SCN5A and atrial standstill: Two closely linked polymorphisms in the promoter of Cx40 gene (−44G→A, rs35594137, and +71A→G, rs11552588) were suggested to decrease Cx40 promoter activity and to be linked to atrial standstill, when expressed homozygously and cosegregating with an SCN5A loss-of-function mutation (Groenewegen et al., 2003), or increased risk of atrial fibrillation (Firouzi et al., 2004).