title: High prevalence of four long QT syndrome founder mutations in the Finnish population.
abstract: OBJECTIVE
  Long QT syndrome (LQTS) is an inherited arrhythmia disorder with an estimated prevalence of 0.01%-0.05%. In Finland, four founder mutations constitute up to 70% of the known genetic spectrum of LQTS. In the present survey, we sought to estimate the actual prevalence of the founder mutations and to determine their effect sizes in the general Finnish population.
  
  
  RESULTS
  We genotyped 6334 subjects aged > or =30 years from a population cohort (Health 2000 study) for the four Finnish founder mutations using Sequenom MALDI-TOF mass spectrometry. The electrocardiogram (ECG) parameters were measured from digital 12-lead ECGs, and QT intervals were adjusted for age, sex, and heart rate using linear regression. A total of 27 individuals carried one of the founder mutations resulting in their collective prevalence estimate of 0.4% (95% CI 0.3%-0.6%). The KCNQ1 G589D mutation (n=8) was associated with a 50 ms (SE 7.0) prolongation of the adjusted QT interval (P=9.0x10(-13)). The KCNH2 R176W variant (n=16) resulted in a 22 ms (SE 4.7) longer adjusted QT interval (P=2.1x10(-6)).
  
  
  CONCLUSIONS
  In Finland 1 individual out of 250 carries a LQTS founder mutation, which is the highest documented prevalence of LQTS mutations that lead to a marked QT prolongation.
authors.affiliation: Research Program in Molecular Medicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland.
authors.forename: Annukka
authors.initials: A
authors.lastname: Marjamaa
authors.forename: Veikko
authors.initials: V
authors.lastname: Salomaa
authors.forename: Christopher
authors.initials: C
authors.lastname: Newton-Cheh
authors.forename: Kimmo
authors.initials: K
authors.lastname: Porthan
authors.forename: Antti
authors.initials: A
authors.lastname: Reunanen
authors.forename: Hannu
authors.initials: H
authors.lastname: Karanko
authors.forename: Antti
authors.initials: A
authors.lastname: Jula
authors.forename: Päivi
authors.initials: P
authors.lastname: Lahermo
authors.forename: Heikki
authors.initials: H
authors.lastname: Väänänen
authors.forename: Lauri
authors.initials: L
authors.lastname: Toivonen
authors.forename: Heikki
authors.initials: H
authors.lastname: Swan
authors.forename: Matti
authors.initials: M
authors.lastname: Viitasalo
authors.forename: Markku S
authors.initials: MS
authors.lastname: Nieminen
authors.forename: Leena
authors.initials: L
authors.lastname: Peltonen
authors.forename: Lasse
authors.initials: L
authors.lastname: Oikarinen
authors.forename: Aarno
authors.initials: A
authors.lastname: Palotie
authors.forename: Kimmo
authors.initials: K
authors.lastname: Kontula
mesh_terms: D015331:Cohort Studies; D003430:Cross-Sectional Studies; D000072237:ERG1 Potassium Channel; D004562:Electrocardiography; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics; D005260:Female; D005387:Finland; D018703:Founder Effect; D005820:Genetic Testing; D006801:Humans; D051657:KCNQ1 Potassium Channel / Q000235:genetics; D008133:Long QT Syndrome / Q000175:diagnosis / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D012737:Sex Factors; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human