CT evaluation of small pulmonary vessels area in patients with COPD with severe pulmonary hypertension

Rationale Severe pulmonary hypertension (PH) is very uncommon in COPD, and a distinct phenotype has been hypothesised. We aimed to evaluate whether CT can help to recognise this condition non-invasively by measuring small pulmonary vessels. Material and methods Patients with COPD who underwent pulmonary function tests, unenhanced CT of the chest and right heart catheterisation (RHC) during a period of stability were included in the study. From 105 included patients, 20 patients with COPD with severe PH (mean pulmonary arterial pressure, mPAP>35mmHg) were compared with 20 FEV1-matched and age-matched patients with COPD with mild or without PH (mPAP<35mmHg). The percentage of total cross-sectional area of vessels less than 5mm(2) normalised by lung area (%CSA(<5)) and 5-10mm(2) (%CSA(5-10)), the mean number of cross-sectioned vessels (CSNs) and bronchial wall thickness (WT) were measured on CT examination and compared between groups. Paw scores combining PaO2 measurement and CT parameters best correlated with mPAP were compared by receiver operating characteristic analysis to predict severe PH in COPD. Results Patients with severe PH COPD had higher %CSA and CSN values than those of patients with COPD without severe PH. Using multiple regression analysis, %CSA(<5) and WT were the best predictors of mPAP in patients with and without severe PH, respectively. A score combining %CSA(<5), PaO2 and WT best predicted severe PH in patients with COPD. Conclusions CT measurements of small vessels support a distinct vessel-related phenotype in patients with COPD with severe PH, and combined with WT and PaO2 parameters in the paw score, which may offer a non-invasive tool to select patients for RHC.