A thallium exercise stress test is an invasive, nuclear scanning tool to see how well blood flows to the heart muscle during rest and exercise. Heart images are taken at rest and immediately following exercise via a gamma camera. The images gather information on how well the heart works while at rest and during exercise when it's under stress. The thallium exercise stress test can decipher if the heart isn't receiving an adequate amount of blood and if there's any damage to the heart muscle, according to the MayoClinic.com.
Candidates
Doctors commonly order a thallium exercise stress test for patients whom they suspect have coronary artery disease, since its cardiovascular screening tool to ensure the patient's heart is working properly. A thallium stress test can show the severity of a coronary artery blockage which may need surgical treatment. A post-surgery thallium stress test can show the effectiveness of a heart procedure and whether it has improved blood circulation to and from the heart. Thallium stress tests may also be recommended to symptomatic individuals, such as those with chest pain, pressure or discomfort to search for an underlying cause to their symptoms.
Procedure
Patients perform the thallium exercise stress test on either the treadmill or bicycle. When the patient reaches his maximal level of exercise, a small amount of a radioactive substance, termed thallium, is injected into the bloodstream. Thallium mixes with blood in the bloodstream and enters the heart muscle cells and arteries. As thallium travels throughout the heart, exercise stops and the patient lies down on a special table under a gamma camera, which can see thallium. The gamma camera takes pictures of the areas thallium traveled to -- these images are termed the "stress" pictures. The patient then lies still for an additional two to three hours until others images are taken, termed the "rest" pictures.
Interpretation
If the images of the heart muscles and arteries are normal during both stress and rest, then blood flow through the coronary arteries is normal, meaning the heart's receiving an adequate amount of blood supply. If the images show blood flow is abnormal during stress, but normal during rest, then the heart's receiving an insufficient amount of blood during stress. This could be due to a blockage in one or more coronary arteries, according to the American Heart Association.
If the images of the heart muscle are abnormal during both stress and rest, the heart is receiving a deficient amount of blood at all times. In relation to this, the American Heart Association states if thallium cannot be seen in some aspects of these images, it represents dead heart cells becoming scar tissue from a prior heart attack.
Risks
In general, thallium stress tests are safe and complications are rare. However, any medical procedure does carry a risk of potential complications, such as allergic reaction, heart attack or chest pain, according to the MayoClinic.com. An allergic reaction may result from the injected radioactive dye. Although very rare, there's a slight chance of heart attack. In some cases exercise stress tests can provoke symptoms to develop such as chest pain, pressure or discomfort, which commonly cease with rest.
