Long QT syndrome

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Complications

By Mayo Clinic staff

Prolonged Q-T intervals may never cause any problems. However, physical or emotional stress may "trip up" a heart susceptible to prolonged Q-T intervals and cause the heart's rhythm to spin out of control, triggering life-threatening, irregular heart rhythms (arrhythmias) including:

  • Torsades de pointes — 'twists of the points.' This arrhythmia is characterized by your heart's two lower chambers (ventricles) beating fast, making the waves on an ECG monitor look twisted. When this arrhythmia occurs, less blood is pumped out from your heart. Less blood then reaches your brain, causing you to faint suddenly and, often, without any warning.

    If a torsades de pointes episode is short — lasting less than one minute — your heart can correct itself seconds later, and you regain consciousness on your own. However, if a torsades de pointes episode persists, it can lead to a life-threatening arrhythmia called ventricular fibrillation.

  • Ventricular fibrillation. This condition causes the ventricles to beat so fast that your heart quivers and ceases pumping blood. Unless your heart is shocked back into a normal rhythm by a device called a defibrillator, ventricular fibrillation can lead to brain damage and death. It's thought that long QT syndrome may explain some cases of sudden death in young people who otherwise appear healthy.
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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.
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  8. Johnson JN, et al. Identification of a possible pathogenic link between congenital long QT syndrome and epilepsy. Neurology. 2009;72:224.
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  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.
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  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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