Association of KCNQ1, KCNE1, KCNH2 and SCN5A polymorphisms with QTc interval length in a healthy population

The QT interval (QT) reflects cardiac ventricular repolarization and varies according to various known factors such as heart rate, gender and age. Nevertheless, a high intrasubject stability of the QT-RR pattern also suggests that a genetic component contributes to individual QT length. To determine whether single nucleotide polymorphisms (SNPs) in genes encoding cardiac ion channels were associated with the heartrate corrected QT (QTc) length, we analyzed two groups of 200 subjects presenting the shortest and the longest QTc from a cohort of 2008 healthy subjects. A total of 17 polymorphisms were genotyped; they were all in the Hardy - Weinberg equilibrium in both groups. Neither allele nor haplotype frequencies of the 10 KCNQ1 SNPs showed a significant difference between the two groups. In contrast, KCNH2 2690 C (K897T) and SCN5A 5457 T (D1819D) minor alleles were significantly more frequent in the group with the shortest QTc interval, whereas KCNE1 253 A (D85N), SCN5A 1673 G (H558R) and 1141- 3 A minor alleles were significantly more frequent in the group with the longest QTc interval. Interestingly, an interaction was also found between the KCNH2 2690 A > C SNP and the KCNQ1 2031+932 A > G SNP suggesting that the effect of the KCNH2 2690 C allele on QTc length may occur within a particular genetic background. This suggests that genetic determinants located in KCNQ1, KCNE1, KCNH2 and SCN5A influence QTc length in healthy individuals and may represent risk factors for arrhythmias or cardiac sudden death in patients with cardiovascular diseases.