An electrocardiogram (also called EKG or ECG) is a test that records the electrical activity of your heart through small electrode patches attached to the skin of your chest, arms, and legs. An EKG may be part of a routine physical exam or it may be used as a test for heart disease. An EKG can be used to further investigate symptoms related to heart problems.

EKGs are quick, safe, painless, and inexpensive tests that are routinely performed if a heart condition is suspected.

Your doctor uses the EKG to:

Assess your heart rhythm.
Diagnose poor blood flow to the heart muscle (ischemia).
Diagnose a heart attack.
Evaluate certain abnormalities of your heart, such as an enlarged heart.

How Should I Prepare for an EKG?

To prepare for an EKG:

Avoid oily or greasy skin creams and lotions the day of the test. They interfere with the electrode-skin contact.
Avoid full-length hosiery, because electrodes need to be placed directly on the legs.
Wear a shirt that can be easily removed to place the leads on the chest.

What Happens During an EKG

During an EKG, a technician will attach 10 electrodes with adhesive pads to the skin of your chest, arms, and legs. Men may have chest hair shaved to allow a better connection. You will lie flat while the computer creates a picture, on graph paper, of the electrical impulses traveling through your heart. This is called a "resting" EKG. This same test may also be used to monitor your heart during exercise.

It takes about 10 minutes to attach the electrodes and complete the test, but the actual recording takes only a few seconds.

Your EKG patterns will be kept on file for later comparison with future EKG recordings.

If you have questions, be sure to ask your doctor.

In addition to the standard EKG, your doctor may recommend other specialized EKG tests, including a holter monitor or a signal-averaged electrocardiogram.

What Is a Holter Monitor?

A holter monitor is a portable EKG that monitors the electrical activity of a freely moving person's heart generally for one to two days, 24-hours a day. It is most often used when the doctor suspects an abnormal heart rhythm or ischemia (not enough blood flow to the heart muscle).

It is a painless test; electrodes from the monitor are taped to the skin. Once the monitor is in place, you can go home and perform all of your normal activities (except showering). You will be asked to keep a diary of your activities and any symptoms you experience and when they occur.

What Is an Event Monitor?

If your symptoms are infrequent your doctor may suggest an event monitor. This is a device that, when you push a button, will record and store the heart's electrical activity for a few minutes. Each time you develop symptoms you should try to get a reading on the monitor. They are used for weeks to months, typically one month. This information can later by transmitted by telephone to the doctor for interpretation.

What Is a Signal-Averaged Electrocardiogram?

This is a painless test used to assess whether a person is at high risk of developing a potentially fatal heart arrhythmia. It is performed in a similar manner to the EKG, but uses sophisticated technology to look for heart arrhythmias.

WebMD Medical Reference

Reviewed by Robert J Bryg, MD on March 07, 2009