Harvard Heart Letter

Exercise stress test

The treadmill test can reveal hidden problems in the heart.

One way to judge the health of the heart and the arteries that supply it with oxygen and nutrients is to make them work harder. That's the principle behind one of the most commonly used tests in cardiology, the exercise stress test (also known as the exercise tolerance test, treadmill test, or just the stress test). It's much the same thing a mechanic does when he or she races a car's engine.

Why it is done

Exercise stress tests are done for a variety of reasons. The most common one is to detect a narrowing or blockage in one or more coronary arteries. This network of blood vessels supplies the heart muscle with oxygen and nutrients. When the heart is at rest, even an artery that is almost completely blocked may have enough blood flow to meet the needs of the section of heart muscle it supplies. But make the heart work harder, and the clogged vessel may not be able to handle the extra rush of blood needed by the hard-working muscle. This mismatch in demand and supply can cause angina — pressure or pain in the chest, jaw, left arm, or elsewhere that comes on with exercise or other stress and disappears with rest.

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