What does the P wave in an ECG represent?

What does the P wave in an ECG represent?

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

Answer: (B)

The P wave reflects atrial depolarization—the electrical activation spreading through the atrial myocardium as the atria prepare to contract and push blood into the ventricles. This happens just before the ventricles depolarize, which is seen as the QRS complex. A normal P wave is a small, smooth deflection that precedes each QRS. In contrast, ventricular depolarization is the QRS complex, and ventricular repolarization is the T wave. Atrial repolarization does occur, but its signal is typically masked by the larger ventricular depolarization and not seen as a separate deflection.

The P wave reflects atrial depolarization—the electrical activation spreading through the atrial myocardium as the atria prepare to contract and push blood into the ventricles. This happens just before the ventricles depolarize, which is seen as the QRS complex. A normal P wave is a small, smooth deflection that precedes each QRS. In contrast, ventricular depolarization is the QRS complex, and ventricular repolarization is the T wave. Atrial repolarization does occur, but its signal is typically masked by the larger ventricular depolarization and not seen as a separate deflection.