does not warrant it. |
| 2 or more, elevated risk | Annual stroke risk rises from roughly 2.2% at a score of 2 to over 10% at the highest scores. Oral anticoagulation is recommended for men with a score >= 2 and women with a score >= 3, after weighing bleeding risk. |
Pitfalls, exclusions and caveats
- CHA2DS2-VASc is validated for non-valvular atrial fibrillation. Do not use it for moderate-to-severe mitral stenosis or a mechanical valve, where anticoagulation is indicated regardless of score.
- The score estimates stroke risk only. Always pair it with a bleeding-risk assessment (for example HAS-BLED) before starting anticoagulation, but a high bleeding score should prompt addressing modifiable factors, not automatic withholding.
- Female sex alone (score of 1 in a woman) is considered low risk; treating it as an indication to anticoagulate over-treats this group.
- Reported annual stroke rates vary across cohorts and rise without anticoagulation. The percentages here are approximate and antithrombotic-naive estimates.
- Risk is dynamic: re-score as the patient ages or accrues comorbidity rather than relying on a one-time value.
Add points: Congestive heart failure / LV dysfunction 1, Hypertension 1, Age >= 75 = 2, Diabetes 1, prior Stroke / TIA / thromboembolism 2, Vascular disease 1, Age 65 to 74 = 1, Sex category female 1. Age contributes 0, 1, or 2 (not both bands). Total 0 to 9.CHA2DS2-VASc was described by Lip et al. (2010). This implementation is an educational tool and is not affiliated with the original authors or any guideline body.
Frequently asked
What CHA2DS2-VASc score means anticoagulation should be offered?
Guidelines commonly recommend oral anticoagulation for men with a score of 2 or more and women with a score of 3 or more, and consideration at a score of 1 in men. These thresholds already account for female sex, which contributes 1 point.
Why does female sex add a point?
Women with atrial fibrillation carry a modestly higher stroke risk than men with the same other risk factors. The point captures that, but female sex alone (a score of 1 in a woman) is treated as low risk, which is why the female treatment threshold is 3 rather than 2.
How is CHA2DS2-VASc different from CHADS2?
CHA2DS2-VASc adds vascular disease, the 65 to 74 age band, and female sex, and splits age into two bands. It reclassifies many CHADS2 low-risk patients more precisely, especially those who are genuinely low risk and can avoid anticoagulation.
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