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Updated: Dec 7 2021

Torsades de Pointes

  • Snapshot
    • A 45-year-old woman presents to the emergency room for a syncopal episode. She currently experiences lightheadedness and palpitations. Her medications include ondansetron and oral contraceptives. An electrocardiogram reveals torsades de pointes. She is given magnesium sulfate.
  • Introduction
    • Clinical definition
      • a polymorphic ventricular tachycardia characterized by sinusoidal and cyclic alterations on electrocardiogram (ECG)
    • Associated conditions
      • congenital long QT syndrome
        • Jervell and Lange-Nielsen syndrome
          • autosomal recessive
          • associated with congenital sensorineural deafness
        • Romano-Ward syndrome
          • autosomal dominant
          • no sensorineural deafness
  • Epidemiology
    • Demographics
      • female > male
        • women have longer QT intervals
    • Risk factors
      • ↓ magnesium
      • ↓ potassium
  • Etiology
    • Familial
    • Drugs (ABCDE)
      • class IA Antiarrhythmics (quinidine, procainamide, and disopyramide) due to ↑ QT interval
      • class III Antiarrhythmics (sotalol and ibutilide)
      • antiBiotics
      • antipsyChotics
      • antiDepressants
      • antiEmetics
      • diuertics (e.g., furosemide)
    • Pathogenesis
      • torsades de pointes is thought to result from prolonged repolarization and early afterdepolarizations
        • when early afterdepolarizations reach the threshold potential and depolarize the cell membrane, triggered activity occurs, resulting in additional action potentials
          • the triggered activity can produce torsades de pointes in susceptible patients
  • Presentation
    • Symptoms
      • palpitations
      • dizziness
      • syncope
      • symptoms may be triggered by stress
      • sudden cardiac death
    • Physical exam
      • tachycardia
      • pallor
  • Studies
    • Labs
      • serum electrolytes (↓ magnesium and potassium)
    • Electrocardiogram (ECG)
      • if in sinus rhythm
        • prolonged QT interval
        • pathological U waves
      • if in an episode
        • change in polarity of QRS around the isoelectric line
        • sinusoidal waveform
  • Differential
    • Supraventricular tachycardia
      • distinguishing factor
        • non-sinusoidal waveforms on electrocardiogram
  • Diagnosis
    • Making the diagnosis
      • based on clinical presentation and electrocardiogram
  • Treatment
    • Conservative
      • discontinue all QT prolonging drugs
        • indication
          • for all patients
        • outcomes
          • torsades de pointes due to drugs typically do not recur after withdrawal of the drug
    • Medical
      • magnesium sulfate
        • indications
          • for all patients
        • mechanism of action
          • suppresses early afterdepolarizations to terminate the arrhythmia
          • Mg2+ decreases the influx of calcium and lowers the amplitude of the early afterdepolarizations
      • β-antagonists
        • indications
          • long-term therapy for patients with congenital long QT syndrome
          • only for those without bradycardia
        • drugs
          • propranolol
          • esmolol
    • Operative
      • pacing
        • indication
          • long-term therapy for patients who are symptomatic despite pharmacologic treatment
          • typically for patients with congenital long QT syndrome
  • Complications
    • Ventricular fibrillation
  • Prognosis
    • Usually preceded by a period of long QT intervals
    • Typically resolves spontaneously but may degenerate into ventricular fibrillation and death
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