What are the ECG symptoms of hyperkalemia?

ECG Manifestations of Hyperkalemia

Hyperkalemia produces a progressive sequence of ECG changes that begins with peaked T waves and can evolve to life-threatening cardiac arrhythmias including asystolic cardiac arrest. 1

Progressive ECG Changes Based on Severity

• Early/Mild Hyperkalemia (K+ >5.5 mmol/L)

  • Peaked/tented T waves - earliest and most common ECG finding 1, 2

• Moderate Hyperkalemia

  • Flattened or absent P waves 1, 2
  • Prolonged PR interval 1, 2
  • Widened QRS complex 1
  • Deepened S waves 1

• Severe Hyperkalemia (K+ >6.5 mmol/L)

  • Progressive QRS widening 1, 3
  • Merging of S and T waves 1
  • Development of sine-wave pattern 1, 2
  • Idioventricular rhythms 1
  • Ventricular fibrillation or asystolic cardiac arrest 1

Risk Stratification Using ECG

• The presence of any hyperkalemic ECG abnormality increases the risk of short-term adverse events 3
• Specific high-risk ECG findings include:
  • QRS prolongation (4.7x increased risk of adverse events) 3
  • Bradycardia (HR<50) (12.3x increased risk) 3
  • Junctional rhythm (7.5x increased risk) 3
• Interestingly, peaked T waves alone do not significantly correlate with increased short-term adverse events 3

Important Clinical Considerations

• ECG changes may be the first indicator of hyperkalemia before symptoms appear 1
• The presence of ECG changes indicates severe cardiotoxicity requiring immediate treatment 1, 4
• Not all patients develop ECG changes at the same potassium level 1
• Patients with chronic kidney disease, diabetes, or heart failure may tolerate higher potassium levels without ECG changes 1
• The absence of ECG changes does not rule out dangerous hyperkalemia 1
• All patients who experience short-term adverse events demonstrate at least one hyperkalemic ECG abnormality 3

Common Causes of Hyperkalemia

• Renal failure is the most common cause 1, 4
• Medications that can contribute include:
  • Renin-angiotensin-aldosterone system inhibitors 5, 1
  • Potassium-sparing diuretics 5, 1
  • NSAIDs 5, 1
  • Beta-blockers 5, 1
  • Trimethoprim-sulfamethoxazole 5
  • Heparin 5
  • Calcineurin inhibitors 5

Treatment Approach When ECG Changes Present

• Stabilize myocardial cell membrane with calcium chloride or calcium gluconate 1, 4, 6
• Shift potassium into cells with:
  • Insulin and glucose 1, 4, 6, 7
  • Nebulized beta-2 agonists 1, 4, 6, 7
  • Sodium bicarbonate (if metabolic acidosis present) 1, 6
• Promote potassium excretion with:
  • Diuretics 1, 7
  • Sodium polystyrene sulfonate 1, 7
  • Dialysis for severe cases 1, 6

Clinical Pitfalls to Avoid

• Do not delay treatment when ECG changes are present, as progression to life-threatening arrhythmias can occur rapidly 1, 3
• Consider pseudo-hyperkalemia when ECG findings don't match laboratory values 5, 1
• Review all medications that may affect potassium homeostasis 5, 4
• Remember that patients with chronic hyperkalemia may develop tolerance to higher potassium levels 1
• Adverse events typically occur prior to treatment with calcium and potassium-lowering interventions 3