Following the observations of a significant enrichment for case variants localized within the S5–Pore–S6 region of Kv7.1, we analysed what proportion of index cases followed in the Toronto LQTS Clinic were represented by mutations in this region, and whether S5–Pore–S6 mutation carriers have a greater QTc or history of cardiac events compared to other sub-domains. Here, KCNQ1 is linked to familial long QT syndrome.