The finding of a restrictive pulmonary defect may divert clinicians from considering the diagnosis of chronic thromboembolic pulmonary hypertension because lung volumes are usually normal in this disorder. We have, however, encountered a significant number of these patients with reduced lung volumes. Furthermore, we have observed many patients who have developed parenchymal scars and/or pleural thickening. To determine whether such findings are associated with lung volume restriction, we analyzed patients evaluated at our institution for chronic thromboembolic pulmonary hypertension over a 20-month period in whom thoracic high-resolution CT scans and pulmonary function testing had been performed. Patients with obstructive or restrictive lung disease from another cause were excluded. We compared the presence of lung restriction (total lung capacity below 80% of predicted) with the extent of parenchymal scarring, pleural thickening, and pulmonary artery diameter on CT scans. Of 191 patients evaluated, 51 met criteria for entry. Eleven patients (22%) had lung restriction. Parenchymal scarring was highly associated with lung restriction (p = 0.01). Neither pleural thickening (p = 0.08) nor pulmonary artery diameter (p = 0.80) was associated with lung restriction.
Conclusions: A significant number of patients with chronic thromboembolic pulmonary hypertension may have restrictive lung defects. The restriction may be due to parenchymal scarring.