Pulmonary function studies in patients with prolapse of the mitral valve.

We studied the pulmonary function and chest x-ray films of 20 nonsmokers with idiopathic prolapse of the mitral valve. Forty-five percent of these patients complained of dyspnea. Of the 16 chest films reviewed, 44 percent had radiographic evidence of pectus excavatum and 25 percent thoracic scoliosis. The most common pulmonary function abnormalities were increased residual volume (63 percent) and a reduced steady state diffusing capacity (50 percent of patients). There was no relationship between the presence of dyspnea and either chest wall deformity of abnormality of pulmonary function. These pulmonary function abnormalities may reflect a pulmonary parenchymal disorder possibly secondary to a connective tissue abnormality in the lung.