DefinitionAn electrocardiogram (ECG) is a test that records the electrical activity of the heart.See also:Holter monitoring.Stress testAlternative NamesECG; EKGHow the test is performedYou 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 t