Myocardial perfusion is an imaging test. It's also called a nuclear stress test. It is done to show how well blood flows through the heart muscle. It also shows how well the heart muscle is pumping. For example, after a heart attack, it may be done to find areas of damaged heart muscle. This test may be done during rest and while you exercise. A myocardial perfusion scan uses a tiny amount of a radioactive substance, called a radioactive tracer. The tracer travels through the blood. It is absorbed by the healthy heart muscle. On the scan, the areas where tracer has been absorbed look different from the areas that don't absorb it. Areas that are damaged or don't have good blood flow don't absorb the tracer. The damaged areas may be called cold spots or defects.
A stress myocardial perfusion scan assesses blood flow to the heart muscle when it is stressed. The heart is often stressed from exercise. If you're not able to exercise, you will be given a medicine to stress the heart instead. This medicine will increase your heart rate or dilate your blood vessels, just as with exercise. This is called a pharmacologic myocardial perfusion scan.
After the radioactive tracer is injected, a special type of camera is used. This can find the radioactive energy from outside the body. The camera takes images of the heart during stress and again later at rest. The 2 sets of images are compared.
You may need a stress myocardial perfusion scan for these reasons:
Chest pain, either new or occurring over a period of days or longer
To diagnose coronary artery disease (CAD), which is the narrowing of the coronary arteries
After a heart attack (myocardial infarction or MI) to assess heart muscle damage
To assess blood flow to areas of the heart muscle after coronary artery bypass surgery, angioplasty, or stent placement.
There may be other reasons for your healthcare provider to advise a stress myocardial perfusion scan.
Risks of the scan may include:
In rare cases, the exercise part of the test may lead to abnormal heart rhythms, chest pain, or heart attack. This can occur due to the stress that exercise causes on the heart.
The needle used to put in the IV (intravenous) line may cause some pain. The injection of the radioactive tracer may cause some slight discomfort. Allergic reactions to the tracer are rare.
If your heart is stressed using medicine, you may feel anxious, dizzy, nauseous, shaky, or short of breath or chest pain for a short time.
You may want to ask your healthcare provider about the amount of radiation used during the test. Also ask about the risks related to your situation.
There may be other risks depending on your specific health condition. Be sure your healthcare provider knows about all of your health conditions. Make a list of questions you have about the test. Discuss these questions with your healthcare provider before the procedure. Bring a family member or friend to the appointment to help you remember your questions and concerns.
Certain factors may interfere with or affect the test results. These include:
Use of medicines containing theophylline
Having caffeine within 48 hours of the procedure
Smoking or using any form of tobacco within 48 hours of the procedure
Certain heart medicines, such as those that slow the heart rate
Your healthcare provider will explain the procedure to you and you can ask questions.
You will be asked to sign a consent form that gives your permission to do the test. Read the form carefully. Ask questions if anything is not clear.
Tell your provider if you are allergic to or sensitive to medicines, local anesthesia, contrast dyes, iodine, tape, or latex.
Follow any directions for not eating or drinking before the procedure. Don't eat or drink anything that contains caffeine for at least 48 hours before the procedure. Also don't take any prescription and over-the-counter medicines that contain caffeine.
If you are scheduled for a pharmacologic myocardial perfusion scan, you will need to not take any medicines containing theophylline or caffeine. Coffee, even decaffeinated, is not allowed. That's because it contains some caffeine. Medicines for asthma may contain theophylline. If you have asthma, inform your healthcare provider. Theophylline medicines should be stopped 48 hours before the test.
Medicines that contain caffeine and all food and drink containing caffeine should also be stopped 48 hours before the test.
tell your healthcare provider if you are pregnant or think you may be pregnant. Radiation exposure during pregnancy may lead to birth defects.
If you are breastfeeding, tell your healthcare provider. Radioactive tracer can contaminate breast milk.
Tell your healthcare provider about all medicines you are taking. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements.
Tell your healthcare provider if you have a pacemaker or implantable cardioverter defibrillator (ICD).
For an exercise scan, plan to wear loose, comfortable clothing, as well as comfortable walking shoes.
Based on your health condition, your healthcare provider may request other specific preparation.
You may have a stress myocardial perfusion scan on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your healthcare providers practice.
Generally, a stress myocardial perfusion scan follows this process:
You will be asked to remove any jewelry or other objects that may interfere with the procedure.
If you are asked to remove your clothing, you will be given a gown to wear.
An IV line will be started in your hand or arm.
You will be connected to an electrocardiogram (ECG) machine with leads that stick to your skin and a blood pressure cuff will be placed on your arm.
Exercise myocardial perfusion scan:
You will exercise on a treadmill. The intensity of the exercise will be slowly increased by increasing the speed of the treadmill.
Your heart rate and blood pressure will be watched closely. Once you have reached your maximal exercise point (determined by the healthcare provider based on your heart rate and age), the radioactive tracer will be injected into your IV line.
After the tracer has been injected, you will continue to exercise for several minutes.
You will then be placed into the heart scanner so images can be taken.
Pharmacologic myocardial perfusion scan:
You will not exercise on a treadmill. Instead, you will lie on the table in the heart scanner while a medicine is injected into your IV line.
Your heart rate and blood pressure will be watched closely.
The tracer will be injected into your IV line.
Procedure completion, both methods:
Tell the healthcare provider or technologist if at any point during the procedure you have any symptoms. These include dizziness, chest pain, extreme shortness of breath, or extreme tiredness (fatigue).
You will lie flat on a table while the images of your heart are taken. About 10 to 60 minutes (depending on the type of tracer used) after the tracer is injected, the gamma camera will begin to take pictures of your heart. In this special kind of test called SPECT (single photon emission computed tomography), the scanner rotates around you as it takes pictures. The table slides into the hole of the scanner, which is a large, doughnut-shaped machine.
Your arms will be on a pillow above your head. You will need to lie very still while the images are being taken. Movement can affect the quality of the images.
After the scan is done, you may be allowed to leave the area. But will need to come back for a second set of scans. The second set of scans will be taken 3 to 6 hours after the first set. During this time, you will not be allowed to eat or use tobacco. You will be allowed limited water, as well as decaffeinated or non-calorie liquids. In some cases, your healthcare provider may decide to have you come back on another day for the second set of scans.
The second set of scans will be much like the first set. But you will not need to exercise or get the medicine. You will lie on the table as before while the scanner takes pictures of your heart.
Once the second set of scans has been completed, the IV line will be removed. You will be allowed to leave, unless your healthcare provider tells you differently.
Move slowly when getting up from the scanner table to avoid any dizziness or lightheadedness from lying flat during the procedure.
Drink plenty of fluids and empty your bladder often for 24 to 48 hours after the test. This helps flush the remaining radioactive tracer from your body.
The IV site will be checked for any signs of redness or swelling. If you notice any pain, redness, or swelling at the IV site after you get home, tell your healthcare provider. This may be a sign of infection or other type of reaction.
Your provider may give your other instructions after the procedure, depending on your particular situation. If the perfusion scan shows you may have a serious or life-threatening cardiac disease, your provider may talk to you about a same-day cardiovascular procedure.
Before you agree to the test or the procedure make sure you know:
The name of the test or procedure
The reason you are having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you are to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you did not have the test or procedure
Any alternative tests or procedures to think about
When and how you will get the results
Who to call after the test or procedure if you have questions or problems
How much you will have to pay for the test or procedure