Coronary Artery Calcium (CAC)
A non-invasive CT scan that directly measures the amount of calcification in the coronary arteries — one of the strongest available predictors of a future heart attack in people without symptoms.
Number of studies
1
Safety
High
Time to effects
Not applicable — CAC is a diagnostic test, not an intervention.
Who it's for
Table of contents
TL;DR
A non-invasive CT scan that directly measures the amount of calcification in the coronary arteries — one of the strongest available predictors of a future heart attack in people without symptoms.
- →Directly visualizes and quantifies atherosclerosis that is already present in the coronary arteries
- →Helps refine the decision about the intensity of prevention in people with intermediate risk
- →A score of zero is associated with very low risk over long-term follow-up
| Test type | A cardiac CT scan measuring calcification in the coronary arteries |
|---|---|
| Level of evidence | Strong — one of the strongest available predictors of cardiovascular risk |
| Target group | People with intermediate cardiovascular risk based on traditional risk factors |
| Result | A numerical index (the Agatston score) — zero means no detectable calcification |
| Radiation exposure | Low dose, comparable to a few standard X-rays |
| Status | A diagnostic test, usually paid for out of pocket, not always reimbursed |
Understand
Overview
A coronary artery calcium (CAC) score is a non-invasive cardiac CT scan that measures the amount of calcified atherosclerotic plaque in the coronary arteries, expressing the result as a numerical index (the Agatston score). Unlike a standard lipid panel, which assesses risk factors indirectly, CAC directly visualizes and quantifies atherosclerosis that is already present in the vessels supplying the heart.
A study by Budoff and colleagues, one of the largest observational studies in this area, found a strong, graded association between CAC score and long-term cardiovascular mortality risk — people with a score of zero had very low risk over long-term follow-up, while a high CAC score identified a group at significantly elevated risk, often underestimated by traditional risk factors alone.
Who can genuinely benefit from this? People with intermediate cardiovascular risk based on traditional risk factors (age, cholesterol, blood pressure, smoking), for whom a CAC score can help make a more informed decision about the intensity of prevention, including whether to start statin therapy. The test is not usually recommended routinely for people at clearly low or clearly high risk, where the treatment decision is already clear enough without an additional test.
Mechanism of action
Calcification in the coronary artery wall forms as part of the atherosclerotic process, in which the body responds to damage and inflammation in the atherosclerotic plaque by depositing calcium — a process analogous to scar formation. CT, thanks to the high radiological density of calcium compared with surrounding soft tissue, allows precise localization and measurement of these calcifications without the need for contrast dye or an invasive procedure.
The CAC score reflects the cumulative, years-long atherosclerotic burden on the coronary arteries, making it a direct, anatomical measurement of disease, unlike traditional risk factors, which only statistically predict the likelihood of its occurrence. A score of zero, however, doesn't mean a complete absence of future risk — it means no detectable calcification at the time of the scan, which in younger people with active risk factors may change in subsequent years.
Calcium deposition in atherosclerotic plaque
The body responds to damage in the atherosclerotic plaque by depositing calcium, analogous to scar formation.
Detection via high radiological density
CT detects calcification thanks to its markedly higher density compared with surrounding soft tissue.
Reflection of cumulative atherosclerotic burden
The CAC score shows the direct, anatomical effect of a years-long atherosclerotic process.
Evidence: strong — based on 1 study in this database.
Benefits
Common myths
MythA CAC score of zero means coronary artery disease will never develop.
FactA score of zero means no detectable calcification at the time of the scan, not a guarantee of no future risk — in younger people with active risk factors, this can change in subsequent years.
MythCAC should be a routine test for every adult.
FactThe test is most valuable in people with intermediate cardiovascular risk — in people at clearly low or high risk, the treatment decision is usually clear without an additional test.
Practice
Frequently asked questions
Mainly middle-aged people with intermediate cardiovascular risk based on traditional risk factors, for whom the result can help make a more informed treatment decision, ideally after consulting a doctor.
It usually doesn't require special preparation or contrast dye, though it's worth avoiding caffeine right before the scan if the facility recommends it.
Yes — the amount of calcification in the coronary arteries usually increases with age, especially with untreated risk factors, so the scan may be repeated after a few years if the risk profile changes.
What to combine with
Good combinations
Lipid Panel — The CAC result is often interpreted together with a lipid panel and other traditional cardiovascular risk factors
Safety
Side effects & contraindications
Possible side effects
Low dose of ionizing radiation
Contraindications
Pregnancy — due to exposure to X-ray radiation
Is it worth taking?
Who it's for
- People with intermediate cardiovascular risk considering more intensive prevention
- People who want a direct, anatomical picture of the state of their coronary arteries
Not for
- Pregnancy — due to exposure to X-ray radiation
Evidence
Worth knowing
The CAC score is expressed as the Agatston score, named after the radiologist who developed this measurement method in the 1990s.
The radiation dose in a CAC scan is low, comparable to a few standard X-rays.
Studies
A score of zero on a coronary artery calcium scan identified a group at very low long-term cardiovascular mortality risk, while a high score indicated significantly elevated risk, often underestimated by traditional risk factors alone.
Budoff MJ et al., Journal of the American College of Cardiology, 2007
Long-term prognosis associated with coronary calcification: observations from a registry of 25,253 patients
Strong evidenceBudoff MJ, Shaw LJ, Liu ST, et al. · Journal of the American College of Cardiology · 2007
A large observational study showing a strong, graded association between coronary artery calcium score and long-term cardiovascular mortality risk.
View studySources & bibliography
Citations are illustrative for this demo version and require full bibliographic verification by the editorial team before production publication.
Compare with similar entries
About the authors of this entry
Author
dr Piotr ZielińskiEndocrinologist
Piotr reviews content on hormones, metabolic health and supplement pharmacology.
131 publications on this site
Medical review
dr Anna KowalczykEditor-in-Chief, Molecular Biology
Anna oversees the editorial process and scientific review of every publication in the knowledge base. She previously researched autophagy and mitochondrial biology.
50 publications on this site
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Comments (2)
- KW
Kasia W. 2 weeks ago
Very clearly explained, especially the interactions section — I hadn't seen it laid out this well anywhere else.
- MT
Marek T. a month ago
Are you planning to update this with the newest study from this year? I saw an interesting meta-analysis.