In LQTS, positive genetic testing was reported for 51/55 probands, with a diagnostic yield of 94% (27 with KCNQ1, 16 with KCNH2, 1 with SCN5A, 2 with KCNJ2, 3 with CACNAC1, 1 with Ankyrin, 1 with CACNA1E, 3 negative and 1 pending). This evidence concerns the gene KCNJ2 and familial long QT syndrome.