Hyperkalemia

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Electrocardiographic findings of hyperkalemia tend to follow a progression as toxicity progresses. Often, the earliest finding is narrow-based, peaked T waves, and at the extreme end of the hyperkalemia spectrum, a sine wave morphology is a harbinger of pending ventricular fibrillation. The ECG can be used to predict short-term hyperkalemic adverse events. According to one retrospective study of 188 patients with severe hyperkalemia, the following three findings predicted adverse outcomes within six hours:

  1. Bradycardia < 50 bpm
  2. QRS > 110 ms
  3. Junctional rhythm

Notice that peaked T waves were not found to predict acute adverse outcomes.

 

Expected electrocardiographic changes with given serum potassium levels.

Examples

ECG Showing Hyperkalemia

Hyperkalemia

Very wide QRS of hyperkalemia approaching sine wave morphology.
ECG Showing Hyperkalemia

Hyperkalemia

Features of hyperkalemia include peaked T waves, wide QRS, and flat or absent P wave.
ECG Showing Hyperkalemia

Hyperkalemia

There are signs of left ventricular hypertrophy including large QRS complexes and associated repolarization abnormalities (i.e., asymmetric T wave inversions primarily in the lateral leads). Additionally, there are peaked T waves indicating hyperkalemia.
ECG Showing Digoxin Toxicity

Digoxin Toxicity

This ECG shows the classic "dig effect" (i.e., scooped ST segment) and a junctional bradycardia in a patient with acute renal failure and hyperkalemia.
ECG Showing Hyperkalemia and Hypocalcemia

Hyperkalemia and Hypocalcemia

QT prolongation by way of lengthened ST segment is specific for hypocalcemia (as opposed to broadening of the T wave or T-U fusion). The peaked T waves also suggest hyperkalemia. This is a classic ECG for patients with end-stage renal disease.
ECG Showing Hyperkalemia

Hyperkalemia

Note the "peaked" morphology of the T waves (e.g., narrow base and pointed at the top) and slightly widened QRS. This patient's potassium was 7.5 mmol/L.
ECG Showing Hyperkalemia

Hyperkalemia

Hyperkalemia can mimic STEMI, especially in leads V1 and V2, as with this case. Hyperkalemic changes include widened QRS complexes and peaked T waves. Additionally, it is not uncommon for hyperkalemia to produce changes of sodium channel toxicity including right axis deviation and a tall terminal R in aVR. This patient was mistaken for having an anterior STEMI, and was taken emergently for cardiac catheterization, which failed to reveal an obstructive lesion. The potassium resulted later, and was 9.1 mEq/L.

References

  1. Long B, Warix JR, Koyfman A. Controversies in Management of Hyperkalemia. Journal of Emergency Medicine. 2018;55(2):192-205.
  2. Durfey N, Lehnhof B, Bergeson A, et al. Severe Hyperkalemia: Can the Electrocardiogram Risk Stratify for Short-term Adverse Events? Western Journal of Emergency Medicine. 2017;18(5):963-971.