Exercise Tolerance Test - Diagnosing Heart Disease: Heart Disease

Content provided by the Faculty of the Harvard Medical School

Exercise tolerance test

For this test, also called an exercise stress test, doctors do an EKG and take blood pressure readings as you walk on a treadmill. You will typically begin walking on a slight incline at a slow pace. If you have had a recent heart attack or are otherwise physically limited, you may be asked to exert yourself even less. Every few minutes, the physician checks your EKG and blood pressure.

If all is well and you feel up to it, treadmill speed and degree of incline are increased until you need to stop because you feel short of breath, lightheaded, or otherwise uncomfortable. In other cases, the physician may end the test if blood pressure drops or abnormalities appear on the EKG. If you are not accustomed to marked physical exertion or have recently had a heart attack, the physician might stop the test after a predetermined period, or after a certain heart rate is reached. When the exercise is over, you are helped to a nearby bed while the EKG continues to record data. Often the information obtained while you are recovering is the most revealing.

Many people worry that this test could be dangerous to someone with coronary artery disease, possibly even inducing a heart attack. But even though people are asked to push themselves to the limit, the screening is extremely safe if physicians examine you beforehand to make sure that you are healthy enough for it. Fatal complications are rare.

What the results mean

If walking on the treadmill produces symptoms such as chest discomfort, shortness of breath, or dizziness, and if these symptoms are accompanied by EKG changes, the test strongly suggests coronary artery disease. A test is considered negative if you can perform a normal amount of exercise without symptoms or EKG changes.

However, many people have chest discomfort but no EKG changes, or vice versa. In these cases, the exercise test is of less help and the result will be interpreted as consistent with coronary artery disease, but not definitive. Furthermore, some people with coronary artery disease don't show any evidence of ischemia in exercise testing because other medical conditions, such as arthritis, prevent them from walking long enough or fast enough to stress their hearts. (For them, other test options exist. See "Nuclear imaging" and "Echocardiography.")

And exercise testing is less sensitive and possibly less accurate in women. Some theorize that women's comparative lack of physical fitness makes them less able to stress their hearts sufficiently. Or it may be that, for women, breast tissue keeps the leads farther from the heart, distorting the findings and making them harder to interpret.

Finally, almost every physician has heard of someone who had a negative exercise test one week and a heart attack the next. Sometimes a negative result may provide false reassurance to someone who had been unable to exercise enough to trigger ischemia during the test. In other instances, a negative result may be accurate, but a heart attack could still occur. For example, an atherosclerotic plaque may not be large enough to cause significant obstruction of a coronary artery during the test, but later suddenly ruptures and leads to the formation of a clot that blocks blood flow.

Stress tests, like all tests, are not foolproof. When the results are unclear, a nuclear-imaging test can help clarify a person's diagnosis and risk status.

Last updated:	May 03, 2007