What is stress myocardial perfusion imaging?
Myocardial perfusion imaging (MPI) is a type of non-invasive imaging test that shows how well blood flows through your heart muscle. It can show areas of the heart that aren’t getting enough blood flow also referred to as a nuclear stress test. It can also show how well the heart muscle is pumping.
Indications for MPI include patients with chest pain to see if the discomfort comes from lack of blood flow to the heart muscle caused by narrowed or blocked heart arteries. MPI doesn’t show the arteries themselves but can tell your doctor if any heart arteries are blocked. MPI can also show if you have had a heart attack in the past.
MPI shows blood flow through your heart during exercise on a treadmill and while at rest. If you are unable to tolerate walking on a treadmill you will get a medicine (chemical/pharmacologic agent) to increase the blood flow to your heart muscle as if you were exercising.
After the radioactive tracer is injected, a special “gamma” camera is used that can detect the radioactive energy from outside the body. The camera takes images of the heart post rest and post stress tracer injection. The two sets of images are compared.
The images will help your doctor see if your heart muscle is getting enough blood, or if blood flow is reduced to parts of the heart muscle because of narrowed arteries. MPI can also tell if there are areas of dead cells or scars from previous heart attack. Some forms of MPI can also tell your doctor if portion of the heart muscle is still alive or viable after a heart attack if a coronary stent is placed or bypass surgery is done. The amount of radiation you get from an MPI test is small.
Why might I need an MPI test?
MPI test shows how well blood flows through your heart muscle. If the test shows a reduction of blood flow during exercise or stress, but is normal on rest, it could mean that an artery that supplies blood to your heart is narrowed or blocked. If the test shows a fixed defect or reduction in blood flow on both rest and stress images it could mean that your heart muscle is scarred possibly from a previous heart attack.
Indications for MPI imaging:
- The diagnosis of coronary artery disease (CAD).
- Diagnosis of symptomatic patients with intermediate probability of CAD.
- Diagnosis of asymptomatic patients with abnormal stress electrocardiogram or multiple risk factors for CAD.
- Risk stratification (preoperative/post infarction/chronic CAD/after unstable angina).
- Evaluation of therapeutic interventions in patients with known CAD (anti-ischemic drug therapy/coronary revascularization).
How do I prepare for a stress myocardial perfusion scan?
- Please bring an updated list of home meds, insurance cards and photo ID.
- ABSOLUTELY NO caffeine or decaffeinated beverages 12 hours prior to the test (including coffees, teas, sodas, and chocolates).
- Fast (4) four hours (no food or drink other than water) prior to your appointment. NO CHOCOLATE!
- If you have diabetes: You can have a light breakfast, take medication as you normally would.
- Please bring a snack and beverage with you, something high in fat is recommended. Nothing that contain caffeine or chocolate. We will have you eat at a certain point during the test to improve your images.
- Medications with caffeine: DO NOT take any over-the-counter medication that contains caffeine (such as Excedrin®, Anacin®, diet pills and No Doz®) for 24 hours before the test. Ask your physician, pharmacist or nurse if you have questions about other medications that may contain caffeine.
- Dipyridamole/Persantine(Aggrenox) is to be held for at least 2 days prior to test day.
- If you have asthma: Your physician will tell you NOT to take theophylline (Theo-Dur®) for 48 hours before the test. Please plan to bring your asthma inhaler medication to the test.
- Wear comfortable clothing, short sleeved shirt and walking shoes/sneakers.
- Please arrive 15 minutes prior to your test.
- Please refrain from applying lotions, creams or oils to skin prior to the test.
- Take all prescribed medication unless you are told otherwise. You will receive a call prior to your test to review instructions and confirm the date and time of your appointment.
What happens during a stress myocardial perfusion scan?
Upon arrival, please check in at the front desk with the receptionist and have a seat in the waiting room. The nurse, exercise physiologist or technician will come and get you from the waiting room after you have been checked in and bring you back to the prep room to get you started.
Brief history will be obtained, vitals checked, medication list will be reviewed and test will be explained in detail. We will be happy to answer any questions you have as well at any point during the test. EKG stickers will be placed on your chest and an IV will be placed in your arm or hand. The technologist will administer the nuclear tracer through the IV, you should not feel anything from this. Resting images will be acquired under the camera followed by the stress portion of the test, walking or non-walking depending on the order. A second small dose of the tracer will be administered through the IV during the stress portion of the test followed by another set of images under the camera. IV and EKG stickers will be removed and you will check out at the reception desk. Test typically takes 2-3 hours from the time you check in to when you check out. When the test is completed you should feel same as when you arrived.