Which component of the ECG represents ventricular depolarization?

• A. P-wave
• B. QRS complex
• C. T-wave
• D. NSR

Answer: (B)

The QRS complex represents ventricular depolarization. On an ECG, the P-wave shows atrial depolarization, followed by the QRS as the impulse rapidly spreads through the ventricles via the His-Purkinje system to trigger ventricular contraction. After depolarization, the ventricles repolarize, which is seen as the T-wave. NSR refers to the rhythm and is not a waveform of depolarization. In normal conduction, the QRS is brief and sharp; a wide QRS can indicate abnormal ventricular conduction.