A computed tomography angiogram (CT angiogram) is a test that uses X-rays to provide detailed pictures of the heart and the blood vessels that go to the heart, lung, brain, kidneys, head, neck, legs, and arms.
During a CT angiogram, you lie on a table that passes through a doughnut-shaped opening in the scanner. A special dye (contrast material) is put in a vein (IV) in your arm or hand to make the blood vessels easier to see on the scan. 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.
Benefits and limitations
A CT angiogram is a less invasive test than a standard angiogram. A standard angiogram involves threading a thin tube called a catheter through an artery in your arm or leg up to the area being studied. But with a CT angiogram, no tubes are put in your body. To learn more, see the topic Angiogram.
If your doctor sees that one or more of your blood vessels are narrowed or blocked, you may need a standard angiogram anyway to double-check the abnormal results from the CT angiogram. This is more likely to happen if your doctor is considering surgery to treat the narrowing or blockage.
If your doctor finds a major blockage in one of your blood vessels during a CT angiogram, you won't be able to get an immediate angioplasty to clear the blockage. You will need a separate procedure. But if you have a standard angiogram and the doctor finds a major blockage, he or she can perform an angioplasty during the 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 the 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 tumour.
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 .
How It Is Done
Before the test
- Take off any jewellery 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.
The risk from having a CT angiogram is small. But some risks include:
- Exposure to radiation. There is a slight chance of developing cancer from some types of CT scans.footnote 1 The chance is higher in children, young women, and people who have many radiation tests. If you are concerned about this risk, talk to your doctor about the amount of radiation this test may give you or your child. Make sure that the test is needed.
- An allergic reaction to the dye (contrast material). But this is rare, and most reactions are mild and can be treated with medicine.
- Kidney problems. The dye used during the test can cause kidney damage in people whose kidneys don't work well.
If you have diabetes or take metformin (Glucophage), the dye may cause problems. Your doctor will tell you when to stop taking metformin and when to start taking it again after the test so you will not have problems.
If you breastfeed and are concerned about whether the dye used in this test is safe, talk to your doctor. Most experts believe that very little dye passes into breast milk and even less is passed on to the baby. But if you prefer, you can store some of your breast milk ahead of time and use it for a day or two after the test.
Results of a CT angiogram are usually ready for your doctor in 1 to 2 days.
The blood vessels look normal, and blood flow is not reduced.
The heart and heart valves look normal.
One or more blood vessels are partially or completely blocked.
The heart or the heart valves look abnormal.
A narrow spot in an artery may suggest that a blood clot or a deposit of fat and calcium is reducing blood flow through the blood vessel.
An abnormal pattern of blood vessels may be a sign that a tumour is present.
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 uses 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
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 centres.
- Einstein AJ, et al. (2007). Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography. JAMA, 298(3): 317–323.
Other Works Consulted
- Blankenstein R (2012). Introduction to noninvasive cardiac imaging. Circulation, 125(3): e267–e271.
- Bluemke, D, et al. (2008). Noninvasive coronary artery imaging: Magnetic resonance angiography and multidetector computed tomography angiography. A scientific statement From the American Heart Association Committee on Cardiovascular Imaging and Intervention of the Council on Cardiovascular Radiology and Intervention, and the Councils on Clinical Cardiology and Cardiovascular Disease in the Young. Circulation, 118: 586–606.
- Budoff M, et al. (2006). Assessment of coronary artery disease by cardiac computed tomography: A scientific statement from the American Heart Association Committee on Cardiovascular Imaging and Intervention, Council on Cardiovascular Radiology and Intervention, and Committee on Cardiac Imaging, Council on Clinical Cardiology. Circulation, 114(16): 1761–1791.
- Einstein A. (2009). Radiation Protection of Patients Undergoing Cardiac Computed Tomographic Angiography. JAMA, 301(5): 545-547.
- Mark DB, et al. (2010). ACCF/ACR/AHA/NASCI/SAIP/SCAI/SCCT 2010 expert consensus document on coronary computed tomographic angiography. Circulation, 121(22): 2509–2543.
- Pagana KD, Pagana TJ (2014). Mosby's Manual of Diagnostic and Laboratory Tests, 5th ed. St. Louis: Mosby.
- Taylor AJ, et al. (2010). ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 – Appropriate use criteria for cardiac computed tomography: A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance. Journal of the American College of Cardiology, 56(22): 1864–1894.
Current as of: December 16, 2019
Author: Healthwise Staff
Medical Review: Rakesh K. Pai, MD - Cardiology, Electrophysiology
Donald Sproule, MDCM, CCFP - Family Medicine
E. Gregory Thompson, MD - Internal Medicine
Adam Husney, MD - Family Medicine
Martin J. Gabica, MD - Family Medicine
Kathleen Romito, MD - Family Medicine
George J. Philippides, MD, FACC - Cardiology
Current as of: December 16, 2019
Author: Healthwise Staff
Medical Review:Rakesh K. Pai, MD - Cardiology, Electrophysiology & Donald Sproule, MDCM, CCFP - Family Medicine & E. Gregory Thompson, MD - Internal Medicine & Adam Husney, MD - Family Medicine & Martin J. Gabica, MD - Family Medicine & Kathleen Romito, MD - Family Medicine & George J. Philippides, MD, FACC - Cardiology