Frequently Asked Questions
- What is a Myocardial Perfusion Imaging Stress Test?
- How safe is a Myocardial Perfusion Stress Test?
- Why would my doctor order a Myocardial Perfusion Imaging Stress Test instead of a regular stress test?
- How is the test performed?
- What happens if you are unable to exercise?
- Are there any special preparations for the study?
- How is the Persantine Myocardial Perfusion Stress Test different from an Exercise Myocardial Perfusion Stress Test?
- Important Points to Remember
What is a Myocardial Perfusion Imaging Stress Test?
Myocardial Perfusion Imaging Stress Test involves an injection of a small amount of radioactive material which circulates in the bloodstream and shows if your heart muscle is receiving adequate blood supply under resting and stress conditions. From this one can determine if there has been a myocardial infarction (heart attack) in the past, and if there are any blockages in the coronary arteries.
The nuclear lab at CAP has been certified by the Inter-Societal Commission for the Accreditation of Nuclear Medicine Laboratories, through a rigorous application and evaluation process.
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How safe is a Myocardial Perfusion Stress Test?
Any stress procedure may have some risks and you should consult your physician regarding the risks and benefits of this procedure. The radioactive materials, Cardiolite and Thallium, have been shown to be safe with low incidence of adverse reactions. This test and materials are used routinely worldwide, under physician supervision, for myocardial perfusion imaging. Neither Cardiolite nor Thallium are "dyes"; they don't contain iodine, and a prior reaction to an iodine containing X-ray contrast "dye" does not preclude the use of these agents.
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Why would my doctor order a Myocardial Perfusion Imaging Stress Test instead of a regular stress test?
Under certain circumstances, a regular stress test may yield indeterminate results. To improve the diagnostic accuracy, your physician may request a myocardial perfusion stress test.
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How is the test performed?
The test usually consists of two parts, an initial resting imaging component as well as a post exercise component. Typically a small IV is placed in your arm and an injection of the Thallium tracer is made. Following this, you lay on a table and a scan of your chest is made. This typically takes about 30-45 minutes.
Following this initial imaging, a treadmill test is performed. As in a regular treadmill stress test, ECG electrodes will be attached to your chest. This permits monitoring of your heart rate before, during and after you have exercised. A blood pressure cuff will be placed on your arm to monitor your blood pressure before, during and after you have exercise. Additionally, an IV line will be placed in your hand or arm vein to allow for ease of the Cardiolite injection. The IV will be removed when the exam is completed.
The exercise part of the exam is done with a treadmill, very similar to one used at a health club. Exercising will begin slowly, and every three minutes, the pace and incline will gradually increase. As you exercise, your heart rate and blood pressure will change. This is normal and remember, you are being closely monitored throughout the exam. At your peak exercise, Cardiolite will be injected into the IV and you be asked to continue exercising for an additional one or two minutes.
After the exercise is complete, pictures will be taken of your heart using a special camera able to see where either Cardiolite or Thallium that has localized in your heart. You will be asked to lie down on a special table. The camera will rotate above and around your chest while special pictures are being taken, which will take approximately 30 minutes to complete. You may breathe normally while the pictures are being taken. It is very important that you hold very still while the camera takes pictures of your heart. Similar to taking a picture with a slow shutter speed, patient movement blurs image and degrades the quality of the data.
Under certain circumstance you will be asked to return the following day for additional imaging. If so, there will be no need for additional exercising, no restriction on your diet or medication, and no additional isotope is administered.
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What happens if you are unable to exercise?
Some people, due to a variety of disabilities, are unable to exercise adequately enough on a treadmill machine to achieve a diagnostic test result. In other cases a specific ECG abnormality known as a left bundle branch block make the treadmill exercise unreliable. In these cases, your physician may decide to use the drug Persantine to mimic the effect of exercise on the heart (pharmacologic stress).
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Are there any special preparations for the study?
You should wear comfortable, loose-fitting clothing for exercise, such as shorts or sweat pants and a t-shirt. In addition, wear comfortable shoes that you can run in, such as tennis shoes or rubber-shoed walking shoes. Because the ECG electrodes used to monitor your heart rate adhesive-backed and need to adhere to the skin, don't use body lotions on your chest or arms the day of the test.
If you are scheduled to have your scan in the morning, do not have any solid food to eat after midnight on the night before the scan. You may take water at any time and may take your medications with sips of water.
If you are scheduled to have your scan in the afternoon, have a light breakfast such as juice and toast only, but nothing else in the way of solid foods. You may take water at any time and may take your medications with sips of water.
Also, you should not have caffeine 24 hours prior to the study.
If you are diabetic and use insulin, we recommend that you take half of your usual dose of morning insulin and follow the above dietary instructions. If you use oral diabetic medications, we recommend that you omit that medication on the morning of the scan, and follow the above dietary instructions.
Consult with the physician regarding whether certain medications should be taken before, or held until after the test. Frequently, beta blockers and calcium channel blockers are withheld a day or two before the study, so that the heart rate can increase to adequate levels. Your physician or the technologist will let you know before the test.
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How is the Persantine Myocardial Perfusion Stress Test different from an Exercise Myocardial Perfusion Stress Test?
With an exercise test, physical exertion increases your heart rate and blood pressure, thereby increasing the stress on the heart and increasing the blood flow requirements. If there is a partial blockage in a coronary artery, this is revealed due to the inadequate tracer uptake in the heart muscle. With a Persantine test, you do not exercise, but the medication is infused through a vein while you are at rest. Persantine dilates blood vessels including the coronary arteries. If there is a blockage in a coronary artery, the vessel cannot dilate fully and the lower blood flow shows up again on the scan. If you are having the Persantine test, there is no need to exercise. However, you should be certain that your are not taking Persantine already in the tablet form, nor should you take either aminophylline or theophylline medications, because these counteract the effects of the Persantine.
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Important Points to Remember
- The radioactive material is ordered especially for you. If you are unable to keep your appointment for any reason, notify the office before the exam.
- A written report of the test will be sent to your primary physician once it its interpreted.
- If you are pregnant or suspect you maybe, or are nursing, notify your doctor. You should not take this test.
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