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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Questions (4)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M1.CV.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 may have contributed to his current arrhythmia? Review Topic

QID: 106903
FIGURES:
1

Hyperchloremia

2%

(2/114)

2

Hypophosphatemia

0%

(0/114)

3

Hyperkalemia

34%

(39/114)

4

Hypercalcemia

10%

(11/114)

5

Hypomagnesemia

54%

(61/114)

M1

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PREFERRED RESPONSE 5

(M1.CV.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? Review Topic

QID: 100738
1

Hypertrophic cardiac myopathy

17%

(2/12)

2

Essential hypertension

0%

(0/12)

3

Cardiac tamponade

0%

(0/12)

4

Torsades de pointes

83%

(10/12)

5

First degree atrioventricular block

0%

(0/12)

M1

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PREFERRED RESPONSE 4
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