What Is An MPI (Myocardial Perfusion Imaging) Test?
An MPI test is a test in which a small amount of radioactive substance is injected into the bloodstream and tracked using a gamma camera scan. The radioactive substance (or tracer) will show up differently in areas in which there is damage or decreased blood flow, which allows doctors to identify decreases in heart and blood flow efficiency.
When Might I Need An MPI?
Your doctor may recommend an MPI for several reasons, including the following:
- You Are Experiencing Chest Pain
- You Have Had a Heart Attack
- You Have Had an Angioplasty, Stent, Bypass Surgery Or Other Procedure That May Have Affected Blood Flow
Note: This list is not exhaustive. Your doctor may recommend this test for other reasons, as well.
What Should I Expect?
An MPI Test can take about 3-4 hours, but may be split into separate days. Your doctor will let you know if your test will be two-part or not.
There are two types of MPI Tests:
- Exercise Stress MPI – During an Exercise Stress MPI Scan, you will have electrodes and a blood pressure cuff placed on your body. These are intended to monitor your heart rate and blood pressure throughout the testing process. Next, you will exercise (typically on a treadmill or bike), with intensity gradually increasing. Once you have reached the maximum heart rate as determined by your doctor, a small amount of tracer will be injected into a vein, you will lie down, and the scan will begin. A gamma camera will capture images of the tracer as it moves through your body, showing areas of decreased blood flow/heart efficiency. Once sufficient images are gathered, you will most likely have another scan after your heart rate has returned to a resting state. This may be hours later or on a separate day.
- Lexiscan (Pharmacologic) Stress MPI – A Lexiscan Stress MPI is an MPI in which a medication is used to increase blood flow when exercise is not deemed safe or wise for the patient. During this test, you will have electrodes and a blood pressure cuff placed on your body, just as with an Exercise Stress MPI. Next, you will lie down, and the Lexiscan will be injected into your blood stream and begin to increase your heart rate. When your heart rate has reached the desired level, a tracer will be injected into your vein. Once the tracer is in your blood stream, a gamma camera will capture images of its journey through your body. You will most likely have another scan done without the Lexiscan, which will show your blood flow when your heart is at rest. You may be asked to do this part of the test on the same day or on a different day.
How Should I Prepare For The Test?
To prepare for an MPI:
- It is important to talk to your doctor about any and all allergies and medical conditions you have. If you have a pacemaker, inform your doctor of that as well.
- It is also important to inform him or her of any medications you are taking.
- Be sure to tell your doctor if you are or may be pregnant.
- If you are having an Exercise Stress MPI, you will want to wear clothing and shoes that are comfortable for exercise.
- It is advised that you refrain from consuming caffeinated products and/or smoking cigarettes before the test. You may also be required to fast.
- Be sure to discuss proper preparation with your doctor.
If you have any questions about an MPI test, please discuss them with your doctor during your next appointment.
