Hypokalemia electrocardiogram

The most notable EKG findings in hypokalemia are due to the delayed ventricular repolarization, manifesting as (QT-U) with prominent U waves. The EKG changes of hypokalemia are commonly seen at potassium levels < 3 meq/Li. 90% of the patients with potassium levels <2.7 meq/L have abnormal ECG findings.

1. ST segment depression, decreased T wave amplitude, and prominent U waves:
   • Seen in 78% of patients with a K < 2.7 meq
   • Seen in 35% of patients with a K > 2.7 and < 3.0
   • Seen in 10% of patients with a K > 3.0 and < 3.5
   • U waves are also prominent in bradycardia and LVH
2. Prolongation of the QRS duration
   • Uncommon except in severe hyperkalemia
3. Increase in the amplitude and duration of the P-wave
4. Cardiac arrhythmias and AV block
5. Contrary to popular belief there is not prolongation of the QTc, this is artifactually prolonged due to the U wave. In some cases there is fusion of the T and U waves making interpretation impossible.
6. Ventricular ectopy
   • Premature ventricular complex
   • Ventricular tachycardia
   • Ventricular fibrillation

Shown below is an example of hypokalemia with long QT interval, ST segment depression, low T waves amplitude and TU wave fusion.

Shown below is an example of hypokalemia with Left Ventricular Hypertrophy.

The EKG below demonstrates characteristics of hypokalemia including: T wave inversions and U waves circled in red; flattening of ST segment and prolonged Q- U interval as circled in green.

The EKG changes of hypokalemia are rapidly reversible with potassium repletion.

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