A stress test is sometimes called a nuclear stress test; your doctor may call it an MPI. An MPI—“myocardial perfusion imaging.” The “myocardium” is your heart muscle. “Perfusion” refers to blood flow. And “imaging” is taking pictures. So, myocardial perfusion imaging is basically just taking pictures of the blood flow to your heart.It can also show how well the heart muscle is pumping. It provides detailed images that can be used to diagnose and assess coronary heart disease. There are two techniques used for MPI: single photo emission computer tomography (SPECT) and positron emission tomography (PET). The difference between these two techniques is the type of camera used to take the images.
MPI is useful in patients with chest discomfort to see if the discomfort comes from lack of blood flow to the heart muscle caused by narrowed or blocked heart arteries (angina). MPI doesn’t show the heart arteries themselves, but can tell your doctor if any heart arteries are blocked and how many. MPI can also show if you’ve previously had a heart attack.
MPI is a noninvasive test. That means it takes place outside of your body and does not involve surgery of any kind. You will stay awake and alert the entire time.
A small needle (catheter) will be placed in a vein in your arm at the start of the test. And a small amount of radioactive liquid (called a tracer) will be injected into your bloodstream through the catheter during the MPI test. This tracer helps the medical team see the blood flow to your heart. You probably will not feel any effects from the tracer, which your body eliminates through the kidneys in 24 to 72 hours.
A special camera will take pictures of your heart once the tracer moves through your arteries. Depending on the type of test, you may be required to have 2 sets of pictures taken by the camera at 2 different times (either later that day or even the next). These pictures give doctors detailed information about blood flow into your heart. They might see that the blood flow in some areas of your heart is lower compared to other areas. This information will help your doctors decide what steps should be taken next.
A stress test normally takes 2 to 2 and a half hours.