A nuclear stress test is a diagnostic test used to determine if the heart gets enough oxygen and blood flow, explains MedlinePlus. The test helps diagnose coronary artery disease, determine if the heart is enlarged or determine if the heart is pumping blood normally.
During the first stage of the test, a doctor injects a radioactive substance into an intravenous line and asks the patient to lie down for up to 45 minutes, notes MedlinePlus. Then a camera produces images to show the substance traveling through the bloodstream and into the heart.
The second stage of the test helps the doctor determine how well the heart functions when it is working hard, reports MedlinePlus. The patient pedals an exercise machine or walks on a treadmill to increase his heart rate. A patient who is unable to exercise due to illness or injury receives a medication that mimics the effects of exercise on the heart. Once the patient reaches his target heart rate, another radioactive substance is injected into the IV line so the camera can take pictures. A doctor compares the first set of images with the second set to determine if there are any problems with the heart.
In people who have already been diagnosed with coronary artery disease, the nuclear stress test is also useful for developing a treatment plan, states MedlinePlus.