A 34-year-old man is admitted because of severe vomiting following prolonged heavy alcohol intake:

• Sinus rhythm, 86/min
• Prolonged Q-TU
• Tall U waves
• Findings compatible with hypokalemia

This patient had been suffering from frequent episodes of severe vomiting. When this ECG was recorded his serum potassium was 2.0 mmol/L.

Shortly after arrival in the Emergency Department the patient has a sudden episode of loss of consciousness without seizures:

• Polymorphic ventricular tachycardia (called “Torsades des pointes” in setting of baseline prolonged QT)
• Ventricular rate approximately 270/min

The arrhythmia subsided spontaneously within 30 seconds and the patient recovered consciousness. He received magnesium sulphate IV. The hypokalemia was treated. Torsades des pointes, a polymorphic ventricular tachycardia, is well known to occur in severe hypokalemia. It is an unstable arrhythmia. It often reverts spontaneously to a more stable rhythm, however, it may degenerate into ventricular fibrillation.