A myocardial perfusion scan (often called a nuclear stress test or stress sestamibi scan) is a specialized test that checks how well blood flows through your heart muscle. It compares images of your heart taken while you are resting with images taken when your heart is beating fast during physical stress.
To create these images, a tiny amount of a radioactive tracer is injected into your vein. A specialized camera (gamma camera) detects the radiation emitted by the tracer, highlighting which parts of your heart muscle are receiving enough blood and which are not.
Common Indications for a Myocardial Perfusion Scan
- Investigating chest pain (angina) or shortness of breath.
- Diagnosing coronary artery disease (suspected blockages in heart arteries).
- Determining if a past heart attack has caused permanent muscle damage.
- Evaluating the success of past heart procedures like bypass surgery or angioplasty.
- Checking if it is safe for you to undergo major non-cardiac surgery.
What exactly does a myocardial perfusion scan show?
The scan estimates relative blood flow within the heart muscle. A reversible defect can suggest inducible ischemia, while a fixed defect may represent scar but can also reflect artifact. The study does not directly show the percentage narrowing of a coronary artery, and findings must be interpreted with symptoms, ECG, stress response, and image quality.
How should I prepare for a myocardial perfusion scan?
Fasting and caffeine restrictions depend on the stress medicine and local protocol. Caffeine can interfere with vasodilator stress agents rather than simply preventing a target heart rate. Follow the center's exact written instructions, including hidden caffeine in medicines and foods, and wear suitable clothing if exercise is planned.
Do I need to stop taking medication?
Some medicines can affect the test, but withholding them may be unsafe. Do not stop beta-blockers, calcium-channel blockers, nitrates, asthma medicines, or any other treatment unless the cardiology or nuclear-medicine team gives patient-specific instructions.
What happens when I arrive for my scan?
You will go to the nuclear medicine suite. A nurse will place an intravenous (IV) line in your arm. They will inject the radioactive tracer. You will wait for about 30 to 45 minutes for your heart muscle to absorb the tracer, and then the first set of resting images will be taken.
How is the procedure performed?
The test has two parts: rest and stress. For the stress part, you will walk on a treadmill (or be given a medication through your IV that mimics exercise if you cannot walk). Once your heart is beating fast, a second dose of tracer is injected. You will lie on a scan table under a large gamma camera, which rotates slowly around your chest to capture images. You must remain very still.
How long does a myocardial perfusion scan take?
The entire scan is a lengthy process that takes about 3 to 4 hours. This includes waiting times for the tracer to distribute, stress testing, and imaging sessions.
Is there any discomfort?
You will feel tired or out of breath during the exercise portion, which is normal. The injection itself is a brief needle pinch. You will not feel the radioactive tracer inside you.
Are there risks?
Yes, but they are low. The tracer exposes you to a small dose of radiation, similar to a few years of background radiation, which is quickly eliminated in your urine. The exercise portion carries a very small risk of chest pain or abnormal rhythms, which are continuously monitored by a medical team.
Can children have this scan?
This scan is performed almost exclusively on adults to assess coronary artery disease.
Can I have this scan if I am pregnant?
Pregnancy Precaution
Tell your doctor and nuclear-medicine team if you are pregnant or may be pregnant. The test is generally avoided when another suitable approach can answer the question, but an urgent study may be considered after an individual benefit-risk assessment.
When should chest symptoms be treated as an emergency?
Do not wait for an outpatient scan
Seek urgent medical care for new or ongoing chest pressure, severe breathlessness, fainting, sweating with chest discomfort, or pain spreading to the arm, back, neck, or jaw. A scheduled perfusion scan is not an emergency service.
When will I get my results?
A nuclear medicine specialist will analyze the rest and stress images side-by-side. A detailed report will be sent to your referring doctor within 24 hours.
What if the scan finds something?
If the scan shows reduced blood flow to a part of your heart, your referring doctor will discuss treatment. This could involve adjusting heart medications, starting cholesterol-lowering drugs, or scheduling a coronary angiogram.
What are the important limitations and safety checks?
Nuclear medicine shows physiology and tracer uptake, but uptake is not always specific to one disease and spatial detail may be lower than CT or MRI. Inflammation, infection, treatment effects, medicines, blood glucose, recent imaging, movement, and the timing of images can change a result. A normal scan does not exclude every abnormality, and an abnormal focus may need correlation with CT, MRI, ultrasound, laboratory tests, biopsy, or follow-up imaging.
Preparation and radiation precautions are radiopharmaceutical- and protocol-specific. Tell the department before the tracer is given if you are or may be pregnant, are breastfeeding, care for a young child, or recently had another nuclear-medicine test. Do not stop medicines, fast, interrupt breastfeeding, or follow a fixed distancing period based only on a general webpage; obtain written instructions for the exact tracer, activity, and examination from the nuclear-medicine team.
Questions to ask your nuclear-medicine team
- Which radiopharmaceutical and protocol will be used, and what clinical question should the study answer?
- What exact fasting, hydration, medicine, diabetes, pregnancy, or breastfeeding instructions apply to me?
- Will CT be included, will contrast be used, and how does that change preparation and radiation exposure?
- What written precautions apply afterward, when will the signed report be ready, and who will explain any next step?
Sources and further reading
- RadiologyInfo.org: General nuclear medicine
- RadiologyInfo.org: Preparing for a nuclear-medicine examination
- IAEA: Basics of quality management for nuclear medicine practices
Conclusion
A myocardial perfusion scan can identify patterns that suggest reduced blood flow or scar, but artifacts and non-obstructive disease can affect the result. Follow the center's stress-agent-specific caffeine, food, diabetes, and medicine instructions, and never stop heart medicines without explicit advice.