Is a Coronary Artery Calcium Scan Right for You?

If you have high cholesterol and are unsure whether you need a statin, a coronary artery calcium (CAC) scan may help clarify your risk. The test measures calcified plaque in the coronary arteries—the arteries that supply blood to the heart. Plaque buildup, known as coronary artery disease, is a leading cause of heart attack.

For some people, the CAC scan helps answer a practical question: Do I really need cholesterol-lowering medication? In certain cases, it can tip the balance toward starting a statin—or support waiting and focusing on lifestyle changes instead.

You may have heard of the CAC scan by a different name: It’s also known as cardiac calcium scoring because it measures—or scores—plaque in the arteries. It’s an increasingly popular type of computed tomography (CT) scan that tripled in usage between 2006 and 2017, according to one study, and interest in it has continued to explode, says Antonio Giaimo, MD, a Yale Medicine cardiologist.

But whether it’s right for you—and how to interpret the results—requires an individualized discussion.

“A positive result should guide you, not define you,” says Andrew Levin, MD, a Yale Medicine cardiologist who researches how to better use CAC results in patient care. “It can help you assess how you can improve. I spend a lot of time talking to patients who have taken this test about their lifestyle. We talk about statins. These are things that can help you take control of your health,” he says.

A CAC scan is a quick, noninvasive CT scan of the chest that measures calcified plaque in the coronary arteries. These arteries supply blood to the heart. Plaque buildup—known as coronary artery disease—is a leading cause of heart attack. The test does not require contrast dye and typically takes about 15 minutes.

During the test, you lie on a table while electrodes are placed on your chest. The electrodes connect to an electrocardiogram (ECG), which times the images with your heartbeat.

The scan detects calcified (hardened) plaque in the coronary arteries. It does not measure “soft” plaque, an early stage of heart artery plaque that is particularly prevalent in people with risk factors such as smoking or diabetes, and may be present in young adults. Because soft plaque can still rupture and cause heart attacks, a low calcium score does not always mean low risk.

Results are reported as a calcium score, usually available within a few days. Scores are interpreted as follows:

• 0: No detectable calcified plaque. In many people, this suggests a low short-term (about 10-year) risk of heart attack. However, if high cholesterol goes untreated for long enough, lifetime risk increases.
• 1–100: Mild plaque. Any score above zero means there is evidence of coronary artery disease. Treatment decisions should be discussed with your doctor.
• 100–300: Moderate plaque, associated with a higher risk of a cardiovascular event in the next 3 to 5 years.
• 300 or higher: Significant plaque and high risk. Scores can reach into the thousands and may indicate risk comparable to someone who has already had a heart attack.

Your score is also compared with others of the same age, sex, and ethnicity.

“If you're 37 years old and you have a score of 2, that is highly concerning because it shows you've already developed calcified plaque,” says Dr. Giaimo. “You really have to work on stopping it from progressing.” Any score between 1 and 100 must be interpreted individually based on risk factors and age.

The CAC scan is generally intended for people who:

• Are between the ages of 40 and 75
• Have elevated cholesterol
• Have no symptoms of heart disease
• Are considered at intermediate risk for heart attack based on risk calculators
• Are unsure whether to start a statin

For example, a 50-year-old whose cholesterol is elevated and whose estimated 10-year heart attack risk is around 10% may be advised to consider medication. A CAC scan showing plaque may strengthen the case for starting a statin, Dr. Giaimo explains.

“There's a lot of data to support the utility of coronary calcium scoring in personalizing a risk assessment,” he says.

However, the scan is not recommended for:

• People with chest pain or other heart symptoms (they need diagnostic testing, not screening)
• People already known to be at high risk or diagnosed with coronary artery disease
• People at very low risk with no cardiovascular risk factors
• Pregnant women

In older adults, a score of zero may predict low short-term risk. In younger adults, even a low score can be more concerning because it suggests early plaque development. “There's the short-term end of it and the long-term. Both have to be part of the risk-benefit discussion with a doctor,” Dr. Giaimo says.

Although several professional societies support CAC scoring to guide treatment decisions, the U.S. Preventive Services Task Force (USPSTF) has stated that there is currently insufficient evidence to recommend it for widespread use in preventing cardiovascular events. One reason: It is not yet clear whether using CAC scans routinely reduces heart attacks or deaths.

The test also has limitations. It does not detect soft plaque, which may be more common in smokers and people with diabetes. In these groups, the scan may underestimate risk.

“The challenge for us is that sometimes we have a patient in front of us who is very high risk even if the calcium score is not elevated,” Dr. Giaimo says.

Another concern is the potential for anxiety in patients who have positive results. “The tool is meant to help improve preventative measures aimed at reducing the likelihood of heart attacks in the future, but a positive result can lead to significant patient anxiety,” Dr. Levin says.

In addition, 10% of CAC scans show findings unrelated to the heart, such as lung or thyroid nodules. Most of those findings are not dangerous, but they can lead to additional testing, Dr. Levin says.

Dr. Giaimo says a CAC screening should not routinely lead to further testing, such as stress tests or invasive procedures. But a person’s score can show how significant their cholesterol is and guide treatment. “The CAC scan is a screening tool that should motivate improvements in risk factors,” he says.

The radiation exposure from a CAC scan is relatively low—similar to that of a mammogram, Dr. Levin says.

For most people, especially if the scan is done only once, this level of radiation is not considered a significant health risk, Dr. Levin says. However, for people who have already had multiple CT scans or who are especially concerned about radiation exposure, this may factor into the decision.

Coverage varies. Some insurers do not cover the test because it is considered a screening tool. Out-of-pocket costs typically range from about $100 to $400, according to the American Heart Association. It’s important to check with your insurance provider beforehand.

You might consider discussing a CAC scan with your primary care provider if:

• You have high cholesterol
• You have risk factors such as high blood pressure, diabetes, or a family history of heart disease
• You are undecided about starting a statin

It’s important to remember that a CAC scan is intended for people who are “asymptomatic,” Dr. Giaimo says. The CAC scan is meant for risk stratification—not for diagnosing active symptoms. “Anyone who gets this test should not have any cardiovascular symptoms of concern,” Dr. Giaimo says.

A CAC score is not a diagnosis—it is one piece of information.

If your score is elevated, your doctor may recommend:

• Starting or intensifying statin therapy
• Improving diet and exercise habits
• Controlling blood pressure or blood sugar
• Avoiding tobacco

If your score is zero, your doctor may recommend continuing healthy lifestyle habits and reassessing risk over time.

Research suggests that knowing your score can motivate positive change. “Once there is hard evidence that plaque is present, people who might have been hesitant will now tend to be more likely to take medications to treat risk factors such as high blood pressure and cholesterol and change their lifestyle,” Dr. Levin says.

For the right patient, a CAC scan can provide clarity and help guide decisions about medication and prevention. But it is not a universal screening test. The most important step is not the scan itself—but the conversation that follows.