The U-wave: A remaining enigma of the electrocardiogram

J Electrocardiol. 2023 Jul-Aug:79:13-20. doi: 10.1016/j.jelectrocard.2023.03.001. Epub 2023 Mar 5.


The U-wave's electrophysiological origin remains unknown and is subject to debate. It is rarely used for diagnosis in clinical practice. The aim of this study was to review new information regarding the U-wave. Further to present the proposed theories behind the U-wave's origin along with potential pathophysiologic and prognostic implications related to its presence, polarity and morphology.

Method: Literature searches were conducted to retrieve publications related to the electrocardiogram U-wave in the literature database Embase.

Results: The review of the literature revealed the following major theories that will be discussed; late depolarisation, delayed or prolonged repolarisation, electro-mechanical stretch and IK1 dependent intrinsic potential differences in the terminal part of the action potential. Various pathologic conditions were found to correlate with the presence and properties of the U-wave, such as its amplitude and polarity. Abnormal U-waves can, for example, be observed in coronary artery disease with ongoing myocardial ischemia or infarction, ventricular hypertrophy, congenital heart disease, primary cardiomyopathy and valvular defects. Negative U-waves are highly specific for the presence of heart diseases. Concordantly negative T- and U-waves are especially associated with cardiac disease. Patients with negative U-waves tend to have higher blood pressure and history of hypertension, higher heart rate, cardiac disease and left ventricular hypertrophy compared to subjects with normal U-waves. Negative U-waves have been found to be associated with increased risk of all-cause mortality, cardiac death and cardiac hospitalisation in men.

Conclusions: The origin of the U-wave is still not established. U-wave diagnostics may reveal cardiac disorders and the cardiovascular prognosis. Including the U-wave characteristics in the clinical ECG assessment may be useful.

Keywords: 12‑lead electrocardiogram; Depolarization; Electrocardiography; Electrophysiology; Repolarization; U-wave.

Publication types

  • Review

MeSH terms

  • Coronary Artery Disease*
  • Electrocardiography
  • Heart
  • Heart Defects, Congenital*
  • Humans
  • Hypertension*
  • Hypertrophy, Left Ventricular
  • Male
  • Myocardial Ischemia* / diagnosis