An electrocardiogram or EKG (from the original Greek abbreviation kardia, meaning heart) is a piece of equipment that measures the electrical impulses that cause the heart to beat as they pass through the body.
The EKG consists of several electrodes which are attached to the body of the patient and are connected by wires to the device. The device itself consists of a graphing device (originally paper, although electronic recorders are becoming more common). Each one of the sensors can detect a change in electrical charge in the skin that can only be the result of the impulses that are travelling through the heart and on to the rest of the body.
The electrical charge is what signals the individual cells of the heart muscle to contract at the same time to force blood through the heart's valves. It starts in the upper right ventrical, which contracts in response, and quickly travels through the other three chambers of the heart, which contract all at once. This impulse travels very quickly and is also transmitted to the cells surrounding the heart as it dissipates throughout the body. This forms a very regular pattern which establishes a control for patients that do have heart problems, such as arythmia.
As an EKG can be performed over as long a period as necessary, and measures the impulse over a wide number of spots, it can be examined for diagnostic clues that would not be obvious to a doctor who merely uses a stethoscope or what can be determined from a heart monitor.
EKG signals are recorded on paper chart or on a patient monitor. EKG signal tracing are described by wave components or segments, as descripted in basic EKG courses. EKGs are used to detect various cardiac abnormalities. Arrhythmia reference guidesand printed books provide annotated descriptions and practice tracings.