Severe pulmonary hypertension associated with lung disease is characterised by a loss of small pulmonary vessels on quantitative computed tomography

Abstract

BackgroundPulmonary hypertension (PH) in patients with chronic lung disease (CLD) predicts reduced functional status, clinical worsening and increased mortality, with patients with severe PH-CLD (≥35 mmHg) having a significantly worse prognosis than mild to moderate PH-CLD (21–34 mmHg). The aim of this cross-sectional study was to assess the association between computed tomography (CT) derived quantitative pulmonary vessel volume, PH severity and disease aetiology in CLD.MethodsTreatment naïve patients with CLD who underwent CT pulmonary angiography, lung function testing and right heart catheterisation were identified from the ASPIRE Registry between October 2012 and July 2018. Quantitative assessments of total pulmonary vessel and small pulmonary vessel volume were performed.ResultsNinety patients had PH-CLD including 44 associated with COPD/emphysema and 46 with interstitial lung disease. Patients with severe PH-CLD (n=40) had lower small pulmonary vessel volume compared to patients with mild to moderate PH-CLD (n=50). Patients with PH-ILD had significantly reduced small pulmonary blood vessel volume, compared to PH-COPD/emphysema. Higher mortality was identified in patients with lower small pulmonary vessel volume.ConclusionPatients with severe PH-CLD, regardless of aetiology, have lower small pulmonary vessel volume compared to patients with mild-moderate PH-CLD and this is associated with a higher mortality. Whether pulmonary vessel changes quantified by CT are a marker of remodelling of the distal pulmonary vasculature requires further study.

Quantitative CT measures of pulmonary vascular volume distribution in pulmonary hypertension associated with COPD: Association with clinical characteristics and outcomes

“…No hemodynamic variable was associated with survival, and qCT was not generally correlated with hemodynamics. This differs from findings reported by Alkhafar et al and may be explained by the lack of a standardized imaging protocol in our study, variability that is known to affect blood vessel measurements, the inclusion of subjects with elevated pulmonary venous pressures, and the user‐dependent nature of RHC readings, which in our case were collected over more than two decades 12 . Also, unlike Alkhanfar, we did not find significant differences in vessel characteristics between severe and mild‐moderate PH despite severe PH being overrepresented in our cohort.…”

“…readings, which in our case were collected over more than two decades. 12 Also, unlike Alkhanfar, we did not find significant differences in vessel characteristics between severe and mild-moderate PH despite severe PH being overrepresented in our cohort. This may stem from the fact that the authors of that paper analyzed the pulmonary arteries only, whereas our data included the pulmonary veins.…”

“…Reduced small vessel volume (SVV) or vessels that have a surface of less than 5 mm 2 is characteristic of pulmonary arterial hypertension (PAH) and correlates with the extent of emphysema and various markers of clinical severity in subjects with COPD, including those with Global Obstructive Lung Disease stages 4 versus 1 and markers of functionality such as 6‐min walk distance 9–11 . Recently, Alkhanfar et al demonstrated that subjects with severe PH‐COPD had lower SVV compared with PH‐COPD subjects with mild‐moderate PH and that SVV was negatively correlated with mean pulmonary artery pressure (mPAP) 12 …”

“…[9][10][11] Recently, Alkhanfar et al demonstrated that subjects with severe PH-COPD had lower SVV compared with PH-COPD subjects with mild-moderate PH and that SVV was negatively correlated with mean pulmonary artery pressure (mPAP). 12 Our study aims were (1) determine whether qCTmeasured vascular volume distribution differed between COPD subjects with and without PH; (2) characterize the relationship of these metrics to conventional metrics of disease severity and clinical outcomes, particularly survival; and (3) characterize how these measurements differed between mild-to-moderate and severe PH. We hypothesized that reduced SVV would be associated with the presence and severity of PH, as well as with worse outcomes.…”

Pulmonary hypertension in interstitial lung disease and in chronic obstructive pulmonary disease: different entities?

“…Some significant differences exist in the CT scan of PH in CLD: although the pulmonary artery to aorta ratio is a solid PH screening tool in COPD [81], its usefulness in ILD is more controversial [7]. Furthermore, although severe PH is associated with total loss of pulmonary vascular bed in both [56 ▪▪ ], ILD patients of any PH severity have half the total pulmonary vascular bed compared with COPD, because of reduced lung volume [56 ▪▪ ]. In any case, mPAP is not correlated with the extent of fibrosis [82] or of emphysema [52,82], but air wall thickness is associated with mPAP in COPD.…”