QRS Complex — ECG/EKG Terminology

Definition: The deflections in the ECG tracing, comprising the Q, R, and S waves, that represent the ventricular activity of the heart (depolarization of the ventricles).

Key Facts

• Represents ventricular depolarization and onset of ventricular contraction.
• Normal duration is typically less than 120 ms in adults.
• Widening suggests intraventricular conduction delay or ventricular origin beats.

ECG Connection: QRS width and shape are core features for differentiating supraventricular versus ventricular rhythms.

Why It Matters: A sudden change in QRS width or morphology can indicate new conduction disease or ischemia.