Test Overview
A cardiac blood pool scan shows how well
your heart is pumping blood to the rest of your body.
During this test, a small amount of a radioactive substance called a
tracer
is injected into a vein. A gamma camera detects
the radioactive material as it flows through the heart and lungs.
The percentage of blood pumped out of the heart with each heartbeat is
called the
ejection fraction
. It provides an estimate of how well
the heart is working.
There are two types of cardiac blood pool
scans.
-
First-pass scan. This scan makes pictures of the
blood as it goes through the heart and lungs the first time. A first-pass scan
can be used in children to look for heart problems that have been present since
birth (
congenital heart disease
).
-
Gated scan or multigated acquisition (MUGA) scan. This scan uses the electrical signals of the heart to trigger the
camera to take a series of pictures that can be viewed later like a motion
picture. The pictures record the heart's motion and determine if it is pumping
(contracting) properly. MUGA scanning may take 2 to 3 hours to obtain all the
needed views and can be done both before and after you exercise. You may be
given nitroglycerin to see how your heart responds to this medicine. MUGA
scanning may be done after a first-pass scan. It is usually not done on
children.
Why It Is Done
A cardiac blood pool scan is done
to:
- Check the size of the heart chambers (
ventricles
).
- Check the pumping action of
the lower ventricles.
- Look for an abnormality in the wall of the
ventricles, such as an
aneurysm.
- Look for abnormal movement of
blood between the heart chambers.
How To Prepare
Before having a cardiac blood pool
scan, tell your health professional if you:
- Are allergic to any medicines.
- Are
or might be pregnant.
- Have recently had any test that uses a
radioactive tracer, such as a bone scan or thyroid scan.
- Have a
pacemaker or other metal device implanted in your chest.
These devices may make it hard to obtain clear pictures of the blood flow
through the heart.
You may be asked not to eat or drink for a few hours before the
test. You should not have any caffeine or smoke for 4 to 6 hours before the
test.
If testing will include exercise, you should wear
comfortable shoes and clothing.
Many medicines may affect the
results of this test. Be sure to tell your health professional about all the
nonprescription and prescription medicines you take.
Talk to your
doctor about any concerns you have regarding the need for the test, its risks,
how it will be done, or what the results will mean. To help you understand
the importance of this test, fill out the
medical test information form
(What is a
PDF
document?)
.
How It Is Done
A cardiac blood pool scan usually is
done in a hospital by a radiology or nuclear medicine technician. Most people do not have to stay overnight in the hospital.
Before the test
You will need to remove any
jewelry that might interfere with the scan. You may need to take off all or
most of your clothes. You will be given a cloth or paper gown to use during the
test.
During the test
You will lie on an examination
table beneath the gamma camera.
Electrocardiogram (EKG, ECG)
electrodes are attached
to your chest so that the electrical signal of your heart can also be detected.
Then the camera, which is a round metal instrument about
3 ft (1 m) wide, will be
positioned close to your body. If you are cold or uncomfortable lying on the
table, ask the technician for a pillow or blanket. The camera may be positioned
in different places across your chest to record different views of your
heart.
The technician cleans the site on your arm where the
radioactive tracer will be injected. An elastic band, or tourniquet, is then
wrapped around your upper arm to temporarily stop the flow of blood through the
veins in your arm. This makes it easier to put the needle into a vein properly.
A small amount of the radioactive tracer is then injected, usually into a vein
on the inside of your elbow.
If you are having a multigated
acquisition (MUGA) scan, a blood sample may be taken and the tracer added to
it, and then it will be reinjected into your vein.
The gamma
camera will take pictures as the radioactive tracer moves through your
bloodstream and into your heart. It is important not to move while the scan is
under way.
The camera does not produce any radiation, so you are
not exposed to any additional radiation while the scan is being done. You will
need to hold still during each view, which may take up to 5 minutes. You may be
asked to:
- Change position for each different
view.
- Do some exercise between scans to see how well your
heart functions after the stress of exercise.
- Take nitroglycerin to
see how well your heart responds to the medicine.
The radioactive tracer is designed to attach to your
blood cells, which takes 20 to 30 minutes. You will then have to wait 2 to 4
hours until the tracer is completely absorbed by your
red blood cells
. During that time, you may have to
stay at the test center. Some test centers may allow you to leave and come back
when it is time for your scan.
Testing usually takes 10 minutes
to an hour, depending on which studies are done. MUGA scanning may require 2 to
3 hours to obtain all the needed views.
After the test
Once your scan is complete, you
usually will be able to leave the testing room right away. You may have to wait
at the test center until all of your scan images have been reviewed. If you
moved during the scan and the images turned out blurry, the scan may have to be
repeated.
Drink lots of water and urinate frequently after your
scan to make sure that the tracer flushes completely out of your body. It takes
a day or two for the tracer to be completely eliminated.
How It Feels
You may feel nothing at all from the
needle puncture when the tracer is injected, or you may feel a brief sting or
pinch as the needle goes through the skin. Otherwise, a cardiac blood pool scan
is usually painless. You will not feel anything from the operation of the gamma
camera. You may find it hard to remain still during the scan. The
examination table may feel cool. Ask for a pillow or blanket to make yourself
as comfortable as possible before the scan begins.
Risks
Allergic reactions
to the radioactive
tracer are rare. Most of the tracer will be eliminated from your body (through
your urine or stool) within a day, so be sure to promptly flush the toilet and
thoroughly wash your hands with soap and water. The amount of radiation is so
small that it is not a risk for the people you come in contact with after the
test.
Occasionally, some soreness or swelling may develop at the
injection site. These symptoms can usually be relieved by applying moist, warm
compresses to your arm.
There is always a slight risk of damage to
cells or tissue from being exposed to any radiation, including the low level of
radiation released by the radioactive tracer used for this test.
Results
A cardiac blood pool scan shows how well
your heart is pumping blood to the rest of your body.
The most commonly reported
value is the
ejection fraction, which is the average amount of
blood pumped out of the heart's
left ventricle during each contraction.
Normal results include:
1
- Ejection fraction is 55%
to 65%.
- Walls of the ventricles
are contracting normally.
Many conditions can affect cardiac
blood pool scan results. Your doctor will discuss any significant
abnormal results with you in relation to your symptoms and past health.
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
- Fast or irregular heart
rhythms.
- Long-acting nitrate medicines and
digoxin.
- Recent nuclear scans, such as thyroid or bone
scans.
- Barium, such as from a
barium enema
, and bismuth, such as
Pepto-Bismol.
- Inability to remain still during the test. You may
not be able to have the test if you have severe back problems or other physical
disabilities that prevent you from lying flat.
-
Obesity
.
What To Think About
- Cardiac blood pool
imaging is not usually done during pregnancy because the radiation could damage
a developing
fetus
.
- The cardiac blood pool scan is a safe and
accurate way to determine overall heart function.
- Multigated
acquisition (MUGA) scans are routinely used before and after receiving a heart
transplant to assess how well the heart is working. MUGA also may be used to
monitor the ejection fraction in people receiving chemotherapy.
- Generally, an
echocardiogram
provides as much information as a MUGA
scan and is less invasive. But a MUGA scan provides more accurate
information about ejection fraction than an echocardiogram, especially in
people who are obese or who have lung disease. For more information, see the
topic
Echocardiogram.
References
Citations
-
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Saunders.
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Saunders.
- Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
Credits
|
By
| Healthwise Staff |
|
Primary Medical Reviewer
| Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology |
|
Specialist Medical Reviewer
| George Philippides, MD - Cardiology |
|
Last Revised
| August 5, 2011 |
