EKG Nomenclature - EKG Basics.
Normal EKG tracings consist of waveform components that indicate electrical events during one heart beat. These waveforms are labeled P, Q, R, S, T and U. The following descriptions are with respect to Lead II.
P wave is the first deflection and is normally a positive (upward) waveform. It indicates atrial depolarization. QRS complex follows the P wave. It normally begins with a downward deflection, Q; a larger upward deflection, R; and then a downward S wave. The QRS complex represents ventricular depolarization and contraction.
T wave is normally a modest upward waveform, representing ventricular repolarization. U wave indicates the recovery of the Purkinje conduction fibers. This wave component may not be observable.
Authors and ReviewersAuthored by Thomas O'Brien
Medically reviewed by Dr. Jonathan Keroes, MD, Cardiology
Last Update: 11/8/2020