Stress test, also called exercise stress test or stress ECG, is a test that measures the functioning of the heart during physical exercise. Physicians use stress tests to detect heart problems, particularly coronary artery disease (CAD). CAD involves narrowing of the coronary arteries, the blood vessels that supply oxygen to the heart. It is the most common form of heart disease. Early detection of CAD can lead to treatment that prevents heart attacks and saves lives.
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In a stress test, the patient exercises at increasing speed and incline on a treadmill or on a stationary bicycle while hooked up to an electrocardiograph. This device produces a record called an electrocardiogram (ECG), which displays the electrical activity of the heart. During exercise, the heart demands more blood and oxygen. When the heart’s demand for blood and oxygen exceeds its supply, an ECG shows changes from the normal pattern of activity. Such changes may indicate a narrowed coronary artery.
Because stress tests are not completely reliable, an abnormal test result requires further procedures to diagnose CAD. After the stress test, doctors sometimes inject a radioactive substance into a patient’s vein. A special camera then shows areas of the heart not getting enough blood. In some cases, the patient must undergo coronary angiography, a technique that makes the coronary arteries visible on an X-ray image (see Angiography).
