Early pulmonary vascular changes in congenital heart disease studied in biopsy tissue.

Patients with congenital heart defects who had or were at risk for developing pulmonary artery hypertension underwent lung biopsy at the time of intracardiac repair. In 95 consecutive patients with either ventricular septal defect, d-transposition of the great arteries, or a defect of the atrioventricular canal, the pulmonary arteries were evaluated microscopically by quantitative morphologic techniques, and the findings were correlated with hemodynamic data obtained at a recent preoperative cardiac catheterization. Three grades of severity of early pulmonary vascular changes were identified, which correlated with hemodynamic evidence of progressive functional impairment. Grade A denotes cases with abnormal extension of muscle into peripheral arteries only; pulmonary blood flow is increased but pulmonary artery pressure is normal. In grade B an increased medial wall thickness of the normally muscular arteries is also present, and in these cases pulmonary artery pressure is also increased. Grade C denotes cases in which in addition to the findings in grade B disease there is a reduction in the number of small peripheral arteries; in these cases pulmonary vascular resistance is increased. Follow-up postoperative hemodynamic evaluation will reveal the significance of these changes in reflecting irreversible functional impairment of the pulmonary vascular bed.