Electrolyte Disorders

Hypercalcemia

Hypercalcemia results in a faster repolarization. Characteristics of hypercalcemia:

• mild: broad based tall peaking T waves
• severe: extremely wide QRS, low R wave, disappearance of p waves, tall peaking T waves.

Hypocalcimia

ECG-characteristics of hypocalcemia:

• narrowing of the QRS complex
• reduced PR interval
• T wave flatteing and inversion
• prolongation of the QT-interval
• prominent U-wave
• prolonged ST and ST-depression

Hyperkalemia

Extreme hyperkalemia. No p-waves, wide QRS, tall peaking T waves.

Same patient after partial correction of the potassium level. Still no p-waves visible, wide QRS, tall peaking T waves.

ECG characteristics of hyperkalemia:

• Tall peaked T waves
• Flattening p-waves. In extreme hyperkalemia p-waves may disappear altogether.
• Prolonged depolarization leading to QRS widening (nonspecific intraventricular conduction defect) sometimes > 0.20 seconds

At concentrations > 7.5 mmol/L atrial and ventricular fibrillation can occur.

Hypokalemia

Consecutive ECGs of a patient with hypokalemia. ECG1

Consecutive ECGs of a patient with hypokalemia. ECG2

Consecutive ECGs of a patient with hypokalemia. After correction of potassium levels.

Hypokalemia is a low blood potassium level. This results in:

• ST depression and flattening of the T wave
• Negative T waves
• A U-wave may be visible