A multigated acquisition (MUGA) scan is a nuclear medicine imaging test that checks how well the heart is pumping during rest or exercise. An MugA scan uses a radioactive material or tracer (radionuclide) that targets the heart, along with a gamma camera and a computer to create images of the blood flowing through the heart.
An MUGA scan is also called gated equilibrium radionuclide ventriculography (RVG), gated equilibrium, radionuclide angiography (RNA) or cardiac blood-pool imaging.
Why an MUGA scan is done
An MUGA may be done to:
- check how well the heart is pumping
- MUGA is used to evaluate the following:
- the size of the heart chambers
- the pumping action of the lower ventricles
- any abnormalities in the wall of the ventricles
- abnormal movement of blood between chambers
- track the effect of certain kinds of chemotherapy drugs on the heart
- MUGA is especially used with anthracyclines such as doxorubicin (Adriamycin), which can affect heart function.
- The scan may be done before and periodically during chemotherapy to determine that it is safe to continue with chemotherapy.
How an MUGA scan is done
An MUGA scan is usually done as an outpatient procedure in the nuclear medicine department of a hospital. The test takes about 1 hour, but may take longer if testing includes exercise.
- It is important for women to tell the nuclear medicine staff if they are breast-feeding, pregnant or think they may be pregnant before having any nuclear medicine test.
- Usually, no special preparation is needed before the scan. The person may be asked to:
- bring a list of current medications and date of last chemotherapy treatment
- fast for 3–4 hours before the test, especially if the test includes exercise
- wear clothing that has no metal zippers, belts or buttons
- change into a gown during the test and remove glasses, jewellery or objects that could interfere with the test
- Before the scan:
- The doctor will take a history of heart disease and previous tests or procedures done on the heart.
- A blood sample is taken. The radiopharmaceutical is mixed with the blood and then injected into the vein.
- The person may feel a sting or pinch with the injection.
- Small pads or electrodes (cardiac leads) are placed on the skin of the chest.
- An electrocardiogram monitors the heart rhythm and synchronizes the images with the person’s heart beat.
- During the scan:
- A special gamma camera detects radiation given off by the radiopharmaceutical in the heart’s cells and tissues.
- It takes pictures of the radiation and sends them to a computer.
- The person may need to change position so the camera can take pictures from different angles.
- Usually, 2 or 3 views are needed to make a complete image of the cardiac cycle.
The scan may be done while the person is resting or exercising (stress MUGA) in between views. A combination of both rest and exercise may also be used.
- People receiving chemotherapy usually have a resting test.
- Stress MUGAs are often done if people have, or the doctor suspects they have, disease of the main arteries in the heart (coronary arteries).
- The person either walks on a treadmill or rides a stationary bike.
- A resting MUGA may be compared to the stress MUGA to study changes in the heart’s pumping function.
- The person may or may not receive a second injection of the tracer, depending on the type of tracer used.
After the scan, the radioactive material quickly loses its radioactivity. It passes out of the body through the urine or stool (feces). Depending on the type of radiopharmaceutical used, it may take a few hours or days to completely pass out of the body.
- Drinking fluids after the procedure helps flush the radiopharmaceutical from the body.
- Instructions may be given for special precautions that need to be taken after urinating, such as to flush the toilet twice and to wash the hands thoroughly.
Potential side effects
The dose of x-rays or radioactive materials used in nuclear medicine imaging can vary widely. Dose depends on the type of procedure and body part being examined. In general, the dose of radiopharmaceutical given is small and people are exposed to low levels of radiation during the test. The potential health risks from radiation exposure are low compared with the potential benefits. There are no known long-term adverse effects from such low-dose exposure.
Some potential side effects that might occur include:
- Bleeding, soreness or swelling may develop at injection site.
- Allergic reactions to the radiopharmaceutical may occur, but are extremely rare.
What the results mean
An MUGA scan can show:
- how well the heart is pumping
- the amount of blood pumped out of the ventricles when it beats (ejection fraction)
- heart muscle damage and the degree of damage
What happens if a change or abnormality is detected
The doctor will decide whether further tests, procedures, follow-up care or additional treatment are needed.
Special considerations for children
Being prepared for a test or procedure can reduce anxiety, increase cooperation and help the child develop coping skills. Parents or caregivers can help prepare children by explaining to them what will happen, including what they will see, feel and hear during the test.
- Check with the doctor to find out if food or liquids are restricted.
- Explain to children that when the radiopharmaceutical is given they will feel:
- a sharp prick when the needle is inserted
- slight pressure or tugging when the radiopharmaceutical is injected
- Some children may find it difficult if they have to lie still during the test.
- Some children may need sedation to be able to lie still for the whole test.
- Let children know that they may hear a clicking noise during the scan.
- Some children feel closed-in when the scanner passes over their body.
- Let them know that the camera may touch their skin, but it will not hurt.
Instructions may be given for special precautions that need to be taken when caring for children during the first 6–24 hours after the test.
- If the caregiver is pregnant, someone else should do most of the child care.
- Wear disposable, waterproof gloves when handling the child’s urine, stool or vomit, including diaper changes.
- Change sheets or clothing that has vomit, urine or stool smears on it.
- Wear disposable, waterproof gloves when handling sheets or clothing.
- Sheets and clothing can be washed in the regular laundry.
- Flush the toilet immediately after the child uses it.
- Place diapers in the outside garbage.
The preparation for an MUGA scan depends on the age and experience of the child. Find out more age-specific information on helping children cope with tests and treatment.