What is a Nuclear Stress Test, and how does it work?

A nuclear stress test is a diagnostic exercise test that’s used to evaluate blood flow to the heart. During a nuclear stress test, a tiny amount of radioactive substance (a tracer) is injected into your bloodstream. This substance mixes with your blood and travels to your heart. A special scanner—which detects the radioactive material in your heart—creates images of your heart muscle. Inadequate blood flow to any part of your heart will show up as a light spot on the images, as not as much of the radioactive substance is making it to that area.

There are two common types of nuclear stress tests:

  • Myocardial Perfusion Scan—During this procedure, the patient will exercise on a treadmill or pedal a stationary bicycle. When the maximum heart rate is reached, the patient is given the injection. Images are taken of the heart shortly after exercise, and again a few hours later. This test helps to determine how well blood flows into the heart muscle, and can detect narrowing that has occurred in any of the coronary arteries (coronary artery disease).
  • Multiple Gated Acquisition (MUGA) Scan—In this test, the patient receives the injection before exercising. Images of the heart are then taken before and after exercise. A MUGA scan shows the motion of the heart and how well it pumps blood back out (ejection fraction).

If you’re unable to exercise for this test, you may be injected with a medication that increases blood flow to your heart muscle in order to stimulate exercise for the purposes of the test.