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 shows the distribution of blood flow within your heart muscle. A healthy heart shows even distribution at rest and stress. If an area shows poor blood flow during stress but normal flow at rest, it indicates a narrowed coronary artery. If flow is poor in both, it represents scar tissue from a past heart attack.
How should I prepare for a myocardial perfusion scan?
You must fast (no food or drinks except water) for at least 4 hours before the scan. Avoid all products containing caffeine (coffee, tea, cola, energy drinks, chocolate, or pain relievers with caffeine) for 24 hours, as caffeine can prevent your heart rate from reaching the target during the stress test. Wear comfortable clothing and walking shoes.
Do I need to stop taking medication?
Yes. You may need to stop taking certain heart medications (especially beta-blockers or calcium channel blockers) for 24 to 48 hours before the test, as they keep your heart rate slow. Always discuss this with your referring doctor or cardiologist beforehand.
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 or radiographer if you are pregnant or think you might be. Because this scan uses radioactive tracers, it is not performed during pregnancy to protect the developing baby.
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.
Conclusion
A myocardial perfusion scan is a safe and detailed test that maps blood flow to your heart under load. Remember to avoid caffeine for 24 hours before the scan and discuss any medication holds with your doctor.