Pathology of the lungs in mitral stenosis in relation to respiratory function and pulmonary haemodynamics.

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Abstract
A histological study of lingular biopsies from 20 patients with stenosis was made, and the pathological features were related to the symptomatology, to the radiological appearances of the lungs, and to abnormalities in pulmonary function and pulmonary hemodynamics. Medial hypertrophy in the small "muscular pulmonary arteries", defined as a medial thickness exceeding 6.8% of the external diameter of the pulmonary arterioles were found when the pulmonary vascular resistance exceeded only 3.3 units m.2 There was no linear relation between the degree of medial hypertrophy and the height of pulmonary vascular resistance. Pulmonary hemosiderosis was found in about 1/3 of patients, most of whom also had radiological evidence of hemosiderosis. Its presence was not related to the height of the pulmonary venous pressure. Radiological evidence of enlargement of the main pulmonary arteries is an indication of the presence of pulmonary aterial hypertension (and associated hypertensive pulmonary vascular disease) but not of its degree. "Pulmonary lymphangiectasis" does not occur with moderate rises in left atrial pressure. Horizontal lines on the chest radio-graph are not related to the presence of dilated lymphatics in the biopsy but to the presence of alveolar fibrosis. Both conditions are probably the result of edema in the lung tissue. The relation between structural changes in the alveolar wall and respiratory function is poor. Diffusing appears to be more closely related to pulmonary vascular disease than to changes in the alveolar walls. The severity and duration of dyspnoea is related to the grade of hypertensive pulmonary vascular disease.