Thallium and Sestamibi Stress Tests

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How is the Test Performed?

In a special room or lab at a medical center, you will be instructed to exercise as hard as you can on a treadmill or bicycle. If your doctor considers that exercise is not safe for you, or that you may be unable to exercise enough because of orthopedic problems, then you will be given an intravenous medication that will challenge your heart as if you were exercising.

When you reach your maximum level of exercise, a nurse will inject in your vein a small amount of a radioactive substance (radiotracer), either thallium or sestamibi. The radiotracer will travel in the bloodstream and, through the coronary arteries, will enter into the heart muscle as you complete your exercise session.

After you finish exercising, you will lie down on a special table under a bulky camera called a gamma camera. The gamma camera can scan your heart and detect the radiotracer in it. The distribution of the radiotracer in your heart will be processed by a computer to create pictures of your heart. The first pictures are made shortly after the exercise test, to show the circulation of blood to your heart during exercise. This is the part considered "a stress test" and is the most challenging for your heart.

Then you will need to lie quietly for 2-3 hours, and at that point the scanner will make another series of pictures of your heart. These images will show the circulation of blood through your heart muscle at rest.

If your doctor has indicated that your test should be performed without exertion, then at the beginning of the test you will not exercise, but instead will receive an intravenous medication, a vasodilator (usually dipyridamole or adenosine). This medication will selectively dilate (widen) the coronary arteries as long as they are normal; arteries with blockages will receive less blood flow and will be less dilated, allowing less blood flow into the heart muscle. After this initial medication, you will receive the injection with the radiotracer. The test done using a vasodilator can potentially show a defect in the same way as the test with exercise does.