Cardiac Perfusion Scan
A cardiac perfusion scan measures the amount of blood in your heart muscle at rest and during exercise. It is often done to find out what may be causing chest pain. It may be done after a heart attack to see if areas of the heart are not getting enough blood or to find out how much heart muscle has been damaged from the heart attack.
During the scan, a camera takes pictures of the heart after a special test medicine (radioactive tracer) is given through an IV. The tracer travels through the blood and into the heart muscle. As the tracer moves through the heart muscle, areas that have good blood flow absorb the tracer. Areas that do not absorb tracer may not be getting enough blood or may have been damaged by a heart attack.
Two sets of pictures may be made during a cardiac perfusion scan. One set is taken while you are resting. Another set is taken after your heart has been stressed, either by exercise or after you have been given a medicine. The resting pictures are then compared with the stress images.
This test is also known by other names including myocardial perfusion scan, myocardial perfusion imaging, thallium scan, sestamibi cardiac scan, and nuclear stress test.
Why It Is Done
A cardiac perfusion scan is done to:
How To Prepare
Before a cardiac perfusion, tell your doctor if you:
Do not eat or drink for at least 3 hours before a cardiac perfusion scan. If you are having a stress scan, avoid alcohol, tobacco, caffeinated beverages, and nonprescription medicines for at least 24 hours before the test.
Wear comfortable shoes and loose shorts or pants suitable for exercise. Remove all jewelry before the test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
How It Is Done
A cardiac perfusion scan is usually done in a hospital radiology or nuclear medicine department, a doctor's office, or at an outpatient clinic. The test is done by a doctor and technologist trained in nuclear medicine.
For resting scans, in which you do not exercise, you will be asked to remove your clothing above the waist, and you will be given a hospital gown to wear. Electrodes might be attached to your chest to keep track of your heartbeats.
You will have a very thin tube, called an IV, going into your arm or hand. A small amount of the radioactive tracer will be put in the IV.
You will lie on your back on a table with a large camera positioned above your chest. The camera records the tracer's signals as it moves through your blood. The camera does not produce any radiation, so you are not exposed to any additional radiation while the scan is being done.
You will be asked to remain very still during each scan, which takes 5 to 10 minutes. The camera will move to take more pictures at different angles. Several scans will be taken.
The entire test takes 30 to 40 minutes, after which you can resume your normal activities.
Stress scan using medicine
The stress scan is done in two parts. In many hospitals, the first images are taken while the person is at rest. Then a second set of images is taken after the person is given a medicine such as adenosine, which makes the heart respond like it would to exercise. Sometimes the stress scan is done first and the resting scan might be done the next day.
A stress test with medicine is usually used when a person cannot exercise for some reason.
For this test, you will be asked to sit or lie on the examining table and you will be given a routine electrocardiogram (EKG or ECG), which takes about 5 to 10 minutes.
Then you will be given the medicine through your IV. You may get a headache and feel dizzy, flushed, and nauseated from the medicine, but these symptoms usually do not last long. Additional EKGs and blood pressure measurements are often taken. After the medicine takes effect (about 4 minutes), a small amount of radioactive tracer is given through your IV.
You will wait about 30 to 60 minutes. You might be asked to eat or drink something. Then you will lie down on a table for a set of scans. The camera records the tracer's signals as it moves through your blood. The camera does not produce any radiation, so you are not exposed to any more radiation while the scan is being done.
Sometimes more pictures are taken after you rest for 2 to 4 hours. Most people can resume their normal diet and activities after the final set of scans.
Stress scan using exercise
For stress scans using exercise, your heart rate will be checked with an electrocardiogram (EKG or ECG). Because EKG electrodes need to be attached to the chest to check the heart, men are usually bare-chested and women usually wear a bra, gown, or loose shirt. To learn more, see the topic Electrocardiogram.
The exercise stress scan is done in two parts. First a set of resting images is taken, then a set of stress images is taken immediately after exercise. Sometimes the stress scan is done first and the resting scan might be done the next day.
In many hospitals, first resting pictures are taken using one type of tracer. More pictures are taken using a different tracer after your heart has been stressed by exercise.
In this stress test, you exercise on a treadmill or stationary bike. Your heart rate will be checked during the test with standard electrocardiography. Your blood pressure is checked using a blood pressure cuff placed on your arm. To learn more, see the topic Exercise Electrocardiogram.
You will begin by walking or pedaling slowly and easily. Every few minutes, the speed or incline of the treadmill or resistance of the bike may be increased. You will exercise until you need to stop or until you reach a suitable heart rate. At that point, you will be given a different tracer medicine through your IV. You will probably continue to exercise for an additional 1 to 2 minutes to circulate the radioactive tracer.
You will then lie down on a table for scanning. Each scan takes 5 to 10 minutes. The camera does not produce any radiation, so you are not exposed to any additional radiation while the scan is being done.
Sometimes more pictures are taken after you rest for 30 minutes to 4 hours. In some hospitals, you are given more radioactive tracer several hours after exercise and before the final image.
Most people can resume their normal diet and activities after the final set of scans.
How It Feels
The cardiac scanning test itself is painless.
Cardiac perfusion scans are usually safe. There is always a slight chance of damage to cells or tissue from radiation, including the low levels of radiation used for this test. But the chance of damage from the radiation is usually very low compared with the benefits of the test.
The risk of exercise depends on the condition of your heart and your general level of health. The risks include:
After the test
Test results are usually available within 1 to 3 days.
A cardiac perfusion scan measures the amount of blood in your heart muscle at rest and during exercise.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
Test results may be difficult to interpret in scans done on women with large breasts.
What To Think About
Stress testing using medicine may be done instead of exercise stress testing for older adults and people with conditions that may make exercise difficult, such as those who are obese or those who have chronic obstructive pulmonary disease (COPD), peripheral arterial disease, spinal cord injury, arthritis, or multiple sclerosis.
Other tests also may be done to evaluate your heart. To learn more, see:
Other Places To Get Help
eMedicineHealth Medical Reference from Healthwise
To learn more visit Healthwise.org
© 1995-2014 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.