As a result, among the four protein regions of titin, i.e., Z-disk, I-band, A-band, and M-band, A-band enrichment of TTNtv in patients with DCM has been repeatedly reported (Herman et al., 2012; Roberts et al., 2015; Akinrinade et al., 2016; Schafer et al., 2017; Rich et al., 2020; Fomin et al., 2021). This evidence concerns the gene TTN and familial dilated cardiomyopathy.