Torsades de pointes
Torsades de pointes is a polymorphic ventricular tachycardia occurring on a background of QT prolongation, with a characteristic twisting of QRS complexes around the baseline. Management is intravenous magnesium, correction of the underlying QT-prolonging cause, and rate acceleration by pacing or isoproterenol; unstable episodes are defibrillated.
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What this article covers
- Overview
Definition: torsades de pointes is a polymorphic ventricular tachycardia arising on a background of QT prolongation, with QRS complexes that appear to twist around the isoelectric baseline.
- Epidemiology
Most commonly acquired, from QT-prolonging drugs and electrolyte disturbance.
- Risk factors
QT-prolonging drugs: antiarrhythmics (sotalol, dofetilide, quinidine), macrolides, fluoroquinolones, antipsychotics, methadone, and ondansetron.
- Pathophysiology
Prolonged repolarization: delayed ventricular repolarization (a long QT) lengthens the vulnerable period.
- Clinical features
Palpitations, presyncope, and syncope. Often self-terminating, with recurrent runs.
- Differential diagnosis
Monomorphic ventricular tachycardia: a uniform QRS morphology, distinguished by a constant single QRS shape rather than the twisting axis of torsades (ventricular tachycardia).
- Diagnosis
Establish with an ECG showing polymorphic VT with a twisting QRS axis on a background of a prolonged QT: the diagnostic basis is a rhythm strip demonstrating the characteristic twisting polymorphic…
- Management
First-line, defibrillate if unstable and give magnesium: deliver an unsynchronized shock for pulseless or hemodynamically unstable torsades, and give magnesium sulfate 2 g IV over 1 to 2 minutes (repeat once), then an infusion.
- Complications
Ventricular fibrillation and sudden cardiac death.
- Prognosis
Excellent when acquired and the cause is corrected.
- Prevention
Avoid combinations of QT-prolonging drugs, and monitor the QT when they are needed.
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Related articles
- Long QT syndrome
Long QT syndrome is prolonged ventricular repolarization, congenital or acquired, that predisposes to torsades de pointes and sudden death. Diagnosis rests on a prolonged corrected QT with clinical and genetic features, and management centers on beta-blockade, avoiding QT-prolonging drugs, and an ICD for high-risk patients.
- Ventricular fibrillation
Ventricular fibrillation is chaotic, disorganized ventricular electrical activity with no effective contraction, producing immediate loss of cardiac output and cardiac arrest. It is the leading shockable arrest rhythm, and survival depends on immediate CPR and defibrillation, followed by treatment of the cause and an ICD for secondary prevention.
- Ventricular tachycardia
Ventricular tachycardia is three or more consecutive ventricular beats at over 100 per minute, a wide-complex tachycardia that is life-threatening when sustained. Any regular wide-complex tachycardia is ventricular tachycardia until proven otherwise: unstable patients are cardioverted or defibrillated, and long-term risk is managed with an implantable defibrillator.