Harvard Health Letter

Ask the doctor: Nuclear stress tests

Q. I recently had a nuclear stress test and the contrast agent got stuck in my gut, so the image couldn't be read. Is this a common problem, and is there anything that can be done about it?

A. The purpose of a stress test is to identify problems with blood supply to the heart muscle or the coronary arteries that supply it with blood. The standard test involves measuring the heart's electrical activity with an electrocardiogram (ECG) while the patient "stresses" his or her heart with exercise, which usually means walking on a treadmill or pedaling a stationary bike.

But for the test to be useful, you have to be able to walk or pedal fast enough to get your heart pumping at 85% of its maximum rate for several minutes. People who cannot exercise that hard — if you are on a treadmill, it means walking pretty briskly — can get a nu clear stress test instead. The test involves infusion of a chemical into a vein to mimic the effect that exercise has on the coronary arteries, followed by infusion of a radioactive material — a radiotracer — that allows a special camera and computer to create very detailed images of the heart.

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