The QRS complex on the ECG represents which of the following events in the cardiac cycle?

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

Answer: (C)

Verified step by step guidance

1. Understand the components of an ECG (electrocardiogram): The ECG is a graphical representation of the electrical activity of the heart. It consists of several waves, including the P wave, QRS complex, and T wave, each corresponding to specific events in the cardiac cycle.
2. Identify the QRS complex: The QRS complex is the sharp, tall spike seen on the ECG. It represents a rapid electrical event in the heart.
3. Relate the QRS complex to ventricular depolarization: Depolarization refers to the electrical activation of the heart muscle. The QRS complex specifically corresponds to the depolarization of the ventricles, which triggers their contraction and pumps blood to the lungs and body.
4. Clarify why other options are incorrect: Ventricular repolarization is represented by the T wave, not the QRS complex. Atrial depolarization is represented by the P wave, and atrial repolarization is typically masked by the QRS complex due to its larger amplitude.
5. Summarize the correct answer: The QRS complex on the ECG represents ventricular depolarization, which is the electrical event leading to the contraction of the ventricles.