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CT MEASURES OF INTRAPARENCHYMAL VASCULAR VOLUME IN COPD PATIENTS WITH AND WITHOUT PULMONARY HYPERTENSION

      TOPIC: Pulmonary Vascular Disease
      TYPE: Original Investigations
      PURPOSE: Pulmonary hypertension (PH) is a significant contributing factor of overall morbidity and mortality in patients with COPD. Pruning in the form of loss of small vessel fractional volume has been shown to be associated with right heart disease and poor outcomes in COPD. In this investigation we sought to explore the relationship between this marker and the presence of precapillary pulmonary hypertension by hemodynamic measures.
      METHODS: We conducted a retrospective chart review study using the Research Patient Data Registry (RPDR) across patients in at Brigham and Women’s Hospital for patients with a diagnosis of Chronic Obstructive Pulmonary Disease (COPD) and measured FEV1/FVC of less than 70%. Patients with other forms of lung disease and risk factors for group 1 PH were excluded. Those patients with CT angiography within one year of right heart catheterization were further reviewed and we excluded those with poor image quality, pneumonia, significant fibrosis or lung collapse. All data collection was approved by the IRB at Mass General Brigham (IRB #2018P000419).We generated 3D models of the pulmonary vasculature using the Chest Imaging Platform (www.chestimagingplatform.org) and measured the total vascular volume (TBV), the volume of vessels with a cross sectional area <= 5 mm2 (BV5) and > 20mm2( BVg20); The small vessel fraction (aBV5/TBV) a marker of pruning, and the lung volume normalized arterial BVg20 (aBVg20/LV), a marker of proximal arterial enlargement were used for analysis. All data was analyzed using R version 4.0.1. Wilcoxon Rank-sum test and Spearman correlation were used for analysis and medians with IQR are reported.
      RESULTS: Of the Total Cohort (N=44), 17 had precapillary PH, 12 had PH associated with elevated wedge pressures and the remaining 15 did not meet diagnostic criteria for PH (mPAP > 20mmHg; PVR > 3 for precapillary, PAOP > 15mmHg for postcapillary). In the full cohort (N = 44), decrease in aBV5/TBV was associated with increase in mean PA pressure (R = -0.40, p = 0.007). We then restricted the analysis to those with less than 5% emphysema (N = 31). Here the aBV5/TBV was again negatively correlated with mean PA pressure (-0.6, p = 0.0004), but additionally aBVg20/LV was proportional to mean PA pressure (R = 0.46, p = 0.01).Within the group with less than 5% emphysema, those with precapillary PH had a lower aBV5/TBV (0.33[0.28-0.43] vs 0.46[0.46-0.55] p = 0.006, N = 13 and 7) than those without PH. There was no difference between age (66[62-80] vs 64[55-70], p = 0.34) and percent predicted FEV1 (53[48-69] vs 63[38-69] p>0.5). In those with > 5% emphysema (N = 13) there were no statistically significant correlations between aBV5/TBV and aBVg20/LV and mean PA pressure.
      CONCLUSIONS: In this retrospective study of COPD patients with CT angiography and hemodynamic assessment, decreased small arterial vascular fraction and proximal arterial volume increase was associated with increasing mPAP and was different between patients with precapillary PH versus those with no PH. The effect appears to be modulated by the presence of significant emphysema which independently may lead to loss of small vessel volume and additionally represents a specific sub-phenotype of COPD.
      CLINICAL IMPLICATIONS: Combining parenchymal and vascular phenotypic markers derived from CT imaging may help improve detection and phenotyping of PH in COPD.
      DISCLOSURES: No relevant relationships by Imama Ahmad, source=Web Response
      No relevant relationships by Sneha Lakshman, source=Web Response
      No relevant relationships by Pietro Nardelli, source=Web Response
      No relevant relationships by Farbod Rahaghi, source=Web Response
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