What is a heart CT scan?

A CT scan uses X-rays to view specific areas of your body. These scans use safe amounts of radiation to create detailed images, which can help your doctor to detect any problems. A heart, or cardiac, CT scan is used to view your heart and blood vessels.

During the test, a specialized dye is injected into your bloodstream. The dye is then viewed under a special camera in a hospital or testing facility.

A heart CT scan may also be called a coronary CT angiogram if it’s meant to view the arteries that bring blood to your heart. The test may be called a coronary calcium scan if it’s meant to determine whether there’s a buildup of calcium in your heart.

Your doctor may order a heart CT scan to look for certain conditions, including:

  • congenital heart disease, or birth defects in the heart
  • buildup of a hard substance known as lipid plaque that may be blocking your coronary arteries
  • defects or injury to the heart’s four primary valves
  • blood clots within the heart’s chambers
  • tumors in or on the heart

A heart CT scan is a common test for people experiencing heart problems. This is because it allows your doctor to explore the structure of the heart and the adjacent blood vessels without making any incisions.

A heart CT scan carries very few risks.

Contrast dye

Most of the contrast material, sometimes referred to as dye, used for CT scans contains iodine. This iodine is later flushed from the body by the kidneys.

If your kidneys have been affected by disease or infection, such as diabetes, you may need to drink extra fluids after the test to help your kidneys remove the dye. However, newer dyes carry much less risk to the kidneys.

Allergic or adverse reactions to iodine-based materials are categorized as mild, moderate, and severe. You should let your doctor know if you experience any of the following symptoms:

You’re at greater risk of an allergic or adverse reaction to iodine-based material if you’ve had a previous reaction or if you’ve received a large amount of contrast material within the past 24 hours.

Other risk factors include dehydration, taking medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), and certain health conditions, such as sickle cell anemia or thyroid disorder.

Talk with your doctor if you feel you’re at risk of a reaction. There may be medication available to help you avoid reactions.


As with any X-ray, there’s some exposure to radiation. While typically harmless, this is an important issue for women who are pregnant or could be pregnant. The levels of radiation are considered safe for adults — there have been no documented side effects from low levels of radiation — but not for a developing fetus.

Your doctor will typically ask you to fast for four to eight hours before the scan. You’ll be able to drink water. However, avoid caffeinated drinks since caffeine can affect your heart rate.

You’ll be required to lie down on a table during the exam, so you may want to wear loose, comfortable clothing. You’ll also need to remove any jewelry and other metal items from your body, such as piercings.

Most people will be able to drive themselves home after the test. Unless you’ve been sedated, there’s no need to arrange for transportation.

A heart CT scan is performed in a hospital’s radiology department or a clinic that specializes in diagnostic procedures.

You may be given a beta-blocker before the scan. This medication slows down your heart so that clearer pictures can be taken. Small, sticky discs called electrodes are placed onto your chest to record the scan. The radiology technician inserts an intravenous line (IV) into a vein so that they can inject the radioactive dye into your arm. You may feel warm or flushed briefly or have a temporary metallic taste in your mouth when they inject the dye.

Before the start of the scan, you lie down on a bench, possibly in a specific position. The technician may use pillows or straps to ensure that you stay in the correct position for long enough to get a quality image. You may also have to hold your breath during brief individual scans, which last only 10 to 20 seconds.

To start the scan, the technician moves the table — via a remote from a separate room — into the CT machine. The CT machine looks like a giant doughnut made of plastic and metal. You’ll most likely go through the machine several times. Although you’re in the room by yourself, the technician can talk to you via an intercom.

After a round of scans, you may be required to wait for a few minutes while the technicians review the images to ensure they’re clear enough for your doctor to read. The whole test shouldn’t take longer than 10 minutes.

After the procedure, you’ll be able to leave and go about your day. The dye will naturally work its way out of your body. Drinking more water will help speed up this process.

Getting the results from your heart CT scan doesn’t take long. Your doctor or the technician will go over the results with you.

Depending on what the images show, your doctor will advise you of any lifestyle changes, treatments, or procedures that need to be done. Common follow-up tests include a stress test and coronary catheterization.