A multiunit gated blood pool scan (MUGA) is an assessment of how your blood pools in your heart during rest or exercise, or both. The test shows how well the heart pumps blood and whether it has to compen- sate for blocked arteries. It also reliably measures your ejection fraction, which is the percentage of your blood pumped out of your ventricles with each heartbeat. The ejection fraction normally increases during exercise.

What to Expect

If you are having only a resting scan MUGA, no special preparation is necessary. You should check with your doctor whether you need to stop taking any heart medications for a day or two beforehand. If you are having an exercise MUGA, you should not eat or drink anything other than water the night before the test. Depending on the extent of the testing, you should allow 2 to 4 hours for its completion. For the test, you will usually be asked to change into a hospital gown, and a techni- cian will attach electrodes to your chest. The electrodes will be wired to a nuclear imaging computer. Then the technician will draw a small amount of your blood and mix it with the radioactive tracing material. About 10 minutes later, he or she will inject the prepared blood back into your arm. Then you will lie down on a table while the technician takes a number of images of your heart with the gamma camera. If you are having only a resting MUGA, the test is complete and you can go home.
If you are having an exercise MUGA, you will move to a different table with pedals at the foot. While you lie on the table, you will pedal as if you were on a bicycle, and the technician will take images. You will pedal through a warm-up stage, and then the exercise will be gradually increased until you are tired. You will be carefully monitored through- out the test.
After your MUGA, you may feel tired, but you can return to your usual activities. The harmless radioactive substance will leave your body in 2 or 3 days. This test should not be performed during pregnancy.

What the Results Mean

The full results of your test will be ready in a few days. In addition to the images produced, the computer also calculates the size and shape of your ventricles and measures the amount of blood in them. A low ejec- tion fraction may be due to blockages in your coronary arteries or a problem with a heart muscle.