What does the P wave represent on an ECG?

The P wave on an ECG represents atrial depolarization, which is the electrical activity that occurs when the atria of the heart contract to pump blood into the ventricles. This depolarization is initiated by the electrical impulse generated by the sinoatrial (SA) node, the natural pacemaker of the heart, which spreads throughout the atria and triggers their contraction.

Understanding the role of the P wave is crucial for interpreting an ECG because it provides insight into the electrical function of the heart and the overall rhythm. A normally shaped and sized P wave indicates that the atria are depolarizing properly, which is essential for coordinated cardiac function. This depolarization precedes the QRS complex, which then represents ventricular depolarization.

The other options do not accurately describe the P wave. Atrial repolarization occurs later in the cardiac cycle, typically represented by a segment of the ECG that is not visually distinct as a wave, while ventricular depolarization corresponds to the QRS complex, and ventricular repolarization is depicted by the T wave. Understanding these distinctions is vital for effective ECG interpretation and diagnosis of arrhythmias.