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The electrocardiogram (ECG or EKG) evaluates the heart's rhythm and electrical activity. A stress test is an ECG that is recorded during exercise.


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Parts of the Body Involved

  • Chest
  • Heart

Reasons for Procedure

An ECG is used to diagnose heart attacks and rhythm problems. It can also offer clues about other heart and lung conditions and conditions not primarily related to heart.

Heart problems can cause a variety symptoms. Conditions that alter the body’s balance of electrolytes (especially potassium and magnesium ) can also cause symptoms and changes in the ECG. An ECG is also used to 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
  • Abdominal pain
  • History of fainting
  • Ingestion of certain drugs

An ECG is also typically 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 over age 40, as a routine baseline
  • Already have heart disease—to monitor your status and check how new medication is working
  • Have had a heart-related procedure, such as getting a pacemaker

Risk Factors for Complications During the Procedure

The process of getting an ECG has no risk of complications. Also, the test is painless. When a stress test is done, the only risk has to do with the exercise, not the ECG itself. During exercise, the ECG monitors your heart function and captures warning signals of heart trouble. In certain cases, an ECG may be normal even though heart disease is present.

What to Expect

Prior to Procedure

  • You will:
    • Have a physical exam and be asked about your medical history
    • Have your chest shaved if you have a hairy chest
  • For a stress test, you should:
    • Allow two hours between your last meal and the stress test
    • Wear comfortable clothing and walking shoes



Description of the Procedure

When your heart beats, it creates electrical signals. The ECG detects these signals from the surface of your skin and records them on a piece of graph paper. You will not feel anything during the procedure.

You’ll be asked to lie quietly on your back, with your shirt off. Six small adhesive pads or suction cups 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.

If you’re having a stress test, your ECG will be recorded while you exercise. This is usually done on a treadmill or bicycle. For treadmills, the speed and slope will be slowly increased as you walk. The test will continue until you have reached a certain heart rate, certain ECG changes occur, or you are too tired to continue, are short of breath, or have chest pain.

After Procedure

Depending on your condition and your doctor’s assessment, you may have to have more tests. If you have a heart condition or abnormal ECG, keep a recent copy of your ECG in your wallet, purse, or car.

How Long Will It Take?

  • Resting ECG: 3-4 minutes
  • Exercise ECG (stress test): 15-30 minutes, plus you'll be monitored after the exercise

Will It Hurt?


Possible Complications

There are no complications for a resting ECG. Complications of a stress test would have to do with the exercise and your heart's response.

Average Hospital Stay

None. If you have serious symptoms, you may need more tests, treatment, or surgery.

Postprocedure Care

You may resume activities as recommended by your doctor.


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

Call Your Doctor If Any of the Following Occurs

  • Worsening of your heart-related symptoms


American Heart Association

American Medical Association


Canadian Cardiovascular Society

Heart and Stroke Foundation of Canada


Diagnostic tests: electrocardiogram. The Harvard Medical School Family Health Guide website. Available at: http://www.health.harvard.edu . Accessed June 11, 2008.

Electrocardiogram. Emedicine website. Available at: http://www.emedicine.com . Accessed January 8, 2003.

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.

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 November 2007 by J. Peter Oettgen, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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