SCN5A and long QT syndrome 3: Mutations within SCN5A underlie a number of clinically defined arrhythmias including long QT syndrome type 3 (LQT3), Brugada syndrome, progressive conduction disease, and AF (Ruan et al., 2010; Wilde and Brugada, 2011) and many of these diseases harbor a propensity for atrial arrhythmias (Eckardt et al., 2001; Zellerhoff et al., 2009).