How the CHA2DS2-VASc Score Works (With a Worked Example)
The CHA2DS2-VASc score estimates the yearly risk of stroke in a patient with non-valvular atrial fibrillation, and it guides whether that patient should be on an oral anticoagulant. You add points for eight risk factors, most worth 1 point but two worth 2 points each, for a total of 0 to 9. The higher the score, the higher the annual stroke risk and the stronger the case for anticoagulation.
This guide breaks down each letter of the acronym, walks through a full worked example, gives you the risk-by-score table, and points out the details that people get wrong (the female-sex point being the biggest one).
What the letters stand for
The name is a mnemonic. Each letter is a risk factor, and the subscript “2” marks the two factors worth 2 points instead of 1.
| Letter | Risk factor | Points |
|---|---|---|
| C | Congestive heart failure or left-ventricular dysfunction | 1 |
| H | Hypertension (or on treatment for it) | 1 |
| A2 | Age 75 or older | 2 |
| D | Diabetes mellitus | 1 |
| S2 | Prior stroke, TIA, or thromboembolism | 2 |
| V | Vascular disease (prior heart attack, peripheral artery disease, or aortic plaque) | 1 |
| A | Age 65 to 74 | 1 |
| Sc | Sex category (female) | 1 |
Two things trip people up. First, age is scored once: 2 points if the patient is 75 or older, 1 point if 65 to 74, and 0 below 65. You never add both. Second, the maximum is 9, not 10, because those two age bands are mutually exclusive (6 single-point items, plus prior stroke worth 2, plus the age-75 band worth 2 = 9).
Why “S” is worth 2 points
A previous stroke, TIA, or systemic embolism is the strongest single predictor that another one is coming. That is why prior stroke and advanced age (75+) are the only two factors weighted at 2 points. If your patient already had a stroke, they are at least at a score of 2 before you count anything else, which on its own usually puts them in the “anticoagulate” range.
Worked example
Take a 68-year-old woman with high blood pressure and type 2 diabetes, no prior stroke, no heart failure, no vascular disease.
| Factor | Applies? | Points |
|---|---|---|
| Congestive heart failure | No | 0 |
| Hypertension | Yes | 1 |
| Age 75+ | No | 0 |
| Diabetes | Yes | 1 |
| Prior stroke/TIA | No | 0 |
| Vascular disease | No | 0 |
| Age 65 to 74 | Yes | 1 |
| Female | Yes | 1 |
| Total | 4 |
A score of 4 maps to an estimated annual stroke risk of about 4.8% per year. At that level, guidelines recommend a long-term oral anticoagulant unless there is a strong reason not to.
Calculate it with your own values
Risk by score
These are the approximate adjusted annual stroke rates from the validation cohorts. Treat them as estimates, not promises: real risk depends on the individual.
| Score | Approx. annual stroke risk |
|---|---|
| 0 | 0.2% |
| 1 | 0.6% |
| 2 | 2.2% |
| 3 | 3.2% |
| 4 | 4.8% |
| 5 | 7.2% |
| 6 | 9.7% |
| 7 | 11.2% |
| 8 | 10.8% |
| 9 | 12.2% |
The general treatment logic behind most guidelines (such as the ESC): a man with a score of 0 or a woman with a score of 1 from sex alone needs no anticoagulation; a score of 1 in men (or 2 in women) is a “consider it” zone; and a score of 2 or more in men (3 or more in women) is where an oral anticoagulant is recommended.
Common mistakes
Counting the female point on its own. Female sex adds risk only when at least one other risk factor is present. A woman whose only point comes from being female is treated like a man with a score of 0: no anticoagulation. This is why some tools and guidelines describe sex as a “risk modifier” rather than a standalone risk factor.
Double-counting age. Age 65 to 74 and age 75+ are separate rows, but a patient falls into exactly one. A 78-year-old scores 2 for age, not 3.
Confusing it with CHADS2 or HAS-BLED. The older CHADS2 score is a different, coarser tool. HAS-BLED estimates bleeding risk, not stroke risk. CHA2DS2-VASc answers “how likely is a stroke,” and you weigh that against a bleeding score before deciding.
Using it in valvular AF. CHA2DS2-VASc is validated for non-valvular atrial fibrillation. Patients with moderate-to-severe mitral stenosis or a mechanical heart valve need anticoagulation regardless of the score.
Frequently asked questions
What is a normal or safe CHA2DS2-VASc score?
A score of 0 in a man, or 1 in a woman (from sex alone), carries the lowest risk and generally means no anticoagulation is needed. There is no score that guarantees zero risk, but 0 is the lowest the tool can report, at roughly 0.2% per year.
At what score should a patient start anticoagulation?
The common threshold is 2 or more in men and 3 or more in women, where guidelines recommend an oral anticoagulant. A score of 1 in men (or 2 in women) is a shared-decision zone. The final call also weighs bleeding risk and patient preference, so this is not a substitute for clinical judgment.
What is the maximum CHA2DS2-VASc score?
9 points. The two age bands (65 to 74 and 75+) are mutually exclusive, so you cannot reach 10.
Is CHA2DS2-VASc the same as CHADS2?
No. CHADS2 is the older, simpler predecessor. CHA2DS2-VASc adds vascular disease, the 65 to 74 age band, and female sex, which makes it better at identifying truly low-risk patients who can safely skip anticoagulation.