What ECG wave reflects atrial depolarization?

The P wave is the component of the electrocardiogram that reflects atrial depolarization. During this process, the electrical impulse generated by the sinoatrial (SA) node spreads through the atria, causing them to contract and pump blood into the ventricles. The P wave represents the moment this electrical activity occurs, making it a key indicator of how well the atria are functioning and depolarizing.

In contrast, other components of the ECG have different functions: the QRS complex represents ventricular depolarization, which occurs after atrial depolarization; the T wave reflects ventricular repolarization, indicating that the ventricles are recovering after contraction; and the U wave is often associated with the repolarization of the papillary muscles or the Purkinje fibers and is less commonly discussed. Understanding the role of the P wave helps in interpreting the overall cardiac cycle and assessing atrial health.