What does a P wave represent on an ECG?

The P wave on an electrocardiogram (ECG) specifically represents atrial depolarization. This is the electrical activity that occurs when the atria of the heart contract and push blood into the ventricles. During depolarization, sodium ions flow into the atrial cells, causing the cells to become electrically positive and leading to the contraction of the atrial muscle.

Recognizing the significance of the P wave is crucial for understanding the overall heart function as it provides insight into the health of the atria and the electrical conduction system of the heart. For instance, abnormalities in the P wave or its characteristics can indicate issues such as atrial enlargement, atrial ectopic beats, or other forms of atrial dysfunction.

Other waveforms on the ECG serve different functions: for example, the QRS complex represents ventricular depolarization (the contraction of the ventricles), while the T wave corresponds to ventricular repolarization (the recovery phase of the ventricles). Atrial repolarization is typically not visible on the ECG because it occurs simultaneously with ventricular depolarization and is obscured by the large QRS complex. Therefore, the P wave's singular representation of atrial depolarization is what solidifies option B as