Imaging of Ca2+ fluxes during electrical pacing of cardiomyocytes demonstrated dysregulated Ca2+ concentration in cells expressing LQTS-associated CaM-D96V, -D130G, -F142L, and in particular the CPVT-mutation N54I showed Ca2+ overload, Ca2+ reuptake errors, or alternans (Limpitikul et al., 2014, 2017; Yin et al., 2014). This evidence concerns the gene CALM2 and familial long QT syndrome.