Hemodynamic Analysis of Arteriovenous Fistula ConfigurationsBriana Conners, Chemical Engineering, University of Cincinnati & Ken echuwku Okoye, Biomedical Engineering, University of Cincinnati

Graduate Mentor: Ehsan Rajabi Jaghargh, Mechanical Engineering, University of CincinnatiFaculty Mentor: Dr. Rupak Banerjee, Professor, School of Dynamic Systems ,College of Engineering and Applied Science, University of Cincinnati

Results Results ContinuedBackgroundArteriovenous Fistula (AVF) Connection of the end of a vein to the side of an artery. Used for hemodialysis in terminal renal patients.

Blood pathway circumvents the high-resistance capillaries in the distal extremities

Vessels must dilate to accommodate the increase in flow Vessel remodeling is triggered by changes in hemodynamics, namely

the shear stress on the wall [2] However, 23-46% of all fistula do not achieve an adequate diameter

and resulting flow as a result of venous stenosis [1]

Inner bend: Axial WSS is negative By the end of the bend, WSS return to the direction of the flow

on the inner bend in the 90° case but not in the 60° case 60° case experiences higher negative levels of axial WSS

Outer bend and Side bend: Experience positive axial WSS throughout the entire curve WSS is greater on the first half of the bend for the 60° case Axial WSS values vary less throughout the 90° bend

ObjectiveTo explore the effects of AVF configuration on hemodynamic

parameters such as flow field and wall shear stress (WSS).

Fistula Model Geometry

Using blood flow and blood vessel data averaged from 6 porcine AVF, the fistula models were created with the above geometry at a 90° and 60 ° angle to be solved numerically under steady state condition.

Flow Streamlines: Areas of Stagnation

Cells lining the blood vessel wall become disoriented from flow not in the axial direction. This likely triggers wall thickening.

Conclusions Stagnant flow on the inner bend is observed in both models in areas

in which stenosis formation has been documented before. The 90° case is preferred for the following reasons:

The 60° case had more pronounced stagnant flow on the inner bend which may result in more prominent stenosis

High WSS on the outer wall of the 60 ° case may damage wall cells and lead to further complications

Axial Wall Shear Stress

Section 1: axial velocity is negative for the inner half. The negative flow velocity is of greater magnitude in the 60° case than the 90° case and even continues to be

negative on the inner curve at the end of the bend.

Axial Velocity Profiles

Along the outer bend of the fistula, velocity magnitude is greater than on the inner bend. The highest velocity fluid is noted on the outer wall of the 60° case.

Velocity Contours

The friction of the flowing blood creates a shear stress on the walls of the vessels. The WSS are higher on the side wall of the 60° case.

Wall Shear Stress Contours References1. Krishnamoorthy, M. K. et al., 2012, “Anatomic configuration affects the flow rate and diameter f porcine arteriovenous fistulae.” Kidney International, 81, pp. 745-750.2. Ene-Iordache, B. et al., 2011, “Disturbed flow in radial-cephalic arteriovenous fistulae for haemodialysis: low and oscillating shear stress locates the sites of stenosis.” Nephrol Dial Transplant, 27, pp. 358-368.3.“What is Arterio-Venous Access.” Cardiac Vascular and Thoracic Surgery Associates. Web. Nov. 2012. <http://www.cvtsa.com/ListofConditions/A-444-176.html.>.

AcknowledgementNSF Type 1 STEP Grant, Grant ID No.: DUE-0756921

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