Myocardial Perfusion Imaging
A test to determine how well your arteries are delivering blood to your heart.
Myocardial Perfusion Imaging (MPI), also known as a Nuclear Medicine Stress Test, is done to determine how well the coronary arteries are delivering blood to your heart, as well as areas of the heart muscle that aren’t getting enough blood flow.
If the test shows a lack of blood flow during exercise or stress, but is normal at rest, it could mean that an artery that carries blood to your heart is narrowed or blocked. If the test shows a lack of blood flow to a portion of the heart muscle during exercise or stress and at rest, it could mean that your heart muscle is scarred, possibly from a past heart attack.
MPI is useful in patients with chest discomfort to see if the discomfort comes from a lack of blood flow to the heart muscle caused by narrowed or blocked heart arteries (angina). Myocardial perfusion imaging doesn’t show the heart arteries themselves, but it can tell your doctor with good certainty if any heart arteries are blocked and how many.
BEFORE THE TEST
- You may have a light breakfast/lunch, such as toast, jam, fruit, juice and water, and then refrain from eating 1 hour before the test.
- Discontinue all caffeine products 24 hours before the test. This includes all tea, coffee, decaffeinated tea/coffee, pop, chocolate, Tylenol 2 & 3 and/or medications containing caffeine.
- Insulin-dependent diabetics should take their insulin and a light meal 1 hour before the test.
- Wear loose fitting clothing, such a t-shirt, track pants, athletic shoes, etc.
- Bring a list of all current prescription medications and check with your physician regarding the discontinuation of any heart medications, such as Beta-Blockers like Metroprolol or Atenolol, as well as Calcium Channel Blockers like Diltiazem or Verapamil.
- Do not take erectile dysfunction medications, such as Viagra, Cialis, Levitra, etc. for 48 hours before the test.
- If you are pregnant or there is a possibility of pregnancy, or if you are breastfeeding, Nuclear Medicine Stress Testing may not be appropriate for you at this time. Please consult with your physician.
DURING THE TEST
The technologist will place an intravenous line into your arm or hand, which is used to inject a small amount of Cardiolite, a radiopharmaceutical, which is carried by the blood stream to your heart. Approximately 1 hour after your injection, the technologist will take pictures of your heart for approximately 20 minutes with a special gamma camera that detects radiation. While the pictures are being taken, you will be lying on a bed and it’s important to remain very still during this time to avoid blurring the images.
Once the first set of images has been taken, you will be prepared for a Stress Test. ECG electrodes will be placed on your chest to monitor your heart rhythm throughout the test. You will begin to exercise on a treadmill during which your heart rate and blood pressure will rise. These are normal responses that are being closely monitored with your ECG.
If you are unable to exercise adequately on a treadmill, similar results can be achieved using a drug called Persantine. Persantine mimics the effects of exercise by dilating the blood vessels of the heart, allowing for increased blood flow.
Once you have reached your maximum level of exercise, a second dose of Cardiolite will be injected and you will continue exercising for an additional 1-2 minutes. If blood flow to the heart is limited due to CAD, then the amount of Cardiolite in your heart is reduced. Following the Stress Test, the IV will be removed.
A second set of pictures taken with the gamma camera is required to complete the test. The technologist will advise you when to return for this last portion (anywhere from 15 minutes to 2 hours after the Stress Test is completed). It is very important that the second set of pictures is taken to compare to the first set and assess the amount of blood supply to the heart at rest and during stress (exercise).
The test will last approximately 3 to 4 hours.
AFTER THE TEST
You will be able to return to your normal activities when the test is complete, unless your physician or technician tells you otherwise. You can drive after the test. If you are travelling by plane, train or crossing the border within one week after your test, please inform the technologist.
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