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Electrocardiogram by Amy Scholten, MPH

Definition | Reasons for Test | What to Expect | Results | Call Your Doctor

Definition

An electrocardiogram (ECG or EKG) measures the electrical activity of your heart. The heart generates electrical signal which flows out from your heart through your body. Small electrical sensors, called electrodes, are put on your skin to sense the electricity that began in your heart. The electrical activity is then turned into a graph. This can give doctors an idea of whether your heart is beating normally.

ECG/EKG Waves

Reasons for Test

An ECG is used to:

Diagnose heart attacks and rhythm problems
Offer clues about other heart conditions and conditions not primarily related to the heart
Detect conditions that alter the body’s balance of electrolytes (eg, potassium and magnesium )
Detect other problems, such as overdoses of certain drugs

Symptoms that may prompt an ECG include:

Chest discomfort or pain
Shortness of breath
Palpitations (fast heartbeats)
Anxiety
Weakness
Nausea or the feeling that you have to vomit
Abdominal pain
History of fainting
Taking certain drugs

An ECG may also be obtained if you:

Are about to have surgery with general anesthesia —to detect heart conditions that could worsen during surgery and put you at risk
Are in occupations that stress the heart or where public safety is a concern
Are an older adult or have diabetes—to obtain a record to compare with future ECGs
Already have heart disease—to check occasionally for any changes
Have had a heart-related procedure, such as getting a pacemaker

What to Expect

Prior to Test

You may:

Have a physical exam and be asked about your medical history
Have your chest shaved if needed

Description of Test

You will be asked to lie quietly on your back with your shirt off. Six small, sticky pads with attached wires will be placed across your chest. Others will be placed on your arms and legs. The wires will connect to the ECG machine. You will not feel anything during the test.

After Test

You may resume activities as recommended by your doctor.

How Long Will It Take?

3-4 minutes

Will It Hurt?

Results

Your doctor will interpret the ECG. Based on the results and your other health information, you may need more tests or a treatment plan.

Call Your Doctor

After the test, call your doctor if you have heart-related symptoms, like chest pain or trouble breathing.

RESOURCES:

American Heart Association http://www.americanheart.org/
American Medical Association http://www.ama-assn.org/

CANADIAN RESOURCES:

Canadian Cardiovascular Society http://www.ccs.ca/home/index_e.aspx/
Heart and Stroke Foundation of Canada http://ww2.heartandstroke.ca/splash/

References:

Diagnostic tests: electrocardiogram. The Harvard Medical School Family Health Guide website. Available at: http://www.health.harvard.edu . Accessed June 11, 2008.
Electrocardiogram. Mayo Clinic website. Available at: http://www.mayoclinic.com/health/electrocardiogram/HB00014 . Updated June 2006. Accessed June 11, 2008.
Electrocardiogram. University of Michigan website. Available at: http://www.med.umich.edu/1libr/aha/aha_elecgram_car.htm . Updated April 2006. Accessed November 15, 2006.
Electrocardiogram (EKG or ECG). American Heart Association website. Available at: http://www.americanheart.org/presenter.jhtml?identifier=3005172 . Updated March 2008. Accessed July 21, 2009.
Exercise electrocardiogram (stress test). Heart and Stroke Foundation website. Available at: http://www.health.harvard.edu . Updated September 2006. Accessed June 4, 2008.
Kasper DL, Braunwald, E, Fauci AS, Hauser SL, Longo DL, Jameson JL. Harrison’s Principles of Internal Medicine . 16 ed. New York, NY: McGraw-Hill Professional; 2004.

Last reviewed July 2010 by Arun Kalyanasundaram, MD, MPH

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