What electrical activity of the heart is indicated by the p wave?

The P wave on an electrocardiogram (ECG) represents atrial depolarization, which is the electrical activity that triggers the contraction of the atria. This depolarization occurs as the electrical impulse from the sinoatrial (SA) node spreads through the atrial muscle, leading to the atria contracting and pushing blood into the ventricles. The P wave is typically the first deflection in the ECG cycle and is crucial for the proper timing of heartbeats.