706afa36_kipedia__the_free_encyclopedia__Description
[Feature] U wave [Pathology] If the U wave is very prominent, suspect hypokalemia, hypercalcemia or hyperthyroidism.[24] [Description] 
The U wave is hypothesized to be caused by the repolarization of the interventricular septum. It normally has a low amplitude, and even more often is completely absent.
Electrocardiography - Wikipedia, the free encyclopedia