In an EKG, the P wave represents which event?

In an EKG, the P wave represents which event?

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

Answer: (A)

The P wave reflects atrial depolarization, the electrical activation that precedes atrial contraction. In other words, it’s the electrical signal telling the atria to activate and prepare to squeeze blood into the ventricles. The actual mechanical contraction (atrial systole) happens a short time after this electrical event, during the latter part of the P wave into the PR interval. The QRS complex is ventricular depolarization, and the T wave is ventricular repolarization. So the P wave is best understood as atrial depolarization—the electrical activity that triggers atrial contraction, not the contraction itself.

The P wave reflects atrial depolarization, the electrical activation that precedes atrial contraction. In other words, it’s the electrical signal telling the atria to activate and prepare to squeeze blood into the ventricles. The actual mechanical contraction (atrial systole) happens a short time after this electrical event, during the latter part of the P wave into the PR interval. The QRS complex is ventricular depolarization, and the T wave is ventricular repolarization. So the P wave is best understood as atrial depolarization—the electrical activity that triggers atrial contraction, not the contraction itself.