Longitudinal Effect of Pressure Drop on the Intima-media Thickening of the Venous Segment of the Arteriovenous Fistula

1 ABSTRACT Venous stenosis is one of the primary causes of the arteriovenous fistula (AVF) maturation-failure and is characterized by vasoconstriction and significant intima-media thickening (IMT). Although the hemodynamic endpoints are believed to play a crucial role in the pathogenesis of venous stenosis, the exact mechanism behind this is unclear. Our hypothesis is that the changes in the pressure drop over time (∆p ́) can influence the remodeling factors in AVFs: changes in luminal diameter (∆Dh) and IMT. Curved (C-AVF; n = 3) and straight (S-AVF; n = 3) AVFs were created between the femoral arteries and veins of 3 pigs. CT-scan and ultrasound were utilized to numerically evaluate the flow field, and thus pressure drop in AVFs at 2D (D: days), 7D, and 28D post-surgery. For each AVF, IMT was also measured at 4 histological blocks along the vein. For the C-AVF, the pressure drop consistently decreased over time (from 18.32 mmHg at 2D to 4.58 mmHg at 28D), while opposite trend was found for the S-AVF (from 12.91 mmHg at 2D to 24.49 mmHg at 28D). The ∆p ́was negative at all the histology blocks for C-AVF which showed the reduction in the resistance over time due to dilation (positive ∆Dh) and outward hypertrophy of the venous segment (positive ∆Dh/IMT). In contrast, ∆p ́was mostly positive for the S-AVF which showed the increase in the resistance due to vasoconstriction (negative ∆Dh) and inward hypertrophy (negative ∆Dh/IMT). Thus, measuring ∆p ́at the successive post-surgery time points can provide important information on the remodeling behavior of AVFs. Also, creating AVFs in a surgical configuration that can result in negative ∆p ́and thus favorable remodeling could influence the life expectancy of the dialysis patients.