What do ECG findings indicate in hyperkalemia (high serum potassium level)?

Updated: Jun 20, 2018
  • Author: Eleanor Lederer, MD, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

ECG is vital for assessing the physiologic significance of hyperkalemia. ECG findings generally correlate with the potassium level, but potentially life-threatening arrhythmias can occur without warning at almost any level of hyperkalemia. In patients with organic heart disease and an abnormal baseline ECG, bradycardia may be the only new ECG abnormality.

ECG changes have a sequential progression, which roughly correlate with the potassium level. [2] Early changes of hyperkalemia include tall, peaked T waves with a narrow base, best seen in precordial leads [3] ; shortened QT interval; and ST-segment depression. These changes are typically seen at a serum potassium level of 5.5-6.5 mEq/L.

At a serum potassium level of 6.5-8.0 mEq/L, in addition to peaked T waves, the ECG shows the following:

  • Prolonged PR interval

  • Decreased or disappearing P wave

  • Widening of the QRS (see the images below)

  • Amplified R wave

    Widened QRS complexes in hyperkalemia. Widened QRS complexes in hyperkalemia.
    Widened QRS complexes in patient whose serum potas Widened QRS complexes in patient whose serum potassium level was 7.8 mEq/L.

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