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Snapshot
  • A 15-year-old girl presents with palpitations and dizziness. She has had similar episodes in the past but has never needed to go to a hospital. Her family history includes sudden cardiac death in her father and congenital sensorineural deafness in multiple family members. An echocardiogram reveals a sinusoidal waveform concerning for torsades de pointes. (Jervell and Lange-Nielsen syndrome)
Introduction
  • Clinical definition
    • a polymorphic ventricular tachycardia characterized by sinusoidal and cyclic alterations on electrocardiogram (ECG)
  • Epidemiology
    • demographics
      • female > male
        • women have longer QT intervals
    • risk factors
      • hypomagnesemia
      • hypokalemia
  • Etiology
    • familial
    • drugs (ABCDE)
      • class IA Antiarrhythmics (quinidine, procainamide, disopyramide) due to ↑ QT interval
      • class III Antiarrhythmics (sotalol, ibutilide) 
      • antiBiotics
      • antipsyChotics
      • antiDepressants
      • antiEmetics
  • 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
  • Associated conditions
    • congenital long QT syndrome
      • Jervell and Lange-Nielsen syndrome
        • autosomal recessive
        • congenital sensorineural deafness
      • Romano-Ward syndrome
        • autosomal dominant
        • no sensorineural deafness
  • Prognosis
    • usually preceded by a period of long QT intervals
    • typically resolves spontaneously, but may degenerate into ventricular fibrillation and death
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
      • a sinusoidal waveform
  • Making the diagnosis
    • based on clinical presentation and electrocardiogram
Differential
  • Supraventricular tachycardia
    • distinguishing factor
      • non-sinusoidal waveforms on 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
        • magnesium decreases 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

References

 

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