HCN4 and familial long QT syndrome: In a WES, pathogenic variants of the LQTS genes (SCN5A, KCNH2, KCNQ1) were found in 7% of SUDEP cases and variants associated with predisposition to malignant arrhythmias (ANK2, AKAP9, HCN4) were found in 15% [7, 75].