Investigation Longitudinal Assessment of Hemodynamic Endpoints in Predicting Arteriovenous Fistula Maturation Ehsan Rajabi-Jagahrgh,* Mahesh K. Krishnamoorthy,* Prabir Roy-Chaudhury,†‡ 1 Paul Succop,§ Yang Wang,† Ann Choe,– and Rupak K. Banerjee* 1 *Mechanical Engineering Program, School of Dynamic Systems, University of Cincinnati, Cincinnati, Ohio, †Dialysis Vascular Access Research Group, Department of Internal Medicine, Division of Nephrology and Hypertension, University of Cincinnati, Cincinnati, Ohio, ‡Cincinnati Veterans Administration Medical Center, Cincinnati, Ohio, §Department of Epidemiology and Biostatistics, University of Cincinnati, Cincinnati, Ohio, and –Department of Radiology, University of Cincinnati, Cincinnati, Ohio ABSTRACT Arteriovenous fistula (AVF) nonmaturation is currently a sig- nificant clinical problem; however, the mechanisms responsible for this have remained unanswered. Previous work by our group and others has suggested that anatomical configuration and the corresponding hemodynamic endpoints could have an important role in AVF remodeling. Thus, our goal was to assess the longitudinal (temporal) effect of wall shear stress (WSS) on remodeling process of AVFs with two different con- figurations. The hypothesis is that early assessment of hemody- namic endpoints such as temporal gradient of WSS will predict the maturation status of AVF at later time points. Two AVFs with curved (C-AVF) and straight (S-AVF) configurations were created between the femoral artery and vein of each pig. Three pigs were considered in this study and in total six AVFs (three C-AVF and three S-AVF) were created. The CT scan and ultrasound were utilized to numerically evaluate local WSS at 20 cross-sections along the venous segment of AVFs at 2D (D: days), 7D, and 28D postsurgery. These cross-sections were located at 1.5 mm increments from the anastomosis junc- tion. Local WSS values at these cross-sections were correlated with their corresponding luminal area over time. The WSS in C-AVF decreased from 22.3 ± 4.8 dyn ⁄ cm 2 at 2D to 4.1 ± 5.1 dyn ⁄ cm 2 at 28D, while WSS increased in S-AVF from 13.0 ± 5.0 dyn ⁄ cm 2 at 2D to 36.7 ± 5.3 dyn ⁄ cm 2 at 28D. Corresponding to these changes in WSS levels, luminal area of C-AVF dilated (0.23 ± 0.14 cm 2 at 2D to 0.87 ± 0.14 cm 2 at 28D) with attendant increase in flow rate. However, S-AVF had minimal changes in area (0.26 ± 0.02 cm 2 at 2D to 0.27 ± 0.03 cm 2 at 28D) despite some increase in flow rate. Our results suggest that the tempo- ral changes of WSS could have significant effects on AVF mat- uration. Reduction in WSS over time (regardless of initial values) may result in dilation (p < 0.05), while increase in WSS may be detrimental to maturation. Thus, creation of AVFs in a specific configuration which results in a decline in WSS over time may reduce AVF maturation failure. Arteriovenous fistulae (AVFs) are the preferred form of vascular access in patients undergoing hemodialysis. Infection and thrombosis rates in AVFs are lower than polytetrafluroethylene grafts (the other major form of vascular access), with an improvement in patency (1). Despite these advantages, a major problem associated with AVFs is a very high rate of maturation failure (1–5). Recent studies suggest that over 60% of AVFs are unsuitable for dialysis between 4 and 5 months postsur- gery and this has been a major impediment to the ‘‘Fis- tula First’’ initiative (6,7). Hemodynamics of the AVF is believed to be responsi- ble for its remodeling patterns which may result in either maturation success or failure. However, the exact rela- tionship between the hemodynamic parameters and remodeling patterns is still unclear. Increase in blood flow soon after the creation of AVF is accompanied by increase in wall shear stress (WSS). This induces com- pensatory changes both in the arterial and venous struc- ture leading to flow-mediated remodeling (8,9). Previous studies have shown that arteries in response to the increased WSS levels dilate to lower the mean WSS over time; thus, restoring baseline WSS (8,10–12). However, the venous response to WSS variation shows variability. Some studies have shown that vein dilates in response to the increased levels of WSS, while others have observed reduction in the luminal area of the vein for similar WSS Address correspondence to: Rupak K. Banerjee, Professor, Mechanical Engineering Program, School of Dynamic Systems, 593 Rhodes Hall, University of Cincinnati, Cincin- nati, OH 45221-0072, e-mail: rupak.banerjee@uc.edu 1 Rupak Banerjee and Prabir Roy-Chaudhury have contrib- uted equally to this paper. Seminars in Dialysis—2012 DOI: 10.1111/j.1525-139X.2012.01112.x ª 2012 Wiley Periodicals, Inc. 1