Regional variation in homeostatic stretch and stiffness in a swine model of branch pulmonary artery stenosis

Branch pulmonary artery stenosis (PAS) often presents in children with congenital heart defects, altering blood flow and pressure in the pulmonary circulation. Perturbations from homeostatic arterial mechanics have been proposed as stimuli for vascular growth and remodeling. However, there is a current lack of quantification of these stimuli in the pulmonary arteries and their alteration during pathology. In this study, we used a 1D fluid dynamics model to simulate pressure-flow relationships in the pulmonary artery tree. Left PAS was surgically created in 4 swine at 2 weeks of age, with 4 additional sham animals. Pressure and imaging measurements were obtained at 20 weeks of age. The unloaded radius of each vessel was determined from the model predicted pressure-area relationship. In each sham animal, our results indicate little variability in regional homeostatic stretch when we prescribed constant arterial stiffness. In addition, there was little inter-animal variation in fitted stiffness or stretch. In contrast, we expect regional differences in stretch and stiffness will be necessary to match the PAS experimental data and that differences from sham will indicate arterial growth and remodeling.