KCNH2 and Arrhythmia: Moreover, in up to 10–15% of patients with drug-induced QT prolongations and TdP arrhythmias single nucleotide polymorphisms (SNPs) have been discovered in LQT-related genes like KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2[9], [10] and it has been demonstrated that some of these SNPs in LQTS-associated genes may increase the risk for drug-induced LQTS up to 9-fold [11].