title: Location of mutation in the KCNQ1 and phenotypic presentation of long QT syndrome.
abstract: BACKGROUND
  Recent data showed that long QT syndrome (LQTS) patients with mutations in the pore region of the HERG (LQT2) gene have significantly higher risk of cardiac events than subjects with mutations in the non-pore region. The aim of this study was to determine whether there is an association between the location of mutations in the KCNQ1 gene and cardiac events in LQT1 patients.
  
  
  RESULTS
  The study population consisted of 294 LQT1 patients with KCNQ1 gene mutations. Demographic, clinical, and follow-up information was compared among subjects with different locations of KCNQ1 mutations defined as pre-pore region including N-terminus (1-278), pore region (279-354), and post-pore region including C-terminus (>354). Cardiac events observed during follow-up from birth until age of last contact or age 40 years were defined as syncope, cardiac arrest, or sudden death. There were 164 (56%) LQT1 patients with pre-pore mutations, 101 (34%) with pore mutations, and 29 (10%) with post-pore mutations. QTc duration did not differ significantly among the three subgroups (mean QTc = 494, 487, and 501 ms, respectively). There was no significant difference between groups with regard to the risk of cardiac events by age 40 years.
  
  
  CONCLUSIONS
  There are no significant differences in clinical presentation, ECG parameters, and cardiac events among LQT1 patients with different locations of KCNQ1 mutations. These findings indicate that factors other than location of mutation influence clinical phenotype in patients with LQT1 mutations.
authors.affiliation: Cardiology Unit of the Department of Medicine, Heart Research Follow-up Program, Box 653, University of Rochester Medical Center, Rochester, NY 14642, USA. wojciech.zareba@urmc.rochester.edu
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Moss
authors.forename: Gloria
authors.initials: G
authors.lastname: Sheu
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Kaufman
authors.forename: Silvia
authors.initials: S
authors.lastname: Priori
authors.forename: G Michael
authors.initials: GM
authors.lastname: Vincent
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Towbin
authors.forename: Jesaia
authors.initials: J
authors.lastname: Benhorin
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Schwartz
authors.forename: Carlo
authors.initials: C
authors.lastname: Napolitano
authors.forename: W Jackson
authors.initials: WJ
authors.lastname: Hall
authors.forename: Mark T
authors.initials: MT
authors.lastname: Keating
authors.forename: Ming
authors.initials: M
authors.lastname: Qi
authors.forename: Jennifer  L
authors.initials: J
authors.lastname: Robinson
authors.forename: Mark L
authors.initials: ML
authors.lastname: Andrews
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D018572:Disease-Free Survival; D004562:Electrocardiography / Q000706:statistics & numerical data*; D005260:Female; D020869:Gene Expression Profiling; D020022:Genetic Predisposition to Disease / Q000453:epidemiology*; D006801:Humans; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D008133:Long QT Syndrome / Q000145:classification / Q000453:epidemiology* / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D015221:Potassium Channels / Q000235:genetics*; D024642:Potassium Channels, Voltage-Gated; D018570:Risk Assessment / Q000379:methods; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D014481:United States
chemical_list: D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated