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 symptoms like angina (such as chest pain or pressure). 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:
- Find the cause of unexplained chest pain or pressure.
- Find the cause of chest pain or pressure 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 breastfeeding. The radioactive tracer used in this test can get into your breast milk. Do not breastfeed your baby for 2 days after this test. During this time, you can give your baby breast milk you stored before the test, or you can give formula. Discard the breast milk you pump for 2 days after the test.
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 non-prescription medicines for at least 24 hours before the test.
Wear comfortable shoes and loose shorts or pants suitable for exercise. Remove all jewellery 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 .
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 dipyridamole, 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 pedalling 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 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.
Drink plenty of fluids for the next 24 hours to help flush the tracer out of your body. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink.
How It Feels
The cardiac scanning test itself is painless.
- You may feel a brief stinging or burning sensation when the IV is inserted into your vein.
- 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. These symptoms only last a few minutes.
- If you are asked to exercise, you may have chest pain, breathlessness, light-headedness, 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.
- You will be asked to remain very still during each scan, which takes about 5 to 10 minutes. The camera will move to take more pictures at different angles. Several scans will be taken.
Cardiac perfusion scans are usually safe.
Anytime you're exposed to radiation, there's a small chance of damage to cells or tissue. That's the case even with the low-level radioactive tracer used for this test. But the chance of damage is very low compared with the benefits of the test.
Most of the tracer will leave your body through your urine or stool within a day. So be sure to flush the toilet right after you use it, and wash your hands well with soap and water. The amount of radiation in the tracer is very small. This means it isn't a risk for people to be around you after 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 or pressure.
- Trouble breathing.
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.
Results are:footnote 1
- Normal if radioactive tracer is evenly distributed throughout your heart muscle.
- Abnormal if areas of abnormal tracer absorption are present. This means 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.
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 breastfeeding (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 who have chronic obstructive pulmonary disease (COPD), peripheral arterial disease, spinal cord injury, arthritis, or multiple sclerosis.
- Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- 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.
- Pagana KD, Pagana TJ (2014). Mosby's Manual of Diagnostic and Laboratory Tests, 5th ed. St. Louis: Mosby.
Current as of: December 16, 2019
Author: Healthwise Staff
Medical Review: Rakesh K. Pai MD, FACC - Cardiology, Electrophysiology
Brian D. O'Brien MD - Internal Medicine
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
George Philippides MD - Cardiology
Current as of: December 16, 2019