Coronary Calcium Score (CAC): What a Heart CT Calcium Scan Shows
What the coronary calcium score is, what the Agatston numbers mean, who it genuinely helps decide about statins, and who does not need it.
Contents
The coronary artery calcium score is the result of a fast, non-contrast CT of the heart that measures calcium in the walls of the coronary arteries. Calcium builds up in atherosclerotic plaque, so its amount shows how much atherosclerosis a person has actually accumulated — not how much their risk factors predict. The test is not for everyone: it earns its place where standard risk scoring leaves the statin decision unclear.
What the test actually measures
Standard risk scoring — from age, blood pressure, cholesterol and smoking — predicts risk for the average person with those numbers. But two people with identical figures can have completely different real atherosclerosis. Coronary calcium looks not at the prediction but at the fact: how much plaque is already in the heart's arteries.
Calcification is part of the healing of an atherosclerotic plaque, so calcium serves as a marker of its presence. The CT scanner counts these deposits and gives a score on the Agatston scale. It is an integrated summary of everything that has happened to the vessels over a lifetime, including factors that ordinary calculators do not capture.
Читайте также: Heart Attack & Stroke Risk Calculator (SCORE2)
How to read the result
| CAC score | Meaning | Risk |
|---|---|---|
| 0 | No calcium found | Very low over 5–10 years |
| 1–99 | Mild calcification | Slightly raised |
| 100–399 | Moderate calcification | Moderately high |
| 400 and above | Extensive calcification | High |
Age matters as much as the score. A CAC of 100 in a seventy-year-old is near-typical for their years, while the same score in a forty-five-year-old means unusually early, aggressive atherosclerosis and changes management more.
Who it helps, and who it does not
The main use is intermediate or borderline calculated risk, where the statin decision hangs in the balance. Here the result genuinely shifts it: a CAC of 0 is a reason to wait, a high score a reason to start without delay.
Who does not need it:
- people with established cardiovascular disease — statins are already indicated, and calcium adds nothing;
- young people at clearly very low risk without risk factors — there is nothing to look for;
- people at clearly very high risk (for example, familial hypercholesterolaemia) — treatment starts regardless of the score.
What to do with the result
The coronary calcium score is useful precisely because it turns an abstract risk percentage into a measured fact, helping avoid over-treating and under-treating alike. But it is still one piece of the picture: it is read alongside cholesterol, blood pressure and overall risk — and alongside a doctor.
Читайте также: Cholesterol: LDL, HDL and what actually lowers risk
Читайте также: Statins: benefits and myths — who needs them and what not to fear
FAQ
What is the coronary artery calcium score?+
It is the result of a non-contrast CT of the heart that measures calcium in the walls of the coronary arteries on the Agatston scale. Calcium builds up in atherosclerotic plaque, so its amount reflects the total burden of atherosclerosis accumulated over a lifetime — something cholesterol alone does not show.
What do CAC scores mean?+
0 means no calcium and very low risk for the coming years (the 'power of zero'). 1–99 is mild, 100–399 moderate, and 400 or above is extensive calcification and high risk. The higher the score and the younger the person, the more it changes management.
Who should have this test?+
People at intermediate or borderline calculated risk when it is unclear whether to start statins. The result refines the decision: a CAC of 0 lets you defer medication, a high score is a reason to start. It is not needed in known cardiovascular disease, where statins are already indicated.
Is the radiation dose dangerous?+
The dose for a calcium scan is low — about 1 mSv, comparable to a few months of natural background radiation and less than many other CT scans. No contrast is injected, no preparation is needed, and the scan takes minutes.
Can a CAC of 0 guarantee everything is fine?+
Almost, but not absolutely. A zero score means very low risk over 5–10 years, but it does not see soft, non-calcified plaque. In smokers and people with diabetes or a very early family history, a zero score is interpreted more cautiously.
References
- 1.Greenland P et al. Coronary Calcium Score and Cardiovascular Risk. J Am Coll Cardiol, 2018
- 2.Detrano R et al. Coronary Calcium as a Predictor of Coronary Events in Four Racial or Ethnic Groups (MESA). N Engl J Med, 2008
- 3.Arnett DK et al. 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease. Circulation, 2019
- 4.Blaha MJ et al. Role of Coronary Artery Calcium Score of Zero and Other Negative Risk Markers (MESA). Circulation, 2016
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