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. Your 10-year cardiovascular event risk is under 2%. 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. Aggressive treatment. Referral for further cardiac workup including stress testing or CTA.
0CAC zero = <2% 10yr risk
>400High risk — act now
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 needs aggressive treatment immediately.

Data from the MESA study — following over 6,800 participants for more than 15 years — showed that CAC scoring reclassified 50% of intermediate-risk patients into either high-risk or low-risk categories. 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 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 (the pre-test probability is so low that a finding would likely be false), or under 40 (coronary calcium hasn't had enough time to develop even in people with risk factors).

At Health Detectors

CAC scoring is part of the CARDIO module. It's recommended for patients over 45 with intermediate cardiovascular risk — which means elevated ApoB, Lp(a) above 50, SCORE2 in the high range, family history of early CVD, or hypertension with diabetes. It's a 10-minute scan that can change your treatment trajectory for years.

References

  1. Blaha MJ, et al. Role of coronary artery calcium score in cardiovascular risk assessment (MESA). Circulation. 2019;139(2):253-263.
  2. Visseren FLJ, et al. 2021 ESC Guidelines on cardiovascular disease prevention. Eur Heart J. 2021;42(34):3227-3337.
  3. Budoff MJ, et al. Long-term prognosis associated with coronary calcification. J Am Coll Cardiol. 2007;49(18):1860-1870.