A myocardial perfusion scan is a type of nuclear medicine procedure.
This means that a tiny amount of a radioactive substance, called a
radionuclide (radiopharmaceutical or radioactive tracer), is used during
the procedure to assist in the examination of the tissue under study.
Specifically, the myocardial perfusion scan evaluates the heart’s
function and blood flow.
A radionuclide is a radioactive substance used as a "tracer," which
means it travels through the blood stream and is taken up (absorbed) by
the healthy heart muscle tissue. On the scan, the areas where the
radionuclide has been absorbed will show up differently than the areas
that do not absorb it (due to possible damage to the tissue from
decreased or blocked blood flow).
A stress myocardial perfusion scan is used to assess the blood flow to
the heart muscle (myocardium) when it is stressed by exercise or
medication and to determine what areas of the myocardium have decreased
blood flow. This is done by injecting a radionuclide (thallium or
technetium) into a vein in the arm or hand.
There are different types of radionuclides. When one type of
radionuclide is used, areas of the myocardium that have blocked or
partially blocked arteries will be seen on the scan as "cold spots," or
"defects," because these areas will be unable to take in the
radionuclide into the myocardium. Another type of radionuclide binds to
the calcium that is released when a heart attack occurs, so it will
accumulate in area(s) of injured heart tissue as a "hot spot" on the
There are two types of stress myocardial perfusion scans, one that is
used in conjunction with exercise (myocardial perfusion scan with
exercise) and one that is used in conjunction with medication
(pharmacologic myocardial perfusion scan).
Myocardial perfusion scan with exercise. A myocardial perfusion
scan with exercise is used to determine what areas of the heart
muscle (myocardium) demonstrate decreased blood flow during
exercise. This is done by injecting a radionuclide (thallium or
technetium) into a vein in the arm or hand during exercise.
After the radionuclide has been injected into a vein and has
circulated through the blood stream, a special machine called a
gamma camera takes pictures of the heart while the person lies
still on a table. This scanning usually lasts about 30 minutes.
Any areas of the myocardium that have blocked or partially
blocked arteries during exercise will be seen on the scan as
"cold spots," or "defects," because these areas will be unable
to absorb the radionuclide into the myocardium.
A second set of scans is taken some hours later, at rest. The
resting phase is done in order to compare the results with the
exercise phase to see if areas that do not get adequate blood
flow while exercising are able to absorb the radionuclide during
Myocardial perfusion scan with pharmacologic intervention. A
pharmacologic myocardial perfusion scan is used when the
physician has determined that exercise on a treadmill is not an
appropriate choice due to the person’s medical condition. In
this situation, a medication is given that causes the coronary
arteries to dilate. This dilation of the coronary arteries
increases blood flow and is very similar to the response of the
arteries during exercise. The medication is injected into a vein
in the arm or hand.
After a given period of time, the radionuclide will be injected
into a vein in the arm or hand. The gamma camera will take
pictures of the heart while the person lies still on a table. A
resting scan will be performed afterwards, just as with the
actual exercise scan.
Other related procedures that may be used to diagnose heart disorders
include exercise and resting electrocardiograms (ECG or EKG), Holter
monitor, signal-averaged ECG, cardiac catheterization, chest X-ray,
computed tomography (CT scan) of the chest, echocardiography,
electrophysiological studies, magnetic resonance imaging (MRI) of the
heart, radionuclide angiography, and cardiac CT scan. Please see these
procedures for additional information.
artery disease (CAD) is the narrowing of the coronary arteries (the
blood vessels that supply oxygen and nutrients to the heart muscle),
caused by a buildup of fatty material within the walls of the arteries.
This process causes the inside of the arteries to become rough and
narrowed, limiting the supply of oxygen-rich blood to the heart muscle.
To better understand how coronary artery disease affects the heart, a
review of basic heart anatomy and function follows.
The heart is basically a pump. The heart is made up of specialized
muscle tissue, called the myocardium. The heart's primary function is to
pump blood throughout the body, so that the body's tissues can receive
oxygen and nutrients and have waste substances taken away.
Like any pump, the heart requires fuel in order to work. The myocardium
requires oxygen and nutrients, just like any other tissue in the body.
However, the blood that passes through the heart's chambers is only
passing through on its trip to the rest of the body. This blood does not
give oxygen and nutrients to the myocardium. The myocardium receives its
oxygen and nutrients from the coronary arteries, which lie on the
outside of the heart.
the heart tissue does not receive an adequate blood supply, it cannot
function as well as it should. If the myocardium's blood supply is
decreased for a length of time, a condition called ischemia may develop.
Ischemia can decrease the heart's pumping ability, because the heart
muscle becomes weakened due to a lack of oxygen.
Fortunately, the technology is available to restore blood flow to heart
tissue when coronary artery blockages are diagnosed. One of several
procedures used to diagnose and evaluate coronary artery disease is the
myocardial perfusion scan.
Indications for an exercise or pharmacologic myocardial perfusion scan
may include, but are not limited to, the following:
Chest pain, either new onset or occurring over a period of days
Following a heart attack (myocardial infarction, or MI)
To assess blood flow to areas of the myocardium that have been
reperfused (coronary artery blood flow restored) by bypass
surgery, angioplasty (the opening of a coronary artery using a
balloon or other method), or stent (a tiny expandable metal coil
placed inside an artery to keep the artery open)
There may be other reasons for your doctor to recommend a myocardial
The exercise portion of the test may lead to rare instances of abnormal
heart rhythms, chest pain, or heart attack due to the stress on the
heart caused by the exercise.
The injection of the radionuclide may cause some slight discomfort.
Allergic reactions to the radionuclide are rare.
If you are pregnant or suspect that you may be pregnant, you should
notify your health care provider due to the risk of injury to the fetus
from a myocardial perfusion scan. Radiation exposure during pregnancy
may lead to birth defects. If you are lactating, or breastfeeding, you
should notify your health care provider due to the risk of contaminating
breast milk with the radionuclide.
Patients who are allergic to or sensitive to medications, contrast dyes,
iodine, tape, or latex should notify their doctor.
There may be other risks depending on your specific medical condition.
Be sure to discuss any concerns with your doctor prior to the procedure.
Certain factors or conditions may interfere with or affect the results
of the test. These include, but are not limited to, the following:
Medications containing theophylline
Caffeine within 24 hours of the procedure
Digitalis, quinidine, or nitrate medications
Your doctor will explain the procedure to you and offer you the
opportunity to ask any questions that you might have about the
You will be asked to sign a consent form that gives your
permission to do the test. Read the form carefully and ask
questions if something is not clear
Notify your doctor if you are allergic to or sensitive to
medications, local anesthesia, contrast dyes, iodine, tape or
Fasting may be required before the procedure. Your doctor will
give you instructions as to how long you should withhold food
If you are scheduled for a pharmacologic myocardial perfusion
scan, you will need to avoid taking any medications containing
theophylline or caffeine. Coffee, even decaffeinated, is not
allowed, as it contains some caffeine. Medications for asthma
may contain theophylline. If you have asthma, inform your
doctor. Theophylline medications should be stopped 48 hours
prior to the test. Medications that contain caffeine and all
food and drink containing caffeine should be held for 12 to 24
hours. Some over-the-counter medications that contain caffeine
include Anacin, Excedrin, and NoDoz. Consult your doctor for
If you are pregnant or suspect that you may be pregnant, you
should notify your doctor
Notify your doctor of all medications (prescription and
over-the-counter) and herbal supplements that you are taking
Notify your doctor if you have a pacemaker
For an exercise scan, plan to wear loose, comfortable clothing
for the exercise portion of the test, as well as a pair of
comfortable walking shoes
Based on your medical condition, your doctor may request other
A stress myocardial perfusion scan may be performed on an outpatient
basis or as part of your stay in a hospital. Procedures may vary
depending on your condition and your doctor's practices.
Generally, a stress myocardial perfusion scan follows this process:
You will be asked to remove any jewelry or other objects that
may interfere with the procedure.
If you are asked to remove clothing, you will be given a gown to
An intravenous (IV) line will be started in your hand or arm.
You will be connected to an ECG machine with leads and a blood
pressure cuff will be placed on your arm.
Exercise myocardial perfusion scan
[Illustration demonstrating an exercise ECG]You will exercise on
a treadmill. The intensity of the exercise will be gradually
increased by increasing the speed of the treadmill.
Your heart rate and blood pressure will be monitored. Once you
have reached your maximal exercise point (determined by the
doctor based on your heart rate and age), the radionuclide will
be injected into your IV line.
After the radionuclide has been injected, you will continue to
exercise for several minutes.
Pharmacologic myocardial perfusion scan
You will not exercise on a treadmill. Instead, you will lie on
the table while a medication is injected into your IV to
increase your heart rate.
Your heart rate and blood pressure will be monitored.
Once you have reached your target heart rate, the radionuclide
will be injected into your IV line.
Procedure completion, both methods
If you experience any symptoms such as dizziness, chest pain,
extreme shortness of breath, or severe fatigue at any point
during the procedure, let the doctor or technologist know.
You will lie flat on a table while the images of your heart are
obtained. Approximately 10 to 60 minutes after the radionuclide
is injected, the gamma camera will begin to take pictures of
your heart. In a special kind of test called SPECT (single
photon emission computed tomography), the scanner will rotate
around you as it takes pictures.
Your arms will be positioned above your head. It will be
necessary for you to lie very still while the images are being
taken, as movement can adversely affect the quality of the
After the scan is completed, you may be allowed to leave the
area, but will need to return at the appropriate time for a
second set of scans. The second set of scans will be taken three
to six hours after the first set. During this time, you will not
be allowed to eat, unless specifically instructed to do so by
the technologist, and will be allowed limited water or
decaffeinated/noncaloric liquids. Your doctor may decide to have
you return on another day for the second set of scans.
The second set of scans will be similar to the first set. You
will lie on the table as before while the scanner takes pictures
of your heart.
Once the second set of scans has been completed, the IV line
will be discontinued, and you will be allowed to leave, unless
your doctor instructs you differently.
You should move slowly when getting up from the scanner table to avoid
any dizziness or lightheadedness from lying flat for the length of the
You will be instructed to drink plenty of fluids and empty your bladder
frequently for 24 to 48 hours after the test to help flush the remaining
radionuclide from your body.
The IV site will be checked for any signs of redness or swelling. If you
notice any pain, redness, and/or swelling at the IV site after you
return home following your procedure, you should notify your doctor as
this may indicate an infection or other type of reaction.
Your doctor may give you additional or alternate instructions after the
procedure, depending on your particular situation.
The content provided here is for informational purposes only, and was
not designed to diagnose or treat a health problem or disease, or
replace the professional medical advice you receive from your physician.
Please consult your physician with any questions or concerns you may
have regarding your condition.
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