Calmodulin is a primary sensor of intracellular calcium levels in eukaryotic cells, playing a key role in the proper mediation of Ca2+ signaling, and interacts with several known LQTS genes (SCN5A [35], SNTA1 [36] and CACNA1C [37]), giving strength to the possibility that these candidate genes also play a pathogenic role in LQTS. This evidence concerns the gene SCN5A and familial long QT syndrome.