An exercise electrocardiogram (EKG or ECG) is a test that checks for changes in your heart while you exercise. Sometimes EKG abnormalities can be seen only during exercise or while symptoms are present. This test is sometimes called a "stress test" or a "treadmill test." During an exercise EKG, you may either walk on a motor-driven treadmill or pedal a stationary bicycle.

The heart is a muscular pump made up of four chambers. The two upper chambers are called atria, and the two lower chambers are called ventricles. A natural electrical system causes the heart muscle to contract and pump blood through the heart to the lungs and the rest of the body.

An exercise EKG translates the heart's electrical activity into line tracings on paper. The spikes and dips in the line tracings are called waves. See an illustration of the EKG components and intervals.

A resting EKG is always done before an exercise EKG test, and results of the resting EKG are compared to the results of the exercise EKG. A resting EKG may also show a heart problem that would make an exercise EKG unsafe.

Why It Is Done

An exercise electrocardiogram is done to:

• Help find the cause of unexplained chest pain.
• Check for some types of heart disease.
• See how well people who have had a heart attack or heart surgery are able to tolerate exercise.
• Help find the cause of symptoms that occur during exercise or activity, such as dizziness, fainting, or rapid, irregular heartbeats (palpitations).
• Check for a blockage or narrowing of an artery after a medical procedure, such as angioplasty or coronary artery bypass surgery, especially if the person has chest pain (angina) or other symptoms.
• See how well medicine or other treatment for chest pain or an irregular heartbeat is working.
• Help you make decisions about starting an exercise program if you have been inactive for a number of years and have an increased chance of having heart disease.

Experts disagree about the use of an exercise EKG to test people who do not have symptoms of heart disease.

• Some experts think that anyone older than age 35 who is generally inactive should have an exercise test to screen for "silent" heart disease before starting a vigorous exercise program.
• Because heart disease is rare in younger people who do not have symptoms, an exercise EKG may not be accurate. A falsely abnormal result (false-positive) may cause needless worry and further unnecessary testing.

How To Prepare

Tell your doctor if you:

• Are taking any medicines, including a medicine for an erection problem (such as Viagra). You may need to take nitroglycerin during this test, which can cause a serious reaction if you have taken a medicine for an erection problem within the previous 48 hours. Ask your doctor whether you need to stop taking any of your other medicines before the test.
• Are allergic to any medicines, such as those used to numb the skin (anesthetics).
• Have had bleeding problems or take blood-thinners, such as aspirin or warfarin (Coumadin).
• Have joint problems in your hips or legs that may make it difficult for you to exercise.
• Are or might be pregnant.