Electrocardiography (ECG), also known as EKG, is a medical test performed by placing electrodes on specific points of the body (typically the chest, arms, and legs) to measure and graphically record the electrical activity of the heart. This procedure allows for the detection of abnormalities in heart rhythm, rate, and electrical propagation, thereby aiding in the diagnosis of various cardiovascular diseases.

When the ECG device is connected to a patient, weak electrical signals generated by the contraction and relaxation of the atria and ventricles during a heartbeat are monitored. These signals reflect the rhythm, propagation, and frequency of the heart's electrical activity.

In an ECG recording, specific waves representing each heartbeat are observed. The 'P wave' indicates the contraction (depolarization) of the heart's upper chambers (atria). The 'QRS complex' represents the contraction (depolarization) of the lower chambers (ventricles). The 'T wave' signifies the relaxation and recharging (repolarization) phase of the ventricles.