MUGA scan: how it checks heart pumping and what the appointment involves

MUGA stands for multigated acquisition. It is a nuclear medicine scan of the heart. The pictures are timed, or gated, to the heartbeat, so that the camera can build up an image of the heart as it squeezes and relaxes. United Lincolnshire Hospitals puts it simply: a doctor has asked for pictures of your heart to measure how well it is pumping blood around your body.

The main number from the scan is the ejection fraction, which is the proportion of blood in the left ventricle that is pumped out with each beat. Chelsea and Westminster Hospital says that the aim is to obtain the ejection fraction of the left ventricle to give an indication of heart function, helping the doctor diagnose your condition and give appropriate treatment.

A MUGA scan does not use contrast dye in the way a CT scan can, and it is not an echocardiogram. It uses a radiolabel that stays inside the blood, which is why it is sometimes called a blood pool scan.

The NHS trust leaflets keep the explanation general: the test provides information about how well the heart is working so that the right treatment can be chosen. The Canadian Cancer Society, a non-UK charity, gives more detail. It says a MUGA scan may be done to check how well the heart is pumping, to evaluate the size of the heart chambers, to track the effect of certain kinds of chemotherapy drugs on the heart to make sure it is safe to continue with chemotherapy, and to follow up late side effects of cancer treatment.

In practice this means that people often have a MUGA scan before starting a medicine that is known to affect heart muscle, and again at intervals to check that the heart is coping. It may also be used when an echocardiogram is not clear enough or when the team wants a repeatable measurement. Your own doctor will explain why they chose this test for you.

Both NHS trust leaflets say there is no special preparation, and that you may eat and drink as normal and continue your medicines. The Canadian Cancer Society notes that other providers may ask you not to eat for 4 to 6 hours, especially if the test includes exercise, or to avoid caffeine and tobacco for 24 hours. This is a reminder that departments differ, so follow the letter you are given.

• Bring a list of your medicines, ideally your repeat prescription sheet.

• Tell the department if you are pregnant, might be pregnant or are breastfeeding, so the test can be rescheduled if needed.

• Let them know if you have mobility problems, are incontinent or are claustrophobic.

• Do not bring children under 18 or anyone who might be pregnant. One adult companion is allowed at United Lincolnshire, and some parts of the test may require them to sit outside the room.

• Remove jewellery and metal items from the chest area before the scan, as Chelsea and Westminster asks.

Two injections are given into veins in the hand or arm. The first contains a compound that prepares your red blood cells, and the second, given about 20 to 30 minutes later according to the two leaflets, contains the radioactive tracer that attaches to those cells. You then lie flat on a bed while ECG electrodes are attached to your chest. The gamma camera is positioned close to your chest and takes pictures. Chelsea and Westminster describes a scan of approximately 30 minutes immediately after the second injection.

You need to stay as still as possible. United Lincolnshire describes the camera as having an open design, and says the majority of patients complete the test without any discomfort. If you are unsure about any part of the test, the department's staff will explain it again before the injection.

When the pictures are finished, you are free to leave the department. There are no restrictions on eating, drinking or driving mentioned in either NHS leaflet.

For the rest of the day, United Lincolnshire advises taking extra care to wash your hands thoroughly after using the toilet, sitting down to pass urine, flushing twice, drinking extra fluids and emptying your bladder frequently. This helps the body clear the radioactivity. Chelsea and Westminster similarly advises drinking plenty of fluids.

The images are reviewed and a report goes to the doctor who requested the test. The Chelsea and Westminster leaflet says this happens within two weeks and that you will not receive results on the day. The doctor will usually explain the ejection fraction and what it means for you at your next appointment.

Ejection fraction is only one part of the picture. Symptoms, blood tests, heart rhythm and other imaging are all considered too, so a single value should be discussed with the clinician who knows your history.