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 your heart. It’s a common test for showing problems
of the heart. During a cardiac CT scan, the x-ray machine will move around your
body in a circle and take a picture of each part of your heart.
Because an x-ray machine is used, cardiac CT scans
involve radiation. However, the amount of radiation used is small. This test
gives out a radiation dose similar to the amount of radiation you’re
naturally exposed to over 3 years. There is a very small chance that cardiac CT
will cause cancer.
Each picture that the machine takes shows a small
slice of the heart. A computer will put the pictures together to make a large
picture of the whole heart. Sometimes an iodine-based dye is injected into one
of your veins during the scan to help highlight blood vessels and arteries on
the x-ray images.
Overview
Cardiac CT is a common test for finding and
evaluating:
- Problems in the heart. Iodine-based dye used with
a cardiac CT scan can show pictures of the coronary arteries. The coronary
arteries are blood vessels on the surface of the heart. If these blood vessels
are narrowed or blocked, you may have chest pain or a
heart attack. The CT scan also can find problems with heart function and
heart valves.
- 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:
- Aneurysms,
which are diseased areas of a weak blood vessel wall that bulge out. Aneurysms
can be life threatening because they can burst.
- Dissections, which can occur when the layers
of the aortic artery wall peel away from each other. This condition can cause
pain and also may be life threatening.
- Blood clots in the lungs. A cardiac CT scan also
may be used to find a
pulmonary
embolism, a serious but treatable condition. A pulmonary embolism is a
sudden blockage in a lung artery, usually due to a blood clot that traveled to
the lung from the leg.
- Pericardial disease. This is a disease that
occurs in the pericardium, a sac around your heart.
Because the heart is in motion, a fast type of CT
scanner, called multidetector computed tomography (MDCT), is used to show
high-quality pictures of the heart.
Another type of CT scanner, called electron-beam
computed tomography (EBCT), is used to detect calcium in the coronary arteries.
Calcium in the coronary arteries may be an early sign of
coronary
artery disease (CAD).
CAD occurs when the coronary arteries (the arteries
that supply blood and oxygen to the heart muscle) harden and narrow due to the
buildup of a material called plaque (plak) on their inner walls. CAD is the
leading cause of death for both men and women in the United States.
Researchers also are studying new ways to use
cardiac CT.
Other Names for Cardiac CT
- CAT scan
- Coronary CT angiography (an-je-OG-ra-fee)
- Coronary artery scan
- CT angiography (CTA)
What To Expect Before Cardiac CT
Your doctor will give you instructions before the
cardiac computed tomography (CT) scan. Usually he or she will ask you to avoid
drinks that contain caffeine before the test. Normally you’ll be able to
drink water, but you won’t be able to eat for 4 hours before the scan.
If you take medicines for diabetes, ask your doctor
whether you will need to change how you take them on the day of your cardiac CT
scan.
Tell your doctor if you:
- Are pregnant or may be pregnant. Even though
cardiac CT uses a low radiation dose, you shouldn’t have the scan if
you’re pregnant. The x-rays may harm the developing fetus.
- Have
asthma or kidney problems or are allergic to any medicines, iodine, and/or
shellfish. These may increase your chance of having an allergic reaction to the
contrast dye.
A technician will ask you to remove your clothes
above the waist and wear a hospital gown. You also will be asked to remove any
jewelry from around your neck or chest.
Taking pictures of the heart can be difficult
because the heart is always beating (in motion). A slower heart rate will help
produce better quality pictures. If you don’t have asthma or
heart
failure, your doctor may give you a medicine called a beta blocker to help
slow your heart rate. The medicine will be given by mouth or injected into a
vein.
What To Expect During Cardiac CT
The cardiac computed tomography (CT) scan will take
place in a hospital or outpatient office.
Because an x-ray machine is used, cardiac CT scans
involve radiation. However, the amount of radiation used is small. This test
gives out a radiation dose similar to the amount of radiation you’re
naturally exposed to over 3 years. There’s a very small chance that
cardiac CT will cause cancer. A doctor who has experience with CT scanning will
supervise the test.
If your doctor wants to use contrast dye during the
cardiac CT scan, a small needle connected to an intravenous (IV) line will be
put in a vein in your hand or arm.
The contrast dye will be injected through the IV
during the scan. You may have a warm feeling during the injection. The dye will
highlight your blood vessels on the x-ray pictures from the cardiac CT scan.
The technician who operates the cardiac CT scanner
will clean areas of your chest and place small sticky patches on those areas.
The patches are attached to an
EKG (electrocardiogram) machine to record the electrical activity of your
heart during the exam.
The CT scanner is a large, square
machine that has a hollow, circular tube in the middle. You will lie on your
back on a sliding table that can move up and down and goes inside the
tunnel-like machine.
Inside the scanner, an x-ray tube moves around your
body to take pictures of different parts of your heart. These pictures can be
shown on a computer as one large, three-dimensional picture. The technician
controls the machine from the next room. The technician can see you through a
glass window and talk to you through an intercom system.
Moving your body can cause the pictures to blur. You
will be asked to lie still and hold your breath for short periods, while each
picture is taken.
A cardiac CT scan usually takes about 15 minutes to
complete. However, it can take over an hour to get ready for the test and for
the medicine to slow your heart rate enough.
What To Expect After Cardiac CT
Once the cardiac computed tomography (CT) scan is
done, you’re able to return to your normal activities.
A doctor who has experience with CT will provide
your doctor with the results of your cardiac CT. Your doctor will discuss the
findings with you.
What Does Cardiac CT Show?
Many x rays are taken while you’re in the
computed tomography (CT) scanner. Each picture that the machine takes shows a
small slice of the heart. A computer can put the pictures together to make a
large picture of the whole heart. This picture shows the inside of the heart
and the structures that surround the heart.
Cardiac CT
Figure A shows the position of the
heart in the body. The arrow shows the point of view of the cardiac CT image.
Figure B is a cardiac CT image showing the coronary arteries on the surface of
the heart. This is a picture of the whole heart, put together by the computer.
Cardiac CT is a common test for finding and
evaluating:
- Problems in the heart. Iodine-based dye used with
a cardiac CT scan can show pictures of the coronary arteries. The coronary
arteries are blood vessels on the surface of the heart. If these blood vessels
are narrowed or blocked, you may have chest pain or a
heart
attack. The CT scan also can find problems with heart function and heart
valves.
- 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:
-
Aneurysms, which are diseased areas of a weak blood vessel wall that bulge
out. Aneurysms can be life threatening because they can burst.
- Dissections, which can occur when the layers of
the aortic artery wall peel away from each other. This condition can cause pain
and also may be life threatening.
- Blood clots in the lungs. A cardiac CT scan also
may be used to find a
pulmonary
embolism, a serious but treatable condition. A pulmonary embolism is a
sudden blockage in a lung artery, usually due to a blood clot that traveled to
the lung from the leg.
- Pericardial disease. This is a disease that
occurs in the pericardium, a sac around your heart.
Because the heart is in motion, a fast type of CT
scanner, called multidetector computed tomography (MDCT), is used to take
high-quality pictures of the heart.
Another type of CT scanner, called electron-beam
computed tomography (EBCT), is used to detect calcium in the coronary arteries.
Calcium in the coronary arteries may be an early sign of
coronary
artery disease (CAD).
What Are the Risks of Cardiac CT?
Cardiac computed tomography (CT) scans are safe,
painless tests. Although cardiac CT uses radiation, the amount is small. This
test gives out a radiation dose similar to the amount of radiation you’re
naturally exposed to over 3 years. There is a very small chance that cardiac CT
will cause cancer.
Some people feel side effects from the contrast dye
that’s used during the cardiac CT scan, including the following:
- An itchy feeling or a rash may appear after the
injection of the contrast dye. Neither one normally lasts for a long time, so
medicine often isn’t needed. If you do want medicine to relieve these
symptoms, you can ask your doctor to prescribe you a medicine called an
antihistamine, which is used to help stop allergic reactions.
- Although rare, it’s possible to have a
serious allergic reaction that may lead to breathing difficulties. Medicines
are used to treat serious reactions.
People who have
asthma
or
emphysema may have breathing problems during cardiac CT if
they’re given beta blockers to slow down their heart rates.
Key Points
- Cardiac computed tomography (CT) is a painless
test that uses an x-ray machine to take clear, detailed pictures of your heart.
- Each picture that the machine takes shows a small
slice of the heart. A computer can put the pictures together to make a large
picture of the whole heart.
- Because an x-ray machine is used, cardiac CT
scans involve radiation. However, the amount of radiation used is small.
- Cardiac CT is a common test for finding and
evaluating heart problems, such as
aortic aneurysm, aortic dissection, and pericardial disease. Cardiac CT
also may be used to find
pulmonary
embolisms.
- Sometimes cardiac CT scans show early signs of
coronary
artery disease (CAD), before a person shows any symptoms.
- Your doctor will give you instructions before the
cardiac CT. Usually he or she will ask you to avoid drinks with caffeine before
the test. You also may be asked not to eat for 4 hours before the test.
- Cardiac CT will take place in a hospital or
outpatient office.
- The CT scanner is a large, square machine that
has a hollow, circular tube in the middle. You lie on your back on a sliding
table that can move up and down and goes inside the scanner.
- Many x rays are taken while you’re in the
CT scanner. A computer can put the pictures together to make a large picture of
the whole heart. This picture shows the inside of the heart and the structures
that surround the heart.
- A cardiac CT scan usually takes about 15 minutes
to complete, but getting ready before the scan can take more time.
- Once the cardiac CT scan is done, you’re
able to return to your normal activities.
- A doctor who has experience with CT will provide
your doctor with the results of your scan. Your doctor will discuss the
findings with you.
- Cardiac CT scans are painless. Some people feel
side effects from the contrast dye that’s used during the scan. Serious
complications are rare.
- Researchers are studying new ways to use cardiac
CT.
Links to Other Information About Cardiac CT
Non-NHLBI Resources
Clinical Trials
|