Stroke risk in atrial fibrillation
Atrial fibrillation makes the upper chambers of the heart quiver instead of contracting, so blood can pool and clot. A clot that travels to the brain causes a stroke. Blood thinners (anticoagulants) cut that risk by about two thirds but increase the risk of bleeding. The CHA₂DS₂-VASc score helps decide who benefits enough to take one.
The points
| Letter | Risk factor | Points |
|---|---|---|
| C | Congestive heart failure | 1 |
| H | Hypertension | 1 |
| A₂ | Age 75 or older | 2 |
| D | Diabetes | 1 |
| S₂ | Prior stroke, TIA or thromboembolism | 2 |
| V | Vascular disease (heart attack, peripheral artery disease, aortic plaque) | 1 |
| A | Age 65 to 74 | 1 |
| Sc | Sex category: female | 1 |
The maximum is 9 points.
Worked example
A 70-year-old man with atrial fibrillation and high blood pressure, without other risk factors.
- Hypertension: 1 point.
- Age 65 to 74: 1 point.
- CHA₂DS₂-VASc = 2, and CHA₂DS₂-VA = 2.
At 2 points in a man, current guidelines recommend oral anticoagulation unless bleeding risk or another reason argues against it.
What the score means
The 2023 ACC/AHA/ACCP/HRS guideline recommends anticoagulation when the yearly stroke risk is about 2% or more, which corresponds to a CHA₂DS₂-VASc of 2 or more in men and 3 or more in women. Anticoagulation is reasonable at 1 in men and 2 in women. At 0 in men or 1 in women, it is generally not needed.
CHA₂DS₂-VA
The 2024 European Society of Cardiology guidelines dropped the point for female sex, because female sex mainly amplifies risk in the presence of other factors. The resulting CHA₂DS₂-VA score recommends anticoagulation from 2 points and suggests considering it at 1. The calculator shows both scores side by side.
Practical points
- The score does not apply to atrial fibrillation with moderate to severe mitral stenosis or a mechanical valve: those patients need anticoagulation regardless.
- Bleeding risk is assessed separately, and modifiable bleeding risks such as uncontrolled blood pressure or NSAID use should be corrected rather than used as a reason to withhold treatment.
- Aspirin alone is no longer recommended for stroke prevention in atrial fibrillation.
- Recalculate the score over time: turning 65 or 75, or a new diagnosis of diabetes, can change the recommendation.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.