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Qt Syndrome, Prolonged

Qt Syndrome, Prolonged is a topic covered in the 5-Minute Emergency Consult.

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A disorder of myocardial repolarization characterized by a prolonged QT interval on the electrocardiogram
  • The pathophysiology is complex and incompletely understood:
    • Alteration in cardiac sodium, potassium, or calcium ion flow
    • Imbalance in the sympathetic innervation of the heart
  • Prolonged ventricular repolarization results in lengthening of QT interval on surface ECG:
    • “Pause-dependent” lengthening due to short–long–short sequence in which a sinus beat is followed by an extrasystole (short), then a postextrasystolic pause (long), concluding with a ventricular extrasystole (short)
    • “Adrenergic-dependent” pauses found in congenital cases
  • Symptoms often preceded by vigorous exercise, emotional stress, or loud noise.
  • Nocturnal bradycardia can lengthen QT interval, causing sleep-related symptoms.
  • Re-entrant rhythm can lead to torsades de pointes, ventricular tachycardia, and ventricular fibrillation.
  • Hemodynamic compromise following dysrhythmia leads to syncope or death.
  • Independent risk factor for sudden cardiac death.

Risk Factors

  • 10 genes linked to long QT syndrome:
    • Autosomal recessive form associated with deafness (Jervell and Lange–Nielsen syndromes)
    • Autosomal dominant form not associated with deafness (Romano–Ward syndrome)
    • Adrenergic stimulation (fright, exertion, delirium tremens, and loud auditory stimulus) becomes prodysrhythmic in certain genotypes, while sleep-related symptoms are found in others.
  • 10–15% of carriers have baseline normal QTc.
  • Death occurs in 1–2% of untreated patients per year.
    • Drug-induced QT prolongation may also have a genetic background.
    • Congenital form occurs in 1 in 3,000–5,000, with mortality of 6% by age 40 yr.

Pediatric Considerations
  • Diagnosis suspected in the young with syncope, cardiac arrest, or sudden death
  • Syncope following emotional stress or exercise suggestive
  • Death occurs without preceding symptoms in 10% of pediatric patients.


  • Drugs:
    • Complete list at http://www.QTDrugs.org
    • Class Ia antidysrhythmics—quinidine, procainamide, disopyramide
    • Class III antidysrhythmics—sotalol, ibutilide, amiodarone
    • Antibiotics—erythromycin, pentamidine, chloroquine, trimethoprim–sulfamethoxazole
    • Antifungal agents—ketoconazole, itraconazole
    • Psychotropic drugs—phenothiazines, haloperidol, risperidone, STCAs
    • Cisapride
    • Antihistamines
    • Organophosphates
    • Narcotics—methadone
  • Electrolyte abnormalities
    • Hypokalemia
    • Hypomagnesemia
    • Hypocalcemia
  • Cardiac
    • Bradyarrhythmias
    • Arteriovenous block
    • Mitral valve prolapse
    • Myocarditis
    • Myocardial ischemia
  • CNS
    • Subarachnoid hemorrhage
    • Stroke
  • Congenital (idiopathic)
  • Other
    • Protein-sparing fasting
    • Anorexia nervosa
    • Hypothyroidism
    • Hypothermia

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Rosen, Peter, et al., editors. "Qt Syndrome, Prolonged." 5-Minute Emergency Consult, 5th ed., Lippincott Williams & Wilkins, 2016. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307507/all/Qt_Syndrome__Prolonged.
Qt Syndrome, Prolonged. In: Rosen P, Shayne P, Barkin AZ, et al, eds. 5-Minute Emergency Consult. 5th ed. Lippincott Williams & Wilkins; 2016. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307507/all/Qt_Syndrome__Prolonged. Accessed April 24, 2019.
Qt Syndrome, Prolonged. (2016). In Rosen, P., Shayne, P., Barkin, A. Z., Wolfe, R. E., Hayden, S. R., Barkin, R. M., & Schaider, J. J. (Eds.), 5-Minute Emergency Consult. Available from https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307507/all/Qt_Syndrome__Prolonged
Qt Syndrome, Prolonged [Internet]. In: Rosen P, Shayne P, Barkin AZ, Wolfe RE, Hayden SR, Barkin RM, Schaider JJ, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. [cited 2019 April 24]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307507/all/Qt_Syndrome__Prolonged.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Qt Syndrome, Prolonged ID - 307507 ED - Rosen,Peter, ED - Shayne,Philip, ED - Barkin,Adam Z, ED - Wolfe,Richard E, ED - Hayden,Stephen R, ED - Barkin,Roger M, ED - Schaider,Jeffrey J, BT - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307507/all/Qt_Syndrome__Prolonged PB - Lippincott Williams & Wilkins ET - 5 DB - Emergency Central DP - Unbound Medicine ER -