Coronary Calcium Score (CAC): The 10-Minute CT Scan That Sees Your Heart Disease Decades Before a Heart Attack

A coronary artery calcium (CAC) score — also called a heart scan, calcium-score CT, or Agatston score — is a specialized, non-contrast CT scan of the chest that quantifies the calcified plaque in the coronary arteries. It takes about 10 minutes, costs roughly $100 to $200 out of pocket in the United States, uses a radiation dose similar to a mammogram, and returns a single number from 0 upward. That number — the Agatston score — is one of the strongest long-range predictors of cardiovascular events available in clinical medicine.

Because calcium in the coronary arteries is visible only after atherosclerotic plaque has been forming for years, a CAC score shows whether your heart disease has already started and how advanced it is. A score of zero in a 55-year-old is one of the most reassuring numbers in medicine; a high score should re-order priorities.

What CAC Scoring Measures
How the Scan Works
Interpreting Your Score
Age and Sex Percentiles
Who Should Consider CAC Testing
Limits — Soft Plaque Invisibility
What to Do with Your Result
Connections
Featured Videos

What CAC Scoring Measures

Atherosclerosis progresses through stages: lipid accumulation in the artery wall, inflammation, fibrous-cap formation, and eventually calcification. Calcium is deposited in mature plaques as a stabilization response; the total volume of coronary-artery calcium is a direct quantitative index of the total atherosclerotic burden a person has accumulated. Critically, calcification does not happen overnight — a score of zero implies no substantial atherosclerosis, while a rising score documents progression.

How the Scan Works

The patient lies on a CT scanner bed, EKG leads are placed, and the scanner acquires a few gated images timed to heart rhythm. No intravenous contrast is used. Software identifies calcified voxels in the coronary arteries and computes the Agatston score from their density and area. Total scan time is typically 10 minutes, radiation exposure is roughly 1 mSv (comparable to one year of background radiation or a mammogram).

Interpreting Your Score

0 — No detectable coronary calcium. Very low 10-year risk of cardiovascular events. The “warranty” may last 5–10 years before re-scanning.
1–99 — Mild plaque. Moderate risk; primary prevention intensifies.
100–299 — Moderate plaque. Strong indication for statin therapy regardless of LDL level in most guidelines.
300–999 — Significant disease. Aggressive risk reduction.
≥1000 — Extensive disease. Cardiology evaluation.

Age and Sex Percentiles

Absolute score alone can be misleading. A score of 100 in a 45-year-old (95th percentile for age) is far more alarming than the same score in a 70-year-old (below 50th percentile). Radiology reports typically include both absolute score and age/sex percentile. Percentile-based interpretation using the MESA risk-score calculator is the standard.

Who Should Consider CAC Testing

Current guidelines most clearly support CAC scoring for:

Adults 40–75 with intermediate 10-year ASCVD risk where statin decision is uncertain.
People with family history of premature CAD.
People with elevated Lp(a) or elevated ApoB.
Patients with metabolic syndrome, type 2 diabetes, or inflammatory disease.
Asymptomatic people over 40–50 seeking to personalize prevention.

CAC scoring is not recommended as a screening tool in very young adults (it usually returns zero regardless of risk) or in patients with already established CAD (where the decision to treat is already made).

Limits — Soft Plaque Invisibility

CAC imaging visualizes only calcified plaque. Early, non-calcified “soft” plaque — which is also dangerous and can rupture — is invisible. A score of zero does not mean zero disease; it means zero calcified disease. In higher-risk patients, coronary CT angiography (CCTA) visualizes both calcified and non-calcified plaque and is increasingly used for comprehensive assessment.

What to Do with Your Result

Score 0 and low other risk factors: Maintain lifestyle; consider re-scan in 5–10 years.
Score 1–99: Intensify lifestyle, optimize ApoB, consider statin if other factors concerning.
Score ≥100: Statin therapy typically indicated. Aggressive ApoB lowering. Lifestyle optimization.
High score + symptoms (chest discomfort, unusual breathlessness): Cardiology evaluation; functional testing or CCTA may be appropriate.

Research Papers and References

The following are curated PubMed literature searches covering the evidence base for coronary calcium score testing, interpretation, and clinical management. Each link opens a live, filtered PubMed query so the results stay current as new studies are indexed.