In an EKG tracing, the QRS complex corresponds to which cardiac event?

In an EKG tracing, the QRS complex corresponds to which cardiac event?

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

Answer: (A)

The QRS complex reflects ventricular depolarization—the electrical activation of the ventricles that triggers their contraction. In the cardiac cycle, the atria depolarize first (seen as the P wave), then the ventricles depolarize with the QRS, leading to ventricular contraction. Afterward, the ventricles repolarize (the T wave), while atrial repolarization is usually hidden within the QRS. So the event tied to this electrical activity is the ventricles contracting, which is why the best match is ventricular contraction.

The QRS complex reflects ventricular depolarization—the electrical activation of the ventricles that triggers their contraction. In the cardiac cycle, the atria depolarize first (seen as the P wave), then the ventricles depolarize with the QRS, leading to ventricular contraction. Afterward, the ventricles repolarize (the T wave), while atrial repolarization is usually hidden within the QRS. So the event tied to this electrical activity is the ventricles contracting, which is why the best match is ventricular contraction.