What does the QRS complex represent on an ECG?

What does the QRS complex represent on an ECG?

• A. Atrial depolarization.
• B. Ventricular depolarization.
• C. Ventricular repolarization.
• D. No electrical activity.

Answer: (B)

The QRS complex represents ventricular depolarization—the rapid electrical activation of the ventricles that triggers their contraction. The atria depolarize earlier, which shows up as the P wave, and ventricular repolarization occurs later, yielding the T wave. A flat line would mean no electrical activity. So the QRS is the signature of the ventricles’ electrical activation, reflecting their large muscle mass and the swift spread of impulse through the ventricles.

The QRS complex represents ventricular depolarization—the rapid electrical activation of the ventricles that triggers their contraction. The atria depolarize earlier, which shows up as the P wave, and ventricular repolarization occurs later, yielding the T wave. A flat line would mean no electrical activity. So the QRS is the signature of the ventricles’ electrical activation, reflecting their large muscle mass and the swift spread of impulse through the ventricles.