Radionuclide
Angiogram, Resting
(Resting
RNA, MUGA, Gated Blood Pool Scan [Resting], Gated
Cardiac Scan, Resting Gated Blood Pool Scan, Cardiac
Blood Pool Imaging)
What
is a resting radionuclide angiogram (RNA)?
Resting
radionuclide angiogram (RNA) 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, resting
RNA evaluates the heart’s chambers in motion.
A radionuclide
(usually technetium) will be injected into an
arm vein to “tag” the blood cells
so their progress through the heart can be traced
with a scanner. A special camera (gamma camera)
will make recordings of the heart wall at work,
like a motion picture. These recordings will be
synchronized with the heartbeat by using the electrocardiogram
(ECG, or recording of the heart's electrical activity).
A cardiologist
(a physician who specializes in heart disease)
trained in nuclear cardiology will study the films
to evaluate the heart's pumping function and ejection
fraction (the volume of blood pumped out with
each heartbeat).
If the
heart muscle does not move in a normal manner,
and/or a less-than-normal amount of blood is pumped
out by the heart, this may indicate one or more
of the following:
- injury to the heart
muscle, possibly as a result of decreased blood
flow to heart muscle due to clogged coronary
arteries
- an enlargement of one
or more of the heart's chambers
- aneurysm (a weak spot
in the heart muscle)
- toxic effects of certain
medications
Other
related procedures that may be used to assess
the heart include resting or exercise electrocardiogram
(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, myocardial perfusion
scans, and ultrafast CT scan. Please see these
procedures for additional information.
Coronary
artery disease:
Coronary
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 buildup 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 through 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.
When
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 is weakened
due to a lack of food and oxygen.
If the
blood supply to the heart muscle continues to
decrease as a result of increasing obstruction
of a coronary artery, a myocardial infarction,
or heart attack, may occur. If the blood flow
cannot be restored to the particular area of the
heart muscle affected, the tissue dies.
Fortunately,
the technology is available to restore blood flow
to heart tissue when coronary artery blockages
are diagnosed. One of several diagnostic procedures
used to diagnose and evaluate coronary artery
disease is RNA.
Reasons
for your physician to request a resting RNA include,
but are not limited to, the following:
- chest pain
- shortness of breath
- dizziness
- fatigue
If a
screening examination (such as an ECG) suggests
a possibility of some type of heart disease process
that needs to be explored further, a resting RNA
may be performed.
There
may be other reasons for your physician to recommend
a resting RNA procedure.
The
amount of the radionuclide injected into your
vein for the procedure is small enough that there
is no need for precautions against radioactive
exposure. The injection of the radionuclide may
cause some sight discomfort. Allergic reactions
to the radionuclide are rare.
If you
are pregnant or suspect that you may be pregnant,
you should notify your physician due to the risk
of injury to the fetus from myocardial perfusion
scan. Radiation exposure during pregnancy may
lead to birth defects. If you are lactating, or
breastfeeding, you should notify your physician
due to the risk of contaminating breast milk with
the radionuclide.
Patients
who are allergic to or sensitive to medications,
contrast dyes, iodine, shellfish, or latex should
notify their physician.
There
may be other risks depending upon your specific
medical condition. Be sure to discuss any concerns
with your physician prior to the procedure.
Nicotine
in cigarettes may cause spasm in the coronary
arteries, which could affect the test results.
- Your physician will
explain the procedure to you and offer you the
opportunity to ask any questions that you might
have about the procedure.
- 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.
- Generally, no prior
preparation, such as fasting or sedation, is
required. In some cases, smoking cigarettes
may be restricted two or three hours before
testing.
- If you are pregnant
or suspect that you may be pregnant, you should
notify your physician.
- Notify your physician
of all medications (prescription and over-the-counter)
and herbal supplements that you are taking.
- Notify the technologist
or physician if you are allergic to or sensitive
to medications, local anesthesia, contrast dyes,
iodine, shellfish, or latex.
- Notify your physician
if you have a pacemaker.
- Based upon your medical
condition, your physician may request other
specific preparation.
A resting
RNA 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
physician's practices.
Generally,
a resting RNA 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
wear.
- An intravenous (IV)
line will be started in your hand or arm.
- You will be connected
to an ECG machine with electrodes (leads) and
a blood pressure cuff will be attached to your
arm.
- You will lie flat on
a table in the procedure room.
- The radionuclide will
be injected into the vein to “tag”
the red blood cells. Alternatively, a small
amount of blood will be withdrawn from your
vein so that it can be tagged with the radionuclide.
The radionuclide will be added to the blood
and will be absorbed into the red blood cells.
- After the tagging procedure,
the blood will be returned into your vein through
the IV tube. The progress of the tagged red
blood cells through your heart will be traced
with a scanner.
- During the procedure,
it will be very important for you to lie as
still as possible, as any movement can adversely
affect the quality of the scan.
- The gamma camera will
be positioned over you as you lie on the table,
and will obtain images of the heart as it pumps
the blood through your body.
- You may be asked to
change positions during the test; however, once
you have changed position, you will need to
lie still without talking.
- After the scan is complete,
the IV line will be discontinued, and you will
be allowed to leave, unless your physician 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 procedure.
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 physician as this may indicate an infection
or other type of reaction.
Your
physician may give you additional or alternate
instructions after the procedure, depending on
your particular situation.
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