An electrocardiogram (EKG or ECG) is a test that checks for problems with the electrical activity of your heart. An EKG translates the heart's electrical activity into line tracings on paper. The spikes and dips in the line tracings are called waves. See a picture of theEKG components and intervals.

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 bloodthrough the heart to the lungs and the rest of the body. See a picture of the heart and its electrical system.

Why It Is Done

An electrocardiogram (EKG or ECG) is done to:

• Check the heart's electrical activity.
• Find the cause of unexplained chest pain, which 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, such as shortness of breath,dizziness, fainting, or rapid, irregular heartbeats (palpitations).
• Find out if the walls of the heart chambers are too thick (hypertrophied).
• Check how well medicines are working and whether they are causing side effects that affect the heart.
• Check how well mechanical devices that are implanted in the heart, such aspacemakers, are working to control a normal heartbeat.
• Check the health of the heart when other diseases or conditions are present, such as high blood pressure, high cholesterol, cigarette smoking, diabetes, or a family history of early heart disease.
  
  

How To Prepare

Many medicines may change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. If you take heart medicines, your doctor will tell you how to take your medicines before you have this test.

Remove all jewelry from your neck, arms, and wrists. Men are usually bare-chested during the test. Women may often wear a bra, T-shirt, or gown. If you are wearing stockings, you should take them off. You will be given a cloth or paper covering to use during the test.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form.

How It Is Done

An electrocardiogram (EKG or ECG) is usually done by a health professional, and the resulting EKG is interpreted by a doctor, such as an internist, family medicine doctor, electrophysiologist, cardiologist, anesthesiologist, or surgeon.

You may receive an EKG as part of a physical examination at your health professional's office or during a series of tests at a hospital or clinic. EKG equipment is often portable, so the test can be done almost anywhere. If you are in the hospital, your heart may be continuously monitored by an EKG system; this process is called telemetry.

During an EKG:

• You will lie on a bed or table. Areas on your arms, legs, and chest where small metal discs (electrodes) will be placed are cleaned and may be shaved to provide a clean, smooth surface to attach the electrode discs. A special EKG paste or small pads soaked in alcohol may be placed between the electrodes and yourskin to improve conduction of the electrical impulses, but in many cases disposable electrodes are used that do not require paste or alcohol.
• Several electrodes are attached to the skin  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 to measure your heart's electrical activity from different locations on your chest. After the procedure, the electrode paste is wiped off.
• 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.