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Harvard Health Publications

Exercise Stress Test

What is the test?

The exercise stress test, also known as the treadmill test or exercise tolerance test, indicates whether your heart gets enough blood flow and oxygen when it's working its hardest, such as during exercise. Often, stress tests are given to people with chest pain or other symptoms who appear to have coronary artery disease, based on a medical exam and electrocardiogram (EKG). In addition, these tests are sometimes used for other purposes, from assessing the effectiveness of heart disease treatment to gauging the safety of a proposed exercise program.

Your heart health can be examined during and after exercise either by using an EKG or an echocardiogram (ultrasound of the heart). When this test uses an echocardiogram it is called an "exercise echo."

Stress tests are among the best tools for diagnosing heart disease, and some research suggests that they may also be useful in estimating disease risk in people who don't have symptoms but have risk factors such as high cholesterol. If you are over age 40 and are at risk for coronary artery disease because you smoke or have high blood pressure or other risk factors, ask your doctor if you should have this test.

How do I prepare for the test?

Wear comfortable, loose-fitting clothing and athletic shoes. Let the doctor performing the test know if you think that you won't be able to walk on a treadmill or use a bicycle for any health reason, such as arthritis. Also let the doctor know if you have diabetes; since exercise can lower blood sugar, he or she may want to check your blood sugar level before the test begins, to be sure it is not too low. It's also important to tell the doctor or other health professional in the testing room if you've had any chest pain or pressure on the day of the test. Try to avoid eating a large meal right before the test, which could make exercising uncomfortable.

In some cases, your medications may be temporarily adjusted prior to the stress test, particularly if you take medications that prevent your heart from increasing its heart rate.

What happens when the test is performed?

If you will be having your heart health measured by an EKG tracing, you will first have an EKG both while lying down and standing up. Your blood pressure is taken. Several plastic coated wires, or leads, are taped to your arms and one leg so that your heart's electrical pattern can be detected while you exercise. Your blood pressure and heart rate also are monitored during the test. You are asked to walk on a treadmill (or in some cases, exercise on a bicycle) for about 10 minutes. The speed and steepness of the treadmill will increase several times while you exercise. Let the person who is monitoring you know immediately if you feel chest pain or heaviness, shortness of breath, leg pain or weakness, or other unusual symptoms, or if you think you can't continue exercising. After the exercise period is completed, your blood pressure will be checked again.

If your heart function is to be examined by echocardiogram rather than by EKG, you will lie down after you are done exercising. After squirting some clear jelly onto your chest to help the ultrasound sensor slide around easily, a technician or doctor places the sensor (which looks like a microphone) against your skin. A picture of your heart appears on a video screen, and the technician or doctor slides the sensor back and forth on your chest to see different views of your heart. At times the volume from the machine might be turned on, transmitting a whooshing noise; this represents the sound of your heart beating and blood flowing.

A variation of this test uses a radionuclide to visualize parts of the heart that are not getting enough blood. This test is called either an exercise-thallium test or exercise-MIBI test (depending on the radionuclides used). If you have this test, you will probably need to repeat it on a day when you have not been exercising hard, for the sake of comparison.

An exercise stress test strongly suggests coronary artery disease if walking on the treadmill produces symptoms such as chest discomfort, shortness of breath, or dizziness, and these symptoms are accompanied by EKG changes that indicate inadequate blood flow to parts of the heart. A test is considered normal if you can perform a normal amount of exercise without symptoms or EKG changes. 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 conclusive. Further testing may then be required.

What risks are there from the test?

If you have cardiac disease, you might develop chest pain during the test. Because this is a sign that your heart isn't getting enough oxygen and could be in danger of damage, it's important that you alert the medical staff immediately so that the test can be stopped. Also the technician will be closely watching your EKG tracing and vital signs for changes that might indicate a problem.

Must I do anything special after the test is over?

If your blood pressure becomes unusually high, or if it suddenly drops during exercise, a nurse will recheck your blood pressure a few minutes after the test and may continue to monitor your EKG. If you develop chest pain, you might be given some nitroglycerin tablets to relieve the pain and lower the demand on your heart by dilating your blood vessels.

How long before the result of the test is known?

It usually takes several days for the doctor to completely evaluate the printout of your heart's electrical pattern.


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