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Quick Facts



The Manual's Editorial Staff

Last full review/revision May 2021| Content last modified May 2021
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What is electrocardiography (ECG, EKG)?

Electrocardiography is a test that measures your heart’s electrical activity. It's quick, painless, and harmless.

The results of that test are shown in an electrocardiogram. It looks like a wavy line with spikes on a grid (a tracing). The electrocardiogram gives doctors information about:

  • The part of your heart that triggers each heartbeat

  • Your heart's electrical pathways

  • Your heart's rate and rhythm

Both the test and the results are referred to as an ECG, sometimes also called an EKG.

Why would I need an ECG?

You may have an ECG:

  • As part of a routine checkup, if you're middle-aged or older

  • As a way for the doctor to evaluate symptoms that could be from a heart problem, such as chest pain, trouble breathing, a fast or abnormal heartbeat, or swelling in your legs

How is an ECG done?

  • Small, round sensors (electrodes) that stick to the skin are placed on your arms, legs, and chest

  • Wires that snap on to the sensors are connected to a machine

  • As your heart beats, the sensors measure your heart’s electrical currents

  • The machine records information from each sensor and develops an ECG (a wavy line with spikes) for your doctor to read

Are there any side effects to an ECG?

There are no side effects. An ECG won't hurt at all during or after the test.

What can my doctor learn from my ECG?

An ECG helps your doctor learn many things about your heart, including:

  • If you’ve had or are having a heart attack

  • If you have an abnormal heart rhythm

  • If your heart isn't getting enough blood and oxygen

  • If the muscular wall of your heart is too thick

  • If there are bulges in weak areas of your heart’s walls (the bulge is called an aneurysm)

Should I carry a copy of my ECG?

If you've had heart problems, you might want to carry a small copy of your ECG in your wallet (ask your doctor if you should). That way, if you have an emergency, the doctor treating you can compare your older ECG with a new ECG.

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