Long QT syndrome

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Symptoms

By Mayo Clinic staff

Many people with long QT syndrome don't have any signs or symptoms. They may be aware of their condition only from results of an electrocardiogram (ECG) performed for an unrelated reason, because they have a family history of long QT syndrome or because of genetic testing results.

For people who do experience signs and symptoms of long QT syndrome, the most common symptoms include:

  • Fainting. This is the most common sign of long QT syndrome. In people with long QT syndrome, fainting spells (syncope) are caused by the heart temporarily beating in an erratic way. These fainting spells may happen when you're excited, angry or scared, or during exercise. Fainting in people with long QT syndrome can occur without warning, such as losing consciousness after being startled by a ringing telephone.

    Signs and symptoms that you're about to faint include lightheadedness, heart palpitations or irregular heartbeat, weakness and blurred vision. However, in long QT syndrome, such warning signs before fainting are unusual.

  • Seizures. If the heart continues to beat erratically, the brain becomes increasingly deprived of oxygen. This can then cause generalized seizures.
  • Sudden death. Normally, the heart returns to its normal rhythm. If this doesn't happen spontaneously and paramedics don't arrive in time to convert the rhythm back to normal with an external defibrillator, sudden death will occur.

Signs and symptoms of inherited long QT syndrome may start during the first months of life, or as late as middle age. Most people who experience signs or symptoms from long QT syndrome have their first episode by the time they reach age 40.

Rarely, signs and symptoms of long QT syndrome may occur during sleep or arousal from sleep.

When to see a doctor
You should see your doctor if you suddenly faint during physical exertion or emotional excitement or after use of a new medication.

Because long QT syndrome can occur in families, see your doctor to be tested for long QT syndrome if a close relative (parent, sibling or child) has been diagnosed with long QT syndrome. 

Causes Definition
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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  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.
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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.
  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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