Heart disease can develop without obvious warning signs, leaving some people unaware of their cardiovascular risk. A specialised CT scan called a coronary artery calcium (CAC) scan can help doctors look for evidence of calcium deposits in the arteries supplying the heart and assess whether a person may face a higher risk of a future heart attack or other cardiovascular event.
However, the scan is not a crystal ball. It cannot predict with certainty who will have a heart attack, and it is not necessary for everyone. New research published in JAMA suggests that its greatest value may lie in helping doctors clarify risk in selected adults whose estimated likelihood of cardiovascular disease falls into an intermediate range.
What does a heart calcium scan detect?
A coronary artery calcium scan uses computed tomography (CT) imaging to detect and measure calcium deposits in the coronary arteries, which carry oxygen-rich blood to the heart muscle.
These deposits are a marker of calcified atherosclerotic plaque. Atherosclerosis occurs when plaque builds up inside artery walls, potentially narrowing the arteries and contributing to cardiovascular disease.
The scan produces a calcium score. In general, a higher score indicates a greater burden of calcified plaque and can signal a higher risk of future cardiovascular events.
A score of zero means no detectable coronary artery calcium was found. However, it does not rule out all coronary artery disease because the scan does not detect every type of plaque, including non-calcified plaque.
The scan therefore provides one piece of the cardiovascular risk picture rather than a complete assessment of heart health.
What did the new study find?
Researchers investigated whether adding coronary artery calcium scores to the PREVENT-ASCVD equations could improve estimates of a person's 10-year risk of atherosclerotic cardiovascular disease (ASCVD).
Published online on August 26, 2026, the study analysed data from 6,098 adults aged 45 to 79 who had no cardiovascular disease at the beginning of the study. Participants were drawn from the Multi-Ethnic Study of Atherosclerosis, a long-running US research project examining cardiovascular disease and its risk factors.
Over approximately 10 years of follow-up, 366 participants, or 6%, experienced an ASCVD event.
When researchers added CAC scores to the PREVENT-ASCVD risk equations, the model's ability to distinguish between people who did and did not experience cardiovascular events improved modestly. The change in the statistical discrimination measure was 0.02, while the categorical net reclassification improvement was 0.095.
The researchers found that the most meaningful improvement in risk classification occurred among people initially assessed as having borderline cardiovascular risk. The findings support selective use of calcium scoring rather than routine scanning across all risk groups.
Who may benefit most from the scan?
The study's findings are particularly relevant to people whose estimated cardiovascular risk does not clearly indicate whether preventive medication should be started.
Under the risk categories used in the study, a person's estimated 10-year ASCVD risk was classified as:
- Low risk: less than 3%
- Borderline risk: 3% to less than 5%
- Intermediate risk: 5% to less than 10%
- High risk: 10% or greater
For people at borderline or intermediate risk, a calcium score may provide additional information when a clinician and patient are uncertain about the next steps, including whether to begin cholesterol-lowering treatment.
Among participants classified as having borderline risk, the observed incidence of cardiovascular events differed according to their calcium scores. During follow-up, event rates were 1.9% among those with a score of zero, 3.9% among those with a score above zero but below 100, 7.4% among those scoring 100 to below 300, and 14.3% among those with a score of 300 or higher.
These figures illustrate how calcium scoring may help distinguish between different levels of risk within a group that initially appears to have a similar risk profile. They are study findings, not individual predictions, and should not be interpreted as the probability of a heart attack for every person with a particular score.
Does everyone need a heart calcium scan?
No. The research found that adding calcium scores across all risk groups produced only a modest overall improvement in risk prediction, with little or no change in some groups.
A scan may be worth discussing with a healthcare professional when a person's cardiovascular risk has been assessed using established factors but uncertainty remains about preventive treatment. The decision should take account of the person's medical history, risk factors, preferences and the potential value of the additional information.
A CAC scan also involves a small amount of radiation. Its cost, the possibility of incidental findings and whether the result would change clinical management are relevant considerations.
Importantly, a calcium score should not replace established cardiovascular risk assessment or routine preventive care. Blood pressure, cholesterol, diabetes, smoking, kidney function, family history and other relevant factors remain important when evaluating heart health.
What should you do if you are concerned about your heart?
People concerned about their cardiovascular risk should discuss their personal risk factors with a qualified healthcare professional rather than arranging a scan solely because of a headline or research finding.
A clinician can assess overall risk and determine whether additional testing, including a coronary artery calcium scan, is appropriate. Preventive measures such as not smoking, maintaining a balanced diet, staying physically active and managing blood pressure, cholesterol and diabetes remain important.
A calcium scan is a risk-assessment tool, not a guarantee that a heart attack will be detected in advance or prevented. A zero score does not eliminate cardiovascular risk, while a higher score does not mean that a heart attack is inevitable.
Anyone experiencing possible heart attack symptoms, such as chest pressure or discomfort, shortness of breath, or pain spreading to the arm, back, neck or jaw, should seek emergency medical attention rather than wait for a calcium scan.
Study details
- Journal: JAMA
- Study title: “Predictive Utility of Coronary Artery Calcium Score Added to the PREVENT Atherosclerotic Cardiovascular Disease Equations”DOI: 10.1001/jama.2026.13233
- Study population: 6,098 US adults aged 45 to 79 without cardiovascular disease at baseline.
- Main finding: Adding coronary artery calcium scores modestly improved overall cardiovascular risk prediction, with the most useful risk reclassification among selected people initially classified as having borderline risk.
- Source: Read the original study in JAMA.
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