Myocardial Perfusion Imaging in Ajax: A Patient Overview

Myocardial perfusion imaging, usually shortened to MPI, is a nuclear cardiology test. Its job is narrow and specific: to show how well blood is reaching the muscle of the heart. Other heart tests look at the heart’s electrical activity, its shape, its valves or how it pumps. MPI looks at supply. It asks whether every part of the heart muscle is receiving the blood flow it needs, both when you are resting and when the heart is working harder.

That focus is why the test is usually ordered for particular clinical questions rather than as a general check-up. If your provider has given you a requisition for MPI with Durham Cardiology, the cardiology team at Rossland Diagnostic Clinic in Ajax, this overview explains the ideas behind the test, the broad shape of the appointment, and the things only your own instructions can tell you.

The problem MPI is designed to answer

The heart muscle is fed by its own set of arteries, the coronary arteries, which wrap around the outside of the heart. When those arteries are healthy, blood flow increases smoothly whenever the heart needs more, such as during exercise.

If an artery is narrowed, there may still be enough flow at rest. The shortfall can show up only when demand rises. That is the reason heart testing so often involves some form of stress: a problem in supply may be invisible while you are sitting still.

Several tests approach this from different directions. A treadmill stress test watches the heart’s electrical tracing and your symptoms during exercise. A stress echocardiogram uses ultrasound to see how the walls of the heart move before and after exercise. MPI takes a third route: it creates pictures of blood flow itself within the heart muscle. Your provider chooses among these based on your history, your symptoms, earlier results and practical factors such as how well you can exercise. If you would like a broader tour of the tests the team offers, our overview of heart testing at Durham Cardiology covers each one briefly.

How a tracer turns blood flow into a picture

MPI uses a small amount of radioactive tracer and a specialized camera. The tracer is generally given through a vein. It travels with the blood, and heart muscle takes it up in proportion to the blood flow reaching it. Areas with good flow collect more tracer; areas with reduced flow collect less.

The camera does not send radiation through you the way an X-ray does. Instead, it detects the tiny signals given off by the tracer already inside the heart muscle and builds images from them. The result is a series of pictures that can be viewed as slices through the heart, showing how evenly the tracer, and therefore the blood flow, has been distributed.

The word “radioactive” understandably makes some people uneasy. The amount used in medical imaging is small and chosen for the purpose, and the test is only performed when a physician has decided the information is worth it. If you have questions about radiation in your own situation, ask the physician who ordered the test. Our general article on X-ray radiation safety explains the principle of keeping exposure as low as reasonably achievable, which applies across medical imaging.

Rest images and stress images

The heart of the test is a comparison. Images may be taken at rest and during stress, depending on the test your physician ordered.

Why two sets of pictures

Comparing the two sets helps answer different questions:

• If flow looks even in both, that is generally reassuring about supply to the heart muscle.
• If an area looks reduced only on the stress images, that pattern suggests blood flow may not keep up when demand rises.
• If an area looks reduced on both, that may point to something different, such as muscle that was affected in the past.

Those are general patterns, not a way to read your own results. The interpretation depends on the full set of images, the quality of the study, your history and other tests, and it is your physician who explains what your report means for you.

Two ways to create stress

Stress can be brought on in one of two ways:

1. Exercise, usually walking on a treadmill while your heart rate, blood pressure and tracing are monitored.
2. Medication, given to imitate some of the effects of exercise on the heart’s blood flow. This is used when a physician decides it is the better choice, for example if walking on a treadmill is not practical.

Which one you have depends on the test your physician ordered. Your appointment instructions will say which approach applies to you.

Planning the day: what varies and what does not

The most important thing to know about MPI preparation is that it varies by testing protocol. There are several ways to perform the test, and the details, including timing and any preparation steps, depend on which one has been ordered. Our clinic team provides your specific instructions when your appointment is confirmed, and confirms the expected appointment length at the same time.

Rather than guessing from what a friend or a website says, treat your own instructions as the authority. Read them as soon as you receive them, not the night before, so there is time to ask questions.

Things that apply to everyone

A few points hold regardless of protocol:

• Tell your health-care team about every medication you take. That includes prescription medicines, over-the-counter products and supplements. Write them down with doses if you can.
• Do not stop any medication unless your physician tells you to. Some heart medicines can affect stress testing, which is why the question is asked, but the decision about whether to hold one belongs to your physician alone.
• Tell the team if you are pregnant, may be pregnant, or are breastfeeding. This matters for any test that uses a tracer, and it should be raised before the appointment, not at the door.
• Bring your signed requisition and your health card.

Clothing and comfort

If your test may involve treadmill exercise, comfortable clothing and walking or running shoes make sense, the same as for any exercise-based cardiac test. Our stress test preparation guide has practical ideas about what to wear and how to approach the treadmill portion, though your MPI instructions take priority wherever they differ.

Because appointment length depends on the protocol, it is wise to keep the rest of that day flexible. Many people find it easier to bring a book, a charged phone, or something to keep them occupied, and to arrange child care or work coverage generously rather than tightly.

During the imaging

While the camera is collecting images, you will typically be asked to lie still on a padded table, often with your arms positioned out of the way above your head. Staying still matters because movement can blur the pictures. The camera may move quite close to your chest, so if you feel uneasy in tight spaces, mention it when you book. If lying in one position is hard for you because of shoulder or back pain, mention it when you arrive so the team knows ahead of time.

During any stress portion, you are monitored throughout. If you feel chest discomfort, unusual shortness of breath, dizziness or anything that worries you, say so straight away. Speaking up is part of how the test is done safely.

After the test

Follow any after-test instructions the team gives you. The tracer leaves the body naturally over time. Your results are reviewed and a report is sent to the physician who ordered the test, who will go over the findings with you and discuss any next steps. If you have not heard back when you expected, contact your physician’s office.

When to seek care instead of waiting

MPI is a scheduled test, not an emergency service. If you have chest pain or pressure that does not settle with rest, pain spreading to the arm, jaw or back, sudden severe shortness of breath, fainting, or a racing or irregular heartbeat with feeling unwell, call 911 right away. Do not drive yourself, and do not wait for a planned appointment.

Questions patients often ask

Is MPI the same as a stress test? Not quite. A stress test looks at the heart’s tracing and your response to exercise. MPI adds images of blood flow to the heart muscle. Stress, by exercise or medication, is often one part of MPI.

Is it the same as an echocardiogram? No. An echocardiogram uses ultrasound to show the heart’s structure, valves and pumping. Our echocardiogram guide explains it. MPI uses a tracer and a specialized camera to look at blood flow in the muscle.

Do I need a referral? Yes. Durham Cardiology tests are performed with a signed requisition from your provider.

How long will I be there? It depends on the protocol your physician ordered. The team confirms the expected timing when your appointment is scheduled.

Can someone come with me? Call the clinic to confirm what works best for your appointment, especially if you are bringing children.

Booking MPI in Ajax

Durham Cardiology is located at Rossland Diagnostic Clinic, Unit 102, 300 Rossland Road East, Ajax, with free parking and ground-floor access. If your physician has ordered myocardial perfusion imaging, call 905-426-3111 or request an appointment, and the team will confirm your protocol, preparation and timing with you.