Which wave represents ventricular depolarization?

• A. U wave
• B. P wave
• C. T wave
• D. QRS complex

Answer: (D)

In ECG interpretation, the different waves reflect distinct electrical events in the heart. The rapid, sharp deflections that come after the preceding wave represent ventricular depolarization—the moment the ventricles are activated to contract. This specific pattern is the QRS complex, which appears as a quick, tall, and narrow series of spikes due to the rapid spread of depolarization through the ventricles via the His-Purkinje system.

The P wave, by contrast, corresponds to atrial depolarization; the T wave marks ventricular repolarization as the ventricles reset after contraction. A U wave, when present, is a less consistent finding and not the main marker of ventricular depolarization. So the waveform that best represents ventricular depolarization is the QRS complex.