Nuclear Stress Test

What is a nuclear stress test?

A nuclear stress test is a heart imaging tool that helps healthcare providers see blood flow in your heart muscle. They use a special camera to pick up an injected radioactive tracer in your heart muscle. Poor blood flow in images helps providers diagnose heart disease. 

This test shows how well blood flows to your heart and if any arteries have blockages. Cardiologists (heart doctors) use nuclear stress tests to diagnose and monitor coronary artery disease (CAD). This disease involves clogged or blocked blood vessels.

The test can also tell your healthcare provider if your heart muscle is pumping well and if you have heart damage from a heart attack.

The test has other names, like:

• Cardiac PET (positron emission tomography)
• Cardiac SPECT (single-photon emission computed tomography)
• MPI (myocardial perfusion imaging)
• Nuclear cardiac stress test

Types of nuclear cardiac stress tests

A healthcare provider can use two different imaging methods for a nuclear cardiac stress test: PET or SPECT. Sometimes, a stress test requires you to exercise to simulate stress. Other times, you may receive medication to stress your heart.

With an exercise stress test, you walk on a treadmill or ride on a stationary bike to increase blood flow to your heart and reach a target heart rate.

If you can’t exercise, you may receive medication to increase blood flow and stress your heart. This is a pharmacological stress test.

When is this test performed?

Healthcare providers may use a nuclear stress test if you have symptoms of chest pain or angina, if they want to test the fitness of your heart before a procedure, or to see if you may have areas of scarring or ischemia (lack of blood flow) in your heart.

How does a nuclear cardiac stress test work?

The test detects the radioactive tracer and uses it to create pictures. Heart muscle that doesn’t get enough blood flow looks different from healthy muscle in images. This is because it absorbs the tracer differently than healthy tissue does.

How do I prepare for the test?

Your healthcare provider will tell you how to prepare for the test. The instructions may include:

• Avoid foods, beverages and medications that contain caffeine for 24 hours before the test. Examples include coffee, tea, soft drinks and chocolate.
• Bring anything with you that helps you breathe, like your inhaler.
• Don’t use tobacco products for eight hours before the test.
• Fast (don’t eat or drink anything but water) for four to six hours before your test.
• Tell your provider about any medications you take. These include prescriptions, over-the-counter medicines, recreational drugs and supplements.
• Stop taking certain medications before the test or change the dose as directed. Don’t do this without talking to your provider first.
• Wear sneakers and comfortable, loose clothes.

What to expect during a nuclear stress test

A technician or another provider usually performs this nuclear stress test procedure in a hospital or clinic. If you can’t exercise, a provider can inject medicine into your arm. The drug stimulates your heart and increases blood flow as if you were physically active.

A healthcare provider will:

1. Insert an IV into your arm to inject the tracer into your bloodstream, which may feel cold at first
2. Wait a few minutes for the tracer to circulate and reach your heart
3. Place patches called electrodes on your skin, usually on the chest, arms and legs (they may have to shave some hair so the patches stick)
4. Connect the patches to an electrocardiogram (EKG) machine to record your heartbeat signals
5. Put a cuff on your arm to monitor your blood pressure
6. Ask you to lie on a table (or sit if the machine allows) and stay still so they can take pictures with a special camera
7. Tell you to exercise for six to 12 minutes (if you can) on a treadmill or stationary bike (you’ll start slowly and then push harder)
8. Ask you to keep moving until you reach a target heart rate or have symptoms that bother you (you can stop the test if you’re uncomfortable continuing)
9. Inject more tracer into your bloodstream
10. Ask you to lie down on a table again to take a second set of pictures after exercise

What are the risks of this test?

This test exposes you to a small amount of radiation. These low-dose radiation tracers are considered very safe. Some people might be allergic to the tracer or have some flushing, nausea or shortness of breath.

Rarely, people can have side effects, like:

• Abnormal heart rhythm (arrhythmia)
• Chest pain
• Heart attack
• Low blood pressure (hypotension)

Who shouldn’t have this test?

A nuclear stress test may be harmful to a fetus or nursing baby. Ask your provider if you can wait until after delivery or prepare milk in advance. You shouldn’t have a nuclear cardiac stress test if you have certain problems that are severe or not managed, like:

• Acute coronary syndrome
• Aortic dissection
• Aortic stenosis
• Hypertrophic cardiomyopathy

What to expect after the test

Your healthcare provider will tell you what to do after the test. People usually can go back to normal activities right away. After the test, you may feel tired. That should go away with time and rest.

What are the test results like?

Results of a nuclear stress test may take a few days. A heart expert (cardiologist) or radiologist (imaging expert) must review the images and interpret the results.

Normal results at rest and under stress mean your blood flow is good.

Poor blood flow at rest and under stress (or only under stress) is abnormal. It could mean you have a blockage in an artery that brings blood to your heart.

If the test doesn’t pick up the tracer, that could mean you have heart muscle damage from a heart attack.

If the results are abnormal, what are the next steps?

If you have abnormal results, your healthcare provider may want to do a coronary angiogram. This test involves putting dye into your heart’s arteries to see how well it gets through.

If a nuclear stress test shows that you have poor blood flow because of artery blockages, your healthcare provider will want to keep CAD from getting worse. They’ll want to prevent you from having a heart attack. To do this, you may need to:

• Stop using tobacco products and lower your salt use
• Manage issues like high blood pressure or cholesterol
• Get angioplasty and a stent to open a blocked artery and keep it open
• Have coronary artery bypass surgery (CABG) to direct blood flow around the blockage

When should I call my healthcare provider?

Contact your provider if you have mild side effects (like nausea or shortness of breath) from the test. Seek medical care right away if you have chest pain or other heart attack symptoms, or if you feel like your heart rhythm is off.