Cardiac Computed Tomography (CT) Scan
What is a heart CT scan?
A cardiac computed tomography (CT) scan is a procedure that utilizes multiple X-ray beams from different angles to acquire high-quality, three-dimensional (3D) images of your heart, along with your great vessels and surrounding structures.
Cardiac CT uses advanced CT technology, with or without intravenous (IV) contrast (dye) to better visualize your heart structure and associated blood vessels. With multi-slice scanning, your healthcare provider can get high-resolution, 3D images of your moving heart and great vessels.
What does a CT scan of the heart show?
Your healthcare provider will be able to see your:
- Coronary arteries that supply your heart.
- Heart chambers, muscle and valves.
- Pulmonary veins.
- Thoracic aorta, and sometimes abdominal aorta.
- Sac around your heart (pericardium).
When would this procedure be needed?
A cardiac CT scan can give your healthcare provider more information and detail than other kinds of imaging. Your healthcare provider may want you to have a cardiac CT scan for various reasons, including:
- To evaluate the cause of chest pain and shortness of breath.
- To check your heart arteries for calcium or plaque buildup, narrowing or blockages.
- To assess your heart valves.
- To see if there’s a problem with your aorta, including aneurysms and dissection.
- To plan for open or minimally invasive/robotic heart surgery.
- To plan for transcatheter/percutaneous valve procedures.
- To plan for arrhythmia ablation procedures.
- To assess for complications associated with the above procedures.
- To see if you have a congenital (since birth) heart problem.
- To see and characterize any tumor or mass in or around your heart.
- To look at the sac around your heart, if there’s fluid or calcification there.
Who performs a cardiac CT scan?
Although your cardiologist (heart specialist) will most likely order your heart CT scan, a different healthcare team does the scan, including:
- Technicians who control the CT scanner to acquire images.
- Nurses who place an IV line and administer medications if needed.
- Doctors who oversee and interpret the scan.
You’ll need to go to a hospital or a place that specializes in medical imaging to get the scan.
How does a cardiac CT scan work?
The scanner’s X-ray beam will circle around you but won’t touch you. You’ll hear the scanner buzz and click while it’s working. A computer puts multiple scans together to create 3D images of your heart.
Cardiac MRI vs. cardiac CT
Although a cardiac MRI and a cardiac CT both create detailed images of your heart in more than one dimension, the tests do have several differences, including:
- A CT machine is more open than an MRI machine when you lie within it.
- An MRI scan takes longer than a CT.
- A CT uses X-ray radiation, but an MRI doesn’t have radiation.
- A CT machine is quieter than an MRI.
- If you receive contrast, a CT uses iodinated contrast while an MRI uses gadolinium-based contrast.
How do I prepare for the test?
On the day before and the day of your cardiac CT scan, you’ll need to follow instructions about what and when you can eat and drink, and if you should withhold certain medications.
Food and drink
- On the day of your exam, don’t eat for four to six hours before your scheduled appointment. You may drink water.
- Avoid any caffeinated drinks on the day before or the day of your exam. This includes coffee, tea, energy drinks or caffeinated sodas.
- Avoid energy or diet pills on the day before or the day of your exam. Ask your healthcare provider if you have questions.
- If you get nervous in tight spaces, ask your healthcare provider for medicine that’ll relax you for the scan.
- Make sure your healthcare provider knows about all the medicines you’re taking, even if you don’t need a prescription for them.
- Don’t use sildenafil (Viagra® or Revatio®) or any similar medication on the day before or the day of the exam. They’re not compatible with the medications you’ll receive during the procedure. Ask your doctor if you have questions.
- If you have diabetes, ask your physician how to adjust your medications the day of your test. If you think your blood sugar is low, tell your healthcare provider immediately.
What to expect on the date of the test
Before your cardiac CT scan, your healthcare provider will want to know if you’re:
- Allergic to iodine and/or shellfish or any medications.
- Undergoing radiation therapy.
- Older than 60 or have a history of kidney problems. You may need to have a blood test to evaluate your kidney function before you receive any contrast agent.
Prepping for your cardiac CT scan
- Leave your jewelry at home.
- You’ll change into a hospital gown.
- Your healthcare provider may ask you to take medicine that slows down your heart rate.
- If you’ll be getting contrast (dye), a nurse will insert an IV line into a vein in your arm to administer contrast during your procedure. This dye helps your blood vessels and heart show up better on scans.
- You’ll lie on your back on a special table that moves into the open space in the middle of a round CT scanner.
- Your healthcare provider will clean three small areas of your chest and place small, sticky electrode patches on them. To help the electrodes stick, they may shave chest hair that’s in the way. The electrodes attach to an electrocardiogram (EKG) monitor, which charts your heart’s electrical activity during the test.
- You’ll lie on the scanner table and raise your arms over your head for the duration of the exam. Your head and feet will stick out of the scanner.
What should I expect during the test?
The entire cardiac CT scan may take 30 to 60 minutes, including preparation time. But the actual CT scan only takes 10 minutes at the most.
During the heart CT scan
- You‘ll feel the table you’re lying on move inside a donut-shaped scanner.
- If you receive contrast to help produce the image, a healthcare provider will inject it through your IV. It’s common to feel a warm sensation as the contrast circulates through your body. You may also have a metallic taste in your mouth for a few seconds.
- To get clear images, you’ll need to avoid moving around and follow instructions carefully.
- You’ll be able to communicate with your healthcare provider, who may tell you to hold your breath for a very short time.
What to expect after the test
Once your healthcare provider is sure they have the images they need, they’ll remove your IV. You can change clothes and go home. You can go back to all normal activities and eat as usual after the test. If you took a sedative to relax, you’ll need someone to drive you home, though.
Your healthcare provider will discuss your test results with you that day or in a few days.
What are the risks of this test?
A CT scan is a low-risk procedure, but some people have problems with the dye or other substances the test uses.
Contrast agent (dye)
Occasionally, people experience an adverse reaction to the contrast agent, which usually has iodine in it. Some people develop itching, nausea, sneezing or a rash after the injection. These symptoms usually go away without treatment, but antihistamines, steroids and histamine blockers can help.
Rarely, a more serious allergic reaction (an anaphylactic reaction) occurs that may result in breathing difficulty. You’ll need medications and treatment to reverse the symptoms of this potentially life-threatening reaction.
If you have diabetes or kidney disease, you may need extra fluids when you’re done with your scan. This’ll help you get the iodine out of your body.
Because the dye you get for a cardiac CT scan can get into your breast milk, you may want to prepare some before your scan to give your baby for a day or two after your scan.
CT scanners use X-rays. Radiation from these carries a small risk of cancer over time. For your safety, the amount of radiation exposure is kept to a minimum. However, because X-rays can harm a developing fetus, this procedure isn’t recommended if you’re pregnant. If you need to have a heart CT scan, your healthcare provider can take measures to protect your baby.
Medicine that slows down your heart rate
If you received medicine to slow your heart rate for the test and you have asthma, heart failure or chronic obstructive pulmonary disorder (COPD), you might have trouble breathing during your scan. It’s important to inform your healthcare provider if you have these conditions.
Results and Follow-Up
What type of results do you get and what do the results mean?
- Your heart and arteries look normal.
- Your calcium score is 0, which means you don’t have coronary artery disease and your risk of a heart attack is low.
- Coronary arteries that have plaque and stenosis (narrowing).
- A high calcium score means you have coronary atherosclerosis. A score of 100 or lower shows mild evidence of coronary artery disease. More than 400 means there’s extensive evidence of coronary artery disease, and between 100 and 400 is moderate. You often get a percentile score with your calcium score, which is how you compare with other people of the same age, sex and race who’ve had this test.
- Heart function or valves that aren’t working normally.
- Pericardial disease — effusion (fluid) and pericarditis (inflamed heart covering).
- A tumor or mass.
- Congenital (present at birth) heart problem.
- Blood vessels that are enlarged (aneurysm), have a tear (dissection) or are narrowed (stenosis/coarctation).
When should I call my doctor?
Contact your healthcare provider if you’re having a reaction to the dye or medicine you got during the test or if you haven’t received results from your heart CT scan after a few days.
A note from Cleveland Clinic
Don’t let a heart CT scan (or the CT machine) intimidate you. It’s a noninvasive test that gives your healthcare provider valuable information about what’s going on with your heart and associated structures. For the best results, follow your healthcare provider’s instructions about diet restrictions before the test and about lying still and holding your breath when asked.
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