What Is an Electrocardiogram?

An electrocardiogram (e-lek-tro-KAR-de-o-gram), or EKG, is a simple, painless test that records the heart's electrical activity. To understand this test, it helps to understand how the heart works.

With each heartbeat, an electrical signal spreads from the top of the heart to the bottom. As it travels, the signal causes the heart to contract and pump blood. The process repeats with each new heartbeat. The heart's electrical signals set the rhythm of the heartbeat.

For more detailed information, see the Diseases and Conditions Index article on How the Heart Works.

An EKG shows:

• How fast your heart is beating
• Whether the rhythm of your heartbeat is steady or irregular
• The strength and timing of electrical signals as they pass through each part of your heart

This test is used to detect and evaluate many heart problems, such as heart attack, arrhythmia (ah-RITH-me-ah), and heart failure. EKG results also can suggest other disorders that affect heart function.

EKGs also are used to monitor how the heart is working. This article focuses on how EKGs are used for testing purposes.

November 2008