In an ECG, what does the QRS complex represent?

In an ECG, what does the QRS complex represent?

• A. Atrial depolarization
• B. Ventricular depolarization
• C. Ventricular repolarization
• D. Atrial repolarization

Answer: (A)

The QRS complex represents ventricular depolarization—the rapid activation of the ventricles as the electrical impulse travels through the His-Purkinje system to make the ventricles contract. This phase is the main spike seen after the P wave, and it is broad because the ventricles are large and rely on fast conduction fibers to activate them quickly. The P wave, preceding the QRS, is atrial depolarization, while the T wave afterward reflects ventricular repolarization as the ventricles reset for the next beat. Atrial repolarization does occur, but it is masked inside the QRS complex and not seen as a separate waveform.

The QRS complex represents ventricular depolarization—the rapid activation of the ventricles as the electrical impulse travels through the His-Purkinje system to make the ventricles contract. This phase is the main spike seen after the P wave, and it is broad because the ventricles are large and rely on fast conduction fibers to activate them quickly. The P wave, preceding the QRS, is atrial depolarization, while the T wave afterward reflects ventricular repolarization as the ventricles reset for the next beat. Atrial repolarization does occur, but it is masked inside the QRS complex and not seen as a separate waveform.