A cardiac scoring test, formally called a coronary artery calcium (CAC) scan, is a quick CT scan of your heart that measures how much calcified plaque has built up in your coronary arteries. The scan takes about 10 minutes, requires no injections or dye, and produces a number called an Agatston score that reflects your risk of a future heart attack or stroke. It’s primarily used for people at intermediate cardiovascular risk, where the results can tip the balance on whether preventive treatment like a statin is worth starting.
How the Scan Works
The test uses a non-contrast CT scanner synced to your heartbeat through EKG electrodes on your chest. Because the scan is timed to your heart’s electrical activity, the images capture your coronary arteries with minimal motion blur. No contrast dye is injected, which keeps the procedure simple and avoids the allergic reactions or kidney concerns that come with contrast-based imaging.
The scanner detects calcium deposits in the walls of your coronary arteries. Calcium in these arteries is a reliable marker of atherosclerosis, the slow buildup of plaque that narrows blood vessels over decades. After the images are captured, software measures each deposit’s size and density, then multiplies the two together to produce the Agatston score. A larger or denser deposit scores higher. All the individual deposits across your coronary arteries are added up into one total number.
What the Score Means
Your Agatston score falls into a risk category that helps your doctor gauge how much plaque has accumulated:
- 0 (very low risk): No detectable calcified plaque. Your likelihood of a major cardiac event over the next several years is very low, around 0.5% over 3.5 years in one large study.
- 1 to 99 (mildly increased risk): A small amount of plaque is present. This signals early atherosclerosis and typically prompts a conversation about cholesterol-lowering treatment.
- 100 to 299 (moderately increased risk): A meaningful plaque burden exists. More aggressive cholesterol management is generally recommended at this level.
- 300 or higher (moderate to severe risk): Significant plaque buildup. In the same study, patients scoring 400 or above had a 6.8% rate of major cardiac events over 3.5 years, compared to 1.9% for those scoring 1 to 399.
Scores are also compared against percentiles for your age, sex, and race. A score of 150 carries different implications for a 45-year-old than for a 75-year-old, because some coronary calcium accumulates naturally with age. If your score lands above the 75th percentile for your demographic group, that’s treated as an additional red flag regardless of the raw number.
Who Should Get the Test
The 2019 ACC/AHA prevention guidelines give their strongest endorsement for using the CAC scan in people at intermediate cardiovascular risk, roughly a 7.5% to 20% estimated chance of a heart attack or stroke over the next 10 years. For these patients, the score can resolve uncertainty about whether to start a statin. If you and your doctor are on the fence about medication after reviewing your cholesterol, blood pressure, family history, and other risk factors, the calcium score can push the decision in a clear direction.
A 2022 expert consensus pathway expanded the recommendation slightly, suggesting the scan for anyone with borderline or intermediate risk where either the clinician is uncertain or the patient is hesitant about starting statin therapy. The test is less useful at the extremes. If your risk is already clearly high (existing heart disease, very elevated cholesterol, diabetes), treatment is warranted regardless of the score. If your risk is very low, the scan is unlikely to change anything.
What to Expect During the Scan
The scan itself is painless and fast. You’ll lie on a table that slides into a CT scanner, and EKG electrodes will be placed on your chest to sync the imaging with your heartbeat. A blood pressure cuff may also be used. The actual imaging takes roughly 10 seconds of breath-holding, and the full appointment is usually done within 10 to 15 minutes.
Preparation is minimal compared to other cardiac tests. You don’t need to fast, and no IV or contrast dye is involved. Some facilities ask you to avoid caffeine for a few hours beforehand, since a slower, steadier heart rate produces cleaner images, though preparation requirements vary by center. Wear comfortable clothing without metal snaps or zippers near your chest.
Radiation exposure is low. The median effective dose is about 2.3 millisieverts, roughly equivalent to a few months of natural background radiation. Doses can range from less than 1 to about 10.5 millisieverts depending on the scanner and protocol, but most modern facilities keep it at the lower end.
Cost and Insurance Coverage
A CAC scan typically costs between $75 and $300 out of pocket. Most insurance plans, including Medicare, do not cover it because it’s considered a screening test rather than a diagnostic one. Some facilities advertise a flat rate, often around $100 to $150, paid before the appointment. Because the price is relatively low and the scan doesn’t require contrast or sedation, it’s one of the more affordable cardiac imaging options available.
What a Zero Score Does and Doesn’t Tell You
A score of zero is reassuring but not a guarantee. It means no calcified plaque was detected, and your short-term risk of a cardiac event is very low. For many patients, a zero score is enough to delay statin therapy and focus on lifestyle measures instead, with a plan to reassess in five to ten years.
However, the scan only detects calcified plaque. Younger plaque that hasn’t yet hardened, sometimes called “soft plaque,” won’t show up. In one study of 367 patients with a zero calcium score who went on to have a contrast-enhanced CT angiogram, 9.3% turned out to have coronary plaques, some of them causing significant narrowing. This doesn’t mean a zero score is meaningless. It means the test is best interpreted alongside your full risk profile rather than treated as a standalone all-clear.
What Happens After a Positive Score
If your score is above zero, your doctor will use it alongside your other risk factors to set cholesterol targets and decide on treatment intensity. For mild scores (1 to 99), the general target is getting LDL cholesterol below 100 mg/dL. For moderate scores (100 to 299) or scores above the 75th percentile, the target drops to below 70 mg/dL. For high scores above 400, some guidelines push the goal to below 50 mg/dL.
Statins are the first-line medication for most people with a positive score. Both commonly prescribed high-potency statins are now available as generics, making them affordable. In many cases, a statin combined with a second cholesterol-lowering medication can reduce LDL cholesterol by about 50% within six weeks. A follow-up blood test within three months checks whether the medication is hitting target.
Beyond medication, the standard recommendations include reducing saturated fat intake, increasing physical activity, quitting smoking, and managing blood pressure and blood sugar if either is elevated. A positive calcium score doesn’t mean a heart attack is imminent. It means atherosclerosis is present and worth treating aggressively to slow or potentially reverse its progression. The score gives you a concrete, visual piece of evidence that plaque is building, which for many people makes the case for lifestyle changes and medication more compelling than abstract risk percentages alone.