Exercise nuclear
scan or nuclear stress test or Cardiolyte stress
test
What is a ‘stress test’ and
why is this called a stress test?
The resting heart muscle’s
blood supply needs are usually well met even in the
presence of blocked arteries. When the heart is
stressed either by exercise or chemicals, the demand
for blood increases. The blood flow through the
blocked arteries- while adequate at rest- may not be
able to keep up with the demands of a stressed
heart. This can show up on the pictures of the
heart taken after stress. This is the principle
behind all the stress tests. The word stress test is
used for any means used to increase heart muscle’s
demand for blood. This can be done by exercise or by
chemical means.
What is a nuclear stress
test?
This is one of the tests done
to look for blockages of heart arteries. During this
test, a radioactive material like Cardiolyte is
injected through a vein. This radioactive material
attaches to the heart muscle. After the injection,
you have to lie still under the camera for a few
minutes so that pictures of the heart can be taken.
After this, your heart is stressed. This can be done
by walking on the treadmill or by chemical means.
During the stress portion of the test, another
injection of radioactive material is given. This is
followed by another session under the camera. The
pre and post stress pictures are compared to look
for an evidence of blockage in heart arteries.
How do you prepare for this
test?
The preparation is the same as
for exercise
treadmill test. This test can take quite a while
to complete. Ask your provider how long it will take
so that you can set aside appropriate amount of
time.
How does this test help?
This test is very helpful for
the diagnosis of coronary artery disease. This test
includes looking at the EKG changes suggestive of
blockages as well as pictures of the heart muscle.
Unlike simple exercise treadmill test, nuclear
stress test can help localize the blockage. This can
also help quantify the amount of heart muscle that
is in jeopardy due to blockage of heart arteries.
What are the shortcomings of
this test?
This test is created to be very
sensitive. It means that it should miss minimum
number of cases with blockage of heart arteries. As
a pay back, this test can be false positive in some
cases. This means that it can be abnormal even if
you do not have blockage of heart arteries that
needs to be fixed by surgery or stenting.
Can radiation from the
nuclear material used to do this test hurt me?
There is no evidence of
clear-cut harmful effects of dosage used for the
stress test. The radiation safety principle, ALARA
is still followed. ALARA is an acronym for As Little
As Reasonably Achievable.
What does an abnormal
nuclear stress test mean?
An abnormal stress test usually
means that you have blockage in heart arteries. A
nuclear stress test result should be interpreted in
the light of a person’s symptoms, his risk for
coronary artery disease etc. The nuclear stress test
has the ability to quantify the severity of
abnormality. Further tests for coronary artery
disease after a nuclear stress test should be
considered based on several different factors. If
needed, usual next step is a coronary angiogram.
I had an abnormal nuclear
stress test and then underwent an angiogram that
came out to be normal. Why was the stress test
abnormal?
Just because you did not have
artery blockage that needed to be fixed by stent or
bypass surgery, it did not mean that you did not
have coronary artery disease. The nuclear stress
test can also be false positive in certain cases.
Back to other stress
tests
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