Diagnosis of congenital long QT syndrome
- Stephen P Seslar, MD, PhD
Stephen P Seslar, MD, PhD
- Assistant Professor of Cardiology and Pediatrics
- University of Washington
- Peter J Zimetbaum, MD
Peter J Zimetbaum, MD
- Section Editor — Cardiac Arrhythmias
- Professor of Medicine
- Harvard Medical School
- Charles I Berul, MD
Charles I Berul, MD
- Section Editor — Cardiac Arrhythmias
- Professor of Pediatrics
- George Washington University
- Section Editors
- John K Triedman, MD
John K Triedman, MD
- Section Editor — Pediatric Cardiology
- Professor of Pediatrics
- Harvard Medical School
- Samuel Asirvatham, MD
Samuel Asirvatham, MD
- Section Editor — Long QT Syndrome
- Professor of Medicine and Pediatrics
- Mayo Clinic College of Medicine
The long QT syndrome (LQTS) is a disorder of ventricular myocardial repolarization characterized by a prolonged QT interval on the electrocardiogram (ECG) (waveform 1) that can lead to symptomatic ventricular arrhythmias and can lead to an increased risk of sudden cardiac death [1-3]. This syndrome is associated with an increased risk of a characteristic life-threatening cardiac arrhythmia, known as torsades de pointes or "twisting of the points" (waveform 2) [4,5]. The primary symptoms in patients with LQTS include palpitations, syncope, seizures, and cardiac arrest.
The long QT syndrome may be congenital or acquired [6-9]. Mutations in at least 13 genes have been identified thus far in patients with genetic LQTS; the distinct genetic types are designated LQT 1 through 13 (table 1). (See "Genetics of congenital and acquired long QT syndrome".)
Two clinical phenotypes have been described in congenital LQTS that vary with the type of inheritance and the presence or absence of sensorineural hearing loss :
●The more common autosomal dominant form, the Romano-Ward syndrome, has a purely cardiac phenotype.
●The autosomal recessive form (or compound heterozygous), the Jervell and Lange-Nielsen (JLN) syndrome, is associated with LQTS and sensorineural deafness. (See "Clinical features of congenital long QT syndrome", section on 'Congenital sensorineural deafness'.)
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- ECG FEATURES
- QT interval
- - Measurement
- - Impact of U waves
- - Special circumstances
- - Correction for rate
- - Normal range
- - Automated measurements
- - Recommendations
- Other ECG features
- - T wave morphology
- - T wave alternans
- - QT dispersion
- LQTS score
- Exercise testing
- - Exercise-recovery QTc
- Summary of initial diagnostic strategy
- Additional testing
- - Ambulatory ECG monitoring
- - Electrophysiology study
- - Drug testing
- - Facial immersion test
- - Genetic testing
- SUMMARY AND RECOMMENDATIONS