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. Doctors use this test to look for heart problems.
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 highlights your coronary (heart) arteries on the x-ray pictures. This type of CT scan is called a coronary CT angiography (an-je-OG-rah-fee), or CTA.
Doctors use cardiac CT to help detect or evaluate:
- Coronary heart disease (CHD). In CHD, a waxy substance called plaque (plak) narrows the coronary arteries and limits blood flow to the heart. A coronary CTA can show whether the coronary arteries are narrow or blocked.
- 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 CHD.
- 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. An aneurysm can be life threatening if it bursts.
- Dissection. A dissection is a split in one or more layers of the artery wall. The split causes bleeding into and along the layers of the artery wall. This condition can cause pain and may be life threatening.
- A pulmonary embolism (PE). A PE is a sudden blockage in a lung artery, usually due to a blood clot.
- Problems in the pulmonary veins. The pulmonary veins carry blood from the lungs to the heart. Problems with these veins may lead to an irregular heart rhythm called atrial fibrillation (AF). The pictures that cardiac CT creates of the pulmonary veins can help guide procedures used to treat AF.
- Problems with heart function and heart valves. In some cases, doctors may recommend cardiac CT instead of echocardiography or cardiac MRI (magnetic resonance imaging) to look for problems with heart function or heart valves.
- Pericardial disease. This is a disease that occurs in the pericardium, the sac around your heart. Cardiac CT can create clear, detailed pictures of the pericardium.
- Results of coronary artery bypass grafting (CABG). In CABG, arteries from other areas in your body are used to bypass (that is, go around) narrow coronary arteries. A CT scan can show whether the grafted arteries remain open after the surgery.
Different types of CT scans are 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 high-quality pictures of the heart. MDCT also might 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.
Because an x-ray machine is used, cardiac CT involves radiation. The amount of radiation used is considered small. Depending on the type of CT scan you have, the amount of radiation is similar to the amount you’re naturally exposed to over 1–5 years.
There is a small chance that cardiac CT will cause cancer because of the radiation. The risk is higher in people younger than 40 years old. New cardiac CT methods are available that reduce the amount of radiation used during the test.
Researchers continue to study new and better ways to use cardiac CT.