title: Congenital long QT 3 in the pediatric population.
abstract: There is insufficient knowledge concerning long-QT (LQT) 3 in the pediatric population to determine whether recommendations for more aggressive therapy in these patients are appropriate. An international multicenter review of 43 children with cardiac sodium channel (SCN5A) mutations and clinical manifestations of LQT syndrome without overlap of other SCN5A syndromes was undertaken to describe the clinical characteristics of LQT3 in children. Patients were aged 7.6 ± 5.9 years at presentation and were followed for 4.7 ± 3.9 years. There was significant intrasubject corrected QT interval (QTc) variability on serial electrocardiography. Forty-two percent presented with severe symptoms or arrhythmia and exhibited longer QTc intervals compared to asymptomatic patients. None of the 14 patients who underwent primary prevention implantable cardioverter-defibrillator (ICD) implantation received appropriate shocks in 41 patient-years of follow-up, while 2 of 6 patients who underwent secondary prevention ICD implantation received appropriate shocks in 30 patient-years of follow-up. Half of patients who underwent ICD implantation experienced inappropriate shocks or ICD-related complications. Mexiletine significantly shortened the QTc interval, and QTc shortening was greater in patients with longer pretreated QTc intervals. Two ICD patients with frequent appropriate ICD shocks showed immediate clinical improvement, with elimination of appropriate ICD shocks after mexiletine loading. In conclusion, severe symptoms are common in children with LQT3 and are associated with longer QTc intervals. ICD implantation is associated with significant morbidity. Mexiletine shortens the QTc interval, and it may be beneficial.
authors.affiliation: Department of Pediatrics, Steven and Alexandra Cohen Children's Medical Center of New York, New Hyde Park, USA. ablaufox@nshs.edu
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Blaufox
authors.forename: Martin
authors.initials: M
authors.lastname: Tristani-Firouzi
authors.forename: Stephen
authors.initials: S
authors.lastname: Seslar
authors.forename: Shubhayan
authors.initials: S
authors.lastname: Sanatani
authors.forename: Bhavya
authors.initials: B
authors.lastname: Trivedi
authors.forename: Peter
authors.initials: P
authors.lastname: Fischbach
authors.forename: Thomas
authors.initials: T
authors.lastname: Paul
authors.forename: Ming-Lon
authors.initials: ML
authors.lastname: Young
authors.forename: Svjetlana
authors.initials: S
authors.lastname: Tisma-Dupanovic
authors.forename: Jennifer
authors.initials: J
authors.lastname: Silva
authors.forename: Bettina
authors.initials: B
authors.lastname: Cuneo
authors.forename: Anne
authors.initials: A
authors.lastname: Fournier
authors.forename: Harinder
authors.initials: H
authors.lastname: Singh
authors.forename: Ronn E
authors.initials: RE
authors.lastname: Tanel
authors.forename: Susan P
authors.initials: SP
authors.lastname: Etheridge
mesh_terms: D000293:Adolescent; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008133:Long QT Syndrome / Q000151:congenital* / Q000453:epidemiology / Q000628:therapy; D008297:Male; D011247:Pregnancy; D015995:Prevalence; D011379:Prognosis; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology
chemical_list: D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents