What does the U wave on an EKG represent?

The U wave on an EKG represents the repolarization of the Purkinje fibers, which are specialized conductive fibers that help in the coordinated contraction of the heart. The presence of a U wave can indicate the heart's recovery phase after depolarization, specifically focusing on the repolarization processes of the ventricles.

In a healthy individual, the U wave is typically small and follows the T wave. It is most prominent in certain conditions, such as in athletes or during bradycardia, where the heart rate is lower than normal. Its significance can also be observed in various clinical situations, such as electrolyte imbalances, particularly hypokalemia, or conditions that may affect the repolarization process.

The other options do not correctly describe the U wave. Heart rate is measured by the frequency of the R-R intervals and is not directly represented by the U wave. Myocardial ischemia is reflected by changes in the ST segment or T wave, whereas ventricular tachycardia is a rapid heart rhythm evident through the overall pattern of the EKG, not specifically connected to the U wave. Understanding the role of the U wave in repolarization helps with recognizing its clinical implications in EKG interpretation.