Electrocardiogram (ECG) illustrates the electrical activity in the heart, and is the most important physiological parameter that gives the correct assessment regarding the functioning of the heart. ECG is the graphical recording of the electrical activity of the heart used for clinical diagnosis. The ECG signal is pseudo-periodic, since the amplitude of every wave varies from one cycle to the other one during the same recording. The variation of the amplitude is related to physiological and pathological conditions of the patient.