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What To Expect During an Electrocardiogram

An electrocardiogram (EKG) is painless and harmless. A nurse or technician will attach soft, sticky patches called electrodes to the skin of your chest, arms, and legs. The patches are about the size of a quarter.

Often, 12 patches are attached to your body. This helps detect your heart's electrical activity from many areas at the same time. The nurse may have to shave areas of your skin to help the patches stick.

After the patches are placed on your skin, you'll lie still on a table while the patches detect your heart's electrical signals. A machine will record these signals on graph paper or display them on a screen.

The entire test will take about 10 minutes.


The photograph shows purpura (bruises) and petechiae (dots) in the skin. Bleeding under the skin causes the purple, brown, and red colors of the purpura and petechiae.

The picture shows the standard setup for an EKG. In figure A, a heart rhythm recording shows the electrical pattern of a normal heartbeat. In figure B, a patient lies in a bed with EKG electrodes attached to his chest, upper arms, and legs. A nurse oversees the painless procedure.

Special Types of Electrocardiogram

The standard EKG described above, called a resting 12-lead EKG, only records seconds of heart activity at a time. It will show a heart problem only if the problem occurs during the test.

Many heart problems are present all the time, and a resting 12-lead EKG will detect them. But some heart problems, like those related to an irregular heartbeat, can come and go. They may occur only for a few minutes a day or only while you exercise.

Doctors use special EKGs, such as stress tests and Holter and event monitors, to help diagnose these kinds of problems.

Stress Test

Some heart problems are easier to diagnose when your heart is working hard and beating fast. During stress testing, you exercise to make your heart work hard and beat fast while an EKG is done. If you can't exercise, you'll be given medicine to make your heart work hard and beat fast.

For more information, go to the Health Topics Stress Testing article.

Holter and Event Monitors

Holter and event monitors are small, portable devices. They record your heart's electrical activity while you do your normal daily activities. A Holter monitor records your heart's electrical activity for a full 24- or 48-hour period.

An event monitor records your heart's electrical activity only at certain times while you're wearing it. For many event monitors, you push a button to start the monitor when you feel symptoms. Other event monitors start automatically when they sense abnormal heart rhythms.

For more information, go to the Health Topics Holter and Event Monitors article.

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October 1, 2010