What does the U wave represent on an ECG?

The U wave on an electrocardiogram (ECG) is commonly associated with the repolarization of the Purkinje fibers, which are specialized conduction fibers in the ventricles of the heart. While the U wave's clinical significance is not entirely understood, it is generally believed to reflect the recovery of the ventricular myocardium following depolarization.

This aspect of ventricular repolarization is important because variations in the U wave can provide insights into cardiac health. For instance, the presence of prominent U waves may indicate underlying conditions such as electrolyte imbalances or other cardiac pathologies. Understanding the role of the U wave helps in accurately interpreting the ECG and diagnosing potential heart issues more effectively.

Other choices, such as atrial contraction, ventricular contraction, and myocardial ischemia, are associated with different components of the ECG. Atrial contraction corresponds to the P wave, while ventricular contraction is represented by the QRS complex. Myocardial ischemia, often due to reduced blood flow to the heart, typically presents with changes in the ST segment and T wave rather than a distinct U wave. Thus, the correct association of the U wave with the repolarization of Purkinje fibers clarifies its significance in cardiac physiology.