National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Long QT syndrome

Not a rare disease Not a rare disease
Long QT syndrome is a disorder of the heart’s electrical activity that can cause sudden, uncontrollable, and irregular heartbeats (arrhythmia), which may lead to sudden death. Long QT syndrome can be detected by electrocardiogram (EKG). It can be caused by a variety of different gene mutations (changes). It can also be acquired (noninherited) and may be brought on by certain medicines and other medical conditions.[1]
Last updated: 10/4/2013
Signs and symptoms of the arrhythmias experienced by people with long QT syndrome includes unexplained fainting, seizures, drowning or near drowning, and sudden cardiac arrest or death.[1] You can read more about these and other symptoms of long QT syndrome on the National Heart Lung and Blood Institute's Web site by clicking here.
Last updated: 10/4/2013

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Arrhythmia
Abnormal heart rate
Heart rhythm disorders
Irregular heart beat
Irregular heartbeat
[ more ] 		0011675
Sensorineural hearing impairment 0000407
30%-79% of people have these symptoms
Atrioventricular block
Interruption of electrical communication between upper and lower chambers of heart
0001678
5%-29% of people have these symptoms
Abdominal situs inversus 0003363
Anemia
Low number of red blood cells or hemoglobin
0001903
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Last updated: 7/1/2020
Acquired long QT syndrome can be caused by certain medicines and medical conditions. Some medications that cause long QT syndrome include antihistamines and decongestants, antibiotics, antidepressants, and cholesterol-lowering medicines. Examples of medical conditions that can cause long QT syndrome include excessive diarrhea or vomiting and certain thyroid disorders.[1]

Inherited forms of long QT syndrome are caused by changes in genes that control the heart muscle’s electrical activity.[1] Inherited long QT syndrome may be isolated (occur alone without other associated symptoms) or be due to a genetic syndrome, such as Romano-Ward syndrome, Jervell Lang-Nielsen syndrome, Anderson-Tawil syndrome, and Timothy syndrome.[2]
Last updated: 10/4/2013
Long QT syndrome is diagnosed on the basis of electrocardiographic (EKG) findings, clinical findings such as congenital deafness or unexplained fainting, and family history of long QT syndrome or sudden cardiac death. Genetic testing is often performed in families in whom the diagnosis of long QT syndrome has been made or is suspected on clinical grounds.
Last updated: 10/4/2013

Testing Resources

  • Orphanet lists international laboratories offering diagnostic testing for this condition.

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to Long QT syndrome. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.
  • Orphanet lists European clinical trials, research studies, and patient registries enrolling people with this condition. 
  • The Research Portfolio Online Reporting Tool (RePORT) provides access to reports, data, and analyses of research activities at the National Institutes of Health (NIH), including information on NIH expenditures and the results of NIH-supported research. Although these projects may not conduct studies on humans, you may want to contact the investigators to learn more. To search for studies, enter the disease name in the "Text Search" box. Then click "Submit Query".

Patient Registry

  • A registry supports research by collecting of information about patients that share something in common, such as being diagnosed with Long QT syndrome. The type of data collected can vary from registry to registry and is based on the goals and purpose of that registry. Some registries collect contact information while others collect more detailed medical information. Learn more about registries.

    Registries for Long QT syndrome:
    CHD GENES Study
     

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The KidsHealth Web site developed by the Nemours Foundation has an information page on arrhythmias. Click on KidsHealth to view the information page.
  • The Mayo Clinic has developed an information page on long QT syndrome. Click on the Mayo Clinic to view the information page.
  • The National Heart, Lung, and Blood Institute (NHLBI) has information on this topic. NHLBI is part of the National Institutes of Health and supports research, training, and education for the prevention and treatment of heart, lung, and blood diseases.

In-Depth Information

  • The Merck Manuals offers a detailed review article on Long QT syndrome. Click on Merck Manuals to view the article.
  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • MeSH® (Medical Subject Headings) is a terminology tool used by the National Library of Medicine. Click on the link to view information on this topic.
  • Online Mendelian Inheritance in Man (OMIM) lists the subtypes and associated genes for Long QT syndrome in a table called Phenotypic Series. Each entry in OMIM includes a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.

Videos/Presentations

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • I have long QT syndrome, as does many of my family members. Some of these family members have been found to carry a mutation in a long QT syndrome gene, others with the condition do not. How can this be? How can I learn more about genetic testing for this syndrome? Is attention deficit disorder and/or celiac diseases related to long QT syndrome? Is genetic testing for celiac disease available? See answer


  1. Long QT syndrome. National Heart Lung and Blood Institute. 2007; http://www.nhlbi.nih.gov/health/dci/Diseases/qt/qt_all.html. Accessed 12/17/2008.
  2. Sovari AA, Kocheril AG, Assadi R Baas AS, Zareba W, Rosero S. Long QT syndrome. eMedicine. 2010; http://emedicine.medscape.com/article/157826-overview . Accessed 4/15/2011.