Measurement of small pulmonary vessels by using computed tomography (CT) in COPD patients with severe pulmonary hypertension

Introduction: Severe pulmonary hypertension (PH) is an unusual complication in COPD, and a distinct phenotype has been evoked. Objectives: We evaluated whether computed tomography (CT) can support this hypothesis, by identifying airways and/or small vessels. Material and Methods: Between 2009 and 2013, 116 COPD patients underwent during a period of disease stability pulmonary function tests (PFT), CT of the chest and right heart catheterization. Among them, 55 subjects had no other condition to explain PH. 20 had severe PH (mean arterial pressure [mPAP]≥40 mmHg) and 35 patients with mild-to-moderate (mPAP≥25; n=20) and without PH (mPAP<25 mmHg; n=15) were chosen as controls. The percentage of total cross sectional area of vessels less than 5 mm2 for the lung area (%CSA<5) and 5 to 10 mm2 (%CSA5-10) were measured on CT examinations (ImageJ) and compared between groups. Correlations were searched between %CSA and PFT values, emphysema (Low Attenuation Area%) and mPAP. Results: Severe PH COPD patients had higher %CSA<5 and %CSA5-10 values than that of COPD controls. In patients with severe PH, a significant positive correlation were observed between mPAP and both %CSA<5 (ρ=0.44; p=0.04)and %CSA5-10 (ρ=0.70; p<0.001), while no correlation was found with PFTs values or LAA%. In controls, %CSA<5 and %CSA5-10 showed significant correlations with PFTs and LAA% but not with mPAP. Inmultivariate regression analyses, %CSA<5 or %CSA5-10 were the sole predictor of mPAP in patients with severe PH. Conclusion: CT measurements of %CSAs support a distinct vessel-related phenotype in COPD patients with severe PH. In those subjects %CSAs positively correlate with mPAP.