Norfolk County Cardiologist Association
MYOCARDIAL PERFUSION IMAGING
What is Myocardial Perfusion Imaging?
Myocardial refers to the heart muscle. Perfusion is the passage of blood through the circulatory system. And imaging refers to computer-generated pictures. Therefore, myocardial perfusion imaging is a procedure that lets the doctor look at the flow of blood to the heart muscle.
What information can be learned from this procedure?
Myocardial perfusion imaging will help your doctor determine:
1. If your heart is receiving enough blood.
2. If you have coronary artery disease (CAD).
3. If more tests are necessary.
Myocardial perfusion imaging may be done before or after treatment for heart ailments.
What is Coronary Artery Disease (CAD)?
Coronary artery disease is the narrowing (stenosis) of the arteries that serve the heart. The narrowing is frequently caused by a build-up of fatty deposits (plaque) on the inside of the artery. Stenosed arteries reduce blood flow, which reduces the amount of oxygen and other nutrients the heart receives. Without proper nutrients, the health of the heart suffers. An unhealthy heart cannot pump efficiently, which may lead to chest pain (angina).
How does this imaging work?
The imaging has two parts to it.
In the first part of the test, the heart is stressed. That is, the heart's arteries are expanded (dilated) using a special medication. Healthy or "normal" coronary arteries dilate more than unhealthy or partially blocked arteries.
Once the blood vessels are dilated, a small amount of a radioactive imaging agent is injected. The imaging agent tends to concentrate in those parts of the heart that have the best blood flow. The imaging agent emits signals that can be detected by a special type of camera.
Images taken by the camera show if any part of your heart is not getting enough blood.
In the second part of the test, two sets of pictures are taken. The first set of images shows the arteries of the heart when the blood vessels are dilated. The second set shows the heart during normal functioning, referred to as "at rest." The two sets of images are compared.
A relatively healthy hart shows little or no difference between images taken during stress and those taken at rest.
In a heart with partially blocked arteries, images taken during stress are different from those taken at rest.
How do you prepare?
For this test, certain ingredients that exist in foods and medications - even in tiny amounts - may interfere with the test. These ingredients include caffeine, theophylline and dipyridamole. What does this mean?
For 24 hours before your test, please do not eat or drink any of the foods, and do not take any of the medications, on the list below.
1. NO coffee or tea that is brewed, instant, iced or decaffeinated.
2. NO colas or other soft drinks that contain caffeine, including those labeled, "Caffeine-free".
3. NO chocolates, including candies, frosting, cookies, pies, cocoa, and chocolate milk.
4. NO aspirin products that contain caffeine, such as Anacin and Excedrin.
5. NO Persantine (dipyridamole)
6. NO theophylline or theophylline containing products such as Constant-T, Primaten, Quibron, Slo-Phylline, or Theo-Dur.
This is only a partial list. Check product labels or ask your pharmacist or doctor to be sure of what products to avoid before your test. You should avoid products that contain caffeine, theophylline, and kipyridamole. This will help assure that your test will go as smoothly as possible.
What happens during the test?
During the test you will be lying on your back. A blood pressure cuff is placed on one arm, and a small intravenous needle (IV) is inserted in your other arm. Small round pads are placed on your chest that are attacked to an electrocardiograph (ECG). This allows your doctor to monitor your heart rhythm.
The dilating medication is injected over a period of approximately 6 minutes. The imaging agent is injected midway through the 6 minutes. When the injections are over, the doctor will continue to monitor your heart for a couple more minutes.
As the dilating medication is given, you may feel flushed, chest pressure/pain, shortness of breath or some other discomfort. This is perfectly normal, but it is important to tell the doctor just what you are feeling. Usually, these effects disappear by themselves within a minute or two after the injection is over. However, the injection of another medication may be required to stop the action of any persistent feelings.
It's possible that you may feel some of the medication's effects for up to 24 hours after the test. If so, please contact your doctor.
The next portion of the test involves taking pictures or "imaging" of the heart.
What happens during imaging?
During this portion of the test, you will rest on your back, usually with your arms comfortably extended above your head. For the next approximately 45 minutes, images of the blood flow of your heart are taken by a special camera. It's important that you lie still during this procedure to ensure the best possible images. The camera is large but should not worry you. It doesn't even come in contact with you during the procedure, and it doesn't hurt or emit any radiation.
You may be asked to return a couple of hours later for a second round of images when your heart is "at rest." These images are compared to the images obtained during the first part of the test.
When your myocardial perfusion imaging is complete, your doctor will know more about the blood flow to your heart muscle and your health.