What Is Cardiac CT?

Cardiac computed tomography (to-MOG-rah-fee), or cardiac CT, is a painless test that uses an x-ray machine to take clear, detailed pictures of the heart. This common test is used to look for problems in the heart.

During a cardiac CT scan, an x-ray machine will move around your body in a circle. The machine will take a picture of each part of your heart. A computer will put the pictures together to make a three-dimensional (3D) picture of the whole heart.

Sometimes an iodine-based dye (contrast dye) is injected into one of your veins during the scan. The contrast dye travels through your blood vessels, which helps highlight them on the x-ray pictures.

Because an x-ray machine is used, cardiac CT involves radiation. Although the amount of radiation used is considered small, it's similar to the amount of radiation you're naturally exposed to over a 3-year period.

There's a small chance that cardiac CT will cause cancer because of the radiation involved. The risk is higher for people younger than 40 years old, especially children. However, new cardiac CT methods are available that reduce the amount of radiation used for this test.

Overview

Cardiac CT is a common test for finding and/or evaluating:

• Calcium buildup in the walls of the coronary arteries. This type of CT scan is called a coronary calcium scan. Calcium in the coronary arteries may be an early sign of coronary heart disease (CHD), also called coronary artery disease. In CHD, a fatty substance called plaque (plak) narrows the coronary (heart) arteries and limits blood flow to the heart.
• CHD. If contrast dye is used during cardiac CT, it helps highlight the coronary arteries on the x-ray pictures. This can show whether the coronary arteries are narrowed or blocked (which may cause chest pain or a heart attack).
• Problems with heart function and heart valves. Doctors may recommend cardiac CT instead of echocardiography or cardiac MRI (magnetic resonance imaging) for some people.
• 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:
  • Aneurysm (AN-u-rism). An aneurysm is a diseased area of a blood vessel wall that bulges out. Aneurysms can be life threatening if they burst.
  • Dissection. Dissection can occur if the layers of the aortic artery wall peel away from each other. This condition can cause pain and may be life threatening.
• Blood clots in the lungs. A cardiac CT scan also may be used to find a pulmonary embolism (PE). A PE is a sudden blockage in a lung artery, usually due to a blood clot that traveled to the lungs from one of the legs. This is a serious but treatable condition.
• Problems in the pulmonary veins. The pulmonary veins carry blood from the lungs to the heart. Problems with these veins may lead to atrial fibrillation (AF), an irregular heart rhythm. The pictures that cardiac CT creates of the pulmonary veins can help guide procedures used to treat AF.
• Pericardial disease. This is a disease that occurs in the pericardium, the sac around your heart. A cardiac CT takes clear, detailed pictures of the pericardium.

Different types of CT scans may be used for different purposes. For example, multidetector computed tomography (MDCT) is a fast type of CT scanner. Because the heart is in motion, a fast scanner is able to produce higher quality pictures of the heart. MDCT also may be used to detect calcium in the coronary arteries.

Another type of CT scanner, called electron-beam computed tomography (EBCT), also is used to detect calcium in the coronary arteries.

Outlook

Researchers continue to study new and better ways to use cardiac CT.

Revised November 2009