Nuclear Stress Test

Overview

A nuclear stress test is an imaging test that shows how blood goes to the heart at rest and during exercise. It uses a small amount of radioactive material, called a tracer or radiotracer. The substance is given through a vein. An imaging machine takes pictures of how the tracer moves through the heart arteries. This helps find areas of poor blood flow or damage in the heart.

A nuclear stress test is one of several types of stress tests. It may be done after a regular exercise stress test. Sometimes it is the first stress test used. If you have coronary artery disease, a nuclear stress test can help your healthcare team learn your risk of a heart attack or other heart event.

The test uses a positron emission technology (PET) scanner or single-photon emission computed tomography (SPECT) scanner.

Other names for a nuclear stress test are:

Cardiac PET study (positron emission tomography)

Cardiac SPECT study (single-photon emission computed tomography)

Myocardial perfusion imaging (MPI) study.

Why it's done

A nuclear stress test helps your healthcare provider visualize what is happening in your heart when you exercise. A nuclear stress test is different than a regular stress test. A regular stress test uses an ECG to record your heart rate and rhythm, while a nuclear stress test captures images of your heart.

The nuclear stress test uses a radioactive tracer to make a picture. The tracer is a very small amount of radioactive material that is delivered into your body through an intravenous (IV) line. The tracer that is commonly used today is called technetium 99 (Tc-99. It provides clearer images than the tracers used in the past. It also exposes a patient to less radiation.

A nuclear stress test is often done to:

Diagnose coronary artery disease. The coronary arteries are the major blood vessels that supply the heart with blood, oxygen and nutrients. Coronary artery disease happens when these arteries are damaged or diseased. A nuclear stress test can diagnose coronary artery disease and show how severe the condition is.

Create a treatment plan. If you have coronary artery disease, a nuclear stress test can tell your healthcare team how well treatment is working. The test also shows how much exercise your heart can handle. This information helps your healthcare team choose the best treatment for you.

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?

The nuclear stress test creates two images. The first shows how blood flows to your heart when you are resting. The second shows the blood flow during exercise. 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.

The presence, location, and size of blockages that are serious enough to affect blood flow during exercise

Show whether your heart has been damaged (for example, by a heart attack).

The images can tell your provider different things about your heart health:

A normal test result will show blood being evenly distributed to the heart in both images.

If both images show a fixed patch of poor blood flow, that means the person had a heart attack at some point.

If an area of poor blood flow is seen on the exercise image, but not on the rest image, it means there is probably a blockage in one of the coronary arteries. The blockage is causing a temporary drop in blood flow.

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.

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.

Risks

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

Cardiac arrhythmias: Exercise-induced heart arrhythmias occur when your heart beats too fast, too slow, or irregularly. Arrhythmias are usually not dangerous. They almost always go away when the person stops exercising. While arrhythmias are a risk of stress testing, their presence can also help with diagnosis. If you're worried about them, keep in mind that if dangerous arrhythmias happen during modest exercise, the safest way to find out about them is in a controlled setting under the care of a provider..

Chest pain, dizziness, or other symptoms: In people with serious CAD, modest exercise can cause symptoms of insufficient blood flow to the heart muscle (cardiac ischemia). While it is a risk of the test, it can also be useful for providers to see exercise-related symptoms during the test. In fact, in people who are being assessed for exercise-related symptoms, one of the goals is to reproduce the symptoms during the test.

Allergic reaction: Some people may have an allergic reaction to the radioactive tracer, but this is very rare.

Heart attack: It's very rare, but if a person has a critical blockage, exercise might produce a heart attack.

Radiation Exposure

During a typical nuclear stress test, you are exposed to 11 millisieverts of radiation. This is about three times the dose of radiation that you get just from going about your normal, day-to-day life for one year. A dose of 11 millisieverts is considered a small amount of radiation exposure. By itself, it should not increase your lifetime risk of cancer by any measurable amount.
The risk of radiation exposure to other people after a nuclear stress test is low. However, some healthcare providers recommend no close contact with children or babies for one to two days after a nuclear stress test. Out of an abundance of caution, you may also want to avoid close contact with pets.

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

Unstable angina

Aortic dissection.

Aortic stenosis (narrowed aorta).

Arrhythmia.

Congestive heart failure.

Heart infection.

Pulmonary embolism.

Pulmonary hypertension.

Pharmacologic Stress Testing

People with physical limitations that make exercise difficult or impossible can have pharmacologic stress testing instead of exercise stress testing. This is done with drugs that cause the same stress on the heart as exercise.

The types of drugs used may include:

Vasodilators such as Adenocard (adenosine), Persantine (dipyridamole), or Lexiscan (regadenoson)

Inotropic drugs, usually Dobutrex (dobutamine)

Vasodilators are usually preferred for the pharmacologic stress test. These are medications that dilate or open the blood vessels. Your provider will choose the best drug for your case if exercise is not an option.

How you prepare for a nuclear 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?

A nuclear stress test usually does not cause significant pain during the procedure. However, you will feel a pinch from the needle during the IV line insertion. Also, the tracer may feel cold as it initially flows into the vein in your arm.
Your experience with the procedure may vary depending on whether a medication was used to achieve stress and the type of medication used.
Cardiologists (heart doctors) often order this test. They may conduct the test themselves, or a radiology technologist can perform the test.

A healthcare provider will:

Insert an IV into your arm to inject the tracer into your bloodstream. It may feel cold at first.

Wait a few minutes for the tracer to circulate and reach the heart.

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.

Connect the patches to an EKG machine to measure the heart’s electrical activity.

Put a cuff on your arm to monitor your blood pressure.

Ask you to lie on a table and stay still so they can take pictures with a special camera.

Instruct you to exercise on a treadmill or stationary bike, starting slowly and then increasing the intensity.

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.

Inject more tracer into your bloodstream.

Ask you to lie down on a table again to take a second set of images after exercise.

Results

Your healthcare professional compares the two sets of pictures taken during your nuclear stress test. The pictures show how blood flows through your heart while at rest and during physical activity.

Your healthcare professional talks with you about your test results.

The results could show:

Typical blood flow during exercise and rest. You might not need any more tests.

Typical blood flow during rest, but not during exercise. Part of the heart doesn't get enough blood during exercise. This might mean there are one or more blocked arteries, which is coronary artery disease.

Low blood flow during rest and exercise. Part of the heart doesn't get enough blood at all times. This could be due to severe coronary artery disease or an earlier heart attack.

Lack of blood flow in parts of the heart. Areas of the heart that don't show the radioactive tracer have damage from a heart attack.

If you don't have enough blood flow through your heart, you may need a test called coronary angiography. This test helps show any blockages in the heart arteries.

If you have a severe blockage in a heart artery, you may need a heart treatment called angioplasty with stenting. Or you might need coronary artery bypass graft surgery, also called CABG. CABG is a type of open-heart surgery that creates a new path for blood to flow around a blockage.

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.

FAQ's about a nuclear stress test

Here are answers to some common questions people ask about nuclear stress tests.
Is a nuclear stress test painful?

A nuclear stress test is usually not painful. But some people may experience headaches, nausea, or dizziness after the test.
How long are you radioactive after a nuclear stress test?

Depending on the type of radioactive tracer used, it may take a few hours to some daysTrusted Source for it to leave your body through urine.
Can you drive after nuclear stress test?

Some people may be able to drive after a nuclear stress test. But it may be safer to bring someone with you who can drive you back after the test.
What should I avoid after a nuclear stress test?

Some people give off small amounts of radiation after a nuclear test. So, it will be best to avoid young children and babies after the test. Also, if you’re breastfeeding or chestfeeding, speak with your doctor about safety precautions.
When will I get the results of a nuclear stress test?

It may take a few days for your healthcare team to process your test results, after which they will give you an appointment to discuss it with you.

One Final Note..

A nuclear stress test is a noninvasive test used to show blood flow through the heart muscle during exercise and at rest. The test takes about 3 to 4 hours and usually doesn‘t cause serious complications. While this test is useful for diagnosing certain heart conditions, it may not be ideal for pregnant people.

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.

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