What does the P wave represent in an EKG?

The P wave in an EKG represents atrial depolarization. This is the electrical activity associated with the contraction of the atria, which occurs when the sinoatrial (SA) node sends out an electrical impulse. As this impulse spreads across the atria, it causes them to depolarize and contract, pushing blood into the ventricles. The presence of the P wave is crucial in assessing the heart's electrical conduction and rhythm, with its shape and duration providing insights into atrial health and function.

Understanding that the P wave corresponds exclusively to atrial activity helps in identifying potential atrial abnormalities such as atrial enlargement or atrial fibrillation. Other options represent different phases of the cardiac cycle: the QRS complex relates to ventricular depolarization, the T wave reflects ventricular repolarization, and there’s no distinct wave solely for atrial repolarization as it typically occurs concurrently with ventricular depolarization and is not visually represented as a separate wave in standard EKGs.