Which wave on an ECG represents atrial depolarization?

The P wave on an ECG represents atrial depolarization, which is the electrical event that triggers the contraction of the atria, causing them to pump blood into the ventricles. When the sinoatrial (SA) node initiates an electrical impulse, this impulse spreads through the atrial myocardium, leading to depolarization. The P wave reflects this process on the electrocardiogram, appearing as a small, upward deflection before the QRS complex.

In contrast, the QRS complex represents ventricular depolarization, the T wave signifies ventricular repolarization, and the U wave is often associated with repolarization of the papillary muscles or the Purkinje fibers, but its clinical significance is less well-defined. Understanding the role of the P wave is crucial in interpreting ECGs, as it provides insights into atrial function and potential atrial abnormalities.