What Is a Nuclear Heart Scan?
A nuclear heart scan is a type of medical test that
allows your doctor to get important information about the health of your heart.
During a nuclear heart scan, a safe, radioactive material called a tracer is
injected through a vein into your bloodstream. The tracer then travels to your
heart. The tracer releases energy, which special cameras outside of your body
detect. The cameras use the energy to create pictures of different parts of
your heart.
Nuclear heart scans are used for three main
purposes:
- To provide information about the flow of blood
throughout the heart muscle. If the scan shows that one part of the heart
muscle isn't receiving blood, it's a sign of a possible narrowing or blockage
in the coronary arteries (the arteries that supply blood and oxygen to your
heart). Decreased blood flow through the coronary arteries may mean you have
coronary
artery disease (CAD). CAD can lead to
angina,
heart
attack, and other heart problems. When a nuclear heart scan is performed
for this purpose, it's called myocardial perfusion scanning.
- To look for damaged heart muscle. Damage may be
due to a previous heart attack, injury, infection, or medicine. When a nuclear
heart scan is performed for this purpose, it's called myocardial viability
testing.
- To see how well your heart pumps blood out to
your body. When a nuclear heart scan is performed for this purpose, it's called
ventricular function scanning.
Usually, two sets of pictures are taken during a
nuclear heart scan. The first set is taken when the heart is beating fast due
to you exercising. This is called a cardiac
stress
test. If you can't exercise, your heart rate can be increased using
medicines such as adenosine, dipyridamole, or dobutamine.
The second set of pictures is taken later, when the
heart is at rest and beating at a normal rate.
Types of Nuclear Heart Scanning
There are two main types of nuclear heart scanning:
- Single positron emission computed tomography
(SPECT)
- Cardiac positron emission tomography (PET)
SPECT is the most well-established and widely used
type, while PET is newer. There are specific reasons for using each, which are
discussed in the following paragraphs.
Single Positron Emission Computed Tomography
Cardiac SPECT is the most commonly used nuclear
scanning test for diagnosing
coronary
artery disease (CAD). Combining SPECT with a cardiac
stress
test can show problems with blood flow to the heart that can be detected
only when the heart is working hard and beating fast.
SPECT also is used to look for areas of damaged or
dead heart muscle tissue, which may be due to a previous
heart
attack or other cause of injury.
SPECT also can show how well the hearts left
ventricle pumps blood to the body. Weak pumping ability may be the result of
heart attack, heart failure, and other
causes.
The most commonly used tracers in SPECT are called
thallium-201, technetium-99m sestamibi (Cardiolite®), and technetium-99m
tetrofosmin (Myoview™).
Positron Emission Tomography
PET uses different kinds of tracers than SPECT. PET
can provide more detailed pictures of the heart. However, PET is newer and has
some technical limits that make it less available than SPECT. Research into
advances in both SPECT and PET is ongoing. Right now, there is no clear cut
advantage of using one over the other in all situations.
PET can be used for the same purposes as
SPECT—to diagnose CAD, check for damaged or dead heart muscle, and
evaluate the heart's pumping strength.
PET takes a clearer picture through thick layers of
tissue (such as abdominal or breast tissue). PET also is better than SPECT at
showing whether CAD is affecting more than one of your heart's blood vessels. A
PET scan also may be used if a SPECT scan wasn't able to produce good enough
pictures.
Other Names for a Nuclear Heart Scan
Names used for nuclear heart scans:
- Nuclear stress test
- SPECT scan
- PET scan
What To Expect Before a Nuclear Heart Scan
Talk to your doctor about how the nuclear heart scan
is done. Discussing your overall health, including health problems such as
asthma,
chronic
obstructive pulmonary disease (COPD), diabetes, and kidney disease, is
important. If you have lung disease or diabetes, your doctor will give you
special instructions before the nuclear heart scan.
Also, let your doctor know about any medicines you
take, including prescription and over-the-counter medicines, vitamins,
minerals, and other supplements. Some medicines and supplements can cause
problems when used with adenosine, dipyridamole, or dobutamine (medicines used
to increase your heart rate during a
stress
test).
If you are having a stress test as part of your
nuclear heart scan, wear comfortable walking shoes and loose-fitting clothes
for the test. You may be asked to wear a hospital gown during the test.
A nuclear heart scan can take a lot of time. Most
take between 2 to 5 hours, especially if two sets of pictures are needed.
What To Expect During a Nuclear Heart Scan
Many, but not all, nuclear medicine centers are
located in hospitals. A doctor who has special training in nuclear heart
scans—a cardiologist or radiologist—will oversee the test.
(Cardiologists are doctors who specialize in diagnosing and treating heart
problems. Radiologists are doctors who specialize in diagnostic techniques such
as nuclear scans.)
Before the test begins, the doctor or a technician
will use a needle to insert an intravenous (IV) line into a vein in your arm.
Through this IV line, he or she will put the radioactive tracers into your
bloodstream at the right time. You also will have
EKG
(electrocardiogram) patches attached to your body to check your heart rate
during the test.
If you're having an exercise
stress test as part of your nuclear scan, you will walk on a treadmill or
pedal a stationary bicycle, while attached to EKG and blood pressure monitors.
You will be asked to exercise until you're too tired
to continue, short of breath, or having chest or leg pain. You can expect that
your heart will beat faster, you will breathe faster, your blood pressure will
increase, and you will sweat. Report any chest, arm, or jaw pain or discomfort;
dizziness; lightheadedness; or any other unusual symptoms.
If you're unable to exercise, your doctor can give
you medicine to make your heart beat faster. This is called a chemical stress
test. The medicine used may make you feel anxious, sick, dizzy, or shaky for a
short time. If the side effects are severe, other medicine can be given for
relief.
Before the exercise or the chemical stress test
stops, the tracer is injected through the IV line.
The nuclear heart scan will start shortly after the
exercise or chemical stress test. You will be asked to lie very still on a
padded table.
The nuclear heart scan camera, called a gamma
camera, is enclosed in a metal housing. The part of the camera that detects the
radioactivity from the tracer can be put in several positions around your body
as you lie on the padded table. For some nuclear heart scans, the metal housing
is shaped like a doughnut and you lie on a table that goes slowly through the
doughnut hole. The computer used to collect the pictures of your heart is
nearby or in another room.
Two sets of pictures will be taken. One will be
taken right after your exercise or chemical stress test and the other will be
taken after a period of rest. The pictures may be taken all in 1 day or over 2
days. Each set of pictures takes about 15 to 30 minutes to do.
Some people find it hard to stay in one position for
some time. Others may feel anxious while lying in the doughnut-shaped scanner.
The table may feel hard. Sometimes, the room feels chilly because of the air
conditioning needed to maintain the machines.
Let the person performing the test know how you're
feeling during the test so he or she can respond as needed.
What To Expect After a Nuclear Heart Scan
You may be asked to return to the nuclear medicine
center the next day for more pictures. Outpatients will be allowed to go home
after the scan or leave the nuclear medicine center between the two scans.
Most people can go back to daily activities after a
nuclear heart scan. The radioactivity will naturally leave the body in the
urine or stool. It's helpful to drink plenty of fluids after the test.
The cardiologist or radiologist will read and
interpret the results of the test within 1 to 3 days. Results will be reported
to your doctor, who will contact you to discuss the results. Or, the
cardiologist may discuss the results directly with you.
What Does a Nuclear Heart Scan Show?
The results from a nuclear heart scan can help
doctors:
What Are the Risks of a Nuclear Heart Scan?
The radioactive tracers used during a nuclear heart
scan expose the body to a very small amount of radiation. No long-term effects
have been reported from these doses.
If you have
coronary
artery disease, you may have chest pain during exercise or when you take
medicine to increase your heart rate. Medicine can be given to relieve this
symptom.
Some people may be allergic to the radioactive
tracers, but this is very rare.
Women who are pregnant should tell their doctor and
technician before the scan is done. It may be postponed until after the
pregnancy.
Key Points
- A nuclear heart scan is a type of medical test
that allows your doctor to get important information about the health of your
heart. The test uses radioactive tracers to study how blood flows in your
heart.
- Nuclear heart scans are used to provide
information about the flow of blood throughout the heart muscle, check for
damaged heart muscle, and see how well your heart pumps blood to your body.
- The two main types of nuclear heart scanning are
single positron emission computed tomography (SPECT) and cardiac positron
emission tomography (PET). SPECT is the most well-established and widely used
type, while PET is newer.
- A nuclear heart scan often takes two sets of
pictures, one while the heart is beating faster than normal and one when the
heart is resting. To get your heart to beat faster than normal, you will be
asked to exercise on a treadmill or stationary bike, or you will be given
medicine.
- After the exercise part of the test, you will lie
very still on a padded table. A camera called a gamma camera will take pictures
of your heart from various positions around your body.
- A nuclear heart scan can take a lot of
time—sometimes 2 to 5 hours in a single day. You may be asked to return
on a second day for another set of pictures.
- Most people can go back to their normal daily
activities after a nuclear heart scan.
- Your doctor or the cardiologist or radiologist
who performed the nuclear heart scan will contact you with the results.
- A nuclear heart scan can help doctors:
- Diagnose and manage certain heart diseases
such as
coronary
artery disease (CAD)
- Determine your risk for a
heart
attack
- Decide whether other heart tests or
procedures will help you
- Monitor procedures or surgeries that have
been done
- Nuclear heart scanning has very few risks. If you
have CAD, you may have chest pain during exercise or when you take medicine to
increase your heart rate. Some people may be allergic to the radioactive tracer
used during the scan, but this is very rare.
Links to Other Information About Nuclear Heart
Scans
NHLBI Resources
Non-NHLBI Resources
Clinical Trials
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