Mechanisms leading to severe pulmonary hypertension (PH) in chronic lung disease (CLD) are unknown. Loss of small pulmonary arteries (vascular pruning) has been reported in PH and in CLD. OBJECTIVE: To investigate the association of pulmonary vascular density with the severity of PH and the extent of parenchymal derangement in COPD and fibrosing idiopathic interstitial pneumonia (FIIP). METHODS: We evaluated 117 patients with CLD: 37 without PH (17 COPD, 20 FIIP), 34 with moderate PH (18 COPD, 16 FIIP) and 46 with severe PH (28 COPD, 18 FIIP); and 38 patients with idiopathic pulmonary arterial hypertension (IPAH). We quantified in chest CT scan: total pulmonary blood (TBV) and arterial (TAV) volumes, volume of vessels (BV5) and arteries (BVart5) less than 5 mm2 in cross-section, and the extension of fibrosis and emphysema. RESULTS: Patients with severe CLD-PH had lower small pulmonary vessel density than patients without PH, as shown by reduced BV5/TBV and BV5art/TAV (Table). Severe COPD-PH patients showed the lowest BV5/TBV and BV5art/TAV values, being significantly lower than in moderate COPD-PH and IPAH. The severity of PH was unrelated to the extent of fibrosis or emphysema. CONCLUSION: Severe PH in FIIP and COPD is associated with a lower density of small pulmonary arteries, unrelated to the extent of parenchymal derangement.

Supported by grant PI18/00383 from the Instituto de Salud Carlos III.