Nuclear stress test: What to expect

What happens during a nuclear stress test?

- Peter / Wisconsin

Mayo Clinic cardiologist Martha Grogan, M.D., and colleagues answer select questions from readers.

Answer

A nuclear stress test measures blood flow to your heart muscle at rest and during stress. It is performed similar to a routine exercise stress test but provides images in addition to electrocardiograms.

During a nuclear stress test, a radioactive substance 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 — because not as much of the radioactive substance is getting there.

There are several types of nuclear stress tests, including:

Myocardial perfusion scan. During this procedure, you exercise on a treadmill or pedal a stationary bicycle. When you reach your maximum heart rate, you're given the injection. Images are made of your heart shortly after exercise and also a few hours later. This test shows how well blood flows into the heart muscle and can detect narrowing of the coronary arteries (coronary artery disease).
Multiple gated acquisition (MUGA) scan. In this test, you receive the injection before exercising. Images are made of your heart before and after exercise. A MUGA scan shows the motion of the heart and how well it pumps out blood (ejection fraction).

If you're unable to exercise, you may be injected with a medication that increases blood flow to your heart muscle — simulating exercise — for the test.