Myocardial Perfusion SPECT
What is it?
A myocardial perfusion SPECT (Single Photon Emission Computed Tomography) study, also called a cardiac stress-rest test, helps your doctor evaluate your heart’s blood supply. Two sets of images showing blood flow are obtained: the first following a period of rest, and the second following a period of stress (i.e., exercise). This is how it works:
- The technologist injects a radiotracer into a vein.
A radiotracer is a compound made of a radioactive isotope and a pharmaceutical agent. In the radiotracer used for myocardial perfusion SPECT, the pharmaceutical part keeps the tracer in the blood until it is filtered out by the kidneys.
- The radioactive isotope releases energy, and a special camera creates an image from it.
The image shows any area with abnormal blood flow indicating a problem in the heart or vessels.
What is it for?
Myocardial perfusion SPECT is used to evaluate damage that might have been caused by a myocardial infarction (heart attack) and to assess the presence and extent of myocardial ischemia (reduced blood flow due to obstruction in the vessels). Your doctor will determine if a myocardial perfusion SPECT examination is necessary.
How will the exam be scheduled?
Your doctor will schedule the examination. When the exam is scheduled, your doctor must send a written order for the test. You should also request a copy of this written order, and you should bring it with you to your appointment. According to Massachusetts state law, the technologist cannot inject the radiotracer without a written order from your doctor. Your examination will be delayed if we do not receive a written order.
When your examination is scheduled, your doctor will be told the time for your injection, which is the time of your appointment. The length of the complete examination, however, is variable and depends on a number of factors that cannot be determined outside of the lab. You should plan to be in the lab for 3-4 hours.
As you plan your visit to our lab, please remember that children under the age of 12 are not permitted within the Nuclear Medicine waiting room or laboratory areas.
How should I prepare for the examination?
You should not eat or drink anything after midnight on the night prior to your examination. If your stomach is empty, you are less likely to become nauseous during the stress portion of the examination. In addition, your cardiac images will be easier to interpret.
It is especially important that you avoid coffee, tea, soda, chocolate, and any other caffeinated beverage or food for at least 12-24 hours before your examination. Keep in mind that even decaffeinated beverages do contain some residual caffeine, so they should also be avoided. Caffeine is a stimulant and may affect the results of your study.
Your doctor may ask you to stop taking certain medications for a specific period prior to the examination. Discuss your medications with your doctor when the examination is scheduled to determine which, if any, you should temporarily discontinue.
This examination does require exercise on a treadmill. You should wear (or bring along) comfortable, appropriate clothing and shoes. We recommend shorts or sweatpants and athletic shoes.
What happens during the examination?
Prior to receiving her injection, any woman between the ages of 12 and 56 will be asked if she might be pregnant. If you think you might be pregnant you should talk to your doctor about it before having a nuclear medicine examination.
A myocardial perfusion SPECT study occurs in two parts. The first part captures images while your heart is in a state of rest. The technologist will place an intravenous (IV) catheter in your arm, then inject the appropriate dose of radiotracer through the catheter. You will then be asked to wait in the waiting room for 45 minutes?1 hour. When you return to the lab for imaging, the technologist will ask you to lie on your back on a bed positioned between a set of cameras. Once you are comfortable on the bed, the imaging will begin. The bed will slide you into the correct position, and the cameras will rotate around your body. The cameras will come quite close you, but will not touch you. It takes about 20 minutes for the cameras to record a complete set of images. It is very important that you remain still during that time.
The second part of the examination captures images while your heart is in a state of stress. The technologist will apply electrodes to your chest so that your heart rhythm can be monitored by electrocardiography (EKG or ECG). You will be asked to walk on a treadmill in order to increase your heart rate—in other words, to induce stress on your heart. As you walk, both speed and incline will increase every three minutes—increasing the intensity of your exercise. You will be asked to walk as long as you can in order to induce maximum stress. If you are unable to exercise, or if you are unable to exercise enough to produce the necessary stress on your heart, stress can be induced by injecting a drug. A drug may also be used in combination with exercise. Shortly before you stop exercising, a second, small dose of radiotracer will be injected through the IV catheter.
Within approximately 30 minutes, you will be ready for the second set of images. This imaging portion will take about 20 minutes. It is important that you remain still while the images are obtained—movement can ruin the images, and the radiologist may have difficulty interpreting them accurately.
After the examination is complete, you will be able to resume normal daily activities. There will be no further restrictions on eating or drinking. The radiotracers do not cause drowsiness, so you will be able to drive.
How will I receive the results?
A nuclear medicine physician will review and interpret the images obtained during your study. The results of your myocardial perfusion SPECT examination will be provided to your doctor within 48 hours.
Are there any side effects?
Most people do not experience any side effects from the radiotracer.
Is the radiation dangerous?
Nuclear medicine examinations do involve the use of a small amount of radiation. The tracer dose is calculated to minimize radiation exposure while providing accurate test results.
Nuclear medicine studies may not be appropriate for pregnant women or those who are breastfeeding. If you think you may be pregnant, discuss this with your doctor. Of course, it is always important to consider the benefits of any diagnostic study along with the risks. In some cases, the importance of making the correct diagnosis outweighs the potential risk to the unborn baby. Your doctor can explain your options.
If you are breastfeeding, you should not nurse your baby for approximately 36 hours after the radiotracer injection, since radiation can be passed through the breast milk. Prepare for your examination by pumping and saving milk for 24-48 hours before your examination, then bottle-feed your baby during the hours following your appointment.
The radiation administered during a nuclear medicine study is eliminated from you body through the kidneys. For that reason, you should drink plenty of fluids and urinate frequently following your examination.
- Catheter: A thin, hollow tube that can be inserted into a vein. Once placed, it permits the technologist to give the patient an injection as the patient moves. It can also be used repeatedly to deliver multiple injections during a particular period of time.
- Myocardial: Relating to the heart muscle
- Perfusion: Blood flow
- Radioactive isotope: A particular form of an element, such as iodine, which releases energy spontaneously
- Treadmill: An exercise machine for walking or running. The machine controls the speed, and the moving belt can tilt up to create the sensation of walking or running up a slope.
Send Feedback to: Cathy Delaware
This page was last modified on 10/20/2011