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Electrocardiogram of a normal heart rhythm

Alternative Names
ECG, electrocardiogram

An electrocardiogram, also called an ECG, is a graphic record of the heart's electrical activity. Doctors use it to help diagnose heart disease. They can also use it to monitor how well different heart medications are working.

Who is a candidate for the test?
An ECG is done on a person to help diagnose heart disease. It may also be used to monitor how well different heart medications are working. Persons coming into the emergency room with chest pain, shortness of breath will have an ECG performed. An ECG may be necessary prior to a person having major surgery as a baseline tracing.

How is the test performed?
A person can have an ECG while either lying down or exercising on a treadmill. A technician will use an adhesive to attach 12 electrodes at specific sites on the skin. These sites are selected on both arms and on the chest. The sites will be cleaned and perhaps shaved before the electrodes are attached. A machine then records the electrical activity of the heart under conditions a doctor has specified. An ECG usually takes about 5 minutes to perform.

What is involved in preparation for the test?
Individuals will be given specific instructions by their doctor if necessary.

What do the test results mean?
Normal results include the following:
  • a heart rate that is between 50 and 100 beats per second
  • a consistent and even rhythm
  • a pattern on the graph that corresponds to pattern profiles established for healthy people
Abnormal results can come from any of the following:
  • a muscle defect
  • an enlargement of the heart
  • defects from birth
  • heart-valve disease
  • abnormal rhythms (or arrhythmias including tachycardia, a heartbeat that is too fast, or bradycardia, a heartbeat that is too slow)
  • coronary artery disease
  • an inflammation of the heart
  • an altered electrolyte balance (including potassium or sodium abnormalities)
  • a past heart attack, one that is happening at the moment, or one that is about to happen
Author: David T. Moran, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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