SCN5A and sick sinus syndrome: Mutations in SCN5A encoding the pore-forming α-subunit of the human cardiac Na+ channel have been associated with an increasingly wide range of cardiac rhythm disorders that include the long QT syndrome type 3 (LQT3), Brugada syndrome (BrS) and cardiac conduction diseases, idiopathic ventricular fibrillation, sinus node dysfunction including sick sinus syndrome (SSS), atrial standstill and sudden infant death syndrome (SIDS) (Akai et al. 2000, Benson et al. 2003, Groenewegen et al. 2003, Tan et al. 2003, Wang et al. 2007).