What does the P wave represent in an ECG?

What does the P wave represent in an ECG?

• A. The P wave represents depolarization of the atria.
• B. The P wave represents depolarization of the ventricles.
• C. The P wave represents repolarization of the atria.
• D. The P wave represents repolarization of the ventricles.

Answer: (B)

The P wave shows atrial depolarization—the electrical activation that triggers atrial contraction as the impulse spreads through the atrial myocardium, typically starting at the SA node and moving toward the AV node. This wave occurs before atrial systole and before the PR segment. The ventricular depolarization that follows is what you see as the QRS complex, while the T wave represents ventricular repolarization. Atrial repolarization does occur, but it is hidden within the QRS complex and not seen as a separate deflection.

The P wave shows atrial depolarization—the electrical activation that triggers atrial contraction as the impulse spreads through the atrial myocardium, typically starting at the SA node and moving toward the AV node. This wave occurs before atrial systole and before the PR segment. The ventricular depolarization that follows is what you see as the QRS complex, while the T wave represents ventricular repolarization. Atrial repolarization does occur, but it is hidden within the QRS complex and not seen as a separate deflection.