Gender differences in the long QT syndrome: effects of beta-adrenoceptor blockade.
BACKGROUND
Gender differences have been reported in patients with the congenital long QT syndrome (LQTS). We analyzed whether electrocardiographic differences existed in females, males, girls and boys in response to beta-adrenoceptor blockade.


METHODS
12-lead ECGs before and during beta-adrenoceptor blockade were collected in 87 genotyped LQTS patients (48 women, 14 men, 12 girls and 13 boys). Up to three QTc intervals were determined in each lead of the ECG. V4 was used for QT/QTc analysis. Difference between longest and shortest QT interval was taken as a measure for dispersion of QT intervals.


RESULTS
(1) Adult males had the greatest shortening of the QTc interval upon treatment with beta-adrenoceptor blockade. During treatment, adult males with LQTS(1) (mutation in the KCNQ1 gene, affecting I(Ks) current) were found to have shorter QTc intervals than adult females; this difference did not exist in LQTS(2) patients (mutation in the HERG gene, affecting I(Kr) current). (2) Female LQTS(2) patients had a 50% larger dispersion than female LQTS(1) patients both before and during treatment. (3) Adult male LQTS(1) patients constitute the only patient group with a marked decrease in QTc intervals and dispersion associated with a 100% efficacy of treatment in response to beta-adrenoceptor blockade.


CONCLUSIONS
These findings indicate that, in addition to underlying differences in repolarization between men and women, cardiac electrophysiological responses to beta-adrenoceptor blockade can be modulated by gender-related factors.
Conrath
Chantal E
CE
Department of Cardiology, University Medical Center, Utrecht, The Netherlands
Wilde
Arthur A M
AA
Jongbloed
Rosalie J E
RJ
Alders
Mariëlle
M
van Langen
Irene M
IM
van Tintelen
J Peter
JP
Doevendans
Pieter A
PA
Opthof
Tobias
T
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000328:Adult; D000704:Analysis of Variance; D002648:Child; D004562:Electrocardiography; D005260:Female; D005838:Genotype; D006801:Humans; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D008133:Long QT Syndrome / Q000188:drug therapy / Q000235:genetics* / Q000503:physiopathology*; D008297:Male; D009154:Mutation; D020125:Mutation, Missense; D015221:Potassium Channels / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated; D012723:Sex
D000319:Adrenergic beta-Antagonists; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated