What does the P wave on an ECG represent?

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

Answer: (B)

The P wave on an electrocardiogram (ECG) represents atrial depolarization, which is the electrical activity that initiates the contraction of the atria. When the sinoatrial (SA) node, the heart's natural pacemaker, sends out an electrical impulse, this causes the atria to contract and push blood into the ventricles.

This process is crucial for effective heart function, as it ensures that blood is adequately filled into the ventricles before they contract. The P wave appears as a small upward deflection on the ECG tracing and is typically seen prior to the QRS complex, which represents ventricular depolarization. Understanding this correlation aids in interpreting the ECG and recognizing normal and abnormal heart rhythms, making it integral for healthcare professionals, particularly in emergency and paramedic settings.