Coronary Artery Calcium (CAC) Test

What is a CAC Test?

A CAC test, also called a heart scan, is a CT scan of your heart done with a multidetector CT (MDCT) that takes detailed images of the arteries that supply blood to the heart muscle. The images show calcium deposits you may have in your coronary arteries. Higher amounts of calcium are associated with more severe disease in the heart arteries.

coronary arteries

See an illustration of coronary arteries

Why do people have it done?

A CAC test can measure the amount of calcium in your heart arteries (“calcium score”). Your calcium score gives your health care team an idea of how much plaque is in your heart arteries and may help predict your risk of a future heart attack. Your CAC score can help you determine your risk of cardiovascular disease. It’s particularly helpful if you’re at “intermediate” risk.

CAC testing is useful for making treatment decisions, such as whether to start low-dose aspirin, statin therapy or other medications. These are some groups where it may be useful:

  • People reluctant to begin statin therapy and who want to understand their risk and potential benefit more precisely.
  • People concerned about restarting statin therapy after stopping treatment because of side effects.
  • Men ages 55 to 80 or women 60 to 80 with few risk factors who question whether they would benefit from statin therapy.
  • People ages 40 to 55 with an estimated 10-year risk for developing heart disease between 5% and 7.5%, and risk factors that increase their chances of heart disease.

Calcium scoring isn’t recommended for routine screening of people who don’t have symptoms of heart disease and have a low risk of heart attacks unless they have a strong family history of premature coronary heart disease. If you’ve already had a heart attack, coronary bypass surgery (PDF) or a coronary stent calcium scoring won’t provide additional information.

What are the risks of the CAC scan?

The scan exposes you to the same amount of radiation exposure as a mammogram. Repeated exposure can have negative health effects such as increased cancer risk. Talk with your health care team about safety and risks for any test you’re undergoing.

Tell your health care team if you’re pregnant. If the test is not urgent, it may be able to be delayed until after your pregnancy.

How do I prepare for the scan?

Since no dye is used for this scan, no special preparation is needed.

What happens during the test?

Technicians perform the CAC scan in hospitals or special outpatient clinics.

  • Electrodes will be attached to your chest to monitor your ECG (measures the electrical activity of the heartbeat). The ECG also helps the computer connected to the MDCT scanner create clear pictures of your heart.
  • When you’re ready, the table slowly moves inside the machine. The scanner arches around you but doesn’t touch you.
  • The technician will watch you closely through a window. You can talk to him or her through a two-way intercom.
  • The technician will ask you to hold your breath for short periods.
  • CT scanning takes about 10-15 minutes.

Are CAC scans covered by insurance?

The test isn't always covered by insurance and can range in cost from $100 to $400.

What happens after the CAC scan?

After the health care team gets the test results, they will make an appointment to discuss the results and next steps with you.