What is a Thallium Stress Test?

‌The thallium stress test is an imaging study that shows your doctor how well blood flows to your heart. It measures your blood flow during rest and after exercise. The thallium stress test is also called a nuclear stress test, a treadmill test, a stress perfusion test, or a cardiac SPECT.

You may have a thallium stress test if:

  • Your previous stress test was inconclusive
  • Your doctor thinks you have coronary artery disease 
  • You’ve had a bypass or angioplasty and your doctor needs to check the results
  • They want to learn how well your heart medications is working
  • You have chest pain

What to Expect During a Thallium Stress Test

The thallium stress test has two parts: at rest and while exercising. It takes about 4 hours to do both parts of the test. Thallium stress tests are done in a hospital, an imaging center, or a cardiologist’s clinic. 

Follow your doctor’s instructions to prepare. They’ll probably tell you to avoid caffeine the day before the test. Don’t eat anything after midnight the night before. Don’t use lotion or any other products on your chest the morning of your test.

You’ll get an IV. When you arrive for your test, a member of the care team will put an intravenous line (IV) into a vein to deliver the thallium.

Resting images will be taken. You will lie on an x-ray table, and the doctor will give you thallium through your IV. Thallium acts like a dye so a gamma camera can show the movement of blood through your body. A gamma camera is a medical imaging device that detects gamma radiation. 

You’ll raise your heart rate. You'll have electrodes placed on your chest and a blood pressure cuff put on your arm. Then, you’ll exercise on a treadmill or stationary bike. The speed and intensity of your exercise will go up until you reach your target heart rate. The team will use the blood pressure cuff and an EKG to monitor your heart as you exercise.

Tell them right away if you notice any chest pain, shortness of breath, or other discomfort during exercise. If you cannot exercise, your doctor can mimic the stress of exercise with medication.

Your exercise images will be taken. After you reach your target heart rate, you will return to the x-ray table for more images with the gamma camera.

Sometimes, exercise images are taken first, and the rest of the images are taken last. In this case, you'll be told to rest for 2 to 3 hours before taking resting images. 

What Are the Risks of Thallium Stress Test?

The thallium stress test is a very safe procedure, and you’re closely monitored the whole time. But it may have some risks, including:

What Do Your Thallium Stress Test Results Mean?

The results of this test will tell you about the flow of blood to your heart through your coronary arteries. An abnormal test result can reveal coronary blockages as well as damage from heart attacks.

The test can also spot an enlarged heart and other heart complications.

Your doctor will compare the resting and exercising sets of images. The results may be:

  • Normal blood flow. If the two sets of images match and look healthy, you have normal blood flow.
  • Abnormal blood flow during exercise. If your images show that part of your heart isn’t getting enough blood flow after exercise, you have a blocked or narrowed artery. This means you have coronary artery disease.
  • Low blood flow during both rest and exercise. If the image shows that part of your heart isn’t getting enough blood during both rest and exercise, you may have a severe blockage. An angioplasty or a stent might be needed to remove the blockage.
  • No thallium visible in parts of the heart. If there is no radioactive dye visible in a certain part of your heart, this is a sign of damage from a heart attack. 
WebMD Medical Reference



American Family Physician: “Exercise Stress Testing: Indications and Common Questions.” 

‌Cedars Sinai: “Cardiac Stress Test.”

Cleveland Clinic: “Nuclear Exercise Stress Test.”

Journal for Nuclear Cardiology: “ASNC imaging guidelines for SPECT nuclear cardiology procedures: Stress, protocols, and tracers.”

Journal of Nuclear Medicine Technology: “Interpretation and Reporting of Myocardial Perfusion SPECT: A Summary for Technologists.”

Mayo Clinic: “Nuclear Stress Test.”‌

Merck Manual: “Radionuclide Imaging."

UC San Diego Health: “Angioplasty with Stent Placement.”

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