Myocardial Perfusion ImagingEn Español (Spanish Version)
Myocardial perfusion imaging is a test that uses a very low dose of a radioactive agent to evaluate the heart’s blood flow and function. Since blood flow to the heart is best evaluated when you increase the work of the heart, this test is usually performed along with exercise. If you can’t exercise, your doctor may use a drug that increases the work of your heart to mimic exercise.
Blood Flow Through the Heart
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Reasons for Procedure
Myocardial perfusion imaging is used to evaluate previous damage to the heart and your risk of future heart damage.
Some specific reasons to do the test include:
- Determine if you are at risk for a heart attack
- Evaluate if you are a candidate for coronary angiography , angioplasty , or heart surgery
- Evaluate your risk of having a cardiac event before you have noncardiac surgery
- Identify which areas of the heart muscle have an inadequate blood supply
- Show how much of the heart muscle has a limited blood flow
- Provide information about the heart’s pumping ability
- Determine the amount of scarring that occurred from a heart attack
- Evaluate the success of angioplasty or coronary bypass surgery
Risk Factors for Complications During the Procedure
Before the test is scheduled, let your doctor know if you have any medical conditions that may limit your ability to exercise. If you can’t exercise, your doctor may order a drug to mimic exercise. Let your doctor know if you have any of the following:
This test may not be appropriate for people with the following conditions:
What to Expect
Prior to Procedure
For 24 to 48 hours before the test, do not eat or drink any foods or take any of the medications listed below:
- Beverages containing caffeine (such as coffee, tea, colas, or other soft drinks)
- Foods containing caffeine, such as chocolate (including candies, frosting, pies, cakes, cookies, cocoa, or chocolate milk)
- Over-the-counter pain relievers that contain caffeine, including Anacin and Excedrin
- Products that contain theophylline such as Constant-T, Primatene, Quibron, Slo-Phylline, or Theo-Dur
- Dipyridamole (Persantine)
Read product labels and ask your doctor or pharmacist for more information about what products you should avoid before the test.
You may be asked to avoid eating or drinking for 4 to 8 hours before the test. Wear loose clothing and low-heeled shoes with rubber soles or tennis shoes. If you smoke, ideally you should avoid smoking for one to two days before the test, or at a minimum for at least four hours before the test. If you have diabetes , and take medication or insulin for this condition, make sure to ask your doctor how to adjust your medication and food intake for this test.
Tell your doctor, or whomever is conducting the test, if you:
- Have a history of allergies
- Are taking any medications or herbal supplements
- Have diabetes
- Are pregnant or might be pregnant
- Are breastfeeding
- Have any prosthetic implants in your body
The test usually consists of two parts. One part of the test looks at the normal functioning of the heart at rest.
The other part of the test, called “stress,” examines the heart after exercise, or after taking a drug that mimics the effect of exercise on the heart. The doctor interpreting the test will compare the exercise and resting images to evaluate the health of your heart. The order of the parts of the test will vary based on the protocol in your hospital. You will be informed if the exercise or the rest portion will be done first.
Anesthesia is not needed.
Description of the Procedure
A blood pressure cuff is placed on one arm. An intravenous line (IV) is inserted in your other arm. Small round pads (ECG electrodes) are placed on your chest and attached to an electrocardiograph. This allows the doctor to monitor your heart rhythm. Your blood pressure and heart rate are monitored before, during, and after you have exercised.
The doctor or nurse will inject a small amount of radioactive material, like thallium, via the IV into your bloodstream. The amount of radioactivity in these materials is very small. The radioactive tracers concentrate in the parts of the heart that have the best blood flow, and emit signals that can be detected by a special camera. Images taken by the camera show any parts of the heart that are not getting enough blood. These images are taken while you are at rest and while you exercise.
The exercise or “stress” part of the test is usually done with a treadmill. You begin by slowly walking on the treadmill, and the pace increases gradually every three minutes. As you exercise, your heart rate and blood pressure will change. At your peak exercise, the tracer is injected into the IV and you will continue exercising for another one or two minutes.
Approximately 15 to 30 minutes after exercising, you will lie down on a special table as images are taken of your heart.
If you are unable to exercise for any reason, the doctor may use a drug that mimics the effect of exercise on the heart. If you notice any changes in the way you feel, or experience any side effects, notify the clinician who is monitoring the test.
You can get dressed and go home. Follow your doctor’s recommendations.
How Long Will It Take?
The entire test takes between 3 to 5 hours. You may receive the entire test in one day, or you may have each part of the test on two separate days.
Will It Hurt?
In general, this test should not be painful. If you were given a dilating medication, you may feel some discomfort such as flushing, chest pressure/pain, or shortness of breath.
If you receive a medication that increases the work of your heart, you may experience symptoms of anxiety , dizziness, nausea, shakiness, or shortness of breath. Let the clinician monitoring you know if you have any of these symptoms. There is a possibility that you may experience some effects from dilating medication for up to 24 hours after the test.
If you have coronary artery disease , you may feel chest pain or angina during the stress portion of the test. A specialist will be nearby and may give you medication for the symptoms or stop the test early. Let the clinician know if you have any symptoms of jaw, neck, arm, or chest discomfort.
You will be exposed to a small dose of a radioactive substance. Your doctor will use the smallest amount of radioactivity possible to get test results. Cardiac nuclear imaging has been performed for more than 30 years and no serious long-term effects have been reported. Of course, if you are pregnant, exposure to radiation should be avoided unless absolutely necessary. If you think you may be pregnant, let your doctor know.
Average Hospital Stay
The test may be conducted on an inpatient or outpatient basis.
There is no special care necessary after this test.
The doctor will compare the images taken of your heart during rest with the images of your heart during stress. If your heart is relatively healthy, there should be little or no difference between the images taken during stress and those taken at rest. If your heart has partially blocked arteries, images taken during stress will be different from those taken at rest.
American College of Cardiology
American Heart Association
Heart and Stroke Foundation of Canada
University of Ottawa Heart Institute
HeartCenter Online website. Available at: http://www.heartcenteronline.com . Accessed on May 2, 2003.
RadiologyInfo: the radiology information resource for patients website. Available at: http://www.radiologyinfo.org . Accessed on May 10, 2003.
University of Texas website. Myocardial perfusion imaging. Available at: http://www.utmb.edu . Accessed on May 2, 2003.
Last reviewed November 2007 by J. Peter Oettgen, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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