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Mycardial Perfusion Scan

A nuclear cardiology exercise stress test, also known as a myocardial perfusion scan, Cardiolite, or thallium scan, is an examination that goes beyond the traditional exercise stress test. In addition to assessing your heart’s electrical activity on an electrocardiogram (EKG) during exercise (or during a chemical infusion for those who cannot exercise), images are also taken of the heart using a gamma camera. An imaging agent is injected first while the heart is at rest, and again during the exercise portion of the test. The gamma camera detects the heart’s activity and produces pictures of the heart’s blood flow. These pictures are acquired both before and after the exercise portion of the test. From these pictures, known as perfusion images, a Minneapolis Heart Institute physician can tell if you have had a prior heart attack, and if so, in which region of the heart. During exercise, decreased blood flow to regions of the heart can also be detected. This decreased blood flow is suggestive of blockages within the heart arteries, also known as coronary artery disease. This procedure also provides an assessment of the overall function of the heart muscle, known as the ejection fraction (EF), as well as a specific look at the individual walls of the heart muscle, which can aid in the evaluation of heart attacks.

While a traditional stress test is useful in determining if a heart’s function is normal or abnormal, only a nuclear cardiology procedure can provide the additional perfusion and function information outlined above. Obviously, this additional information can be quite valuable in assessing the status of your heart and deciding on the most appropriate treatment for you. There are several different forms of “stress” testing. Exercising on a treadmill while being monitored by a technologist, nurse and/or physician remains the preferred form of stress testing, but there are a wide variety of reasons why an exercise stress test may not be appropriate for you. The most common reason an exercise test is unsuitable is a patient’s inability to adequately exercise due to orthopedic limitations, vascular disease, lung disease, or a general physical disability. People with an abnormal EKG may be best evaluated by other means than a treadmill stress test even if they are physically capable of exercise. Or your physician may simply feel it is most appropriate for you to not exercise based upon your specific situation. Please note that the information in the following sections is provided for two distinctly different types of nuclear stress test: treadmill and pharmacologic (drug-induced stress).

Before the Test

Treadmill stress testing:

  • Do not eat, drink, or smoke four hours prior to the test.

  • Wear lightweight clothing including shoes you will be comfortable walking briskly with or jogging in.

  • Medications, including inhalers, may be taken the morning of the procedure unless otherwise instructed. If you are taking a beta-blocker medication, your physician may ask that you not take this medication since it may inhibit your ability to obtain a high heat rate with exercise. Examples include atenolol (Tenormin), and metoprolol (Lopressor, Toprol XL).

  • A change may be required in the diabetic patient’s insulin or diabetic pill regimen on the morning of the procedure. Some patients will hold the morning dose and take half the morning dose following the completion of the test (or base the dose on a finger stick result.) Prior to the day of the procedure, diabetics should discuss any necessary changes with their physicians.

Pharmacologic stress testing:

  • Do not eat, drink, or smoke four hours prior to the test.

  • Wear lightweight clothing.

  • Medications, including inhalers, may be taken the morning of the procedure unless otherwise instructed.

  • A change may be required in the diabetic patient’s insulin or diabetic pill regimen on the morning of the procedure. Some patients will hold the morning dose and take half the morning dose following the completion of the test (or base the dose on a finger stick result.) Prior to the day of the procedure, diabetics should discuss any necessary changes with their physicians.

  • No coffee or tea for 24 hours prior to the test.

  • No colas or other soft drinks that contain caffeine, including those labeled, “caffeine-free” 24 hours prior to the test.

  • No chocolates, including candies, frosting, cookies, pies, cocoa, or chocolate milk for 24 hours prior to the test.

  • No aspirin products that contain caffeine, such as Anacin and Excedrin, 24 hours prior to the test.

  • No Persantine (dypyridamole) 24 hours prior to the test.

  • No theophylline or theophylline containing porducts such as Constant-T, Primatene, Quibron, Slo-Phylline, or Theodur.
During the Test
Treadmill stress:
The treadmill begins very slowly but increases in slope and speed at three-minute intervals until you become too tired to continue or if the monitoring nurse or physician feels it is appropriate to stop.

If treadmill stress testing is performed as part of a nuclear cardiology examination, a small amount of imaging agent is injected into a vein approximately one minute prior to stopping exercise. This substance is rapidly taken-up by the heart muscle. The pictures of the heart, obtained several minutes later, will reflect the blood flow of the heart muscle at the time the imaging agent was injected.

Pharmacologic stress:
The most common medication infusion used for non-exercise stress testing is called adenosine (Adenoscan). This medication dilates the heart arteries and highlights discrepancies between arteries that have little to no blockage, from those that may have severe blockages. This medicine is infused over a six-minute period under the supervision of a nurse or physician. A small amount of imaging agent is injected halfway through the infusion and pictures are acquired following the infusion. You may experience a variety of brief symptoms during the infusion including flushing, shortness of breath, chest pain, nausea, headache, or anxiety. Fortunately these symptoms in no way reflect something wrong with your heart and they resolve within seconds of completing the infusion.

A second less commonly utilized medication for pharmacologic stress testing is called dobutamine. This medication acts to speed the heart and improve the force of contraction. Like exercise stress, it tends to highlight regions of heart muscle that may be receiving inadequate blood flow under stressful conditions such as at high heart rates. This medication is typically used for individuals who cannot exercise and have severe lung disease. The infusion dosage is gradually increased until a target heart rate is achieved. At this point, a small amount of imaging agent is injected. This liquid dye is taken-up by the heart muscle and then provides a signal that is analyzed by the nuclear cardiology camera. Side effects of the medication may include chest pain, shortness of breath, nausea, or a “jittery” feeling. The occurrence of these symptoms does not necessarily indicate that anything is wrong with your heart, and they should resolve within a few minutes following the completion of the infusion. Final pictures are taken once the infusion is complete and your heart rate has returned to near normal.
After the Test

After the procedure you may leave without restrictions. There are no after-effects from the test. A cardiologist and radiologist together will interpret the scans and report the results to your physician within a few days of its completion. This team approach of utilizing both a cardiologist and radiologist together is unique to the Minneapolis Heart Institute and Abbott Northwestern hospital. No other Twin Cities nuclear cardiology program goes to these lengths to provide the most accurate interpretation of your test results.

There are no measurable risks associated with the nuclear imaging agents. There is minimal risk associated with the treadmill exercise test, including abnormal blood pressure, fainting or heart attack. This risk is minimized by a thorough examination beforehand and by careful monitoring during the test. Trained nurses, physicians, and emergency equipment are always available if needed.

Other Information

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