Cardiac Tests
Stress Nuclear Testing (Exercise Myocardial Perfusion Imaging)
Stress nuclear testing is a form of stress test that may provide added useful information about your prognosis. A nuclear material is injected into your blood stream while you exercise on the treadmill. The material is safe and medically approved. Similar nuclear materials are used to obtain bone scans, brain scans, thyroid scans etc. The nuclear material is taken up by your heart and is distributed through the heart muscle according to blood flow. Areas of the heart that are supplied by narrowed arteries will have reduced blood flow that will show up on scanning as reduced areas of radioactivity. These techniques are more accurate than routine treadmill testing in finding coronary disease and determining its severity. Scanning agents include the isotpes thallium
and Technetium 99m. Technetium 99m is bound to carrier molecules bound to carrier molecules (MIBI or Myoview®; tetrafosmin or Cardiolyte®). Technetium 99m-based scanning has the added advantage of providing information on the pump function of
the heart. Both stress and persantine nuclear stress tests are useful in excluding falsely abnormal treadmill stress tests and
carry 90-95% accuracy.
MPI is a widely used and safe non invasive test that has been well validated over more than 30 years. As with many non invasive tests, it results in a small radiation exposure. By appropriate selection of patients, the very small risk associated with the radiation exposure is far outweighed by the benefits of the test. In relative quantitative terms the exposure from a MPI test (8-10 mSv)
is roughly 3 times naturally occurring annual background radiation (approximately 3 mSv).
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