Torsades de Pointes


  • Torsade de pointes ( TdP ) is a form of polymorphic ventricular pro-arrhythmia
  • Associated with QT interval prolongation and prominent U waves on resting ECG
  • ECG = prolonged re-polarisation and so, early after depolarisation (EAD)
  • Can be congenital
  • Usually acquired due to potassium channel dysfunction
  • It may degenerate to VF


  • Ventricular re-polarisation is initiated by exodus of intracellular K+
  • Drugs can block this K+ channel - delaying re-polarisation (prolonging Q-T interval)
  • Other factors are:
    • Female
    • ↑ Age
    • Electrolyte disturbance CCF, Bradycardia, Ischaemia Congenital Main drug culprits listed below
Torsade de Pointes rhythm strip - Thank you Dr Peter Kearney
Rhythm strip courtesy Dr Peter Kearney

(Drug) Causes

  • Antiarrhythmics especially Class Ia and III
  • Phenothiazines and butyrophenones
  • Tricyclic antidepressants
  • Non-sedative antihistamines
  • Some antibiotics especially macrolides and anti-fungals
  • Organophosphates
  • Cocaine
  • Electrolyte abnormalities (hypokalaemia, hypomangesaemia)
  • SAH


Aim of treatment in TdP :

  1. To treat haemodynamic compromise immediately
  2. To alter the after-depolarisation effect
  3. To shorten the QT interval
  4. Haemodynamic compromise requires immediate DC cardioversion. (Synchronised 150-200J)
  5. Magnesium, at a dose of 2g magnesium sulphate intravenously over one to two minutes, is used to suppress EAD`s in the emergency situation. The serum magnesium level need not be known prior to treatment
  6. Correction of hypokalaemia to a serum K+ concentration of > 4.5 mmol/l also helps suppress EAD`s
  7. Lignocaine has been used:
    1. However its effect is inconsistent with a reported success rate of only 50%
  8. Cardiac pacing at 100-140/min is the treatment of choice. The basic heart rate should be accelerated, as there is an inverse relationship between rate and the re-polarisation duration
  9. Isoprenaline should only be a temporising measure as in can promote EADs
  10. Involve a cardiologist early

Content by Dr Íomhar O' Sullivan . Last review Dr ÍOS 11/04/23.