U wave

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A U wave as seen on ECG
An electrocardiogram of an 18-year-old man showing U waves, most evident in lead V3.

The U wave is a wave on an electrocardiogram that is not always seen. It is typically small, and, by definition, follows the T wave. U waves are thought to represent repolarization of the papillary muscles or Purkinje fibers.[1]


Prominent U waves are most often seen in hypokalemia, but may be present in hypercalcemia, thyrotoxicosis, or exposure to digitalis, epinephrine, and Class 1A and 3 antiarrhythmics, as well as in congenital long QT syndrome, and in the setting of intracranial hemorrhage.

An inverted U wave may represent myocardial ischemia or left ventricular volume overload.[2]

A U-wave could normally be seen in younger, athletic individuals.[3]


  1. ^ Pérez Riera AR, Ferreira C, Filho CF, et al. (2008). "The enigmatic sixth wave of the electrocardiogram: the U wave". Cardiol J 15 (5): 408–21. PMID 18810715. 
  2. ^ Conrath C, Opthof T (2005). "The patient U wave". Cardiovasc Res 67 (2): 184–6. doi:10.1016/j.cardiores.2005.05.027. PMID 15979057. 
  3. ^ EKG-boken Ylva Lind, Lars Lind, Liber, 2011