In this regard, it is of interest that INaL was increased in cardiac failure and yet no differences were found in isoform NaV1.1, 1.3, 1.5 subunits and in the subunit b1 and b2, leading to the conclusion that INaL increase was not due to a subunit isoform switching or to an altered b subunit expression (Valdivia et al. 2005). This evidence concerns the gene SCN1A and heart failure.