(Multi Gated Acquisition Scan, First Pass Scan, Gated Blood Pool Scan, Cardiac Blood Pooling Imaging, Radionuclide Ventriculography, Nuclear Ventriculography)

Summary

What is a MUGA scan?
How does a patient prepare for a MUGA scan?
How is a MUGA scan done?
What happens after a MUGA scan?
What do the results of a MUGA scan mean?

Summary

Also known as a nuclear ventriculogram, a multi-gated acquisition (MUGA) scan is a type of radionuclide imaging that provides the physician with a comprehensive look at blood flow and the function of the lower chambers of the heart (ventricles). It involve intravenous (I.V.) line. The substance travels through the bloodstream to the heart, enabling a gamma camera to take very clear very small amounts of a radioactive isotope called a tracer, which is administered through any pictures of the heart tissues.

People may experience some slight discomfort from the needle used to insert the intravenous (I.V.) line, usually in the crook of the arm. Otherwise, these tests are painless. If the physician has also ordered an exercise component of the test, then some preparation will be necessary, such as wearing appropriate clothes and shoes for exercising.

Although the tracer is flushed harmlessly from the bodies of most people in about 48 hours, there are some people (e.g., pregnant or nursing women) who should not have a radionuclide test. People are encouraged to discuss with their physician any concerns they may have about radiation.

What is a MUGA scan?

Also known as a nuclear ventriculogram, a MUGA (multi-gated acquisition) scan is a type of radionuclide imaging that provides the physician with a comprehensive look at blood flow and the function of the lower chambers of the heart (ventricles). It is called multi-gated because a gamma camera takes multiple (sometimes over 60) pictures at very specific times. One of the most important indicators revealed by these pictures is the left ventricle’s ejection fraction a measure of the amount of blood being pumped from the left ventricle with each heartbeat. The ejection fraction is a very important predictor of the patient’s risk for future cardiac events and death, and also helps to guide treatment.

The test is used primarily to detect or assess damage from a heart attack, or to establish a patient’s risk of coronary artery disease or complications from heart disease. It may also be performed if the following conditions are suspected:

Congestive heart failure. A serious condition in which the heart is not pumping well enough to meet the body’s demand for oxygen. It got its name because the heart is failing to pump efficiently, which often results in congestion in the lungs. The condition may also be associated with swelling (edema) in the legs.
Dilated cardiomyopathy. A condition in which the heart's ability to pump blood is reduced because the left ventricle is enlarged and the muscle is weakened. This enlargement leads to less blood being pumped from the heart — a reduced ejection fraction.
This test involves the injection of a radionuclide substance called a tracer. Although most people are not harmed by the tracer, not everyone is an appropriate candidate for a MUGA scan. People who should avoid this test include the following:

Women who are or may be pregnant.
Women who are breast-feeding.
Patients with severe narrowing (stenosis) of the aortic valve, if the test will be performed with an exercise component.
Patients with severe congestive heart failure, if the test will be performed with an exercise component.

How does a patient prepare for a MUGA scan?

Preparations necessary for the test depend on whether a resting MUGA or an exercise MUGA has been ordered. For a resting MUGA, no special preparation is necessary.

For an exercise MUGA, some steps must be taken before arriving at the test facility:

The patient may be told not to eat or drink anything (especially anything containing alcohol or caffeine) for at least three hours before the test.
Patients who smoke are often requested not to so in the hours before the test.
Comfortable clothing and appropriate shoes for exercise are also recommended.

How is a MUGA scan done?

The test may be performed in a nuclear medicine laboratory or in an outpatient center. Just prior to the test, the patient’s arm is prepared for an intravenous (I.V.) line to receive medications and the tracer. Small metal devices (electrodes) (which are connected by wires (leads) to an electrocardiograph [EKG] machine) will be attached to the patient’s skin.

The EKG will monitor the heart’s electrical activity throughout the test and to enable EKG-gating. This means that the EKG is used to time exactly when the gamma camera (in conjunction with the cardiac cycle) will take pictures of the left ventricle. The precise timing is required to avoid any blurring of the images due to the heart's motion.

As the patient lies still on the examination table, the radioactive isotope is administered through the I.V. line and the gamma camera begins the imaging process.

If an exercise component of the MUGA scan is required, then the patient will lie down on a bed equipped with pedals. As the patient pedals with some resistance, more images are taken with the gamma camera. Performing the study with exercise gives information about cardiac performance under physical stress. This information can help determine, for example, the timing of a heart valve procedure to treat a leaky valve (valvular regurgitation).

The test can take up to three hours, depending on whether the exercise component is completed. Without an exercise component, the test takes less than one hour.

What happens after a MUGA scan?

After the test, patients can expect to go right back to their normal daily activities, including driving themselves from the test facility. Side effects and complications are rare. Any possible complications would likely be related to the additional stress placed on the heart during the exercise portion of the test, and the EKG usually displays any serious problems immediately.

What do the results of a MUGA scan mean?

Normal results of a MUGA scan are images showing a normal pumping ability of the heart and a normal ejection fraction. The tracer labels red blood cells, and this reveals the blood volume within the myocardial chambers. The MUGA scan is the best method to measure the blood volumes within the heart’s chambers and the performance of the heart muscle.