Pulmonary arterial hypertension (PAH) is characterized by structural changes in the pulmonary vasculature. To date, evaluation of these changes has been primarily qualitative, making it challenging to accurately measure disease extent and progression. Therefore, we aim to quantify arteriolar changes in end-stage PAH using a novel micro computed tomography (?CT)-based approach.

Explanted PAH (n=3) and control lungs (n=3) were inflated, frozen, sliced and processed in small cylinders (cores, 1.4 cm diameter) which were scanned by ?CT (reconstructed voxel size 8.5?m). Airways and internal lumen of accompanied arteries were segmented (Materialise Mimics) to determine the artery-to-airway ratio (AAR, mean diameter artery/mean diameter airway) (fig a-c), based on the fact that airways in PAH are not affected. A linear mixed model was used to compare AAR values.

AAR was significantly decreased with 31.5% in PAH compared to control (p=0.0013) (fig d). Also, the AAR decreased with increasing airway diameter in PAH (slope=-0.0002265, p=0.0081), but not in controls (fig e).

This study demonstrates for the first time the feasibility of quantifying pulmonary arteriolar structural changes in PAH using a novel ?CT-based approach. Interestingly, 31.5% reduction of luminal vascular diameter in PAH was observed, however contradictory, this was more present in arteries which accompanied bigger airways.