Respiratory and circulatory studies in patients with mitral stenosis. Circulation

Sixteen patients with severe mitral stenosis have been studied by means of cardiac catheterization, ventilatory and respiratory tests. A decrease in the oxygen diffusing capacity and an increase in venous admixture were observed in a majority of the cases. The degree of pulmonary arterial and arteriolar abnormality observed in lung biopsies failed to correlate with the pulmonary arteriolar resistances calculated from the hemodynamic data. It is suggested that reversible vasoconstriction plays an important role in the pathogenesis of the pulmonary hypertension associated with mitral stenosis. T HE DEVELOPMENT of effective sur-gical therapy for mitral stenosis has focused interest on the pathologic phys-iology of this disease. Careful appraisal of abnormalities in circulatory and pulmonary function of patients with mitral stenosis may help in the proper selection of cases for opera-tion and should aid in evaluating the results of surgery. It has been clearly recognized that with long standing mitral stenosis striking pathologic changes in the lungs are found at autopsy. " 2 Intimal thickening of the arteries, hyperplastic arteriolar sclerosis, and dilata-tion of the capillaries are frequently observed. In addition to vascular lesions, the alveolar walls may be affected by edema, fibrosis, and emphysema. Extensive hemodynamic studies have been carried out which demonstrate that narrowing of the mitral valve produces hypertension throughout the lesser circulation and often an increased resistance to flow through the pulmonary arterioles.3-8 However, to date there are few reports of abnormalities in pul-monary function in mitral stenosis and the majority of these have dealt with disturbances in ventilation.1 ' 10 11 Blount and coworkers'2 have recently demonstrated an increased alveolar-arterial oxygen tension gradient i