Which statement about the QRS complex is true?

Which statement about the QRS complex is true?

• A. Represents atrial depolarization
• B. Represents ventricular depolarization
• C. Represents ventricular repolarization
• D. Represents atrial repolarization

Answer: (B)

The QRS complex represents ventricular depolarization, the rapid electrical event that triggers the ventricles to contract and pump blood. The atria depolarize earlier, which appears as the P wave, and ventricular repolarization occurs later, shown as the T wave. Atrial repolarization does occur but is usually masked by the larger QRS complex, so it’s not seen as a separate deflection. The QRS duration tends to be short because conduction through the ventricles is fast via the His-Purkinje system. Thus, this complex truly reflects ventricular depolarization.

The QRS complex represents ventricular depolarization, the rapid electrical event that triggers the ventricles to contract and pump blood. The atria depolarize earlier, which appears as the P wave, and ventricular repolarization occurs later, shown as the T wave. Atrial repolarization does occur but is usually masked by the larger QRS complex, so it’s not seen as a separate deflection. The QRS duration tends to be short because conduction through the ventricles is fast via the His-Purkinje system. Thus, this complex truly reflects ventricular depolarization.