Mechanical properties of native and ex vivo remodeled porcine saphenous veins

When grafted into an arterial environment in vivo, veins remodel in response to the new mechanical environment, thereby changing their mechanical properties and potentially impacting their patency as bypass grafts. Porcine saphenous veins were subjected for one week to four different ex vivo hemodynamic environments in which pressure and shear stress were varied independently, as well as an environment that mimicked that of an arterial bypass graft. After one week of ex vivo culture, the mechanical properties of intact saphenous veins were evaluated to relate specific aspects of the mechanical environment to vein remodeling and corresponding changes in mechanics. The compliance of all cultured veins tended to be less than that of fresh veins; however, this trend was more due to changes in medial and luminal areas than changes in the intrinsic properties of the vein wall. A combination of medial hypertrophy and eutrophic remodeling leads to significantly smaller (p<0.05) wall stresses measured in all cultured veins except those subjected to bypass graft conditions relative to stresses measured in fresh veins at corresponding pressures. Our results suggest that the mechanical environment effects changes in vessel size, as well as the nature of the remodeling, which contribute to altering vein mechanical properties.