Reduced pulmonary vascular density in severe pulmonary hypertension associated with chronic lung disease

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.