An electrocardiogram or an ECG uses an instrument to record the electrical activities of the heart. It records the electrical impulses, more specifically the change in the electrical impulses of the heart, and plots it on a graph. The readings of an individual’s ECG are compared with a standard ECG to evaluate the working of the heart and checking it for any abnormalities or diseases. It basically records the electrical activity of an individual in the form of waves that recur with each next beat of the heart. The end of the T wave depicts the end of the ventricular depolarization.