What does the P wave in an ECG represent?

The P wave in an electrocardiogram (ECG) represents atrial depolarization, which is the electrical activity that causes the atria to contract. This phase is crucial for the heart's functioning, as it allows the atria to push blood into the ventricles prior to ventricular contraction.

During atrial depolarization, the sinoatrial node (the natural pacemaker of the heart) generates an electrical impulse that spreads through the atria, leading to their contraction. This is illustrated in the ECG as the P wave, which appears as a small upward deflection before the larger QRS complex that represents ventricular depolarization. Understanding this distinct representation is vital for interpreting the heart's electrical activity in various clinical situations.