(A) RV miR-21 expression is upregulated in children with PI+PS (n = 4) and end-stage RV failure (n = 2) compared with those with mild RVOTO (n = 3) and infants with unrepaired TOF (n = 7). (B and C) Increasing fibrosis is seen in children with PI+PS (n = 4) and end-stage RV failure (n = 2). Scale bar: 100 μm. RV, right ventricle; RVOTO, RV outflow tract obstruction; TOF, tetralogy of Fallot; PI+PS, pulmonary insufficiency and pulmonary stenosis. Data are presented as mean ± SEM. ANOVA with multiple testing correction was used. Correlation was assessed using Pearson’s correlation. *P < 0.01, **P < 0.001.