The different subgroups of LQTS are caused by variants in distinct genes (Bohnen et al., 2017) with most of these variants located in either KCNQ1 (MIM *607542, LQTS 1), KCNH2 (MIM *152427, LQTS 2), or SCN5A (MIM *600163, LQTS 3) (Giudicessi & Ackerman, 2013; Schwartz, Crotti, & Insolia, 2012), coding for potassium or sodium ion channels, respectively. Here, SCN5A is linked to familial long QT syndrome.