Cardiac CT

Cardiac computed tomography, or cardiac CT, is a painless test that uses an x-ray machine to take clear, detailed pictures of your heart. It’s a common test for showing problems of the heart. During a cardiac CT scan, the x-ray machine will move around your body in a circle and take a picture of each part of your heart.

Because an x-ray machine is used, cardiac CT scans involve radiation. However, the amount of radiation used is small. This test gives out a radiation dose similar to the amount of radiation you’re naturally exposed to over 3 years. There is a very small chance that cardiac CT will cause cancer.

Each picture that the machine takes shows a small slice of the heart. A computer will put the pictures together to make a large picture of the whole heart. Sometimes an iodine-based dye is injected into one of your veins during the scan to help highlight blood vessels and arteries on the x-ray images.

Overview

Cardiac CT is a common test for finding and evaluating:

• Problems in the heart. Iodine-based dye used with a cardiac CT scan can show pictures of the coronary arteries. The coronary arteries are blood vessels on the surface of the heart. If these blood vessels are narrowed or blocked, you may have chest pain or a heart attack. The CT scan also can find problems with heart function and heart valves.
• Problems with the aorta. The aorta is the main artery that carries oxygen-rich blood from the heart to the body. Cardiac CT can detect two serious problems in the aorta:
  • Aneurysms, which are diseased areas of a weak blood vessel wall that bulge out. Aneurysms can be life threatening because they can burst.
  • Dissections, which can occur when the layers of the aortic artery wall peel away from each other. This condition can cause pain and also may be life threatening.
• Blood clots in the lungs. A cardiac CT scan also may be used to find a pulmonary embolism, a serious but treatable condition. A pulmonary embolism is a sudden blockage in a lung artery, usually due to a blood clot that traveled to the lung from the leg.
• Pericardial disease. This is a disease that occurs in the pericardium, a sac around your heart.

Because the heart is in motion, a fast type of CT scanner, called multidetector computed tomography (MDCT), is used to show high-quality pictures of the heart.

Another type of CT scanner, called electron-beam computed tomography (EBCT), is used to detect calcium in the coronary arteries. Calcium in the coronary arteries may be an early sign of coronary artery disease (CAD).

CAD occurs when the coronary arteries (the arteries that supply blood and oxygen to the heart muscle) harden and narrow due to the buildup of a material called plaque (plak) on their inner walls. CAD is the leading cause of death for both men and women in the United States.

Researchers also are studying new ways to use cardiac CT.

Other Names for Cardiac CT

• CAT scan
• Coronary CT angiography
• Coronary artery scan
• CT angiography (CTA)

What To Expect Before Cardiac CT

Your doctor will give you instructions before the cardiac computed tomography (CT) scan. Usually he or she will ask you to avoid drinks that contain caffeine before the test. Normally you’ll be able to drink water, but you won’t be able to eat for 4 hours before the scan.

If you take medicines for diabetes, ask your doctor whether you will need to change how you take them on the day of your cardiac CT scan.

Tell your doctor if you:

• Are pregnant or may be pregnant. Even though cardiac CT uses a low radiation dose, you shouldn’t have the scan if you’re pregnant. The x-rays may harm the developing fetus.
• Have asthma or kidney problems or are allergic to any medicines, iodine, and/or shellfish. These may increase your chance of having an allergic reaction to the contrast dye.

A technician will ask you to remove your clothes above the waist and wear a hospital gown. You also will be asked to remove any jewelry from around your neck or chest.

Taking pictures of the heart can be difficult because the heart is always beating (in motion). A slower heart rate will help produce better quality pictures. If you don’t have asthma or heart failure, your doctor may give you a medicine called a beta blocker to help slow your heart rate. The medicine will be given by mouth or injected into a vein.

What To Expect During Cardiac CT

The cardiac computed tomography (CT) scan will take place in a hospital or outpatient office.

Because an x-ray machine is used, cardiac CT scans involve radiation. However, the amount of radiation used is small. This test gives out a radiation dose similar to the amount of radiation you’re naturally exposed to over 3 years. There’s a very small chance that cardiac CT will cause cancer. A doctor who has experience with CT scanning will supervise the test.

If your doctor wants to use contrast dye during the cardiac CT scan, a small needle connected to an intravenous (IV) line will be put in a vein in your hand or arm.

The contrast dye will be injected through the IV during the scan. You may have a warm feeling during the injection. The dye will highlight your blood vessels on the x-ray pictures from the cardiac CT scan.

The technician who operates the cardiac CT scanner will clean areas of your chest and place small sticky patches on those areas. The patches are attached to an ECG (electrocardiogram) machine to record the electrical activity of your heart during the exam.

The CT scanner is a large, square machine that has a hollow, circular tube in the middle. You will lie on your back on a sliding table that can move up and down and goes inside the tunnel-like machine.

Inside the scanner, an x-ray tube moves around your body to take pictures of different parts of your heart. These pictures can be shown on a computer as one large, three-dimensional picture. The technician controls the machine from the next room. The technician can see you through a glass window and talk to you through an intercom system.

Moving your body can cause the pictures to blur. You will be asked to lie still and hold your breath for short periods, while each picture is taken.

A cardiac CT scan usually takes about 15 minutes to complete. However, it can take over an hour to get ready for the test and for the medicine to slow your heart rate enough.

What To Expect After Cardiac CT

Once the cardiac computed tomography (CT) scan is done, you’re able to return to your normal activities.

A doctor who has experience with CT will provide your doctor with the results of your cardiac CT. Your doctor will discuss the findings with you.

What Does Cardiac CT Show?

Many x rays are taken while you’re in the computed tomography (CT) scanner. Each picture that the machine takes shows a small slice of the heart. A computer can put the pictures together to make a large picture of the whole heart. This picture shows the inside of the heart and the structures that surround the heart.

Cardiac CT is a common test for finding and evaluating:

• Problems in the heart. Iodine-based dye used with a cardiac CT scan can show pictures of the coronary arteries. The coronary arteries are blood vessels on the surface of the heart. If these blood vessels are narrowed or blocked, you may have chest pain or a heart attack. The CT scan also can find problems with heart function and heart valves.
• Problems with the aorta. The aorta is the main artery that carries oxygen-rich blood from the heart to the body. Cardiac CT can detect two serious problems in the aorta:

• Aneurysms, which are diseased areas of a weak blood vessel wall that bulge out. Aneurysms can be life threatening because they can burst.
• Dissections, which can occur when the layers of the aortic artery wall peel away from each other. This condition can cause pain and also may be life threatening.

• Blood clots in the lungs. A cardiac CT scan also may be used to find a pulmonary embolism, a serious but treatable condition. A pulmonary embolism is a sudden blockage in a lung artery, usually due to a blood clot that traveled to the lung from the leg.
• Pericardial disease. This is a disease that occurs in the pericardium, a sac around your heart.

Because the heart is in motion, a fast type of CT scanner, called multidetector computed tomography (MDCT), is used to take high-quality pictures of the heart.

Another type of CT scanner, called electron-beam computed tomography (EBCT), is used to detect calcium in the coronary arteries. Calcium in the coronary arteries may be an early sign of coronary artery disease (CAD).

What Are the Risks of Cardiac CT?

Cardiac computed tomography (CT) scans are safe, painless tests. Although cardiac CT uses radiation, the amount is small. This test gives out a radiation dose similar to the amount of radiation you’re naturally exposed to over 3 years. There is a very small chance that cardiac CT will cause cancer.

Some people feel side effects from the contrast dye that’s used during the cardiac CT scan, including the following:

• An itchy feeling or a rash may appear after the injection of the contrast dye. Neither one normally lasts for a long time, so medicine often isn’t needed. If you do want medicine to relieve these symptoms, you can ask your doctor to prescribe you a medicine called an antihistamine, which is used to help stop allergic reactions.
• Although rare, it’s possible to have a serious allergic reaction that may lead to breathing difficulties. Medicines are used to treat serious reactions.

People who have asthma or emphysema may have breathing problems during cardiac CT if they’re given beta blockers to slow down their heart rates.

Key Points

• Cardiac computed tomography (CT) is a painless test that uses an x-ray machine to take clear, detailed pictures of your heart.
• Each picture that the machine takes shows a small slice of the heart. A computer can put the pictures together to make a large picture of the whole heart.
• Because an x-ray machine is used, cardiac CT scans involve radiation. However, the amount of radiation used is small.
• Cardiac CT is a common test for finding and evaluating heart problems, such as aortic aneurysm, aortic dissection, and pericardial disease. Cardiac CT also may be used to find pulmonary embolisms.
• Sometimes cardiac CT scans show early signs of coronary artery disease (CAD), before a person shows any symptoms.
• Your doctor will give you instructions before the cardiac CT. Usually he or she will ask you to avoid drinks with caffeine before the test. You also may be asked not to eat for 4 hours before the test.
• Cardiac CT will take place in a hospital or outpatient office.
• The CT scanner is a large, square machine that has a hollow, circular tube in the middle. You lie on your back on a sliding table that can move up and down and goes inside the scanner.
• Many x rays are taken while you’re in the CT scanner. A computer can put the pictures together to make a large picture of the whole heart. This picture shows the inside of the heart and the structures that surround the heart.
• A cardiac CT scan usually takes about 15 minutes to complete, but getting ready before the scan can take more time.
• Once the cardiac CT scan is done, you’re able to return to your normal activities.
• A doctor who has experience with CT will provide your doctor with the results of your scan. Your doctor will discuss the findings with you.
• Cardiac CT scans are painless. Some people feel side effects from the contrast dye that’s used during the scan. Serious complications are rare.
• Researchers are studying new ways to use cardiac CT.