Characterization of CT Imaging-Derived Pulmonary Vascular Abnormalities Associated With Pulmonary Hypertension in Chronic Lung Disease.

BACKGROUND

Pulmonary vascular remodeling is implicated in the pathophysiologic characteristics of pulmonary hypertension (PH) in chronic lung diseases. CT imaging metrics of pulmonary vessels may provide insight into the impact of vessel morphologic features on PH severity in chronic lung diseases (CLDs).

RESEARCH QUESTION: Are CT imaging-assessed pulmonary vascular abnormalities associated with the presence and severity of PH in COPD and fibrosing interstitial lung disease (ILD), and how are they related to parenchymal damage?

STUDY DESIGN AND

METHODS

We evaluated 117 patients with CLD (63 patients with COPD and 54 patients with ILD), and 38 patients with idiopathic pulmonary arterial hypertension as a comparator group. Patients with COPD and ILD were stratified according to the presence and severity of PH using right heart catheterization. Pulmonary vessel volumes, stratified in arteries and veins, and the extent of emphysema and fibrosis were assessed by volumetric, noncontrast chest CT scans.

RESULTS

Patients with COPD exhibited greater vascular and lung volumes (LVs) than those with ILD, although they showed lower small-vessel volume when adjusted for LV. In both diseases, severe PH was associated with a reduced volume of small arteries normalized to total arterial volume (TAV; blood volume in arteries < 5 mm2 in cross-section [BV5art] to TAV ratio) and was more pronounced in patients with COPD, who also showed larger central vessel volumes. In COPD, the extent of emphysema did not correlate with either hemodynamic impairment or small-vessel volume. In contrast, in ILD, the extent of fibrosis was unrelated to hemodynamic impairment, but was corelated inversely with the volume of small arteries and veins.

INTERPRETATION: Our results show that COPD and fibrosing ILD exhibit marked differences in pulmonary vessel morphologic features and their relationship with parenchymal remodeling, suggesting distinct mechanisms underlying PH development. In lung disease, the BV5art to TAV ratio seems to be a sensitive marker of hemodynamically confirmed severe PH, particularly in COPD, reflecting intravascular volume redistribution resulting from peripheral vessel remodeling.