Nuclear Stress Test
What is a Nuclear* Stress Test?
*May also be referred to as "Cardiolyte" or "Thallium" or "Adenosine" Test
By producing an image of the heart, radioactive "tracers" such as Thallium and Myoview/Cardiolyte can increase the accuracy of a traditional stress test. Nuclear scanning of the heart shows how well blood flows to the heart muscle. It's usually done in conjunction with an exercise stress test on a treadmill, but can also be performed using medicines such as Regadenoson and Dobutamine that effectively simulate the effects of exercise on the heart. Cardiac Nuclear Stress Imaging helps determine whether coronary artery stenoses (blockages) are so severe as to limit blood flow to heart muscle when it needs it most... during physical activity. In addition, nuclear imaging allows a determination of the heart's pumping function (ejection fraction).
When a patient reaches his or her maximum level of exercise, or after simulating exercise with medications, a small amount of tracer is injected into a vein. The patient then lies down on a table under a camera that detects the energy emitted from the radioactive tracer and generates pictures (or scans) that reflect the heart's blood flow both at rest and following stress. If a portion of the heart muscle is under-perfused (doesn't receive a normal blood supply), a deficiency of tracer activity in that area will appear on the finished images as a "defect".
At the Heart Care Centers of Illinois offices, resting pictures are first obtained using a radioactive tracer, 99mTc Tetrofosmin. Next, stress is induced using either a treadmill exercise routine or medication (Regadenoson or Dobutamine). At the peak of exercise or the appropriate time during a medication induced stress test, the tracer 99mTc Tetrofosmin is injected into the bloodstream to determine the heart's blood flow during activity. Our "tracers" and methods are both widely used and quite safe. Cardiologists, nurses and technologists with expertise in nuclear cardiology supervise the testing process and analyze the results.
Examples of possible nuclear stress test results:
- If the scan is normal during both exercise and rest, then blood flow through the coronary arteries is most likely normal as well. No significant coronary artery blockage is suspected.
- If the scan is normal at rest but abnormal following exercise (a reversible perfusion defect), then the heart isn't receiving enough blood when it's under stress. This may be due to blockage in one or multiple coronary arteries.
- If abnormal blood flow is detected both at rest and with stress, this suggests that part of the heart has suffered injury in the past. This is often the case following a heart attack.