ECG is representation of electrical activity of heart during a cardiac cycle. To obtain ECG a patient is connected to a machine that monitors the activity of the heart. Each peak of ECG is identified with a letter from P to T that corresponds to a specific electrical activity of the heart.

P-Wave :It represents depolarization (or electrical excitation) of atria. It leads to contraction of both the atria (Atrial systole).

QRS-Complex :It represents depolarization of ventricles which initiates ventricular contraction (Ventricular systole).

T-Wave: It represents return of ventricles from excited to normal state (Repolarization). The end of T- wave marks the end of systole.

The heartbeat of a person can be determined by counting the number of QRS complexes that occur in a given time period.

It has a great clinical significance. As if QRS complex becomes wider then it can lead to heart attack or myocardial infarction.

If T wave becomes flat then it can lead to Coronary Artery Disease (CAD) also known as atherosclerosis which affects vessels that supply blood to the heart (Coronary artery).

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