Re: Thallium Stress Test

Posted By CCF CARDIO MD - MTR on July 09, 1998 at 23:27:14:

In Reply to: Thallium Stress Test posted by Steve on July 06, 1998 at 13:38:30:






My father had a Thallium Stress Test, which did not involve any exercise
during the test.  This was about a week ago.  Unfortunately, I was not
present at the test, but my dad has some concerns about it.  I am trying to
gather some information about the test.  Why was there no exercise
involved, and what are the potential risks?  I have done some browsing and
found that instead of exercise, a drug call dipyridamole is sometimes used.
Can you tell about this drug and what its side effects may be.  My dad is
on several medications and I am concerned about the possible interaction
between this drug and the medications he is on.  Finally, during the test
he had a lot of lower back pain and had the sensation he lost feeling in
his legs and feet.  Is this a possible side effect?  Also, he is still
having some lower back pain.  How long should this last?
thanks for you help!







Dear Steve, thank you for your question.  Thallium stress tests are designed
to image blood flow to different parts of the heart muscle to evaluate suspected
or known blockages in the coronary arteries.  Thallium is a radioisotope that
is taken up in the heart muscle after intravenous injection when there are not
significant blockages in the coronary arteries.  Before a thallium stress test,
the patient receives an injection of thallium at rest and a gamma counter (large
camera) images blood flow to the heart.  Then, the stress test is performed.
An exercise stress test involves walking on a treadmill or riding a stationary
bicycle to increase the heart rate and thus the oxygen demand of the heart muscle.
When blockages are present in the coronary arteries, the coronary blood flow
cannot increase enough to meet the metabolic demands of the heart muscle at
peak exercise and a "defect" is seen on the thallium images.  Patients usually
experience chest pain during the stress test when this happens and the ECG
tracings sometimes change but some patients with blockages may have neither
chest pain nor ECG changes.  As you can see, thallium significantly improves
a routine ECG-only stress test.  The thallium images at peak exercise are compared
to the images at rest.  When a defect in blood flow occurs at peak exercise and
not at rest, a significant coronary artery blockage is strongly suspected.  When
a defect in blood flow occurs both at rest and with exertion, that indicates that
previous damage from a heart attack has already occurred and that the heart
muscle has been irreversibly damaged.  Pharmacologic thallium tests are often used
in place of exercise thallium tests for patients who are unable to exercise and
for other specific reasons according  to the ordering physician.  Dipyridamole
(referred to as persantine) is an intravenous medication that selectively dilates
the coronary arteries.  Persantine causes selective dilation of coronary arteries
that are normal while arteries with blockages receive less blood flow.  A defect
thus occurs on a persantine thallium in much the same way one does on a stress
thallium.  Common side effects of persantine include nausea, headaches, shortness
of breath, and rhythm disturbances in the heart.  Persantine can interact with
other medications so you should ask your father's physicians about that.  However,
he seemed to tolerate the test fairly well so presumably no major reaction occurred.
The symptoms of lower back pain and loss of sensation in the feet/legs most likely
were not caused by the persantine.  Your father could have problems with the
discs in his lower back and/or sciatica to explain these symptoms.  Again, you
should ask his physician about this problem.  I hope you find this information useful.
Information provided in the heart forum is for general purposes only.  Specific
diagnoses and therapies can only be provided by your physician.

[david516]

A related discussion, thallium stress test side effects was started.

[david516]

A related discussion, thallium stress test side effects was started.

[vedkumar]

A related discussion, drug interaction was started.