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

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 mm(2) (CSA(<5)) and 5 to 10 mm(2) (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 (<(Ppa)over bar>) obtained by right heart catheterization were evaluated. Multiple linear regression analysis using (Ppa) over bar as the dependent outcome was also performed. Measurements and Main Results: The %CSA(<5) had a significant negative correlation with <(Ppa)over bar> (r = -0.512, P < 0.0001), whereas the correlation between %CSA(5-10) and <(Ppa)over bar> 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 (DLCO) % predicted were independent predictors of <(Ppa)over bar> (r(2) = 0.541): %CSA(<5) (P < 0.0001), and DLCO % predicted (P = 0.022). Conclusions: The %CSA(<5) measured on CT images is significantly correlated to <(Ppa)over bar> in severe emphysema and can estimate the degree of pulmonary hypertension.