Abstract

The structure of the pulmonary circulation throughout the lung has been analysed by morphometric techniques in 4 infants dying with ventricular septal defect and pulmonary hypertension. Failure of the intra-acinar pulmonary circulation to develop normally is shown by a reduction in arterial size and number, and an increase in muscularity is judged by the degree of medial hypertrophy and by extension of muscle further along the arterial pathway than is normal. For these features, one section of lung tissue, 1 cm square, proved to be representative of the entire pulmonary vascular bed, and also gave satisfactory assessment of lung growth and development. Lung biopsy can help in the clinical management of children with congenital cardiac defects and pulmonary hypertension if, in selecting tissue at biopsy, allowance is made for any regional differences in pulmonary blood flow.