KCNH2 and atrial fibrillation: TBX20, and TBX5. Some ion channel encoding genes, such as SCN5A, HERG, KCNE1, and KCNE2, have been associated with long QT syndrome (LQTS; Tristani-Firouzi et al., 2001), atrial fibrillation (AF) and Brugada Syndrome (Hedley et al., 2011).