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Electrocardiogram and specialised ECGs

An electrocardiogram, or ECG, uses sticky electrodes on the arms, legs and chest to record the heart’s electrical activity and rhythm.

An ECG may be arranged as a test for suspected heart disease or other problems.

Doctors uses the ECG to:

  • Assess heart rhythm
  • Diagnose poor blood flow to the heart muscle (ischaemia)
  • Diagnose a heart attack
  • Evaluate certain abnormalities of the heart, such as an enlarged heart

How should I prepare for an ECG?

To prepare for an ECG:

  • Avoid oily or greasy skin creams and lotions the day of the test. They interfere with the electrode skin contact
  • Avoid full-length tights or stockings because electrodes need to be placed directly on the legs
  • Wear a shirt that can be easily removed to place the leads on the chest

What happens during an ECG

During an ECG, a technician will attach a number of electrodes with adhesive pads to the skin of your chest, arms, and legs. Men may have chest hair shaved to allow a better connection. You will lie flat while the computer creates a picture, on graph paper, of the electrical impulses travelling through your heart. This is called a "resting" ECG. This same test may also be used to monitor your heart during exercise.

It takes about 10 minutes to attach the electrodes and complete the test, but the actual recording takes only a few seconds.

Your ECG patterns will be kept on file for later comparison with future ECG recordings. If you have questions, ask your doctor.

In addition to the standard ECG, your doctor may recommend other specialised ECG tests, including a holter monitor or a signal-averaged electrocardiogram.

What is a holter monitor?

A holter monitor is a portable ECG that monitors the electrical activity of a freely moving person's heart generally for one to two days, 24 hours a day. It is most often used when the doctor suspects an abnormal heart rhythm or ischaemia (not enough blood flow to the heart muscle).

It is a painless test. Electrodes from the monitor are taped to the skin. Once the monitor is in place, you can go home and perform all of your normal activities (except showering). You will be asked to keep a diary of your activities and any symptoms you experience and when they occur.

What is an event monitor?

If your symptoms are infrequent, your doctor may suggest an event monitor. This is a device that, when you push a button, will record and store the heart's electrical activity for a few minutes. Each time you develop symptoms you should try to get a reading on the monitor. They are used for weeks to months, typically one month. This information can later be transmitted by telephone to the doctor for interpretation.

What is a signal-averaged electrocardiogram?

This is a painless test used to assess whether a person is at high risk of developing a potentially fatal heart arrhythmia. It is performed in a similar manner to the ECG, but uses sophisticated technology to look for heart arrhythmias.

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WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on June 01, 2016

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