According to the results, there was no significant difference in the serum miR-21 levels in children with CHD-PAH who had different ages, sex, BMI, disease type, EF, HR, SBP, DBP, LVEDd, dPAP, mRAP, PVR, and CK-MB (all P > 0.05), but the sPAP, mPAP, and BNP levels of the children in the miR-21 high group were significantly higher than those of the children in the miR-21 low group, and the CI in the miR-21 high group was lower than those in the miR-21 low group (all P < 0.05, Table 3). The gene discussed is NPPB; the disease is coronary artery disorder.