Which wave is associated with atrial contraction on an ECG?

The P wave on an ECG represents atrial depolarization, which occurs just before the atrial contraction. During this phase, the electrical signals spread through the atria, leading to their contraction, which pumps blood into the ventricles. This wave illustrates the initial part of the cardiac cycle, highlighting the start of the heart's pumping action within the atria. Since the P wave is a direct indicator of the electrical activity associated with atrial contraction, it is crucial in understanding the phases of heart function as shown on an ECG.

Other waves, such as the T wave, represent ventricular repolarization, while the QRS complex signifies ventricular depolarization, related to the contraction of the ventricles rather than the atria. The U wave is less commonly featured in standard ECG interpretations and is linked with repolarization of the ventricles or might be present in certain pathological conditions, but it does not indicate atrial contraction.