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Research Papers

Stability of Carotid Artery Under Steady-State and Pulsatile Blood Flow: A Fluid–Structure Interaction Study

[+] Author and Article Information
Seyed Saeid Khalafvand

Department of Mechanical Engineering,
The University of Texas at San Antonio,
San Antonio, TX 78249
e-mail: seyedsaeid.khalafvand@utsa.edu

Hai-Chao Han

Fellow ASME
Department of Mechanical Engineering,
The University of Texas at San Antonio,
San Antonio, TX 78249
e-mail: hchan@utsa.edu

1Present address: K. N. Toosi University of Technology, Tehran 43344, Iran.

2Corresponding author.

Manuscript received September 1, 2014; final manuscript received March 2, 2015; published online March 25, 2015. Assoc. Editor: Alison Marsden.

J Biomech Eng 137(6), 061007 (Jun 01, 2015) (8 pages) Paper No: BIO-14-1430; doi: 10.1115/1.4030011 History: Received September 01, 2014; Revised March 02, 2015; Online March 25, 2015

It has been shown that arteries may buckle into tortuous shapes under lumen pressure, which in turn could alter blood flow. However, the mechanisms of artery instability under pulsatile flow have not been fully understood. The objective of this study was to simulate the buckling and post-buckling behaviors of the carotid artery under pulsatile flow using a fully coupled fluid–structure interaction (FSI) method. The artery wall was modeled as a nonlinear material with a two-fiber strain-energy function. FSI simulations were performed under steady-state flow and pulsatile flow conditions with a prescribed flow velocity profile at the inlet and different pressures at the outlet to determine the critical buckling pressure. Simulations were performed for normal (160 ml/min) and high (350 ml/min) flow rates and normal (1.5) and reduced (1.3) axial stretch ratios to determine the effects of flow rate and axial tension on stability. The results showed that an artery buckled when the lumen pressure exceeded a critical value. The critical mean buckling pressure at pulsatile flow was 17–23% smaller than at steady-state flow. For both steady-state and pulsatile flow, the high flow rate had very little effect (<5%) on the critical buckling pressure. The fluid and wall stresses were drastically altered at the location with maximum deflection. The maximum lumen shear stress occurred at the inner side of the bend and maximum tensile wall stresses occurred at the outer side. These findings improve our understanding of artery instability in vivo.

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References

Figures

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Fig. 1

Schematic illustration of numerical domain including fluid, solid, and porous medium interfaces in a longitudinal cross section of the 3D artery model. Le is entrance segment length; L is the main artery segment length; and Lo is the tail segment length. See text for dimensions.

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Fig. 2

(a) Axial and circumferential stretch ratios plotted as functions of lumen pressure. Symbols are experimental data from a previous study [17] and the solid lines are fitting curves using Ogden model. (b) Prescribed inlet velocity and outlet pressure waves during three cardiac cycles.

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Fig. 3

Comparison of the maximum deflection at the middle of the artery plotted as a function of the mean pressure when buckling under (a) steady-state flow (b) pulsatile flow conditions at two axial stretch ratios (SR = 1.5 and 1.3) and two flow rates (Qm = 160 and 350 ml/min). SR = stretch ratio and Qm = mean flow rate.

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Fig. 4

Temporal variation of deflection under pulsatile flow at two mean lumen pressures (Pm = 100 and 130 mmHg). Axial stretch ratio SR = 1.3 and mean flow rate Qm = 160 ml/min.

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Fig. 5

The flow velocity distribution at the peak deflection for the artery under pulsatile flow with a stretch ratio of SR = 1.3, mean flow rate of Qm = 160 ml/min, and mean pressure of Pm = 130 mm Hg. At the maximum deflection area, pressure contours are depicted.

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Fig. 6

The lumen shear stress contours under pulsatile flow with SR = 1.3; Qm = 160 ml/min for a mean pressure of: (a) Pm = 130 mmHg and (b) Pm = 100 mmHg. (c) The variation of shear stress on the lumen surface at the inner side and outer side of the bend at the maximum deflection area. SR = stretch ratio; Qm = mean flow rate; and Pm = mean pressure.

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Fig. 7

Schematics: definition of inner, outer, M1, M2 points, and axial curves which are equally distributed along the circumference of vessel lumen. Graphs: temporal variation of normal and shear stresses at the inner, outer, M1 and M2 points of artery under pulsatile flow with Qm = 160 ml/min, Pm = 130 mm Hg, and SR = 1.3. The results are compared with a control straight artery under the same conditions. SR = stretch ratio; Qm = mean flow rate; and Pm = mean pressure.

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Fig. 8

Circumferential variation of wall stress at the time of maximum deflection at different outlet pressures (mean pressure Pm = 90–130 mm Hg). Pulsatile flow mean flow rate Qm = 160 ml/min and axial stretch ratio SR = 1.3.

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Fig. 9

Axial variation of wall stress at the time of maximum deflection along the outer and M2 curves at two different axial stretch ratios (SR = 1.3 and 1.5). Pulsatile flow mean pressure Pm = 130 mmHg and mean flow rate Qm = 160 ml/min.

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