title: Congenital long QT syndrome and 2:1 atrioventricular block: an optimistic outcome in the current era.
abstract: BACKGROUND
  Previous studies of patients with long QT syndrome (LQTS) and 2:1 atrioventricular block (AVB) have reported a mortality rate greater than 50% during infancy.
  
  
  OBJECTIVE
  The purpose of this study was to determine the outcome of this high-risk population in the current era.
  
  
  METHODS
  A retrospective study from four tertiary care pediatric centers assessed patients with congenital LQTS and 2:1 AVB from January 2000 to January 2009. All neonates who presented with 2:1 AVB and prolonged QTc unrelated to medication were included in the study. Statistical analysis was performed using a paired t-test. Medical records were reviewed for ECG findings, genotype, medications, and device therapy.
  
  
  RESULTS
  Twelve patients that met the inclusion criteria were identified. All patients underwent diagnostic ECG in the first 24 hours of life. The average QTc interval prior to therapy was 616 +/- 99 ms (range 531-840 ms). Over a follow-up period of 71 +/- 45 months (range 15-158 months), 11 of 12 patients received devices (8 permanent pacemaker, 3 implantable cardioverter-defibrillator). Average age of device placement was 48 months (median 2 months, range 3 days to 10.5 years). All patients were treated with beta-blockers; mexiletine was added in three patients, and mexiletine and flecainide were added in one patient. Three (25%) patients experienced torsades de pointes while receiving beta-blockers, one of which was refractory to medical therapy. This patient underwent left cardiac sympathetic denervation and implantable cardioverter-defibrillator placement. Genotyping was available for 6 (50%) patients (2 SCN5A mutation, 4 KCNH2 mutation). At last follow-up, no mortality was observed. Follow-up QTc intervals had decreased (mean 480 +/- 20 ms, range 450-507 ms, P <.002).
  
  
  CONCLUSIONS
  Management of patients with LQTS and 2:1 AVB presents unique challenges. Despite historical data indicating poor prognosis, our study represents a cohort of high-risk LQTS patients with a relatively optimistic outcome. This finding reflects early diagnosis and intervention, coupled with improved management strategies, in the current era.
authors.affiliation: Division of Cardiology, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA. aziz@email.chop.edu
authors.forename: Peter F
authors.initials: PF
authors.lastname: Aziz
authors.forename: Ronn E
authors.initials: RE
authors.lastname: Tanel
authors.forename: Ilana J
authors.initials: IJ
authors.lastname: Zelster
authors.forename: Robert H
authors.initials: RH
authors.lastname: Pass
authors.forename: Tammy S
authors.initials: TS
authors.lastname: Wieand
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Vetter
authors.forename: R Lee
authors.initials: RL
authors.lastname: Vogel
authors.forename: Maully J
authors.initials: MJ
authors.lastname: Shah
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D054537:Atrioventricular Block / Q000151:congenital / Q000188:drug therapy / Q000473:pathology* / Q000628:therapy; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D017147:Defibrillators, Implantable; D005260:Female; D005424:Flecainide / Q000627:therapeutic use; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008133:Long QT Syndrome / Q000151:congenital / Q000188:drug therapy / Q000473:pathology* / Q000628:therapy; D008297:Male; D008801:Mexiletine / Q000627:therapeutic use; D015999:Multivariate Analysis; D011379:Prognosis; D011412:Propanolamines / Q000627:therapeutic use; D011433:Propranolol / Q000627:therapeutic use; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D016171:Torsades de Pointes / Q000151:congenital / Q000188:drug therapy / Q000473:pathology* / Q000628:therapy; D016896:Treatment Outcome
chemical_list: D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents; D011412:Propanolamines; D008801:Mexiletine; D011433:Propranolol; D005424:Flecainide; C036604:esmolol