Nuclear Stress Testing

         Basic Facts

  • Stress testing is a painless, safe method to measure how well the heart responds to exertion from exercise.
  • Nuclear imaging is used to evaluate blood flow to the heart. During a nuclear stress test, a physician injects a small amount of a radioactive isotope into a person’s bloodstream.
  • The distribution of the radioactive isotope in the heart muscle is recorded by a camera while the person is resting and again while exercising.  
  • The camera produces three-dimensional images of the heart that show the physician exactly where the heart muscle may not be receiving enough blood during activity versus at rest.

During a nuclear stress test, a small dose of a radioactive isotope is injected into the bloodstream. The radioisotope, or tracer, is carried through the bloodstream and into the myocardium, or heart muscle. Shortly after exercising, a special camera senses the radioactivity of the tracer and constructs an image of the heart. Parts of the heart muscle that receive normal blood flow receive larger amounts of tracer and appear brighter than areas that have inadequate blood flow.

The results of a nuclear stress test typically fall into three broad categories.

  • Normal,
  • Blood flow defects during exercise, but not at rest, and
  • Blood flow defects during exercise and rest.
Nuclear imaging is used to:
  • visualize blood flow patterns to the heart walls, called a myocardial perfusion scan,
  • evaluate the presence and extent of suspected or known coronary heart disease, and 
  • determine the extent of injury to the heart following a heart attack.

Nuclear Stress Testing FAQ