South Bay Cardiovascular Center
A nuclear heart scan is a test that allows your doctor to get important information about the health of your heart.
During a nuclear heart scan, 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:
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 may be given medicine to increase your heart rate. This is called a pharmacological stress test.
The second set of pictures is taken later, while your heart is at rest and beating at a normal rate.
The two main types of nuclear heart scanning are single positron emission computed tomography (SPECT) and cardiac positron emission tomography (PET). SPECT is the most well-established and widely used type, while PET is newer. There are specific reasons for using each, which are discussed below.
SPECT is the most common nuclear scanning test for diagnosing coronary heart disease (CHD). Combining SPECT with a stress test can show problems with blood flow to the heart that only can be detected when the heart is working hard and beating fast. SPECT also is used to look for areas of damaged or dead heart muscle tissue. These areas may 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 may be the result of a heart attack, heart failure, and other causes.
The most commonly used tracers in SPECT are called thallium-201, technetium-99m sestamibi (Cardiolite®), and technetium-99m tetrofosmin (Myoview™).
PET uses different tracers than SPECT. PET can provide more detailed pictures of the heart. However, PET is newer and has some technical limits that make it less available than SPECT. Research into advances in both SPECT and PET is ongoing. Right now, there's no clear cut advantage of using one over the other in all situations. PET can be used for the same purposes as SPECT—to diagnose CHD, check for damaged or dead heart muscle tissue, and check the heart's pumping strength. PET takes a clearer picture through thick layers of tissue (such as abdominal or breast tissue). PET also is better than SPECT at showing whether CHD is affecting more than one of your heart's blood vessels.
A PET scan also may be used if a SPECT scan doesn't produce good pictures.
Other names for a nuclear heart scan
A nuclear heart scan can take a lot of time. Most scans take between 2 to 5 hours, especially if two sets of pictures are needed.
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 may be used during the stress test to increase your heart rate.
Many, but not all, 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.
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 the 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.
If you're having an exercise stress test as part of your nuclear scan, you'll walk on a treadmill or pedal a stationary bicycle. You'll be attached to EKG and blood pressure monitors.
You'll be asked 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 the doctor if you have any chest, arm, or jaw pain or discomfort. Also report any dizziness, lightheadedness, or other unusual symptoms.
If you're unable to exercise, your doctor may give you medicine to make your heart beat faster. This is called a pharmacological stress test. The medicine used may 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 for relief.
Before the exercise or pharmacological stress test stops, the tracer is injected through the IV line.
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 a metal housing. The part of the camera that detects the tracer's radioactivity 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 and you lie on a table that goes slowly through the doughnut hole. The computer used to collect the pictures of your heart is nearby or in another room.
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 may be taken all in 1 day or over 2 days. It takes about 15 to 30 minutes to take each set of pictures.
Some people find it hard to stay in one position for some time. Others may feel anxious while lying in the doughnut-shaped scanner. The table may feel hard. Sometimes, the room feels chilly because of the air conditioning needed to maintain the machines.
Let the doctor or technician know how you're feeling during the test so he or she can respond as needed.
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 activities 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.
The cardiologist or radiologist will read and interpret the results of the test within 1 to 3 days. Results will be reported to your doctor, who will contact you to discuss them. Or, the cardiologist or radiologist may discuss the results directly with you.
The results from a nuclear heart scan can help doctors:
The radioactive tracer used during a nuclear heart scan 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 very rare.
If you have coronary heart disease, you may have chest pain during the stress test when you exercise or are given medicine to increase your heart rate. Medicine can relieve this symptom.
If you're pregnant, tell your doctor or technician before the scan. It may be postponed until after the pregnancy.
Reference: National Heart, Lung and Blood Institute Last updated May 1, 2017