U wave

A small, low-amplitude ECG deflection occurring after the T wave, thought to reflect delayed repolarization of the Purkinje fibers or mid-myocardial M-cells.

Causes

• Prominent or tall U waves

  • Hypokalemia

  • Hypomagnesemia

  • Hypocalcemia

  • Bradycardia

  • Hypothermia

• Medications

  • Quinidine

  • Sotalol

  • Digoxin

• Inverted U waves

  • Coronary artery disease

  • Hypertension

  • Cardiomyopathy

  • Hyperthyroidism

  • Valvular heart disease