| Radionuclide angiography | |
|---|---|
| Intervention | |
| MeSH | D011875 |
| OPS-301 code: | 3-704, 3-708 |
A MUGA scan (Multi Gated Acquisition Scan) is a time-proven yet dated nuclear medicine test designed to evaluate the function of the right and left ventricles of the heart, thus allowing informed diagnostic intervention in heart failure. It is also called radionuclide angiography, as well as gated blood pool imaging. This modality uniquely provides a cine image of the beating heart, and allows the interpreter to determine the efficiency of the individual heart valves and chambers. MUGA/Cine scanning represents a robust adjunct to the now more common echocardiogram. Mathematics regarding acquisition of Q is well served by both of these methods as well as other inexpensive models supporting ejection fraction as a product of the heart/myocardium in systole.
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MUGA is typically ordered for the following patients:
At a high level, the MUGA test involves the introduction of a radioactive marker into the bloodstream of the patient. The patient is subsequently scanned to determine the circulation dynamics of the marker, and hence the blood.
The introduction of the radioactive marker can either take place in vivo or in vitro. In the in vivo method, stannous (tin) ions are injected into the patient's bloodstream. A subsequent intravenous injection of the radioactive substance, technetium-99m-pertechnetate, labels the red blood cells in vivo. With an administered activity of about 800 MBq, the effective radiation dose is about 8 mSv to 12 mSv. In the in vitro method, some of the patient's blood is drawn and the stannous ions (in the form of stannous chloride) are injected into the drawn blood. The technetium is subsequently added to the mixture as in the in vivo method. In both cases, the stannous chloride reduces the technetium ion and prevents it from leaking out of the red blood cells during the procedure.
The patient is placed under a gamma camera, which detects the low-level 140keV gamma radiation being given off by technetium-99m. As the gamma camera images are acquired, the patient's heart beat is used to 'gate' the acquisition. The final result is a series of images of the heart (usually sixteen), one at each stage of the cardiac cycle.
Depending on the objectives of the test, the doctor may decide to perform either a resting or a stress MUGA. During the resting MUGA, the patient lies stationary, whereas during a stress MUGA, the patient is asked to exercise during the scan. The stress MUGA measures the heart performance during exercise and is usually performed to assess the impact of a suspected coronary artery disease. In some rare cases, a nitroglycerin MUGA may be performed, where nitroglycerin (a vasodilator) is administered prior to the scan.
The resulting images show that the volumetrically derived blood pools in the chambers of the heart and timed images may be computationally interpreted to calculate the ejection fraction and injection fraction of the heart. This nuclear medicine scan yields an accurate, inexpensive and easily reproducible means of measuring and monitoring the ejection and injection fractions of the ventricles, which are one of many of the important clinical metrics in assessing global heart performance.
In normal subjects, the left ventricular ejection fraction (LVEF) should be about 60% (range, 50-80%). There should be no area of abnormal wall motion (hypokinesis or dyskinesis). Abnormalities in cardiac function may be manifested as a decrease in LVEF and/or the presence of abnormalities in global and regional wall motion. For normal subjects, peak filling rates should be between 2.4 and 3.6 end diastolic volume (EDV) per second, and the time to peak filling rate should be 135-212 msec. (source?)
An uneven distribution of technetium in the heart indicates that the patient has coronary artery disease, a cardiomyopathy, or blood shunting within the heart. Abnormalities in a resting MUGA usually indicate a heart attack, while those that occur during exercise usually indicate ischemia. In a stress MUGA, patients with coronary artery disease may exhibit a decrease in ejection fraction. For a patient that has had a heart attack, or is suspected of having another disease that affects the heart muscle, this scan can help pinpoint the position in the heart that has sustained damage as well as assess the degree of damage. MUGA scans are also used to evaluate heart function prior to and while receiving certain chemotherapies (e.g. doxorubicin (Adriamycin)) or immunotherapy (specifically, herceptin) that have a known effect on heart function.
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