Definition of Electrocardiogram:

An electrocardiogram (ECG) is a test that records the electrical activity of the heart.

See also:

• Holter monitoring.
• Stress test

How the test is performed:

You will be asked to lie down. The health care provider will clean several areas on your arms, legs, and chest, and then attach small patches called electrodes to the areas. It may be necessary to shave or clip some hair so the patches stick to the skin. The number of patches used may vary.

The patches are connected by wires to a machine that turns the heart's electrical signals into wavy lines, which are often printed on paper. The test results are reviewed by the doctor.

You usually need to remain still during the procedure. The health care provider may also ask you to hold your breath for a few seconds as the test is being done. Any movement, including muscle tremors such as shivering, can alter the results. So it is important to be relaxed and relatively warm during an ECG recording.

Sometimes this test is done while you are exercising or under minimal stress to monitor changes in the heart. This type of ECG is often called a stress test.

How to prepare for the test:

Make sure your health care provider knows about all the medications you are taking, as some can interfere with test results.

Exercising or drinking cold water immediately before an ECG may cause false results.

How the test will feel:

An ECG is painless. No electricity is sent through the body. The electrodes may feel cold when first applied. In rare cases, some people may develop a rash or irritation where the patches were placed.

Why the test is performed:

An ECG is used to measure:

• Any damage to the heart
• How fast your heart is beating and whether it is beating normally
• The effects of drugs or devices used to control the heart (such as a pacemaker)
• The size and position of your heart chambers

An ECG is a very useful tool for determining whether a person has heart disease. Your doctor may order this test if you have chest pain or palpitations.