What is the P wave of the heart?

As a cardiac electrophysiologist, I specialize in the study of the electrical activity of the heart. When it comes to the P wave of the heart, it's a crucial part of the heartbeat cycle that can be observed on an electrocardiogram (ECG or EKG). The P wave represents the initial depolarization of the atria, which is the process by which the atrial muscle fibers prepare to contract. This depolarization is what initiates the atrial contraction, which then propels blood from the atria into the ventricles. The P wave is typically the first wave seen on the ECG and follows the isoelectric portion of the heart's electrical cycle, which is the period between the end of one heartbeat and the beginning of the next. It's important to note that the wave of atrial repolarization, which occurs after depolarization, does not typically appear on the ECG because it has a low amplitude and is often obscured by the much larger QRS complex that follows. The QRS complex represents the depolarization of the ventricles, which is a more powerful contraction necessary for pumping blood throughout the body. In summary, the P wave is a vital sign of atrial activity and its observation on an ECG is critical for diagnosing various cardiac conditions related to atrial function.

Atrial and ventricular depolarization and repolarization are represented on the ECG as a series of waves: the P wave followed by the QRS complex and the T wave. The first deflection is the P wave associated with right and left atrial depolarization. Wave of atrial repolarization is invisible because of low amplitude.