Nonetheless, the expansion of genes tested has only slightly improved the overall diagnostic yield of SUD (on average from 20% to nearly 35%), mostly because of the major role still played by the 5 most common channelopathy-related genes (KCNH2, KCNJ2, KCNQ1, RYR2, and SCN5A), which should be tested in all SUD cases. Here, KCNH2 is linked to channelopathy.