KCNQ1 and familial long QT syndrome: Some years later, Chugh et al. tested 5 LQTS-associated genes (KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2) in 12 SUD cases, and identified the same KCNH2 missense mutation in 2 subjects (17%) [17].