Typical ECG signal

ECG signal

P-wave: a small low-voltage deflection caused by the depolarisation of the atria prior to atrial contraction.

QRS complex: the largest-amplitude portion of the ECG, caused by currents generated when the ventricles depolarise prior to their contraction.

T-wave: ventricular repolarisation.

P-Q interval: the time interval between the beginning of the P wave and the beginning of the QRS complex.

Q-T interval: characterises ventricular repolarisation.