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Technical Brief

Are Non-Newtonian Effects Important in Hemodynamic Simulations of Patients With Autogenous Fistula?

[+] Author and Article Information
S. M. Javid Mahmoudzadeh Akherat

Mechanical, Materials, and Aerospace
Engineering Department,
Illinois Institute of Technology,
Chicago, IL 60616
e-mail: smahmou1@iit.edu

Kevin Cassel

Mechanical, Materials, and Aerospace
Engineering Department,
Illinois Institute of Technology,
Chicago, IL 60616
e-mail: cassel@iit.edu

Michael Boghosian

Mechanical, Materials, and Aerospace
Engineering Department,
Illinois Institute of Technology,
Chicago, IL 60616
e-mail: boghmic@iit.edu

Promila Dhar

Biomedical Engineering Department,
Illinois Institute of Technology,
Chicago, IL 60616
e-mail: dhar@iit.edu

Mary Hammes

Department of Medicine,
University of Chicago,
Chicago, IL 60637
e-mail: mhammes@medicine.bsd.uchicago.edu

1Corresponding author.

Manuscript received May 23, 2016; final manuscript received January 19, 2017; published online March 1, 2017. Assoc. Editor: Alison Marsden.

J Biomech Eng 139(4), 044504 (Mar 01, 2017) (9 pages) Paper No: BIO-16-1217; doi: 10.1115/1.4035915 History: Received May 23, 2016; Revised January 19, 2017

Given the current emphasis on accurate computational fluid dynamics (CFD) modeling of cardiovascular flows, which incorporates realistic blood vessel geometries and cardiac waveforms, it is necessary to revisit the conventional wisdom regarding the influences of non-Newtonian effects. In this study, patient-specific reconstructed 3D geometries, whole blood viscosity data, and venous pulses postdialysis access surgery are used as the basis for the hemodynamic simulations of renal failure patients with native fistula access. Rheological analysis of the viscometry data initially suggested that the correct choice of constitutive relations to capture the non-Newtonian behavior of blood is important because the end-stage renal disease (ESRD) patient cohort under observation experience drastic variations in hematocrit (Hct) levels and whole blood viscosity throughout the hemodialysis treatment. For this purpose, various constitutive relations have been tested and implemented in CFD practice, namely Quemada and Casson. Because of the specific interest in neointimal hyperplasia and the onset of stenosis in this study, particular attention is placed on differences in nonhomeostatic wall shear stress (WSS) as that drives the venous adaptation process that leads to venous geometric evolution over time in ESRD patients. Surprisingly, the CFD results exhibit no major differences in the flow field and general flow characteristics of a non-Newtonian simulation and a corresponding identical Newtonian counterpart. It is found that the vein's geometric features and the dialysis-induced flow rate have far greater influence on the WSS distribution within the numerical domain.

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Figures

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Fig. 1

A very severe cephalic arch stenosis detected in a patient under observation in our study at 12 months postaccess surgery. The blood flow is from right to left. Two-dimensional reconstructed geometry (top) and the 3D reconstructed geometry (bottom).

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Fig. 2

Hematocrit and resulting apparent viscosity (cP) comparison between normal and ESRD patients blood samples. Red dots represent the ESRD patients under observation, while blue dots are representative of a healthy population.

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Fig. 3

Postdialysis Hct and consequent apparent viscosity increase through time for subject 11 at 0, 3, and 12 months

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Fig. 4

Reconstructed cephalic vein geometry for subject 27 at 3 months. Venogram (top), 2D (middle), and the 3D geometry (bottom).

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Fig. 5

Reconstructed cephalic vein geometry for subject 12 at 3 months. Venogram (top) 2D (middle), and the 3D geometry (bottom).

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Fig. 10

Streamlines at the last cardiac cycle of the simulation, t/tp=1, for subject 27. The colors represent velocity magnitude.

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Fig. 11

Cross-sectional velocity contours superimposed on velocity magnitude pseudocolor plots at three different locations for three simulations

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Fig. 12

Streamlines at the sixth half cycle time t/tp=0.5 for subject 12. A recirculation zone close to the inlet in the Newtonian flow is absent in the two non-Newtonian counterparts.

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Fig. 13

Critical TAWSS for subject 27 at t/tp=1 of the sixth cycle. Red zones mark the locations where TAWSS has dropped below 0.076 Pa. Newtonian flow exhibits a slightly larger red zone.

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Fig. 14

Instantaneous WSS for subject 12 at t/tp=0.5. Newtonian flow shows a slightly higher instantaneous WSS at the locations indicated with arrows.

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