SCN4B and familial long QT syndrome: Twelve additional genes encoding either ion channel subunits (KCNJ5, KCNE1, KCNE2, and SCN4B) or proteins that regulate ion channel function (AKAP9, CAV3, ANKB, SNT1, CALM1, and CALM2) have been associated with LQTS; however, most of them are only rarely implicated (<1%) [7].