The U wave is a smaller structure after the T wave that resembles a second T wave, kind of like Baby Mario, M&M’s Minis or Pichu. It’s best seen in V2 and V3.

Prominent U waves are most commonly found in:

• Bradycardia
• Hypokalaemia

Inverted U waves are abnormal and point to cardiac disease.

References

1. Burns, E. (2019). U Wave. [online] Life in the Fast Lane. Available at: https://litfl.com/u-wave-ecg-library/ [Accessed 29 Jan. 2020].