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 injected into a vein in the arm. 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:
- Find the cause of unexplained chest pain or chest pain brought on by exercise.
- Check for the location and amount of damage caused by a heart attack.
- Identify coronary artery disease (CAD).
- Help make treatment decisions for a person with CAD.
- Check to see that the heart is getting enough blood after heart surgery or angioplasty.
- Identify a congenital heart defect and determine how serious it is. These scans may also be done following surgery to correct a congenital heart defect.
How To Prepare
Before a cardiac perfusion, tell your doctor if you:
- Are taking any medicines, including erection-enhancing medicines (such as Cialis, Levitra, or Viagra). You may need to take nitroglycerin during this test, which can cause a serious reaction if you have taken an erection-enhancing medicine within the previous 48 hours. Ask your doctor whether you need to stop taking any of your other medicines before the test.
- Are allergic to any medicines or anesthetics.
- Are or might be pregnant.
- Are breast-feeding. Use formula and throw out your breast milk for 1 to 2 days after the scan.
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. Four electrodes will be attached to your chest to keep track of your heartbeats.
For a resting scan, the injection site on your arm will be cleaned and an elastic band will be placed around your upper arm. Then a small amount of the radioactive tracer is injected, usually into a vein on the inside of your elbow.
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 immediately after the person is given a medicine such as adenosine, which makes the heart respond like it would to exercise. 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 the medicine is injected into your arm. 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 injected. 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 additional radiation while the scan is being done.
Sometimes more pictures are taken after you rest for 2 to 4 hours. You may resume your 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. For more information, see the medical test 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. 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. For more information, see the medical tests Exercise Electrocardiogram and 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, a different tracer medicine is injected. You will probably continue to exercise for an additional 30 to 60 seconds 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. You may usually resume your normal diet and activities after the final set of scans.
In some hospitals, a second injection of radioactive tracer is repeated several hours after exercise and before the final image. You may be asked to return 24 hours after the test to have another set of pictures taken.
How It Feels
The cardiac scanning test itself is painless.
- You may feel a brief stinging or burning sensation when the needle is inserted into the vein in your arm.
- You may be uncomfortable lying still for an extended period of time on the table during the scans.
- If medicine to stress your heart is used, you may have symptoms of mild nausea, headache, dizziness, flushing, or chest pain (angina). These symptoms only last a few minutes.
- If you are asked to exercise, you may have chest pain, breathlessness, lightheadedness, aching in your leg muscles, and fatigue. Report these to the technician. If the symptoms are severe, the exercise part of the test may be stopped.
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:
- Chest pain.
- An irregular heartbeat.
- Heart attack. There is a slight risk that death may result if a heart attack occurs during the test.
After the test
Call 911 or other emergency services immediately if you develop:
- Chest pain.
- Trouble breathing.
A cardiac perfusion scan measures the amount of blood in your heart muscle at rest and during exercise. Test results are usually available within 1 to 3 days.
The radioactive tracer is evenly distributed throughout your heart muscle.
No areas of abnormal tracer absorption are present.
Some areas of heart muscle are not getting enough blood (ischemia). This may mean that the heart has been damaged or that coronary artery disease is present.
The heart is enlarged and the left pumping chamber (ventricle) is not working well.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- A recent, serious heart attack.
- Inflammation of the heart, such as myocarditis or sarcoidosis.
- Bruising of the heart muscle (cardiac contusion).
- Weakening of the heart muscle.
- Stiffening of the heart muscle (myocardial fibrosis).
- A severely narrowed heart valve.
- Implanted cardiac devices, such as a pacemaker.
- A condition that makes it difficult to exercise, such as lung disease, arthritis, or a neuromuscular problem.
- Some medicines, such as dipyridamole (Persantine) and pentoxifylline (Trental).
- Severe electrolyte imbalances (especially calcium, potassium, sodium, or magnesium).
- Pregnancy or breast-feeding (except in an emergency).
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 with chronic obstructive pulmonary disease (COPD), peripheral arterial disease, spinal cord injury, arthritis, or multiple sclerosis.
- A cardiac perfusion scan is a less invasive method than cardiac catheterization and angiography for determining whether a person with moderate risk of coronary artery disease (CAD) has the disease. For more information, see the medical tests Angiogram and Cardiac Catheterization.
- Cardiac perfusion scans cannot distinguish an area of old injury (scar tissue) from a newer injury caused by a recent heart attack.
- A normal result can help reassure a person with unexplained chest pain and an abnormal stress electrocardiogram that there is not significant coronary artery disease.
- A few small areas of abnormal tracer absorption may mean that only small areas of the heart muscle are not getting enough blood flow. In this case, treatment with medicine may be an option.
- A cardiac perfusion scan is often the first test done in younger women (when the cause of chest pain is uncertain) after the medical history and physical examination. This is because a simple stress electrocardiogram is less accurate in younger women.
- Some cardiologists believe that a stress echocardiogram provides information similar to a cardiac perfusion scan. But a cardiac perfusion scan may provide better information than a stress echocardiogram about blood flow to the heart muscle. For more information, see the medical test Echocardiogram.
- If you have a health condition that prevents you from having an exercise scan, a resting scan may be done. Other tests also may be done to evaluate your heart. For more information, see the medical tests Cardiac Catheterization, Echocardiogram, Electrocardiogram, and Positron Emission Tomography (PET).
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Klocke FJ, et al. (2003). ACC/AHA/ASNC guidelines for the clinical use of cardiac radionuclide imaging—Executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation, 108(11): 1404–1418. Available online: http://circ.ahajournals.org/content/vol108/issue11/index.shtml.
|Author||Robin Parks, MS|
|Associate Editor||Tracy Landauer|
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||John A. McPherson, MD, FACC, FSCAI - Cardiology|
|Last Updated||December 23, 2009|