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:Weevaluatedthecorrelationof total cross-sectional areaof 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 (Ppacombining overline) obtained by right heart catheterization were evaluated. Multiple linear regression analysis using Ppacombining overline as the dependent outcome was also performed. Measurements and Main Results:The%CSA_<5 had a significant negative correlation with Ppacombining overline (r= -0.512, P<0.0001),whereas thecorrelation between %CSA_5-10 and Ppa 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 Ppacombining overline (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 Ppacombining overline in severe emphysema and can estimate the degree of pulmonary hypertension.