An electrocardiogram (ECG) shows the electrical activity of the heart. The action of the heart will appear as a pattern on a graph. The ECG can show changes in rhythm or movement, and what areas of the heart are affected. ECGs are also known as EKGs.

ECG Waves

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Reasons for Test

An ECG may be done are to:

  • Look for the cause of chest pain, rapid heartbeat, and other symptoms that may be heart-related
  • Diagnose heart attacks and heart rhythm problems
  • Check heart health before a surgery
  • Check heart health after a heart-related procedure, such as a pacemaker implant
  • See how well heart medicines are working

Possible Complications

There are no major problems linked to this test.

What to Expect

Prior to Test

The care team will need to know about any current medicine or supplements. They may also ask about any allergies. It is also important to share if you are a smoker. Smoking can affect how the heart works.

Description of Test

Small, sticky pads will be placed across the chest. Other pads will be placed on the arms and legs. Wires from the ECG machine will be attached to the pads. You will not feel anything during the test. You may simply rest during the test or other steps may be needed. Some ECGs will be worn over a few days while you do normal activity. You may also be exercising or given medicine.

How Long Will It Take?

5 to 10 minutes

Will It Hurt?

You will not have any problems after this test.


Your doctor will review the ECG. It may help to make a diagnosis and, if needed, a treatment plan. Other tests may be needed.

Call Your Doctor

Call your doctor if you have heart-related symptoms. This includes chest pain or problems breathing.

If you think you have an emergency, call for medical help right away.


American Heart Association
Heart Rhythm Society


Canadian Cardiovascular Society
Heart and Stroke Foundation of Canada


Electrocardiogram. National Heart, Lung, and Blood Institute website. Available at:
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Accessed September 22, 2020.
Electrocardiogram (ECG)—12-lead and in-hospital ECG monitoring. EBSCO DynaMed website. Available at: https://www.dynamed.com/evaluation/electrocardiogram-ecg-12-lead-and-in-hospital-ecg-monitoring. Accessed September 22, 2020.
Electrocardiogram (EKG or ECG). American Heart Association website. Available at:
...(Click grey area to select URL)
Accessed September 22, 2020.
Noninvasive tests and procedures. American Heart Association website. Available at:
...(Click grey area to select URL)
Accessed September 22, 2020.
Last reviewed April 2021 by EBSCO Medical Review Board Kari Kassir, MD
Last Updated: 4/13/2021

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