Since the body fluids and tissue is good conductor of electricity. The electrical activity with in the heart is detected by attaching electrodes to the surface of the body.

        The instrument on which electrical activity is recorded is called Electro Cardio Graph, and tracing is called Electro Cardio Gram(ECG).

        The Normal ECG tracing shows five waves which have been named P,Q,R,S,T

        *The P wave arises when the impulse from the SA node sweeps over the atria.
        *The QRS Complex represents the very rapid spread of the impulse from the AV node to bundle of His and purnkinje fibres and the electrical activity of the ventricular muscles.
        *The T wave represents the relaxation of the ventricular muscle.