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ECG Findings

  • Flattened or inverted T waves

  • Prominent U waves that can merge with the T waves producing the appearance of a prolonged QT

  • ST-segment depression

  • Conduction disturbances


  1. Hypokalemia can produce varied ECG changes associated with the repolarization phase of the cardiac cycle.

  2. Unlike hyperkalemia, in hypokalemia, there is no direct correlation with the potassium level and the severity of ECG changes. However, more ECG changes may become apparent as the potassium level falls.

  3. Suspect hypomagnesemia if the ECG does not normalize after potassium replacement.


Hypokalemia. (ECG contributor: R. Jason Thurman, MD.)


This ECG demonstrates multiple findings consistent with hypokalemia: flattened T waves (blue arrowhead), U waves (black arrowhead), prolonged QT (QU) intervals (double arrow), and ST-segment depression (arrow). This patient’s potassium level was 1.9.

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