What is a Nuclear Scan?
A myoview scan is a test that uses a radioactive substance,
known as a tracer, to produce images of the heart
muscle. When combined with an exercise test, the nuclear
scan helps determine if areas of the heart are not receiving
enough blood. NOTE: Nuclear tracer is not an iodine
dye.
The exercise nuclear scan is especially useful in diagnosing
coronary heart disease, the presence of blockages in the
coronary arteries (the vessels that supply oxygen-rich blood
to the heart muscle).
In most cases, doctors use two tracers during one test (dual-isotope
imaging), one tracer for the rest portion (thallium) and
the other for the exercise portion (myoview or sestamibi).
What Does it Show?
During
the test, a small amount of myoview tracer is injected into
a vein in your arm while you walk on a treadmill.
The tracer travels in the bloodstream, is carried through
the coronary arteries, and is picked up by the heart muscle
cells.
Areas of the heart muscle that have an adequate blood supply
pick up the tracer right away and more completely. Areas
that do not have an adequate blood supply pick up the tracer
very slowly or not at all.
The tracer gives off a small amount of radiation that is
detected with a scanning camera. A computer processes the
information and produces images of the radioactivity distributed
in the heart.
If an area of the heart receives less blood than the rest
of the heart (because of a blocked or narrowed artery),
it will pick up less radioactivity and will show up as a
lighter area, called a "defect".
Preparing for the Test
What Happens During the Test?
The nuclear scan is usually performed at a hospital,
office, or test center. For one-day nuclear tests the rest
portion is done first, then the exercise portion. In
two-day nuclear tests the rest portion is done one day and
the exercise portion is done another day.
Rest Portion
The tracer will be injected and a set of pictures will be
taken, while you are at rest. You will lie flat on a special
table under a large scanning camera. During imaging,
the camera takes pictures of your heart at various angles.
Remain still while the pictures are being taken. This part
of the test may take twenty (20) minutes. These images are
compared to the images obtained during the exercise portion
of the test.
Exercise Portion
You will walk on a treadmill. The treadmill moves slowly
at first, then the speed and incline increase gradually.
If walking on the treadmill is not possible you will
receive an injection of a vasodilator for four (4) minutes
of either adenosine or persantine. During infusion with
adenosine or persantine you may experience chest pain, shortness
of breath, headache, nausea, etc. These symptoms are transient
and can be reversed within two (2) minutes with another
medication.
Be sure to report any symptoms, such as chest pain or discomfort,
dizziness, or severe shortness of breath. Try to exercise
for as long as you are able to, because it increases the
accuracy of the test.
When you reach the point where you feel you can't exercise
for much longer, let the technician know. The technician
will inject the tracer into the intravenous line. You will
then be asked to continue exercising for another minute
or so after the injection.
Another set of pictures will be taken. These images will
be compared to the images obtained during the rest portion
of the test.
How Long Does it Take?
For a 1-day test allow four to five (4-5) hours for the
entire test, which includes preparation, the exercise portion,
imaging waiting time.
For a 2-day test allow two (2) hours for the "resting"
day portion of the test and three (3) hours for the "stress"
day portion of the test.
Is the Test Safe?
The radiation exposure during a nuclear scan is small, and
the doses used are safe. However, if you are pregnant, suspect
you may be, or are a nursing mother, be sure to let the
doctor know.
The exercise test is also safe. A small amount of risk
does exist, however, because it stresses the heart. Possible
complications include abnormal heart rhythms and chest pain.
Experienced personnel are available to handle any emergency.
Your Test Results
Your doctor will discuss the test results with you during
a future office visit. The test results help the doctor make
an accurate diagnosis and develop a treatment plan that's
best for you.
Note: On an average a stress nuclear examination is 80%
accurate and can miss coronary disease 1 out 5 times on an
average. The test can also be postive even if you do not have
blockages 20% of the time. In addition a negative stress test
does not mean that you do not have risk for heart attacks.
Your risk factor profile (family history, cholesterol smoking
etc) predicts heart attacks and medicines modify this risk.
At Florida Cardiolgoy we take every care to discuss both positive
and negative results with our patients on a follow up visit
so be sure to ask us any questions on your follow up appointment
