find a cardiologist
find a cardiac surgeon

What Is a Thallium Exercise Scan?

The thallium exercise scan is also called a thallium stress test. For the test, a technician injects radioactive thallium into the bloodstream and takes pictures with a scanning camera. The test reveals how adequate the blood flow is through the coronary arteries of the heart. The thallium stress test is combined with an exercise stress test that uses a treadmill or bicycle. Test results show that the blood flow to the heart muscle is either normal, limited, or blocked.

The thallium stress test begins with the exercise test. The patient exercises until reaching his or her maximum level of exercise. Then the exercise is stopped and a very small amount of thallium is injected into a vein. The scanning camera measures the flow of thallium into the heart muscle. The first series of pictures is taken when the heart has been "stressed" by the exercise test. A second series of pictures is taken after the patient has rested for 2 to 3 hours, so the pictures will show blood flow to the heart muscle in a resting state.

The test is very helpful if a person is having chest pain and the cause is not clear. For people who are too sick or have physical problems that prevent them from doing an exercise test, a drug can be used to stimulate the heart.

In a normal healthy heart there is no blockage of blood flow and no damage to the heart muscle. If there is a problem with blood flow to a part of the heart, the thallium will not show up in that part. If there is a temporary blockage of blood, one that is worse with exercise, the first picture will show a blockage. The second picture will show that the thallium has finally spread throughout the heart. If the heart has permanent damage, usually a scar from an old heart attack, the thallium will not spread, even after rest. The radioactivity absorbed from the thallium is not harmful.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional. HIL File CARD4291.RF2 VRS# 6101 Data Version 7.0
Copyright 1999, 2002
McKesson Health Solutions LLC. All rights reserved.