What is a coronary calcium score?
A coronary calcium score — also called a coronary artery calcium (CAC) score — measures the amount of calcified plaque in the arteries that supply blood to your heart. It is worked out from a quick, non-invasive CT scan of the heart.
Plaque is a build-up of fat, cholesterol and other substances in the artery walls. Over time, some plaque can harden with calcium, and this calcium shows up clearly on a CT scan.
In general, the more calcified plaque the scan detects, the higher the CAC score, and the higher a person’s risk of future heart problems, especially a heart attack.
A CAC score can reveal early, symptom-free coronary artery disease in people who feel perfectly well and may not otherwise be recognised as being at increased risk. However, it does not show all types of plaque, and it is not designed to diagnose blocked arteries in people with symptoms such as chest pain.
What does the scan involve?
A CAC scan is a short, non-invasive CT scan. It does not require an injection of contrast dye, and there are no needles — most people are in and out within a 15-minute appointment. The scan uses a small amount of radiation to capture detailed images of the heart's arteries, which are then used to calculate the score.
What do the results mean?
Results are usually given as a single number, often grouped into broad bands:
- A score of zero means no calcified plaque was detected. This is generally reassuring and points to a low risk of heart attack in the near future, although it does not mean a person has no risk at all.
- Higher scores indicate more calcified plaque has been detected. This can indicate a higher risk of future heart problems and may prompt a discussion about prevention, such as lifestyle changes and cholesterol-lowering treatment.
A CAC score is one piece of the picture rather than a diagnosis on its own. Your doctor interprets it alongside your age, sex, blood pressure, cholesterol level and other risk factors to build a fuller view of your heart health.
Who might benefit from a calcium scan?
CAC scoring is most useful when a person’s risk of heart disease is uncertain and the result could change the prevention plan. It can be particularly helpful for people at intermediate risk, or people who appear low risk but have extra risk factors, such as a strong family history of premature heart disease. In these cases, a CAC score can help decide whether preventative treatment, such as cholesterol-lowering medication, is likely to be beneficial.
For people already known to be at high risk, or who already have diagnosed heart disease, a CAC scan may add little, because the decision to treat has usually already been made.
As with any test, whether it's right for you — and what it may cost — is a conversation to have with your doctor.