Schematic representation of normal EKG In electrocardiography, the<unk>  is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120 and 200 ms in duration. The<unk>  is sometimes termed the<unk> .
PR interval
QRS complex
P wave 
T wave
QT interval
J wave
ST segment
Delta wave