Computed Tomography Angiogram (CT Angiogram)

Why It Is Done

A CT angiogram is done to look for:

• A narrowing (stenosis) or blockage in the coronary arteries. This can occur when there is a buildup of fat (cholesterol) and calcium in the arteries. This buildup is called plaque.
• Heart problems, such as pericarditis (a buildup of fluid around the heart) and damage or injury to the heart valves.
• A bulge (aneurysm) or tear (dissection) in the aorta, which is a large blood vessel that carries blood from the heart to the rest of the body.
• A blood clot in the lungs (pulmonary embolism).
• A narrowing of arteries in the legs and in other parts of the body (peripheral arterial disease).
• An abnormal pattern of blood vessels that may be a sign of a tumor.

How To Prepare

Before you have a CT angiogram, tell your doctor if you:

• Are or might be pregnant.
• Are allergic to any medicines, including iodine dyes.
• Have a heart condition, such as heart failure.
• Have diabetes.
• Take metformin. You may have to adjust your medicine for a day before and after the test.
• Have a history of kidney problems.
• Have asthma.
• Have a history of thyroid problems.
• Have had multiple myeloma.
• Have had an X-ray test using barium contrast material (such as a barium enema) in the past 4 days. Barium shows up on X-ray films and makes it hard to see the picture clearly.
• Become very nervous in small spaces. You will have to lie still inside the CT scanner, so you may need a medicine (sedative) to help you relax. If you are given a sedative, you may need to have someone take you home after the test.

You may be asked not to eat or drink anything for several hours before the test. Your doctor will let you know if there are certain foods or liquids you should avoid.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?).

How It Is Done

A CT angiogram is usually done by a radiology technologist. The pictures are usually read by a radiologist. But some other types of doctors may also review the test results.

Before the test

• Take off any jewelry and any other metal objects.
• Take off all or most of your clothes. You will be given a gown to wear during the test.

During the test

• You will lie very still on a table that is attached to the CT scanner.
• A dye (contrast material) will be put in a vein in your arm or hand. If you are having a CT angiogram to look at your heart and the blood vessels that go to it (coronary arteries), you may be given a medicine called a beta-blocker to slow your heart rate during the test.
• The table will slide into the round opening of the scanner and move slightly while the scanner takes pictures. You may hear a click or buzz as the table and scanner move.
• The technologist may ask you to hold your breath for a few seconds at a time.
• You may be alone in the scanning room. But the technologist will watch you through a window. You will be able to talk to him or her through an intercom.

A CT angiogram usually takes 30 to 60 minutes but could take up to 2 hours.

After the test

Drink plenty of fluids for 24 hours after the test to help flush the dye out of your body.

How It Feels

A CT angiogram is not painful. The table you lie on may feel hard, and the room may be cool. It may be hard to lie still during the test.

When the dye is given, you may:

• Feel a brief sting or pinch from the needle going into your vein.
• Feel warm and flushed.
• Feel sick to your stomach or get a headache.
• Have a metallic taste in your mouth.

Tell the technologist or your doctor how you are feeling.

What Affects the Test

You may not be able to have a CT angiogram if:

• You are pregnant. A CT angiogram isn't usually done when a woman is pregnant, because there is a chance that the baby might be harmed by the radiation.
• You have had an X-ray test that used barium contrast material (such as a barium enema) in the past 4 days. Barium shows up on a CT angiogram and makes it hard to see the picture clearly. A CT angiogram should be done before any tests that use barium.
• You are allergic to the dye (contrast material) that is used during the test.
• You have kidney problems. The dye used during the test can cause kidney damage in people whose kidneys don't work well.
• You take metformin (such as Glucophage) to control your diabetes. The dye used during the test may cause problems if you take this medicine.
• You are obese. A person who is very overweight may not fit into a standard CT machine, or the X-ray table may not be able to support his or her weight.
• You can't lie still during the test.
• You have metal objects in your body, such as surgical clips or metal in joint replacements. These objects may prevent a clear view of the areas being examined.

Certain things can make CT angiograms hard to read. For example, a fast heart rate may make it hard to get a clear picture of the coronary arteries. Or a large buildup of calcium may show a narrowing of the arteries when there isn't one (false-positive) or show that the arteries are fine when they are not (false-negative). But with a standard angiogram, these things don't interfere with the test.

What To Think About

Other tests

Another test, called a coronary calcium scan, also uses a CT scan to show how much calcium is in your coronary arteries. This test is for people who have no symptoms of heart disease but may be at risk for getting it. To learn more, see the topic Coronary Calcium Scan.

CT technology

If your doctor suggests a CT angiogram, you may want to ask what kind of scanner will be used. In most cases, a 16- or 64-multi-slice (or multi-detector) CT scanner is used for the CT angiogram. These scanners provide more detailed images of the blood vessels and organs in less time than other imaging tests. But they may not be available in all medical centers.