A Sestamibi stress test is a is a nuclear test performed while your heart is stressed, either by having you exercise or injecting a medicine that makes your heart beat harder and faster. Before the test, the patient is injected with a small amount of a radiotracer material. The doctor will use a special camera to capture images emitted by the radiotracer in the body. This test provides clear images of the heart tissue and allows the physician to compare it before the test starts, when the patient's heart is at rest, and after stress. A Sestamibi stress test, which can last up to four hours (to allow enough time for the radiotracer material to flow through your body), is used to evaluate the function of various parts of your heart. It can spot areas that aren’t getting enough blood.