Torsade de Pointes (TdP)

Introduction

Is a form of a polymorphic ventricular tachycardia associated with a long QT interval on the resting ECG. TdP is characterized by morphology in which the QRS complexes “twist” around the isoelectric line (cycling of the QRS axis through 180 degrees every 5 to 20 beats).

It occurs in the setting of acquired or congenital QT interval prolongation and typically has a rate between 160 and 250 beats per minute. 

Drug-related TdP ia caused by early afterdepolarizations and triggered activity resulting from prolonged repolarization.

Symptoms

TdP usually leads to hemodynamic instability and collapse. Moreover TdP can also degenerate into ventricular fibrillation.

Treatment

  • Withdrawal of any QTc prolonging drugs 
  • Correction of electrolyte abnormalities (potassium repletion up to 4.5 to 5 mmol/liter).
  • MgSO4 1-2 g i.v (decreases early afterdepolarizations- magnesium achieves this by decreasing the influx of calcium, thus lowering the amplitude of EADs)
    - magnesium can be given at 1-2 g IV initially in 30-60 seconds, which then can be repeated in 5-15 minutes. Alternatively, a continuous infusion can be started at a rate of 3-10 mg/min.
  • DC version
  • Beta blockers as a prevention to patients with congenital LQT
  • ICD implantation

ECG 1  Torsade de Pointes episode in a patient with drug induced LQT

TdP.jpg

ECG 2 R on T phenomenon leading to TdP in a patient with LQT

ECG 3 Long QT interval associated with TdP


References

  1. Priori SG, Blomström-Lundqvist C, Mazzanti A, Blom N, Borggrefe M, Camm J, Elliott PM, Fitzsimons D, Hatala R, Hindricks G, Kirchhof P, Kjeldsen K, Kuck KH, Hernandez-Madrid A, Nikolaou N, Norekvål TM, Spaulding C, Van Veldhuisen DJ; Task Force for the Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death of the European Society of Cardiology (ESC). 2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: The Task Force for the Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death of the European Society of Cardiology (ESC)Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC). Europace. 2015 Nov;17(11):1601-87. doi: 10.1093/europace/euv319. Epub 2015 Aug 29. PMID: 26318695.
  2. Long QT syndrome. UpToDate. 
  3. https://en.ecgpedia.org/wiki/Long_QT_Syndrome
  4. https://litfl.com/qt-interval-ecg-library/