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JAMA Patient Page
September 13, 2006


JAMA. 2006;296(10):1314. doi:10.1001/jama.296.10.1314

An electrocardiogram (ECG or EKG) is a recording of the electrical activity of the heart made from electrodes (electrical conductors) placed on the surface of the skin, usually on each arm and leg and across the chest. The function of the heart in expanding and contracting to pump blood to the body is controlled by small electrical impulses within the heart. These impulses can be detected by electrodes on the skin and transmitted to the electrocardiogram machine by wires. The impulses are then translated into peaks and valleys or squiggles by the ECG machine, which includes a pen that moves up and down over a long strip of paper passing through the machine at a steady rate. Each cardiac cycle, or heartbeat, is recorded as a particular series of peaks and valleys.