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What Is a Nuclear Heart Scan?

A nuclear heart scan is a test that provides important information about the health of your heart.

For this test, a safe, radioactive substance called a tracer is injected into your bloodstream through a vein. The tracer travels to your heart and releases energy. Special cameras outside of your body detect the energy and use it to create pictures of your heart.

Nuclear heart scans are used for three main purposes:

  • To check how blood is flowing to the heart muscle. If part of the heart muscle isn't getting blood, it may be a sign of coronary heart disease (CHD). CHD can lead to chest pain called angina (an-JI-nuh or AN-juh-nuh), a heart attack, and other heart problems. When a nuclear heart scan is done for this purpose, it's called myocardial perfusion scanning.
  • To look for damaged heart muscle. Damage might be the result of a previous heart attack, injury, infection, or medicine. When a nuclear heart scan is done for this purpose, it's called myocardial viability testing.
  • To see how well your heart pumps blood to your body. When a nuclear heart scan is done for this purpose, it's called ventricular function scanning.

Usually, two sets of pictures are taken during a nuclear heart scan. The first set is taken right after a stress test, while your heart is beating fast.

During a stress test, you exercise to make your heart work hard and beat fast. If you can't exercise, you might be given medicine to increase your heart rate. This is called a pharmacological (FAR-ma-ko-LOJ-ih-kal) stress test.

The second set of pictures is taken later, while your heart is at rest and beating at a normal rate.

Types of Nuclear Heart Scans

The two main types of nuclear heart scans are single photon emission computed tomography (SPECT) and cardiac positron emission tomography (PET).

Single Photon Emission Computed Tomography

Doctors use SPECT to help diagnose coronary heart disease (CHD). Combining SPECT with a stress test can show problems with blood flow to the heart. Sometimes doctors can detect these problems only when the heart is working hard and beating fast.

Doctors also use SPECT to look for areas of damaged or dead heart muscle tissue. These areas might be the result of a previous heart attack or other cause.

SPECT also can show how well the heart's lower left chamber (left ventricle) pumps blood to the body. Weak pumping ability might be the result of a heart attack, heart failure, and other causes.

Tracers commonly used during SPECT include thallium-201, technetium-99m sestamibi (Cardiolite®), and technetium-99m tetrofosmin (Myoview™).

Positron Emission Tomography

Doctors can use PET for the same purposes as SPECT—to diagnose CHD, check for damaged or dead heart muscle tissue, and check the heart's pumping strength.

Compared with SPECT, PET takes a clearer picture through thick layers of tissue (such as abdominal or breast tissue). PET also is better at showing whether CHD is affecting more than one of your heart's blood vessels.

Right now, however, there's no clear advantage of using one scan over the other in all situations. Research into advances in both SPECT and PET is ongoing.

PET uses different tracers than SPECT.

Other Names for a Nuclear Heart Scan

  • Nuclear stress test
  • SPECT scan
  • PET scan
  • Radionuclide scan

What To Expect Before a Nuclear Heart Scan

A nuclear heart scan can take a lot of time. Most scans take between 2–5 hours, especially if your doctor needs two sets of pictures.

Discuss with your doctor how a nuclear heart scan is done. Talk with him or her about your overall health, including health problems such as asthma, COPD (chronic obstructive pulmonary disease), diabetes, and kidney disease.

If you have lung disease or diabetes, your doctor will give you special instructions before the nuclear heart scan.

If you're having a stress test as part of your nuclear heart scan, wear comfortable walking shoes and loose-fitting clothes for the test. You may be asked to wear a hospital gown during the test.

Let your doctor know about any medicines you take, including prescription and over-the-counter medicines, vitamins, minerals, and other supplements. Some medicines and supplements can interfere with the medicines that might be used during the stress test to raise your heart rate.

What To Expect During a Nuclear Heart Scan

Many nuclear medicine centers are located in hospitals. A doctor who has special training in nuclear heart scans—a cardiologist or radiologist—will oversee the test.

Cardiologists are doctors who specialize in diagnosing and treating heart problems. Radiologists are doctors who have special training in medical imaging techniques.

Before the test begins, the doctor or a technician will use a needle to insert an intravenous (IV) line into a vein in your arm. Through this IV line, he or she will put radioactive tracer into your bloodstream at the right time.

You also will have EKG (electrocardiogram) patches attached to your body to check your heart rate during the test. (An EKG is a simple test that detects and records the heart's electrical activity.)

During the Stress Test

If you're having an exercise stress test as part of your nuclear scan, you'll walk on a treadmill or pedal a stationary bike. During this time, you'll be attached to EKG and blood pressure monitors.

Your doctor will ask you to exercise until you're too tired to continue, short of breath, or having chest or leg pain. You can expect that your heart will beat faster, you'll breathe faster, your blood pressure will increase, and you'll sweat.

Tell your doctor if you have any chest, arm, or jaw pain or discomfort. Also, report any dizziness, light-headedness, or other unusual symptoms.

If you're unable to exercise, your doctor may give you medicine to increase your heart rate. This is called a pharmacological stress test. The medicine might make you feel anxious, sick, dizzy, or shaky for a short time. If the side effects are severe, your doctor may give you other medicine to relieve the symptoms.

Before the exercise or pharmacological stress test ends, the tracer is injected through the IV line.

During the Nuclear Heart Scan

The nuclear heart scan will start shortly after the stress test. You'll lie very still on a padded table.

The nuclear heart scan camera, called a gamma camera, is enclosed in metal housing. The camera can be put in several positions around your body as you lie on the padded table.

For some nuclear heart scans, the metal housing is shaped like a doughnut (with a hole in the middle). You lie on a table that slowly moves through the hole. A computer nearby or in another room collects pictures of your heart.

Usually, two sets of pictures are taken. One will be taken right after the stress test and the other will be taken after a period of rest. The pictures might be taken all in 1 day or over 2 days. Each set of pictures takes about 15–30 minutes.

Some people find it hard to stay in one position during the test. Others may feel anxious while lying in the doughnut-shaped scanner. The table may feel hard, and the room may feel chilly because of the air conditioning needed to maintain the machines.

Let your doctor or technician know how you're feeling during the test so he or she can respond as needed.

What To Expect After a Nuclear Heart Scan

Your doctor may ask you to return to the nuclear medicine center on a second day for more pictures. Outpatients will be allowed to go home after the scan or leave the nuclear medicine center between the two scans.

Most people can go back to their daily routines after a nuclear heart scan. The radioactivity will naturally leave your body in your urine or stool. It's helpful to drink plenty of fluids after the test, as your doctor advises.

The cardiologist or radiologist will read and interpret the results of your test. He or she will report the results to your doctor, who will contact you to discuss them. Or, the cardiologist or radiologist may contact you directly to discuss the results.

What Does a Nuclear Heart Scan Show?

The results from a nuclear heart scan can help doctors:

  • Diagnose heart conditions, such as coronary heart disease (CHD), and decide the best course of treatment.
  • Manage certain heart diseases, such as CHD and heart failure, and predict short-term or long-term survival.
  • Determine your risk for a heart attack.
  • Decide whether other heart tests or procedures will help you. Examples of these tests and procedures include coronary angiography (an-jee-OG-rah-fee) and cardiac catheterization (KATH-eh-ter-ih-ZA-shun).
  • Decide whether procedures that increase blood flow to the coronary arteries will help you. Examples of these procedures include angioplasty (AN-jee-oh-plas-tee) and coronary artery bypass grafting (CABG).
  • Monitor procedures or surgeries that have been done, such as CABG or a heart transplant.

What Are the Risks of a Nuclear Heart Scan?

The radioactive tracer used during nuclear heart scanning exposes the body to a very small amount of radiation. No long-term effects have been reported from these doses.

Radiation dose might be a concern for people who need multiple scans. However, advances in hardware and software may greatly reduce the radiation dose people receive.

Some people are allergic to the radioactive tracer, but this is rare.

If you have coronary heart disease, you may have chest pain during the stress test while you're exercising or taking medicine to raise your heart rate. Medicine can relieve this symptom.

If you're pregnant, tell your doctor or technician before the scan. It might be postponed until after the pregnancy.

Clinical Trials

The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.

NHLBI-supported research has led to many advances in medical knowledge and care. Often, these advances depend on the willingness of volunteers to take part in clinical trials.

Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions. For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.

By taking part in a clinical trial, you might gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.

If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.

If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.

For more information about clinical trials related to nuclear heart scanning, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:

Links to Other Information About Nuclear Heart Scans

NHLBI Resources

Non-NHLBI Resources

Clinical Trials

March 09, 2012 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.