An electrocardiogram (EKG or ECG) is a test that checks for problems with the electrical activity of your heart. An EKG shows the heart's electrical activity as line tracings on paper. The spikes and dips in the tracings camera.gif are called waves.

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

An ECG is done to:

Check the heart's electrical activity.

Find the cause of unexplained chest pain or pressure. This could be caused by a heart attack, inflammation of the sac surrounding the heart (pericarditis), or angina.

Find the cause of symptoms of heart disease. Symptoms include shortness of breath, dizziness, fainting, and heartbeats that are rapid and irregular (palpitations).

Find out if the walls of the heart chambers are too thick.

Check how well medicines are working and see if they are causing side effects that affect the heart.

Check how well mechanical devices that are implanted in the heart, such as pacemakers, are working. These devices help to control the heartbeat.

Check the health of the heart when other diseases or conditions are present. These include high blood pressure, high cholesterol, cigarette smoking, diabetes, and a family history of early heart disease.

ECG procedure

You may get an ECG as part of a physical exam. This may be done at your health professional's office or during a series of tests at a hospital or clinic. ECG equipment is often portable. This means the test can be done almost anywhere. If you are in the hospital, your heart may be constantly monitored by an ECG system.

During an ECG:

You will lie on a bed or table. Certain areas of your arms, legs, and chest will be cleaned and may be shaved. This provides a clean, smooth surface to attach the electrodes.

Several electrodes are attached to the skin camera.gif on each arm and leg and on your chest. These are hooked to a machine that traces your heart activity onto a paper. If an older machine is used, the electrodes may be moved at different times during the test. This measures your heart's electrical activity from different places on your chest.

You will be asked to lie very still and breathe normally during the test. Sometimes you may be asked to hold your breath. You should not talk during the test.

After the test, the electrode paste is wiped off.