CT derived quantification of vascular morphology may be useful for detection, classification and understanding of pulmonary vascular disease. Changes such as pruning and proximal dilation of the vessels have been described in pulmonary hypertension, but the differential effect on arterial and venous pulmonary circulation has not been well characterized. In this study, we attempted to quantify blood volume distribution in small and large sized vessels in the arterial and venous pulmonary vasculature using clinically acquired CT scans.
A cohort of 700 patients evaluated for unexplained dyspnea at Brigham and Women’s Hospital was retrospectively identified. 179 patients had CT angiography within 1 year of RHC. 49 patients with PH(15 Group II, 16 PAH, and 18 CTEPH) and 15 subjects with no pulmonary vascular disease were identified. Lung segmentation and 3D reconstruction of parenchymal vasculature was generated as previously described. Arteries and veins were manually labeled in the right lung. Primary analysis focused on the small vessel fraction, the fraction of volume in vessels with cross sectional area of less than 5mm2, divided by the total vessel volume. Medians, inter-quartile range and Wilcoxon Rank-Sum Test, (SAS 9.3) were used for group comparisons.
Arterial small vessel fraction was significantly lower in all groups of PH: Group I (0.45[0.40-0.52] p=0.001); Group II (0.42[0.37-0.48] p=0.0002; Group IV (0.49[0.40-0.58] p=0.001); as compared to controls (0.60[0.54-0.66]). In the venous pulmonary vasculature, however, the difference reached statistical significance only in Group II patients (0.43[0.41-0.50] p=0.008) but not in Group I (0.49[0.40-0.55] p=0.09) or group IV (0.51[0.44-0.58]) p=0.09) subject compared to controls (0.54[0.49-0.58]).
Arterial remodeling can be observed and quantified using CT imaging in patients with both pre-capillary and post-capillary PH compared to controls without any pulmonary vascular disease. Venous volume redistribution measured by small vessel fraction is additionally present in post-capillary disease.