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Technical Briefs

Hemodynamics of Ulcerated Plaques: Before and After

[+] Author and Article Information
Megan Cummins

Department of Biology, Lafayette College, Easton, PA 18042

Jenn Stroud Rossmann

Department of Mechanical Engineering, Lafayette College, Easton, PA 18042rossmanj@lafayette.edu

J Biomech Eng 132(10), 104503 (Sep 27, 2010) (9 pages) doi:10.1115/1.4002372 History: Received December 04, 2009; Revised August 02, 2010; Posted August 16, 2010; Published September 27, 2010; Online September 27, 2010

The hemodynamics and fluid mechanical forces in blood vessels have long been implicated in the deposition and growth of atherosclerotic plaque. Detailed information about the hemodynamics in vessels affected by significant plaque deposits can also provide insight into the mechanisms and likelihood of plaque weakening and rupture. In the current study, the governing equations are solved in their finite volume formulation in several patient-specific stenotic geometries. Of specific interest are the flow patterns and forces near ulcerations in the plaque. The flow patterns and forces in vessels with ulcerated plaques are compared with those in stenotic vessels without evidence of ulceration and to the hemodynamics in the same vessels as they likely appeared prior to ulceration. Hemodynamics “before” and “after” hemorrhage may suggest fluid mechanical and morphological factors of diagnostic and predictive value. Recirculation zones, vortex shedding, and secondary flows are captured by both laminar and turbulent solutions. The forces on vessel walls are shown to correlate with unstable plaque deposits. Performing before and after studies of vessels in long-term radiology studies may illuminate mechanisms of hemorrhage and other vessel remodeling.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Waveform for pulsatile blood flow from Ref. 20. Markers signify points of interest during the flow cycle: (1) diastole t/tp=0, (2) acceleration t/tp=0.5, (3) systole t/tp=0.1, and (4) deceleration t/tp=0.18.

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Figure 2

Clinical images of vessels and corresponding meshed geometries for patient-specific ulcerated geometries A and B. The ECA is on the left, the ICA is on the right, and flow is upward.

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Figure 3

Location of geometry measurements on typical carotid bifurcation and plaque geometry measurements on representative stenosis. Similar measurements were made for all geometries using a standardized method described in Sec. 2.

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Figure 4

Instantaneous streamlines calculated in typical carotid bifurcation geometry. Contours reflect velocity magnitude (in m/s). Numbers 1–4 refer to times defined in Fig. 1: (1) diastole, (2) acceleration, (3) systole, and (4) deceleration.

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Figure 5

Instantaneous streamlines calculated in typical bifurcation, showing three-dimensionality of flow at systole (left) and deceleration phase of flow cycle (right). Streamlines are shaded by velocity magnitude (in m/s).

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Figure 6

Instantaneous streamlines calculated in vessel A “before” (bottom) and “after” (top) ulceration. Contours represent velocity magnitude.

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Figure 7

Comparison of ulcerated and nonulcerated vessel A. (a) Location of points (i)–(viii) on ulcerated/after vessel. (b) Location of points (i)–(viii) on nonulcerated/before vessel. Note that all but points (iii) and (iv) are in the same exact position on both vessels. (c) WSS and (d) pressure at each point during systole and diastole.

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Figure 8

Comparison of ulcerated and nonulcerated vessel B. (a) Location of points (i)–(viii) on ulcerated/after vessel. (b) Location of points (i)–(viii) on nonulcerated/before vessel. Note that all but points (iii) and (iv) are in the same exact position on both vessels. (c) WSS and (d) pressure at each point during systole and diastole.

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Figure 9

For vessel B in its ulcerated (top) and nonulcerated before (bottom) morphologies; WSS calculated at various locations over one flow cycle

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Figure 10

Comparison of COSI, measure of temporal variation of WSS in vessel B after and before ulceration at locations C, E, and F as labeled in Fig. 9

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Figure 11

Results of laminar and turbulent simulations showing WSS distribution along plaque surface in vessel B at systole (left) and diastole (right)

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