How are ECG findings likely to change as blood potassium levels increase in hyperkalemia?

Updated: Apr 09, 2020
  • Author: Eleanor Lederer, MD, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Early ECG changes of hyperkalemia, typically seen at a serum potassium level of 5.5-6.5 mEq/L, include the following:

  • Tall, peaked T waves with a narrow base, best seen in precordial leads [3]
  • Shortened QT interval
  • ST-segment depression

At a serum potassium level of 6.5-8.0 mEq/L, the ECG typically shows the following:

  • Peaked T waves
  • Prolonged PR interval
  • Decreased or disappearing P wave
  • Widening of the QRS
  • Amplified R wave

At a serum potassium level higher than 8.0 mEq/L, the ECG shows the following:

  • Absence of P waves
  • Progressive QRS widening
  • Intraventricular/fascicular/bundle branch blocks

The progressively widened QRS eventually merges with the T wave, forming a sine wave pattern. Ventricular fibrillation or asystole follows.

See Workup for more detail.


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