• Potassium (K⁺)
• Causes of Hypokalemia
• ECG and Hypokalemia
• Arrhythmias and Hypokalemia

Potassium (K⁺)

• Potassium is the main intracellular cation
• The physiological concentration is 3.4 - 5.6 mmol/l
• Hypokalemia has 3 stages:
• Mild (3 - 3.4 mmol/l) hypokalemia
• Moderate (2.5 - 3 mmol/l) hypokalemia
• Severe (< 2.5 mmol/l) hypokalemia
• Hypokalemia
• Prolongs repolarization of the atria and ventricles
  
  
• Potassium is mainly found in
• Bananas, potatoes, beans

ECG and Hypokalemia

• ECG changes occur with hypokalemia < 2.7 mmol/l
• The degree of hypokalemia slightly correlates with the ECG findings
  
  
• When potassium falls below 2.7 mmol/l, the following occur:
• Dominant U wave (higher than the T wave)
• Prolongation of QT (QU) interval
• Flattened to negative T wave
• Prolongation of PQ interval
  
  
• Mild ST depressions
• Enlargement of P wave

Hypokalemia (1.7 mmol/l)

• ST depressions (I, II, V4 - V5)
• Negative T waves (V2 - V6)
• Positive U waves (V2 - V6)
• Prolonged QT (QU) interval ( > 0.44s)
• Risk of malignant ventricular arrhythmia Torsades de Pointes

Hypokalemia (1.9 mmol/l) and Torsades de Pointes

• ST depressions (II, III, aVF)
• Present U wave
• Prolonged QT (QU) interval ( > 0.44s)
• R-on-T phenomenon triggered malignant ventricular arrhythmia Torsades de Pointes