The negative U wave: a pathogenetic enigma but a useful, often overlooked bedside diagnostic and prognostic clue in ischemic heart disease.

The pathogenesis of U-wave inversion and its clinical value are still not clear, although the U wave was described by Einthoven together with the other electrocardiographic (ECG) waves. Not considered a useful diagnostic clue, it is not usually mentioned in ECG reports. In recent years, stimulated by the long QT syndromes and by the discovery of U-wave changes in some pathologic, mostly cardiac states, this neglected wave has attracted new interest.