1. A painless procedure in which the heart's electrical impulses are amplified for making a graphic recording (electrocardiogram) of the electrical impulses which pass through the heart to initiate and to control its activity: Electrocardiography is accomplished by placing metal plates called electrodes on body surfaces and they cause no discomforts.

These plates are attached to a recording instrument, and they pick up the electrical impulses of the heart during which small changes occur as the heart beats. The normal form of these beats is altered by heart disease.

2. The creation and study of graphic records produced by electric currents originating in the heart and the interpretation of electrocardiograms: Electrodes connected to a recording machine are applied to the chest, wrists, and ankles. 3. The specialty or science of recording and interpreting the electrical activity of the heart: An ECG, or EKG, can be taken at home, in the physician's office, or in the hospital where a 24-hour record can be obtained from a tape recorder worn by the patient.