A coronary calcium scan is a quick CT scan that uses a small amount of X-ray radiation to look for hardened calcium deposits in the arteries that supply your heart. These deposits are a sign of plaque buildup and can help estimate future heart disease risk. The scan produces a calcium score, which a healthcare professional considers alongside your cholesterol, blood pressure, age, family history, and other risk factors.
A coronary calcium scan is also called a coronary artery calcium (CAC) scan or cardiac calcium scoring test. It can help identify signs of coronary artery disease before symptoms develop and provide additional information when deciding how to prevent a future heart attack. However, it is not necessary for everyone, and its results do not provide a complete picture of heart health.
What does a coronary calcium scan look for?
The scan looks for calcium deposits in the coronary arteries, which carry oxygen-rich blood to the heart muscle. These deposits can form as fatty substances, cholesterol, and other materials build up in artery walls over time. This buildup is called plaque, and the underlying process is known as atherosclerosis.
Some plaque becomes calcified, meaning it contains hardened calcium deposits that can be detected on a CT scan. Their presence provides evidence of coronary artery disease and can help estimate future cardiovascular risk. According to Mayo Clinic, calcium scan results may help healthcare professionals assess heart attack risk and plan preventive care.
The test is usually performed without injecting contrast dye into a vein. It creates detailed images of the heart arteries using X-rays and specialized computer processing. The scan is noninvasive, meaning it does not require a catheter or surgical procedure.
Who may benefit from a coronary calcium scan?
A coronary calcium scan is mainly used for adults who do not have diagnosed coronary artery disease but would benefit from a clearer assessment of their future heart disease risk. It may be particularly helpful when a person's estimated risk is not clearly low or high and the healthcare professional is uncertain whether cholesterol-lowering medication would be appropriate.
The 2026 cholesterol guideline from the American College of Cardiology and the American Heart Association recommends considering CAC testing for men aged 40 and older and women aged 45 and older with borderline or intermediate estimated cardiovascular risk when the result could help guide a decision about cholesterol-lowering treatment.
A clinician may discuss this scan when factors such as cholesterol levels, blood pressure, diabetes, smoking, or a family history of early heart disease affect the overall risk assessment. The decision also depends on age, existing health conditions, current medication, and whether the scan is likely to change the prevention plan.
When is the scan less useful?
The test is not intended as routine screening for every adult. It may add little information when a person's risk and treatment plan are already clear. It is also generally less useful for people who already have diagnosed coronary artery disease or have had a heart attack, coronary stent placement, or coronary artery bypass surgery.
People who have chest pain or other symptoms that could indicate a heart problem usually need an appropriate diagnostic assessment rather than a calcium scan alone. A calcium score is primarily a tool for estimating risk and supporting prevention decisions, not for determining the cause of current symptoms.
What happens during the scan?
A coronary calcium scan is usually performed in a hospital or outpatient imaging center. The procedure is generally painless and takes around 10 to 15 minutes, although the total appointment may take longer.
- Preparation: You may be asked to remove jewelry near your chest and change into a medical gown. Instructions about food, drinks, caffeine, and smoking vary by facility, so follow the directions you receive before the appointment.
- Heart monitoring: Small adhesive electrodes are placed on your chest to record your heartbeat. This helps synchronize image collection with the heart's movement.
- Positioning: You lie on your back on a movable table that slides into a CT scanner. The machine takes images while you remain still and briefly hold your breath when instructed.
- Image review: A radiologist or another appropriately qualified healthcare professional reviews the images and prepares a report for the clinician who requested the test.
The American Heart Association explains that the scan uses electrodes to monitor the heart's electrical activity and generally requires only brief periods of breath-holding. Most people can return to their usual activities immediately afterward unless their healthcare team advises otherwise.
What does the coronary calcium score mean?
The scan produces a numerical result commonly called the Agatston score. This score estimates the amount and density of calcified plaque visible in the coronary arteries. In general, a higher score indicates more calcified plaque and is associated with a higher risk of future cardiovascular events.
A score of zero means the scan did not detect calcified plaque in the coronary arteries. This is generally reassuring because it is associated with a lower risk of future heart disease. However, it does not guarantee that the arteries are completely free of plaque or that a heart attack cannot occur.
A score above zero indicates that calcium has been detected. The amount of calcium, the person's age, and other cardiovascular risk factors help determine the significance of that finding. A higher score may lead a clinician to recommend closer attention to prevention, including a review of cholesterol levels, blood pressure, lifestyle habits, and medication options.
Some reports also compare a person's score with results from people of a similar age and sex. This comparison can provide additional context, but neither the numerical score nor the percentile should be interpreted in isolation. The findings need to be considered alongside the person's full medical history and estimated cardiovascular risk.
Can a score of zero rule out heart disease?
No. A zero score means that the scan has not detected calcified plaque; it does not mean that every coronary artery is free of disease. Some plaque has not yet become calcified and may not be visible on this type of CT scan. This limitation can be especially relevant in younger adults, who may have coronary artery disease without detectable calcium.
According to RadiologyInfo.org, a calcium scan does not measure noncalcified plaque or show directly whether an artery is narrowed. It therefore cannot replace other investigations when symptoms, medical history, or examination findings suggest that a different test is needed.
What are the risks and limitations?
The main direct risk is exposure to a small amount of ionizing radiation from the CT scan. The actual dose depends on the scanner and imaging protocol. A healthcare professional can help weigh the possible benefit of the information against the radiation exposure, particularly when considering repeated scans. Anyone who is pregnant or might be pregnant should tell the healthcare team before the examination.
Another limitation is that the scan may not answer every question raised by a person's cardiovascular risk assessment. A high calcium score may prompt additional testing in some circumstances, but further investigations are not automatically necessary for everyone. The scan also does not directly measure the blood flow through the coronary arteries.
The test may be less helpful when a clinician already knows which treatment is appropriate. Availability and insurance coverage can also vary. For these reasons, it is best to discuss the purpose of the scan and how its results could affect care before arranging the examination.
What happens after the results are available?
Your healthcare professional will interpret the report alongside your cholesterol results, blood pressure, smoking history, diabetes status, family history, age, and other relevant factors. The result may support continuing your current prevention plan or considering changes to lifestyle measures or cholesterol-lowering medication.
A scan showing calcified plaque does not automatically mean that a procedure such as angioplasty or bypass surgery is needed. Decisions about further testing and treatment depend on the person's overall clinical picture, including whether symptoms are present and whether there is evidence of impaired blood flow.
A calcium scan is also not necessarily repeated on a fixed schedule. Whether another scan would provide useful information depends on the initial findings, the passage of time, and whether the result could change future decisions. A healthcare professional can explain what follow-up, if any, is appropriate.
How is a coronary calcium scan different from other heart tests?
A coronary calcium scan focuses on calcium deposits in the walls of the heart's arteries. It differs from other heart tests in what it measures and the questions it can answer.
- Cholesterol and blood tests: These measure substances or other markers in the blood that contribute to cardiovascular risk. They do not directly show calcified plaque in the arteries.
- Electrocardiogram (ECG or EKG): This records the heart's electrical activity. It does not measure coronary calcium.
- Coronary CT angiography: This uses CT imaging and injected contrast material to show the coronary arteries and assess features such as plaque and narrowing. It serves a different purpose from calcium scoring.
- Stress testing: These tests assess how the heart responds to exertion or medication that increases its workload. They may be used when clinicians need to evaluate possible problems with blood supply to the heart.
The most appropriate test depends on whether the goal is to estimate future cardiovascular risk, investigate symptoms, or assess a known heart condition. A clinician can help determine which approach is likely to provide useful information without unnecessary testing.