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Posted on Fri, Dec 9, 2011 : 5 a.m.

Exercise stress test measures your heart's health

By Ask Dr. K


I recently had some mild chest pains, so my doctor scheduled an exercise stress test. What will happen during this test?


An exercise stress test is also known as an exercise tolerance test. As in your case, stress tests are often given to people with chest pain or other symptoms that could indicate coronary artery disease.

The idea behind an exercise stress test is simple. The heart is a kind of muscle, and it requires a blood supply to get the energy it needs. Its blood supply comes from the coronary arteries. In coronary artery disease, plaques of atherosclerosis can block and slow the supply of blood to a part of the heart.

Three things can happen when a part of the heart is not getting enough blood -- enough energy supply -- to do the work it is being asked to do. First, it starts to cause pain. Second, the strain of working too hard causes changes on an electrocardiogram (EKG), a recording of the heart's electrical activity. Third, the affected part of the heart doesn't pump as forcefully as the unaffected parts of the heart. A test called an echocardiogram (or cardiac ultrasound) can spot parts of the heart that aren't pumping normally.

If you are resting, your heart doesn't need to work hard. Even if you have coronary artery disease, you may feel no pain. Your EKG and echocardiogram may be normal. But if your heart is forced to work harder, the underlying problem is revealed: You may have pain, and your EKG or echocardiogram may become abnormal.

Usually you walk on a treadmill to force your heart to work hard. During the test, your heart health is always examined by the EKG. Several electrodes are taped to your chest, arms and one leg. The electrodes read electricity being generated by your heart as it pumps. Your blood pressure and heart rate will also be monitored. Sometimes, an echocardiogram is used, too, or a kind of X-ray technique called nuclear medicine.

The test takes about 10 minutes. The speed and steepness of the treadmill will increase several times while you exercise. You should wear comfortable, loose-fitting clothing and athletic shoes for the test.

Alert someone immediately if you feel chest pain or heaviness, shortness of breath, feel like you might faint or have other unusual symptoms. This is a sign that your heart isn't getting enough oxygen and could be in danger of damage.

If walking on the treadmill produces symptoms such as chest discomfort, shortness of breath or dizziness -- especially if these symptoms are accompanied by certain EKG or echocardiogram changes -- you are likely to have coronary artery disease.

We have more information on diagnosing and treating heart disease in our Special Health Report called "Heart Disease: A Guide to Preventing and Treating Coronary Artery Disease." You can find out more about it at my website.

(Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information:

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