This test is done at a medical center or health care provider's office. It is done in stages:
You will have an IV (intravenous line) started.
A radioactive substance, 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 substance 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.
If you are not able to exercise, you may given a medicine called a vasodilator. This drug widens (dilates) your heart arteries.
In other cases, you may get a medicine (dobutamine) that will make your heart beat faster and harder, similar to when you exercise.
Your blood pressure and heart rhythm (ECG) will be watched throughout the test.
When your heart is working as hard as it can, a radioactive substance 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.
Your health care provider will compare the first and second set of pictures using a computer. This can help detect 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 non-skid soles. You may be asked not to eat or drink after midnight. You will be allowed to have 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
Many medicines can interfere with blood test results.
Your provider will tell you if you need to stop taking any medicines before you have this test.
DO NOT stop or change your medicines without talking to your doctor first.
How the Test will Feel
During the 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. This is followed by a feeling of warmth. Some people also have a headache, nausea, and a feeling that their heart is racing.
If you are given medicine to make your heart beat stronger and faster (dobutamine), you may have a headache, nausea, or your heart may pound faster and more strongly.
A normal test most often means that you were able to exercise as long as or longer than most people of your age and gender. You also did not have symptoms or changes in blood pressure, your ECG or the images of your heart that caused concern.
A normal result means blood flow through the coronary arteries is probably normal.
The meaning of your test results depends on the reason for the test, your age, and your history of heart and other medical problems.
What Abnormal Results Mean
Abnormal results may be due to:
Reduced blood flow to a part of the heart. The most likely cause is a narrowing or blockage of one or more of the arteries that supply your heart muscle.
Scarring of the heart muscle due to a previous heart attack
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Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.