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In general, the patient comes to the exercise location, either in
a physician's office or at the hospital and is given a dose of radioactive
material at rest. Pictures of the heart are taken with a large and
bulky, but totally non-invasive, radioactive camera showing the
heart rather clearly. An hour or so later, the patient is exercised
on a treadmill or is "exercised"** using an intravenous medication
instead of true exercise. At the appropriate time, a second dose
of radioactive material is given intravenously. Then, some minutes
later, additional pictures of the heart are taken with the radioactive
camera.
The initial
resting pictures obtained are compared to the exercise pictures.
The data is manipulated in a computer, and additional diagrams are
obtained showing whether or not there is evidence of reduced blood
supply to a particular area of the heart muscle. If no changes from
the resting to the exercise pictures are noted, then it is assumed
that no blockages are present. If there is a difference with exercise,
then it is assumed that a blockage may indeed be present. Further
study or adjusted medications would be required in that circumstance.
**Occasionally
a person is unable to do exercise such as walking because they are
ill or have physical limitations. In this case, a medication such
as Dipyridamole (di-pi-RID'-ah-mol) is given to the patient instead
of performing an exercise test. This medication increases blood
flow to the heart and thus "mimics" an exercise test. The Thallium
portion of the test is then performed as usual.
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