Updated: 9/20/2018

Torsades de Pointes

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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, and disopyramide) due to ↑ QT interval
      • class III Antiarrhythmics (sotalol and 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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(M1.CV.14.79) A 52-year-old patient with a complicated past medical history becomes unstable in the intensive care unit. His monitor depicts the rhythm shown in Figure A. Which of the following electrolyte disturbances most likely contributed to his current arrhythmia? Tested Concept

QID: 106903
FIGURES:
1

Hyperchloremia

1%

(3/217)

2

Hypophosphatemia

0%

(0/217)

3

Hyperkalemia

36%

(79/217)

4

Hypercalcemia

8%

(17/217)

5

Hypomagnesemia

53%

(116/217)

M 2 E

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(M1.CV.12.222) An ECG from an 8-year-old male with neurosensory deafness and a family history of sudden cardiac arrest demonstrates QT-interval prolongation. Which of the following is this patient most at risk of developing? Tested Concept

QID: 100738
1

Hypertrophic cardiac myopathy

4%

(3/82)

2

Essential hypertension

0%

(0/82)

3

Cardiac tamponade

0%

(0/82)

4

Torsades de pointes

93%

(76/82)

5

First degree atrioventricular block

2%

(2/82)

M 2 E

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