Thallium stress test is a nuclear imaging method that shows how well blood flows into the heart muscle, both at rest and during activity.
How the test is performed
This test is done at a medical center or physician's office. It is done in parts, or stages:
You will have an IV (intravenous line) started.
A radiopharmaceutical, such as thallium or sestamibi, will be injected into one of your veins.
You will lie down and wait for between 15 and 45 minutes.
A special camera will scan your heart and create pictures to show how the radiopharmaceutical has traveled through your blood and into your heart.
Most people will then walk on a treadmill (or pedal on an exercise machine).
After the treadmill starts moving slowly, you will be asked to walk (or pedal) faster and on an incline. It is like being asked to walk fast or jog up a big hill.
If you are not able to exercise, your doctor may give you a medicine called a vasodilator, which dilates your heart arteries. Or you may get a medicine that will make your heart beat faster and harder, similar to when you exercise.
Your blood pressure and heart rhythm (ECG) will be watched (monitored) the whole time.
When your heart is working as hard as it can, a radiopharmaceutical is again injected into one of your veins.
You will wait for 15 to 45 minutes.
Again, the special camera will scan your heart and create pictures.
You may be allowed to get up from the table or chair and have a snack or drink.
Using a computer, your doctor can compare the first and second set of images. This can help your doctor tell if you have heart disease or if your heart disease is becoming worse.
How to prepare for the test
You should wear comfortable clothes and shoes with nonskid soles. You will probably be asked not to eat or drink anything after midnight, except for a few sips of water if you need to take medicines.
You will need to avoid caffeine for 24 hours before the test. This includes:
Tea and coffee
All sodas, even ones that are labeled caffeine-free
Chocolates, and certain pain relievers that contain caffeine
Your doctor will tell you if you need to stop taking any medicines before the test. Medications used to treat asthma and angina may interfere with test results. Never stop taking any medicine without first talking to your doctor.
It is important to tell your doctor if you have taken a dose of the following medications within the last 24 hours:
Sildenafil citrate (Viagra)
How the test will feel
During the treadmill test, some people feel:
Muscle cramps in the legs or feet
Shortness of breath
If you are given the vasodilator drug, you may feel a sting as the medication is injected, followed by a feeling of warmth. Some patients also have a headache, nausea, and a feeling that their heart is racing.
If you are given medication to make your heart beat stronger and faster (dobutamine), you may have a headache, nausea, or your heart may pound more strongly.
Your health care provider will explain the risks before the test.
Breast tissue in women and non-heart tissues, such as the diaphragm, can sometimes cause false positive test results when older (rest-stress) methods are used to show how well blood flows into your heart muscle. Special techniques can prevent this problem and reduce the need for further testing.
Udelson JE, Dilsizian V, Bonow RO. Nuclear cardiology. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. St. Louis, Mo: WB Saunders; 2011:chap. 17.
Mahajan N, Polavaram L, Vankayala H, et al. Diagnostic accuracy of myocardial perfusion imaging and stress echocardiography for the diagnosis of left main and triple vessel coronary artery disease: a comparative meta-analysis. Heart. 2010;96(12):956-966.
Fraker TD Jr, Fihn SD, Gibbons RJ, et al. 2007 chronic angina focused update of the ACC/AHA 2002 Guidelines for the management of patients with chronic stable angina: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines Writing Group to develop the focused update of the 2002 Guidelines for the management of patients with chronic stable angina. Circulation. 2007;116:2762-2772.
Michael A. Chen, MD, PhD, Assistant Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.