Nuclear Cardiac Stress Test

What is a nuclear cardiac stress test?

This test helps diagnose heart disease. A healthcare provider injects a small amount of a radioactive substance (called a tracer or radiopharmaceutical) into the bloodstream. Your blood vessels and heart muscle absorb the tracer, making them more visible in images. Then the provider uses a special camera to take pictures of blood flow in and around the heart.

The test may also be called:

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

Types of nuclear cardiac stress tests

A healthcare provider can use two different imaging technologies for a nuclear cardiac stress test: PET or SPECT.

Another way a nuclear stress test can be classified is whether it involves physical activity or medication to stress the heart:

• Exercise stress test: You exercise on a treadmill or stationary bike to increase blood flow to the heart and reach a target heart rate.
• Pharmacologic stress test: If you can’t exercise, you receive medication to increase blood flow and stress the heart.

What does a cardiac nuclear stress test show?

Cardiac stress testing is commonly used to diagnose and monitor coronary artery disease (CAD) by showing blood flow to your heart. CAD occurs when blood vessels are clogged or blocked.

The test can also:

• Determine whether your heart muscle is pumping well.
• Identify poor blood flow.
• Locate blocked arteries.
• Show whether your heart has been damaged (for example, by a heart attack).

It also may be used in people with:

• Acute coronary syndrome.
• Bundle branch block.
• Congestive heart failure.
• Other confirmed or suspected heart problems.
• Trouble breathing.

Who performs a nuclear cardiac stress test?

Cardiologists (heart doctors) often order this test. They may conduct the test themselves, or a radiology technologist can perform the test.

What’s the difference between a stress test and a nuclear stress test?

A regular exercise stress test and a nuclear stress test are similar. Both assess your heart’s electrical activity using an electrocardiogram (EKG). Both evaluate how your heart performs under stress. But a nuclear stress test is a more advanced method that provides more detailed information.

An exercise stress test uses only an EKG to monitor your heart while you’re resting and then exercising. But a nuclear stress test includes images of your heart. A tracer is injected into your veins, and a special camera takes pictures of your heart before and after exercise.

How do I prepare for a nuclear cardiac stress test?

Your healthcare provider will give you specific instructions to help you 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, such as your inhaler.
• Don’t smoke before the test.
• Fast (don’t eat or drink anything but water) for a few hours beforehand.
• Inform your healthcare provider about any medications you take, including prescriptions, over-the-counter medicines, illegal drugs and supplements.
• Wear sneakers and comfortable, loose clothes.

Your healthcare provider may ask you to skip certain medications before the test or change the dose. But don’t change the way you take prescription medications without talking to your doctor first.

What can I expect during a nuclear stress test?

The test is usually performed in a hospital or clinic by a specialized technician or doctor.

A healthcare provider will:

1. Insert an IV into your arm to inject the tracer into your bloodstream. It may feel cold at first.
2. Wait a few minutes for the tracer to circulate and reach the 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 EKG machine to measure the heart’s electrical activity.
5. Put a cuff on your arm to monitor your blood pressure.
6. Ask you to lie on a table and stay still so they can take pictures with a special camera.
7. Instruct you to exercise on a treadmill or stationary bike, starting slowly and then increasing the intensity.
8. Ask you to keep exercising until you reach a target heart rate or experience bothersome symptoms. You can stop the test anytime you aren’t comfortable continuing.
9. Inject more tracer into your bloodstream.
10. Ask you to lie down on a table again to take a second set of images after exercise.

What if I can’t exercise for a nuclear stress test?

If you have a medical condition that prevents you from exercising, a healthcare provider can inject a medication into your arm. The medication stimulates the heart and increases blood flow to mimic exercise conditions.

How long does a nuclear stress test take?

A nuclear stress test usually takes about three or four hours.

What should I avoid after a nuclear cardiology stress test?

Your healthcare provider will give you instructions to follow after the test. People usually can go back to normal activities immediately. You may want to drink plenty of fluids to help flush the tracer out of your body.

After the test, you may feel tired or dizzy or have a headache. Those symptoms should go away with time and rest.

What are the risks of nuclear stress testing?

Nuclear stress tests are generally safe. But the procedure can cause a problem in about 1 in 5,000 people, such as:

• Arrhythmia.
• Chest pain.
• Heart attack (myocardial infarction).
• Low blood pressure (hypotension).

The procedure involves a small amount of radiation exposure. Radiation exposure can cause cancer, but scientists believe that requires large or frequent doses.

You should not have a nuclear stress test if you have certain conditions that are severe or not controlled, such as:

• Angina.
• Aortic dissection.
• Aortic stenosis (narrowed aorta).
• Arrhythmia.
• Congestive heart failure.
• Heart infection.
• Pulmonary embolism.
• Pulmonary hypertension.

When will I know my nuclear cardiac stress test results?

Results of a nuclear stress test may take a few days. A healthcare provider such as a cardiologist or radiologist must review the images and interpret the results.

A note from Cleveland Clinic

A nuclear cardiac stress test helps diagnose and monitor heart problems such as coronary artery disease. A healthcare provider connects you to an EKG machine, injects a tracer into your bloodstream and takes images of blood flow to your heart before and after exercise. If you need a stress test, tell your doctor about any medications you take, and ask how you should prepare.