Long QT syndrome

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Risk factors

By Mayo Clinic staff

People at risk of long QT syndrome include:

  • Children, teenagers and young adults with unexplained fainting, unexplained near drownings or other accidents, unexplained seizures, or a history of cardiac arrest
  • Family members of children, teenagers and young adults with unexplained fainting, unexplained near drownings or other accidents, unexplained seizures, or a history of cardiac arrest
  • Blood relatives of people with known long QT syndrome
  • People taking medications known to cause prolonged Q-T intervals

Long QT syndrome often goes undiagnosed or is misdiagnosed as a seizure disorder, such as epilepsy. However, researchers believe that long QT syndrome may be responsible for some otherwise unexplained deaths in children and young adults. For example, an unexplained drowning of a young person may be the first clue to inherited long QT syndrome in a family.

People with low potassium, magnesium or calcium blood levels — such as those with the eating disorder anorexia nervosa — may be susceptible to prolonged Q-T intervals. Potassium, magnesium and calcium are all important minerals for the health of your heart's electrical system.

Complications Causes
References
  1. Ackerman MJ, et al. Congenital long QT syndrome. In: Gussak I, et al. Electrical Diseases of the Heart; Genetics, Mechanisms, Treatment, Prevention. New York, NY.: Springer; 2008:462.
  2. Priori SG. Genetics of cardiac arrhythmias. In: Libby P, et al, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2007. http://www.mdconsult.com/book/player/book.do?method=display&type=bookPage&decorator=header&eid=4-u1.0-B978-1-4160-4106-1..50012-1--cesec6&uniq=174957165&isbn=978-1-4160-4106-1&sid=927975209#lpState=open&lpTab=contentsTab&content=4-u1.0-B978-1-4160-4106-1..50012-1--cesec1%3Bfrom%3Dtoc%3Btype%3DbookPage%3Bisbn%3D978-1-4160-4106-1. Accessed Dec. 10, 2009.
  3. Spazzolini C, et al. Clinical implications for patients with long QT syndrome who experience a cardiac event during infancy. Journal of the American College of Cardiology. 2009;54:832.
  4. Goldenberg I, et al. Risk factors for aborted cardiac arrest and sudden cardiac death in children with the congenital long-QT syndrome. Circulation. 2008;117:2184.
  5. Hobbs JB, et al. Risk of aborted cardiac arrest of sudden cardiac death during adolescence in the long QT syndrome. Journal of the American Medical Association. 2006;296:1249.
  6. Sauer AJ, et al. Long QT syndrome in adults. Journal of the American College of Cardiology. 2007;49:329.
  7. Goldenberg I, et al. Long-QT syndrome after age 40. Circulation. 2008;117:2192.
  8. Johnson JN, et al. Identification of a possible pathogenic link between congenital long QT syndrome and epilepsy. Neurology. 2009;72:224.
  9. Tester DJ, et al. Cardiomyopathic and channelopathic causes of sudden unexplained death in infants and children. Annual Review of Medicine. 2009;60:69.
  10. Tester DJ, et al. Effect of clinical phenotype on yield of long QT syndrome genetic testing. Journal of the American College of Cardiology. 2006;47:764.
  11. Kapa S, et al. Genetic testing for long QT syndrome - Distinguishing pathogenic mutations from benign variants. Circulation. 2009;120:1752.
  12. Ackerman MJ, et al. Molecular diagnosis of the inherited long-QT syndrome in a woman who died after near-drowning. New England Journal of Medicine. 1999;341:1121.
  13. Tester DJ, et al. Postmortem long QT syndrome genetic testing for sudden unexplained death in the young. Journal of the American College of Cardiology. 2007;49:240.
  14. Genetic testing: Where to start. The Sudden Arrhythmia Death Syndromes (SADS) Foundation. http://www.sads.org/index.php/General/Where-to-Start.html. Accessed Feb. 6, 2010.
  15. Taggart NW, et al. Diagnostic miscues in congenital long QT syndrome. Circulation. 2007;115:2613.
  16. Collura CA, et al. Left cardiac sympathetic denervation for the treatment of long QT syndrome and catecholaminergic polymorphic ventricular tachycardia using video-assisted thoracic surgery. Heart Rhythm. 2009;6:752.
  17. Zipes DP, et al. Journal of the American College of Cardiology. 2005;45:1354.
  18. Farnsworth MM, et al. When I go in to wake them ... I Wonder: Parental perceptions about congenital long QT syndrome. Journal of the American Academy of Nurse Practitioners. 2006;18:284.
  19. Ackerman MJ (expert opinion). Mayo Clinic, Rochester, Minn. Feb. 1, 2010.
  20. Anand RG, et al. The role of fish oil in arrhythmia prevention. Journal of Cardiopulmonary Rehabilitation and Prevention. 2008;28:92.
DS00434 March 2, 2010

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