Mechanisms of Pulmonary Hypertension Related to Ventricular Septal Defect in Congenital Heart Disease

Abstract

The aim of this study was to investigate differences in molecular mechanisms of pulmonary hypertension between patients with complete transposition of the great arteries (TGA) combined with ventricular septal defect (VSD) and those with VSD alone. Twenty-four consecutive patients with pulmonary hypertension (mean pulmonary artery pressure > 30 mm Hg) underwent surgical correction of TGA + VSD (n = 10) or VSD alone (n = 14). Lung specimens were taken from the right middle lobe before cardiopulmonary bypass (CPB). Extent of pulmonary hypertension was graded according to the Heath-Edwards pathologic classification. Enzyme-linked immunosorbent assay (ELISA) was used to determine expression of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), endothelin-1 (ET-1), endothelin A and B receptors (ET-AR, ET-BR), matrix metalloproteinases 2 and 9 (MMP-2, MMP-9), and tissue inhibitor of metalloproteinase (TIMP). There were no statistically significant differences in age, height, weight, VSD diameter, or preoperative pulmonary artery pressure between groups. Hemoglobin level, pulmonary artery oxygen saturation, and reduction in postoperative pulmonary artery pressure were significantly higher in patients undergoing correction of TGA + VSD (p < 0.05). All patients had grade 0 to II Heath-Edwards morphologic changes in lung biopsy samples. Expression of eNOS and MMP-2 was significantly lower in the TGA + VSD group than in the VSD-alone group (eNOS, 280.13 ± 101.92 ng/mg versus 488.41 ± 249.60 ng/mg; p < 0.05; MMP-2, 31.68 ± 15.36 ng/mg versus 69.28 ± 49.12 ng/mg; p < 0.05). There were no statistically significant differences between groups in expression of iNOS, ET-1, ET-AR, ET-BR, MMP-9, or TIMP. In patients with TGA + VSD, high oxygenation in the pulmonary circulation decreases expression of MMP-2 and eNOS, which may affect the progress and reversibility of pulmonary hypertension.