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What is a Cardiac Calcium Scan?

For your heart to be healthy, the arteries that nourish your heart (the coronary arteries) need to be healthy, too. And a test called a cardiac calcium scan may help.

Jay S. Leb, MD, a cardiothoracic imaging specialist at Columbia, explains what a cardiac calcium scan is and when it can provide useful heart health data for some patients and their doctors.

What is a cardiac calcium scan?

A cardiac calcium scan, also known as a coronary artery calcium (CAC) scan, is a non-invasive medical test used to detect calcium deposits in the coronary arteries, which are the vessels that supply blood to the heart muscle. The test uses computed tomography technology, commonly called a CT scan, to produce detailed images of the heart and blood vessels. The images allow us to detect and quantify calcium buildup. The test is a non-invasive, relatively quick exam that requires no significant patient preparation.

Why calcium? Isn’t cholesterol the usual culprit when it comes to coronary artery disease?

While cholesterol is indeed a major player in coronary artery disease, calcium buildup in the coronary arteries is a key indicator of how much cholesterol-based plaque has developed. As plaque forms in the coronary arteries, the body will, over time, stabilize these plaque areas by causing them to calcify. We call this process calcification.

The areas of calcium are easily detected on CT scans, as opposed to the non-calcified plaque itself, which is harder to image. A higher coronary artery calcium score means more plaque is present in the coronary arteries. This means a higher risk of cardiac events, even if cholesterol levels in the blood seem normal.

So, to be clear, calcium does not drive coronary artery disease. Cholesterol and the plaque it forms drive the disease. We just use calcium as a marker of existing plaque buildup.

Could you say a bit more about the role of coronary arteries?

Certainly. The coronary arteries are the blood vessels located on the surface of the heart. These vessels supply oxygen- and nutrient-rich blood to the heart. Since the heart constantly pumps blood to the rest of the body, it needs its own reliable blood supply to function.

Without adequate blood flow through the coronary arteries, the heart muscle does not get enough oxygen and nutrients. Healthy coronary arteries are essential for maintaining a properly functioning heart and body.

What are the potential harms of coronary artery disease?

When we talk about heart disease and specifically coronary artery disease, we are talking about a condition where the coronary arteries become narrowed or blocked with cholesterol-based plaque. This can lead to chest pain, which is very uncomfortable, or a heart attack, which can be fatal.

Also, a chronic reduction in blood flow to the heart will weaken the heart muscle, impairing its ability to pump effectively. Additionally, damaged heart tissue, which can result from a heart attack, can disrupt the electrical signals in the heart. This can lead to irregular heartbeats, which can be life-threatening.

What does your calcium score mean?

In addition to images of your coronary arteries, a calcium scan will give you a calcium score. A higher calcium score indicates a greater risk for coronary artery disease. This table summarizes the scale used by radiologists such as Dr. Leb.

Score Amount of Calcified Plaque Risk Action to Consider
0 None Low No Treatment
1-10 Minimal Low Lifestyle modification
11-100 Mild Mild Lifestyle modification; discuss medication with your doctor
101-400 Moderate Moderate Lifestyle modification; medication; discuss further testing
Over 400 Substantial High Lifestyle modification; aggressive medication; likely further testing

When is a calcium scan needed? Why not make it part of annual recommended care, like a mammogram?

A calcium scan is warranted only in specific clinical situations—typically when a person is at low-intermediate risk for coronary artery disease, and the results of the scan could change how we manage the condition: for example, deciding whether to start statin therapy. Patients between the ages of 40 and 70 who have risk factors like family history, smoking, high blood pressure, high cholesterol, diabetes, obesity, or a sedentary lifestyle should be considered for a calcium scan.

There are a couple of reasons calcium scans are not routinely performed on all patients. One is the risk of radiation exposure, which is low but not zero. For most patients, the cancer risk from this small dose is negligible, but it is still a consideration, especially for younger patients or those needing repeated scans.

Another reason is the limited usefulness of the scan for very low- and high-risk patients. In the case of very low-risk patients, the scan is unlikely to change clinical decisions. In the case of high-risk patients, we usually recommend interventions such as statins (a class of cholesterol-lowering drugs) and lifestyle changes. Again, the scan would not change these recommendations.

Are there any other limitations or downsides to a cardiac calcium scan?

Occasionally, the calcium scan can detect calcium deposits that do not necessarily indicate serious heart disease. For example, a small deposit that does not block blood flow. These findings can lead to unnecessary worry or follow-up tests.

It is also true that the lack of calcium in the arteries does not exclude the possibility of having significant non-calcified plaque. We often see this in younger patients, where the plaque has not had time to calcify.

And let me add this: A calcium score is just one measure among many factors in assessing cardiovascular risk. It does not replace a thorough evaluation by a skilled doctor who can assess your overall cardiovascular risk and health.

References

Jay S. Leb, MD, is an assistant professor of radiology at the Columbia University Vagelos College of Physicians and Surgeons, with subspecialty training in cardiothoracic imaging.