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Pulmonary Hypertension and Computed Tomography Measurement of Small Pulmonary Vessels in Severe Emphysema

¹ Department of Radiology, ² Pulmonary and Critical Care Division, ³ Surgical Planning Laboratory, Laboratory of Mathematics in Imaging, Department of Radiology, and ⁴ Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; ⁵ Department of Radiology, University of Iowa, Iowa City, Iowa; ⁶ Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland; ⁷ Division of Pulmonary and Critical Care Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania; ⁸ Division of Pulmonary and Critical Care Medicine, University of Maryland, Baltimore, Maryland; and ⁹ Division of Pulmonary and Critical Care Medicine, University of Michigan Health System, Ann Arbor, Michigan

Correspondence and requests for reprints should be addressed to Shin Matsuoka, M.D., Ph.D., Department of Radiology, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan. E-mail: shin4114{at}mac.com

Rationale: Vascular alteration of small pulmonary vessels is one of the characteristic features of pulmonary hypertension in chronic obstructive pulmonary disease. The in vivo relationship between pulmonary hypertension and morphological alteration of the small pulmonary vessels has not been assessed in patients with severe emphysema.

Objectives: We evaluated the correlation of total cross-sectional area of small pulmonary vessels (CSA) assessed on computed tomography (CT) scans with the degree of pulmonary hypertension estimated by right heart catheterization.

Methods: In 79 patients with severe emphysema enrolled in the National Emphysema Treatment Trial (NETT), we measured CSA less than 5 mm² (CSA_<5) and 5 to 10 mm² (CSA_5–10), and calculated the percentage of total CSA for the lung area (%CSA_<5 and %CSA_5–10, respectively). The correlations of %CSA_<5 and %CSA_5–10 with pulmonary arterial mean pressure () obtained by right heart catheterization were evaluated. Multiple linear regression analysis using as the dependent outcome was also performed.

Measurements and Main Results: The %CSA_<5 had a significant negative correlation with (r = –0.512, P < 0.0001), whereas the correlation between %CSA_5–10 and did not reach statistical significance (r = –0.196, P = 0.083). Multiple linear regression analysis showed that %CSA_<5 and diffusing capacity of carbon monoxide (DL_CO) % predicted were independent predictors of (r² = 0.541): %CSA _<5 (P < 0.0001), and DL_CO % predicted (P = 0.022).

Conclusions: The %CSA_<5 measured on CT images is significantly correlated to in severe emphysema and can estimate the degree of pulmonary hypertension.

Key Words: chronic obstructive pulmonary disease • emphysema • pulmonary hypertension • CT

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Pulmonary hypertension in patients with chronic obstructive pulmonary disease (COPD) with predominate emphysema phenotype is likely caused by small pulmonary vessel vascular remodeling. However, the in vivo relationship between pulmonary hypertension and morphological alteration of the small pulmonary vessels has not been assessed. What This Study Adds to the Field Vascular alteration, measured from the cross-sectional area (CSA) of small pulmonary vessels by computed tomography correlates with the magnitude of pulmonary hypertension. These data suggest that CSA can be used to estimate pulmonary arterial pressure in subjects with severe emphysema.