To assess whether increased MYH7 expression extended to the protein level, levels of β-MHC protein in the same pair-matched atrial septal and right ventricular discards were compared by Western blotting; this revealed that β-MHC was substantially increased in HLHS subjects with MYH6 variants (generalized linear model/ANOVA, +62%, ± 0.15 SE, P < 1 × 10−3) (Fig. 4B, Supplemental Table S4). This evidence concerns the gene MYH6 and hypoplastic left heart syndrome.