A nuclear stress test measures blood flow to your heart at rest and while your heart is working harder as a result of exertion or medication. The test provides images that can show areas of low blood flow through the heart and damaged heart muscle.

The test usually involves taking two sets of images of your heart — one while you're at rest and another after you heart is stressed, either by exercise or medication.

You may be given a nuclear stress test, which involves injecting a radioactive dye into your bloodstream, if your doctor suspects you have coronary artery disease or if a routine stress test didn't pinpoint the cause of symptoms such as chest pain or shortness of breath. A nuclear stress test may also be used to guide your treatment if you've been diagnosed with a heart condition.

Diagnose coronary artery disease. Your coronary arteries are the major blood vessels that supply your heart with blood, oxygen and nutrients. Coronary artery disease develops when these arteries become damaged or diseased — usually due to a buildup of deposits called plaques.

If you have symptoms that might indicate coronary artery disease, such as shortness of breath or chest pains, a nuclear stress test can help determine if you have coronary artery disease

In 2009 they ran me on the treadmill until I thought I was going to pass out.  They said for a 69 year old man my heart and lungs were in great shape!