A cardio scan, most commonly referring to a coronary artery calcium (CAC) scan, is a quick CT scan that detects calcium buildup in the arteries supplying your heart. The scan takes pictures of your coronary arteries to find early signs of plaque, a mix of calcium, fat, and other substances that narrows blood vessels and leads to heart disease. The key benefit is timing: it can reveal coronary artery disease before you have any symptoms, giving you and your doctor a window to act.
What the Scan Actually Measures
Your heart’s arteries can accumulate plaque over years without causing chest pain or shortness of breath. As plaque hardens, calcium deposits form within it. A coronary calcium scan uses a series of low-dose X-rays (CT imaging) to photograph your heart’s arteries and spot those calcium deposits. The more calcium present, the more plaque has built up, and the higher your risk of a future heart attack.
The scan doesn’t require any injected dye or contrast. It’s a straightforward, non-invasive test that typically takes about 10 to 15 minutes. The radiation exposure is low, around 1 to 2 millisieverts, which is roughly comparable to a mammogram.
Understanding Your Score
After the scan, you receive a number called a calcium score (also known as an Agatston score). A score of zero means no detectable calcium in your coronary arteries, which is a strong indicator of low heart disease risk. As the number climbs, so does your risk.
The numbers carry real weight. A large study published in the New England Journal of Medicine found that people with scores between 101 and 300 had nearly 8 times the risk of a coronary event compared to those with no calcium. Scores above 300 raised that risk by a factor of almost 10. Even smaller increases matter: each time the calcium score doubled, the probability of a major coronary event rose by roughly 25%. These findings held across different racial and ethnic groups, with a doubling of the score increasing risk of any coronary event by 18 to 39% depending on the population studied.
Who Should Get One
A calcium scan isn’t recommended for everyone. It’s most useful for people whose heart disease risk falls in a gray zone, where standard risk factors like cholesterol, blood pressure, and family history don’t paint a clear enough picture. The 2019 ACC/AHA guidelines on cardiovascular prevention recommend calcium scoring for adults whose estimated 10-year risk of a cardiovascular event lands between 5% and 20%. That covers both borderline and intermediate risk groups.
Several international cardiology societies echo this guidance. Canadian guidelines advise the scan for adults 40 and older at intermediate risk, plus younger adults with a strong family history of early heart disease. Australian and New Zealand guidelines extend the recommendation to adults aged 45 to 75 at intermediate risk and to people with diabetes between ages 40 and 60. The common thread: the scan is most valuable when your risk profile is uncertain and a concrete number could change the treatment plan.
If you’re already at high risk (established heart disease, very high cholesterol, or diabetes with other risk factors), the scan likely won’t change your treatment. And if you’re young with no risk factors, there’s little calcium to find.
Calcium Scan vs. CT Angiography
A basic calcium score scan and a coronary CT angiography (CTA) are related but different tests. The calcium scan detects only calcified plaque, the hard, mineral-dense deposits. It’s inexpensive, fast, and doesn’t require contrast dye. A CT angiography goes further: it uses injected contrast to visualize both calcified and non-calcified (soft) plaque, and it shows how much the arteries have narrowed.
Soft plaque matters because certain types of it are more likely to rupture and trigger a heart attack. CT angiography can identify high-risk plaque features like abnormal artery remodeling and low-density deposits that a standard calcium scan would miss entirely. Your doctor might recommend a CTA if your symptoms or calcium score suggest the need for a more detailed look at your arteries.
What to Expect During the Test
Preparation is minimal. You’ll typically be asked to avoid caffeine for a few hours beforehand, since caffeine can raise your heart rate and affect image quality. No fasting is usually required. During the scan, you lie on a table that slides into the CT machine. Sensors are placed on your chest to synchronize the images with your heartbeat. You’ll be asked to hold your breath for a few seconds at a time while the scanner captures images. The entire process, from arriving to walking out, is usually under 30 minutes.
Cost and Insurance Coverage
Here’s the frustrating part: despite strong clinical evidence supporting its use, nearly all insurance payers, including Medicare, still deny coverage for calcium scoring when it’s used for primary prevention in people without symptoms. The American Heart Association has called on insurers to change this policy, noting that cost barriers disproportionately reduce access for women, Black individuals, and people in lower-income areas.
The good news is that many hospitals and imaging centers have responded by dropping their prices significantly. Out-of-pocket costs at these facilities typically range from $50 to $100, making it one of the more affordable cardiac tests available. If your doctor recommends one and insurance won’t cover it, it’s worth asking about self-pay pricing, which is often much lower than the listed rate.