Located on the skin over the heart, a pair of surface electrodes will record a repeating pattern pattern of electrical changes. The voltage measured between these 2 electrodes will change as action potentials spread via the conduction system from the atria to the ventricles. A “picture” of the electrical activity of the heart is offered by recordings of these changes. Distinguished perspectives are offered by changing the location of the electrodes, thus enable an observer to obtain a more comprehensive picture of the electrical events.
For that tissue fluids include a high concentration of ions that move (creating a current) in response to potential differences, the body is a good conductor of electricity. Generated by the heart, potential differences thus conducted to the body surface, where they can be recorded by electrodes on the skin. The recording device is named an electrocardiograph, and the recording is named an electrocardiogram (ECG or EKG).
Designated P, QRS, and T, the wave deflections are formed as particular events of the cardiac cycle happen. Characteristic changes in one or more of these waves will be formed by any heart disease that disturbs the electrical activity, therefore, it is clinically important to understand the common wave-deflection patterns.