Quantitative CT assessment of bronchial and vascular alterations in severe precapillary pulmonary hypertension

Little is known about in vivo alterations at bronchial and vascular levels in severe pulmonary hypertension (PH) of different etiologies. We aimed to compare quantitative computed tomography (CT) data from the following three groups of severe precapillary PH patients: COPD, idiopathic pulmonary arterial hypertension (iPAH), and chronic thromboembolic PH (CTEPH).

This study was approved by the institutional review board. Severe PH patients (mean pulmonary arterial pressure [mPAP] ≥35 mmHg) with COPD, iPAH, or CTEPH (n=24, 16, or 16, respectively) were included retrospectively between January 2008 and January 2017. Univariate analysis of mPAP was performed in each severe PH group. Bronchial wall thickness (WT) and percentage of cross sectional area of pulmonary vessels less than 5 mm² normalized by lung area (%CSA_<5) were measured and compared using CT, and then combined to arterial partial pressure of oxygen (PaO₂) to generate a "paw score" compared within the three groups using Kruskal-Wallis and its sensitivity using Fisher's exact test.

WT was higher and %CSA_<5 was lower in the COPD group compared to iPAH and CTEPH groups. Mosaic pattern was higher in CTEPH group than in others. In severe PH patients secondary to COPD, mPAP was positively correlated to %CSA_<5. By contrast, in severe iPAH, this correlation was negative, or not correlated in severe CTEPH groups. In the COPD group, "paw score" showed higher sensitivity than in the other two groups.

Unlike in severe iPAH and CTEPH, severe PH with COPD can be predicted by "paw score" reflecting bronchial and vascular morphological differential alterations.