You can have perfect cholesterol numbers and still have a heart attack. This uncomfortable fact has haunted cardiology for decades. The coronary artery calcium (CAC) score exists to close that gap — and it's one of the most powerful risk reclassification tools in cardiovascular medicine.

What it is

A CAC scan is a non-contrast, low-dose CT of your heart that takes about 10 minutes. It doesn't require fasting, injection, or preparation. The scanner detects calcium deposits in your coronary arteries — the arteries that supply blood to your heart muscle. These deposits are a direct, physical marker of atherosclerosis.

The result is an Agatston score, named after the cardiologist who developed it:

  • CAC = 0: No detectable calcium. In the MESA study, the 10-year rate of heart attack, stroke or cardiovascular death was about 3% — lower in younger people, higher in the elderly. This is remarkably reassuring — a CAC of zero in an asymptomatic person is one of the strongest negative predictors in cardiology.
  • CAC 1–100: Mild calcification. Risk is elevated. Lifestyle intervention, statin discussion.
  • CAC 100–400: Moderate. Aggressive lipid-lowering therapy. Consider additional imaging.
  • CAC >400: Extensive. High risk. Intensive treatment. Further cardiac work-up may be considered, particularly if there are symptoms.
0CAC zero ≈ 3% 10yr risk (MESA)
>400High risk — treat promptly
10 minScan duration

Why it matters: the reclassification effect

Traditional cardiovascular risk calculators — like SCORE2 in Europe or the ACC/AHA Pooled Cohort Equation in the US — use age, sex, blood pressure, cholesterol, smoking, and diabetes to estimate your risk. They're useful, but they operate on population averages. They can't see your arteries.

CAC scanning adds a direct measurement. And it routinely reclassifies patients. Someone who looks "intermediate risk" on the calculator but has a CAC of zero can often safely defer statin therapy. Someone who looks "low risk" but has a CAC of 250 has a strong case for lipid-lowering therapy.

Data from the MESA study, which enrolled 6,814 adults, showed that adding CAC to standard risk factors moved more than half of participants at intermediate risk (about 55%) into either the high-risk or the low-risk category over a median follow-up of 5.8 years. That's not a marginal improvement. That's transformative.

A CAC of zero doesn't mean you're immune. But it means your near-term risk is remarkably low. For someone deciding whether to start a statin, that information can change the conversation entirely.

Who should get one — and who shouldn't

CAC scoring is most useful for people in the intermediate risk category — those where the traditional risk calculator leaves you unsure. The ESC gives it a Class IIb (level B) recommendation for exactly this group.

It is less useful in people who are clearly high risk (they need treatment regardless of their CAC), clearly low risk (a result is unlikely to change management), or under 40 (coronary calcium hasn't had enough time to develop even in people with risk factors).

What this means for you

A CAC scan is worth discussing with your doctor if you are over 45 and your cardiovascular risk is intermediate or unclear — for example with elevated ApoB, Lp(a) above 50, SCORE2 in the high range, a family history of early cardiovascular disease, or hypertension combined with diabetes. The key question to ask beforehand: would the result change what you do? If the answer is yes, it's a 10-minute scan that can change your treatment trajectory for years.

References

  1. Budoff MJ, et al. Ten-year association of coronary artery calcium with atherosclerotic cardiovascular disease (ASCVD) events: the Multi-Ethnic Study of Atherosclerosis (MESA). Eur Heart J. 2018;39(25):2401-2408.
  2. Polonsky TS, et al. Coronary artery calcium score and risk classification for coronary heart disease prediction. JAMA. 2010;303(16):1610-1616.
  3. Visseren FLJ, et al. 2021 ESC Guidelines on cardiovascular disease prevention. Eur Heart J. 2021;42(34):3227-3337.
  4. Budoff MJ, et al. Long-term prognosis associated with coronary calcification: observations from a registry of 25,253 patients. J Am Coll Cardiol. 2007;49(18):1860-1870.
Prof. Dr. med. Markus Guba

Head of Liver Surgery and Transplantation at LMU University Hospital Munich. Edits this independent journal in a private capacity; views are his own. About →

This article is general information and not individual medical advice. Decisions about tests and treatment belong in a conversation with your own physician.