KCNQ1 and familial long QT syndrome: In summary, our study identified two novel mutations causing LQTS, the L187P mutation in KCNQ1 and the 2020insAG mutation in KCNH2. Most interestingly, we showed that the rare T allele of SNP K897T conferred a protective effect on LQTS patients with KCNH2 mutation A490T located in cis orientation.