Impact of shear stress on early vein graft remodeling: A biomechanical analysis

In this study, an analytical technique was developed to estimate the dynamic, three-dimensional wall shear and tensile forces within the arterial circulation and applied to our established model of flow-mediated graft remodeling within the rabbit carotid system. Through selective unilateral distal ligation, vein grafts were exposed to distinct flow environments, characterized by a sixfold difference in mean flow rate. Implanted vein grafts were harvested at 1, 3, 7, 14, and 28 days to evaluate graft morphology. Hemodynamic and real-time imaging data, obtained at graft implantation and harvest, served as input for estimation of dynamic shear stress and wall tension. Marked differences in the remodeling process were observed in high vs. low flow grafts, with low flow grafts demonstrating accelerated intimal hyperplasia and reduced outward remodeling. The impact was a peak in the maximum and minimum shear stress at Day 7, with a delayed increase in lumen diameter leading to partial normalization of the wall shear by Day 28. Intramural wall tension reached a maximum at Day 3, with an increase in wall thickness leading to a significant reduction in these forces by Day 14. Despite the significant morphologic changes, no differences in the incremental moduli of elasticity were observed.