High prevalence of four long QT syndrome founder mutations in the Finnish population.
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.
Marjamaa
Annukka
A
Research Program in Molecular Medicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland.
Salomaa
Veikko
V
Newton-Cheh
Christopher
C
Porthan
Kimmo
K
Reunanen
Antti
A
Karanko
Hannu
H
Jula
Antti
A
Lahermo
Päivi
P
Väänänen
Heikki
H
Toivonen
Lauri
L
Swan
Heikki
H
Viitasalo
Matti
M
Nieminen
Markku S
MS
Peltonen
Leena
L
Oikarinen
Lasse
L
Palotie
Aarno
A
Kontula
Kimmo
K
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
D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human