Peripheral pulmonary vascular and airway abnormalities in adolescents with rheumatic mitral stenosis.

Lung biopsy specimens were taken from 15 adolescents (aged 11-21 years), at the time a mitral valvotomy was performed. In addition to quantitative light microscopic studies three specimens were also examined by scanning and transmission electron microscopy. In all cases, the pulmonary vascular abnormalities were most marked in the capillary bed and in the vessels immediately proximal and distal to it. The capillaries showed a marked increase in basement membrane material at the blood/gas barrier, and were embedded in dense connective tissue within the alveolar walls. Intra-acinar and, to a lesser extent, pre- and post-acinar vessels showed an increase in muscularity, severe circumferential intimal fibrosis, and abnormally thick and dense adventitial connective tissue. The peripheral airways were encased in dense connective tissue, which appeared to compress them. Bronchial smooth muscle was increased. Six months after the mitral valvotomy was performed, the mean pulmonary arterial pressure had fallen from 42 mm Hg to 23 mm Hg. Despite this satisfactory haemodynamic result, the long-term effects of small airway compression on the growing lung indicate the need for early relief of mitral valve obstruction, possibly made easier by the new technique of balloon angioplasty.