In the world of business, a stress test might be a tally of pencils with chewed-off erasers. In the world of medicine, a stress test—known technically as an “exercise tolerance test’’—is a tally of heart rate, blood pressure and other signs that indicate the heart’s ability to deliver blood to hard-working muscles.
Usually recommended for people who have chest pain suspected to be angina or an abnormal electrocardiogram, a stress test helps doctors diagnose coronary artery disease by showing whether the heart is getting enough oxygen during times of activity. One limitation: The test gives a fairly high number of false-positive results in women, which can lead to unnecessary additional testing.
The test may be recommended for certain people prior to starting an exercise program. The American Heart Association estimates that 3 million to 4 million Americans have silent ischemia, a symptomless condition in which the heart doesn’t get enough oxygen. (This condition can cause a heart attack or sudden cardiac death during exercise, when the heart’s need for oxygen increases.)
In addition to telling doctors whether a person can exercise safely, a stress test can help doctors set exercise limits for patients who have heart disease or who have undergone heart surgery.
The test involves an electrocardiogram (ECG) together with monitoring of heart rate (pulse) and blood pressure. All this is done while the person being tested exercises at increasingly demanding levels. A stationary bicycle is sometimes used in stress testing, but most specialists prefer a treadmill that’s programmed to increase gradually in speed and degree of incline.
Dressed in comfortable clothing and wearing sneakers, the person being tested is wired to an ECG machine by means of electrodes. A blood pressure cuff is wrapped around the patient’s arm. The treadmill is started, and the person begins to walk—easily at first, then with more effort as the speed and inclination of the treadmill are increased.
The test continues until the individual reaches his or her maximum level of exertion. If blood pressure drops or heart rhythm abnormalities are observed, the test is stopped immediately.