title: Modern Incidence of Complete Heart Block in Patients with L-looped Ventricles: Does Univentricular Status Matter?
abstract: OBJECTIVE
  Individuals with L-transposition of the great arteries and two normally sized ventricles are at risk for complete heart block. Little is known about the incidence of complete heart block in those with a single ventricle L-transposition of the great arteries. In this study, we compare the incidence of complete heart block in a modern cohort of patients with L-looped single ventricle anatomy to patients with L-transposition of the great arteries and two ventricles.
  
  
  METHODS
  We conducted a retrospective cohort study of patients with L-transposition of the great arteries who were seen at Yale-New Haven Hospital between 2001 and 2013. Patients were classified as having isolated L-transposition of the great arteries (group I), L-transposition of the great arteries and major cardiac defects with two-ventricle anatomy (group II), or L-transposition of the great arteries and single ventricle anatomy (group III). We recorded the age of onset and the circumstances of CHB in each group. We calculated the incidence rate of complete heart block and compared this between the groups.
  
  
  RESULTS
  We identified 64 patients with L-transposition of the great arteries, median age of 21 years (range 6 months-52 years): 21 in group I, 15 in group II, and 28 in group III. In total, 15 subjects developed complete heart block, incidence of 21.9% and rate of 1.3% per person years. Although group III patients were significantly less likely to develop complete heart block than dual ventricle patients (7.1% vs. 33% and 40%, P = .01), this difference is not significant when only spontaneous complete heart block was analyzed (P = .16).
  
  
  CONCLUSIONS
  All patients with L-transposition of the great arteries have similar risk of spontaneous complete heart block and should be routinely screened for this complication.
authors.affiliation: Section of Pediatric Cardiology, Department of Pediatrics, Yale University School of Medicine, New Haven, Conn, USA.
authors.forename: M Abigail
authors.initials: MA
authors.lastname: Simmons
authors.affiliation: Section of Pediatric Cardiology, Department of Pediatrics, Yale University School of Medicine, New Haven, Conn, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Rollinson
authors.affiliation: Section of Pediatric Cardiology, Department of Pediatrics, Yale University School of Medicine, New Haven, Conn, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Fishberger
authors.affiliation: Center for Outcomes Research and Evaluation, Yale University/Yale-New Haven Hospital, New Haven, Conn, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Qin
authors.affiliation: Section of Pediatric Cardiology, Department of Pediatrics, Yale University School of Medicine, New Haven, Conn, USA.
authors.forename: John
authors.initials: J
authors.lastname: Fahey
authors.affiliation: Section of Pediatric Cardiology, Departments of Pediatrics and Internal Medicine, Yale University School of Medicine, New Haven, Conn, USA.
authors.forename: Robert W
authors.identifier: http://orcid.org/0000-0002-4956-8604
authors.initials: RW
authors.lastname: Elder
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003237:Connecticut / Q000453:epidemiology; D018572:Disease-Free Survival; D005260:Female; D006327:Heart Block / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D006352:Heart Ventricles / Q000002:abnormalities* / Q000503:physiopathology; D006801:Humans; D015994:Incidence; D007223:Infant; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D014188:Transposition of Great Vessels / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D055815:Young Adult
keywords: Atrioventricular-ventriculoarterial Discordance; Complete AV Block; Complete Heart Block; Congenitally Corrected Transposition of the Great Arteries; L-transposition of the Great Arteries; Third Degree Heart Block