In this common type of scan, the radioactive isotope thallium is injected into your vein at rest and at the end of an exercise or pharmacologic stress test. Images are taken after each injection that show how the blood is flowing through your heart arteries. If the heart arteries have blockages, there is not enough blood flow through them during stress, resulting in an abnormality on the scan. This test can also identify regions of damage or scarring of the heart muscle due to previous heart attack. scarring of the heart muscle due to blocked coronary arteries or a previous heart attack.

For the thallium test, you will be connected to an electrocardiogram . You will be asked to exercise as hard as you can on a treadmill. When you are at peak exercise, a small amount of thallium will be injecting into your vein, where it will travel in the blood stream through the coronary arteries and will be taken up into the heart muscle.

If your doctor thinks that exercise is appropriate for you, you will be given a drug that increases the blood flow to through your heart arteries, mimicking what happens during exercise (pharmacologic stress).

After the stress injection, you will lie down on a special table under a camera, which obtains an image of your heart muscle blood flow. Either before or after the stress portion of the test, a rest scan is performed, usually with a separate injection of the radioisotope at rest.

The entire test takes up to four hours. At some point, you may be given a long break for lunch or a snack. Because you are not sedated, you will be able to drive yourself home after the test.