A multigated acquisition (MUGA) scan is an imaging test that evaluates how effectively the heart pumps blood. It uses a small amount of a radioactive substance and a specialized camera to capture images of the heart’s chambers. This non-invasive procedure helps healthcare providers assess heart function.
What a MUGA Scan Measures
A MUGA scan provides detailed insights into the heart’s pumping action, focusing on the left ventricle, the main pumping chamber. It precisely measures the global left ventricular ejection fraction (LVEF), the percentage of blood pumped out with each contraction. This measurement assesses the heart’s squeezing strength and efficiency.
The scan also evaluates the motion of the heart’s muscular walls, known as wall motion. Irregularities in wall movement can indicate areas of the heart muscle that are not contracting normally. A small amount of technetium-99m (Tc-99m), a radioactive tracer, is injected and binds to red blood cells. A gamma camera then detects the low-level radiation emitted by these tagged blood cells as they circulate through the heart, creating a “movie” of the beating heart.
Why a MUGA Scan is Performed
Doctors order a MUGA scan to assess heart function in patients with heart failure or those at risk of developing heart conditions. It helps determine if the heart is pumping enough blood to meet the body’s needs. It can also aid in diagnosing cardiomyopathy, a condition where the heart muscle is weakened.
A common reason for a MUGA scan is to monitor the heart for potential damage from certain chemotherapy drugs, known as cardiotoxicity. Oncologists use it to track cardiac health during cancer treatment and decide if it is safe to continue specific medications. It may also evaluate heart health before major surgeries or when other tests like an electrocardiogram (EKG) suggest a heart problem.
How a MUGA Scan is Conducted
Before a MUGA scan, patients receive specific instructions, which may include avoiding caffeine and food for several hours. Patients are advised to wear comfortable clothing. During the procedure, electrodes are placed on the chest to monitor heart activity and synchronize imaging with the heart’s contractions.
A small amount of the radioactive tracer, Technetium-99m, is injected into a vein. This tracer attaches to red blood cells, making them visible to a gamma camera. The patient lies still on an exam table while the camera captures images from various angles, creating a detailed view of blood flow through the heart. The entire resting MUGA scan usually takes between 60 to 90 minutes.
Interpreting MUGA Scan Results
The primary result of a MUGA scan is the left ventricular ejection fraction (LVEF), expressed as a percentage. This indicates how much blood the left ventricle pumps out with each beat. A normal LVEF typically falls within the range of 50% to 75%.
Results below 50% or above 75% may suggest a heart issue, though a doctor will interpret this in the context of the patient’s overall health. For instance, an LVEF below 50% can indicate mild, moderate, or severe heart dysfunction. Doctors also examine the “movie” of the heart to identify any areas of the heart muscle not contracting normally, known as wall motion abnormalities. These findings help healthcare providers assess heart health, diagnose specific conditions, and guide treatment decisions.
Safety and Considerations for a MUGA Scan
MUGA scans involve exposure to a minimal amount of radiation from the radioactive tracer. The radiation dose is small, comparable to other common imaging tests like a CT scan. The body eliminates the tracer through the kidneys, typically within 24 hours.
Patients should inform their healthcare provider about any allergies. Pregnant or breastfeeding individuals should discuss these conditions with their doctor, as the tracer could affect the fetus or infant. After the scan, patients are advised to drink plenty of fluids to flush the tracer from their body.