Remodeling of the zero-stress state of femoral arteries in response to flow overload

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Abstract
The goal of this study is to quantitatively describe the remodeling of the zero-stress state of the femoral artery in flow overload. Increased blood flow, approximately as a unit step change, was imposed on the femoral artery by making an arteriovenous (a-v) fistula with the epigastric vein. The a-v fistula was created in the right leg of 36 rats, which were divided equally into six groups (2 days and 1, 2, 4, 8, and 12 wk after the fistula). The vessels in the left leg were used as controls without operative trauma. The in vivo blood pressure, flow, and femoral outer diameter and the in vitro zero-stress state geometry were measured. The in vivo shear rate at the endothelial surface increased approximately as a step function by ∼83%, after 2 days, compared with the control artery. The arterial luminal and wall area significantly increased postsurgically from 0.15 ± 0.02 and 0.22 ± 0.02 mm2 to 0.28 ± 0.04 and 0.31 ± 0.05 mm2, respectively, after 12 wk. The wall thickness did not change significantly over time ( P > 0.1). The opening angle decreased to 82 ± 4.2 degrees postsurgically when compared with controls (102 ± 4.4) after 12 wk and correlated linearly with the thickness-to-radius ratio. Histological analysis revealed vascular smooth muscle cell growth. The remodeling data are expressed mathematically in terms of indicial functions, i.e., change of a particular feature of a blood vessel in response to a unit step change of blood flow. The indicial function approach provides a quantitative description of the remodeling process in the blood vessel wall.