What does the P wave on an ECG indicate?

The P wave on an ECG represents atrial contraction, specifically the depolarization of the atria. This electrical activity occurs just before the atria contract and push blood into the ventricles. The P wave is the first wave in the sequence of the cardiac cycle as displayed on an electrocardiogram, and it reflects the activation of the sinoatrial (SA) node, which is the natural pacemaker of the heart.

In a normal ECG, the P wave occurs before the QRS complex, which represents ventricular depolarization and contraction. Understanding the significance of the P wave is critical in assessing cardiac function, as it provides insight into the atrial health and rhythm of the heart. Identifying this wave can help clinicians detect abnormalities such as atrial enlargement or other conditions affecting the atria.