During a nuclear stress test, the doctor injects a small amount of a harmless radioactive substance, and then the doctors use a special camera that tracks the rays emitted by the substance as it flows through the body. This produces a very clear image of the heart that allows the doctors to identify areas with decreased blood flow, because less of the nuclear marker will appear in those areas.
A nuclear stress test is often administered twice – once while you are at rest, and again as you exercise on a treadmill. This allows the doctors to take pictures of the heart both while it is resting and under exertion. The two sets of images are then compared to determine the status of blood flow through the heart and surrounding coronary arteries. Another type of specialized nuclear stress test called a MUGA (multigated acquisition scan) is sometimes used to evaluate the pumping function of the ventricles, your heart’s lower chambers.