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Pediatric Long QT Syndrome Differential Diagnoses

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

Diagnostic Considerations

As previously mentioned, long-QT syndrome can be mistaken for palpitations, neurocardiogenic syncope, and epilepsy.[1] Other conditions to consider in the differential diagnosis of long QT syndrome include the following:

  • Brugada syndrome
  • Short QT syndrome
  • Other causes of sudden cardiac death - Including hypertrophic cardiomyopathy and coronary artery anomalies
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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