What Is the MUGA scan?

What to expect when undergoing the MUGA scan

A MUGA scan—the acronym for multiple gated acquisition scan—is a noninvasive, nuclear medicine test used to examine the ventricles (lower chambers) of the heart. It uses gamma rays and a radioactive tracer to create a computerized image of the heart as it beats. A MUGA scan is particularly useful for evaluating the overall ability of the heart to pump blood.

Also Known As

  • Radionuclide ventriculography (RVG)
  • Equilibrium radionuclide angiogram (RNA)
  • Blood pooling imaging
  • Nuclear heart scan
A doctor talking to his patient
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Purpose of Test

A MUGA scan typically is performed to evaluate how well the heart is pumping blood. It can help a doctor understand why a patient might be experiencing symptoms such as angina (chest pain), dizziness, tiredness, or dyspnea (shortness of breath). A MUGA scan also is sometimes used as a follow-up to other tests of cardiac health, such as an electrocardiogram (ECG).

Several features of cardiac function can be measured with the MUGA scan. After a heart attack, this test can reveal which portion of the heart muscle is functioning abnormally. By localizing areas of heart muscle damage, the MUGA scan can provide clues about which coronary arteries are likely to be blocked or partially blocked by atherosclerosis. 

A MUGA scan also is an effective way to measure overall heart function, particularly if there is any degree of dilated cardiomyopathy. It is an accurate and reproducible means of determining left ventricular ejection fraction (LVEF), a measurement of the amount of blood the left ventricle is able to pump out with each beat and is useful in assessing and treating heart failure.

The MUGA scan has several advantages over other tests that assess cardiac function.

  • Accuracy: An LVEF obtained with a MUGA scan is regarded as being more precise than LVEF measurements obtained by other kinds of cardiac tests, such as an echocardiogram (echo).
  • Reproducibility: This means that after an initial MUGA scan, subsequent scans that show a difference in LVEF is likely due to an actual change in the heart rather than an artifact of an inaccurate measurement.

While MUGA is a highly regarded test there are some downfalls, including:

  • Reduced accuracy in some cases: The accuracy of the left ventricle ejection fraction obtained with a MUGA scan is diminished in people with irregular heart rhythms, especially atrial fibrillation.
  • Limited findings: The MUGA scan usually does not provide much information about the function of the heart valves, or whether there is ventricular hypertrophy. The echocardiogram, in contrast, is excellent for obtaining information like this. So, for many people with suspected heart problems, the MUGA scan must be used in combination with other heart tests to obtain the most complete picture of the person’s overall cardiac condition.

Risks and Contraindications

The MUGA scan is noninvasive and generally is safe for most people. The only potential concern is exposure to a very small dose of radiation. This is because the scan relies on the injection of a radioactive tracer in order to illuminate the workings of the heart. The tracer is flushed out of the body by the kidneys within 24 hours.

That said, women who are pregnant or breastfeeding should not undergo a MUGA scan. Although the radiation dose is minimal, it may enough to harm a developing baby or nursing infant.

Before the Test

Timing

A MUGA scan typically takes one to two hours to complete. When planning your day, allot enough time to travel to the facility where the test will be performed. In addition, you also may need to fill out paperwork and/or wait to be brought into the room where the test will take place. Ask your doctor how much time you realistically will need to block off for your MUGA scan.

Location

The MUGA scan is an outpatient test. It typically is performed in a hospital or clinic.

What to Wear

When dressing to go to your appointment, keep in mind what sort of test you'll be having. If you will be running on a treadmill or riding a stationary bike during your MUGA scan, wear the same type of clothing you would for a workout, including appropriate shoes.

If exercise will not be part of your test, wear loose-fitting clothing and comfortable shoes. This will make it easier to change into a hospital gown if asked.

Food and Drink

If you'll be having a resting scan, you likely will be directed to avoid alcohol or caffeine (not only in coffee or tea but also in soda) several hours before the test.

If you'll be exercising during your test, you will be told to not eat or drink anything except water for four hours beforehand.

What to Bring

You may be able to fill out any necessary paperwork at home prior to having a MUGA scan; if so, bring that paperwork with you to your appointment. In addition, bring your health insurance card, your driver's license or another form of official identification, and an acceptable form of payment should you owe a co-pay at the time of the test.

If you do not have health insurance and must pay out of pocket, you also will need to bring payment. The cost of the test will depend on where you live but by some estimates the national average for the test is around $1200.

During the Test

Knowing how to prepare for a MUGA scan and what to expect during it and afterwards will relieve any anxiety you may have about the test.

Pre-Test

Before a resting MUGA scan, you may be asked to put into a hospital gown. If you'll be exercising during your test and did not wear appropriate clothing or shoes, you will need to change into those.

Either way, once you're properly dressed a technician will attach electrodes (small, round adhesive patches) to your chest. If you have chest hair it may need to be shaved where the electrodes will be positioned.

The electrodes are attached to an electrocardiograph monitor (EKG) that charts the heart’s electrical activity during the test.

Next, a small amount of Technetium 99 (a radioactive substance) will be injected into a vein in your arm. The Technetium 99 will attach to red blood cells and thereby circulate within your bloodstream.

Throughout the Test

During the test, you will either be at rest, exercising, or both. If you are doing a resting test, you will lie down on a table under a special camera (a gamma camera), which is able to detect the low-level radiation being given off by the Technetium-labelled red cells. The gamma camera is able to produce what is essentially a movie of the beating heart as the radiated red blood cells fill your cardiac chambers. This digital “movie” can be analyzed with various computer algorithms, which can determine a lot of useful information about the overall health of your heart.

If you are asked to exercise you will pedal on a specialized stationary bike or walk on a treadmill while the camera takes pictures of your heart.

After the Test

After the test, you can change back into your street clothing, leave, and resume your normal activities right away.

Your doctor will receive a written report later and go over it at your scheduled appointment. There, you will learn what the next steps are for your care.

Managing Side Effects

There is a risk of having an allergic reaction to the tracer, but it's small because the dose is so small. Drinking plenty of water for several days after a MUGA scan will effectively flush the radioactive material from your system.

Interpreting Results

The MUGA test measures your ejection fraction, which is the amount of blood pumped out of the heart during each heartbeat (contraction). Your results will usually be shown as a percentage. For example, an ejection fraction of 30% means that 30% of the total amount of blood in the left ventricle when it is full is pumped out with each heartbeat. A normal ejection fraction is between 50% and 75%.

Follow-up

If a MUGA scan indicates an abnormal ejection fraction, you and your doctor will discuss what this might mean and how to proceed with your care.

MUGA scans often are used to assess cardiac function during a course of chemotherapy for cancer as some chemotherapy drugs can be toxic to the heart muscle—notably Adriamycin (doxorubicin). By measuring the LVEF with periodic MUGA scans, oncologists can determine whether it is safe to start or continue chemotherapy, or whether certain drugs need to be stopped.

Other Considerations

Before you meet with your doctor about your results, it helps to write down any questions so you won't forget any. Your doctor is the best person to guide you in your care so having an open dialogue about your questions and concerns is important.

If you would also like a second opinion on the scan's findings or what to do next, you can ask your doctor what the process is to get medical records.

A Word From Verywell

The MUGA is most useful when it's important for you to have an accurate measurement of your LVEF, or to closely follow your LVEF over time.

Cancer survivors who specifically benefit from MUGA monitoring include people who have had radiation therapy to the chest and people who have had a bone marrow/stem cell transplant.

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Article Sources
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