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Pediatric Long QT Syndrome Clinical Presentation

  • Author: Sreekanth S Raghavan, MBBS, , FACC; Chief Editor: Stuart Berger, MD  more...
Updated: Jun 26, 2014


The clinical diagnosis of long QT syndrome is prompted by a high degree of clinical suspicion, which arises from the presenting complaints.[6] A detailed family history for similar symptoms is warranted. The presenting complaints may include the following:

  • Unexplained bradycardia - Especially in the newborn
  • Syncope - Especially when associated with a triggering event (eg, drowning, near drowning)[6]
  • Epilepsy - Especially not controlled by conventional medications
  • Palpitations
  • Aborted or sudden cardiac death in the patient or family history of sudden cardiac death
  • Sudden infant death syndrome (SIDS)
  • Depressive symptoms[7]

Physical Examination

Certain physical findings in long QT syndrome, such as skeletal abnormalities (eg, short stature, scoliosis), may suggest Andersen syndrome, whereas congenital heart diseases, along with cognitive and behavioral problems, musculoskeletal diseases, and immune dysfunction, may suggest Timothy syndrome. Congenital deafness is seen in JLN syndrome, although the incidence of long QT syndrome in patients with congenital deafness is very low.

Contributor Information and Disclosures

Sreekanth S Raghavan, MBBS, , FACC Consulting Pediatric Cardiologist, Head and Director of Pediatric Cardiac Services, Manipal Heart Institute, India

Sreekanth S Raghavan, MBBS, , FACC is a member of the following medical societies: American College of Cardiology, American Society of Echocardiography, Pediatric Cardiac Society of India

Disclosure: Nothing to disclose.

Chief Editor

Stuart Berger, MD Medical Director of The Heart Center, Children's Hospital of Wisconsin; Associate Professor, Department of Pediatrics, Section of Pediatric Cardiology, Medical College of Wisconsin

Stuart Berger, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American College of Chest Physicians, American Heart Association, Society for Cardiovascular Angiography and Interventions

Disclosure: Nothing to disclose.


John W Moore, MD, MPH Professor of Clinical Pediatrics, Section of Pediatric Cardiology, Department of Pediatrics, University of California San Diego School of Medicine; Director of Cardiology, Rady Children's Hospital

John W Moore, MD, MPH is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, and Society for Cardiac Angiography and Interventions

Disclosure: Nothing to disclose.

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

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Marked prolongation of QT interval in a 15-year-old male adolescent with long QT syndrome. Abnormal morphology of repolarization can be observed in almost every lead (ie, peaked T waves, bowing ST segment). Bradycardia is a common feature in patients with long QT syndrome. R-R = 1 s; QT interval = 0.56 s; QT interval corrected for heart rate (QTc) = 0.56 s.
Genetically confirmed long QT syndrome with borderline values of QT corrected for heart rate (QTc) duration in a 12-year-old girl. Note the abnormal morphology of the T wave (notches) in leads V2-V4. R-R = 0.68 s; QT interval = 0.36 s; QTc = 0.44 s.
ECG of a 13-year-old female who had a syncopal event while running to a school bus. She awoke after a few seconds, and her subsequent clinical course was uneventful.
Table 1. Genetic Basis of Long QT Syndrome, Including Jervell and Lang-Nielsen (JLN) Syndrome
Type of Long QT Syndrome Chromosomal Locus Mutated Gene Ion Current Affected
LQT111p15.5KVLQT1or KCNQ1 (heterozygotes)Potassium (IKs)
LQT27q35-36HERG, KCNH2Potassium (IKr)
LQT33p21-24SCN5ASodium (INa)
LQT44q25-27ANK2, ANKBSodium, potassium and calcium
LQT521q22.1-22.2KCNE1 (heterozygotes)Potassium (IKs)
LQT621q22.1-22.2MiRP1, KNCE2Potassium (IKr)
LQT7 (Andersen syndrome)17q23KCNJ2Potassium (IK1)
LQT8 (Timothy syndrome)12q13.3CACNA1CCalcium (ICa-Lalpha)
JLN111p15.5KVLQT1or KCNQ1 (homozygotes)Potassium (IKs)
JLN221q22.1-22.2KCNE1 (homozygotes)Potassium (IKs)
Table 2. Genetic Basis of Long QT Syndrome
Group Prolonged QTc (s) Borderline QTc (s) Reference Range (s)
Children and adolescents (< 15 y)>0.460.44-0.46< 0.44
Men>0.450.43-0.45< 0.43
Women>0.460.45-0.46< 0.45
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