What does a "u wave" represent?

A "u wave" represents the repolarization of the Purkinje fibers, which are specialized conductive fibers in the heart responsible for transmitting electrical impulses to the ventricular muscle. During the cardiac cycle, after the T wave that reflects the repolarization of the ventricles, the U wave may appear, indicating that this phase of repolarization is occurring.

The presence of the U wave can provide information on the heart’s electrical activity and may sometimes be seen more prominently in certain conditions or specific populations. It is essential to recognize that the U wave is generally not related to the contraction phase of the heart (which is represented by the QRS complex) or conduction through the atrioventricular node, as those processes are distinct parts of the heart's electrical activity sequence. Understanding the significance of the U wave and its association with Purkinje fibers underscores its role in evaluating cardiac health.