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Research Papers

Blood Damage Through a Bileaflet Mechanical Heart Valve: A Quantitative Computational Study Using a Multiscale Suspension Flow Solver

[+] Author and Article Information
B. Min Yun

G.W. Woodruff School of Mechanical Engineering,
801 Ferst Drive,
Atlanta, GA 30332-0405
e-mail: min@gatech.edu

Cyrus K. Aidun

G.W. Woodruff School of Mechanical Engineering,
801 Ferst Drive,
Atlanta, GA 30332-0405
Parker H. Petit Institute for
Bioengineering and Bioscience,
315 Ferst Dr. NW,
Atlanta, GA 30332
e-mail: cyrus.aidun@me.gatech.edu

Ajit P. Yoganathan

G.W. Woodruff School of Mechanical Engineering,
801 Ferst Drive,
Atlanta, GA 30332-0405
Parker H. Petit Institute for
Bioengineering and Bioscience,
315 Ferst Dr. NW,
Atlanta, GA 30332
Wallace H. Coulter Department of
Biomedical Engineering,
School of Chemical and
Biomolecular Engineering,
313 Ferst Drive,
Atlanta, GA 30332-0535
e-mail: ajit.yoganathan@bme.gatech.edu

1Corresponding author.

Manuscript received December 9, 2013; final manuscript received July 18, 2014; accepted manuscript posted July 30, 2014; published online August 12, 2014. Assoc. Editor: Alison Marsden.

J Biomech Eng 136(10), 101009 (Aug 12, 2014) (17 pages) Paper No: BIO-13-1569; doi: 10.1115/1.4028105 History: Received December 09, 2013; Revised July 18, 2014; Accepted July 30, 2014

Bileaflet mechanical heart valves (BMHVs) are among the most popular prostheses to replace defective native valves. However, complex flow phenomena caused by the prosthesis are thought to induce serious thromboembolic complications. This study aims at employing a novel multiscale numerical method that models realistic sized suspended platelets for assessing blood damage potential in flow through BMHVs. A previously validated lattice-Boltzmann method (LBM) is used to simulate pulsatile flow through a 23 mm St. Jude Medical (SJM) Regent valve in the aortic position at very high spatiotemporal resolution with the presence of thousands of suspended platelets. Platelet damage is modeled for both the systolic and diastolic phases of the cardiac cycle. No platelets exceed activation thresholds for any of the simulations. Platelet damage is determined to be particularly high for suspended elements trapped in recirculation zones, which suggests a shift of focus in blood damage studies away from instantaneous flow fields and toward high flow mixing regions. In the diastolic phase, leakage flow through the b-datum gap is shown to cause highest damage to platelets. This multiscale numerical method may be used as a generic solver for evaluating blood damage in other cardiovascular flows and devices.

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References

Figures

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Fig. 1

(a) SJM 23 mm Regent valve, (b) diagram of BMHV in forward flow phase with three orifices, and (c) BMHV in reverse flow phase and domain split into (1) ventricular chamber, (2) ventricular side within valve, (3) aortic side within valve, and (4) aortic sinus expansion

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Fig. 2

Computational setup of SJM valve in aortic position, (a) domain split into regions: (1) ventricular side chamber, (2) valve, (3) sinus expansion, and (4) aortic side chamber, (b) zoomed view showing fully open leaflets in valve region, and (c) angled view

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Fig. 3

(a) Prescribed flowrate and (b) leaflet motion throughout one cardiac cycle of 860 ms from experimental data

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Fig. 4

Modeled platelet (3D ellipsoid—oblate spheroid) with surface mesh of 292 triangular elements, 3 μm major axis diameter, 1.3 μm minor axis diameter

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Fig. 5

Maximum instantaneous particle shear stress (normalized by ambient fluid shear stress) variation with respect to angular orientation for an isolated platelet-shape ellipsoid in simple shear flow (Jeffery's orbit), with decreasing particle diameter d from supergrid to subgrid resolution. Smallest diameter represents size of subgrid platelets in BMHV blood damage simulations.

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Fig. 6

300 platelets seeded randomly upstream of BMHV. (a) Side view showing platelets with same initial axial position, and (b) cross-sectional view showing platelets with randomized cross-sectional position

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Fig. 7

BDI histogram for 4200 platelets after simulation of 260 ms of systolic flow: (a) positions and angles randomized for every seed of 300 platelets and (b) same positions and angles for every seed of 300 platelets. Interval: 0.05 dynes·s/cm2, damage beyond 1.0 dynes·s/cm2 not shown

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Fig. 8

(a) 300 platelets initially seeded upstream of valve and (b) 5400 platelets distributed throughout domain at end of simulation

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Fig. 9

BDI histogram for 5400 platelets after simulation of 460 ms of damage accumulation representing full systole and early diastole. Interval: 0.05 dynes·s/cm2, damage beyond 1.0 dynes·s/cm2 not shown.

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Fig. 10

(a) BDI contour plot for small cubic regions of domain—Eulerian view, (b) contours blanked if damage in region is less than 0.5 dynes·s/cm2 (c) flowrate curve at end of simulation at early-to-mid diastolic flow (Re = 75 in reverse flow)

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Fig. 11

(a) Angled view, (b) cross-sectional view, (c) zoomed view of platelet, demonstrating high damage values of a platelet traversing near the bottom leaflet surface

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Fig. 12

Perpendicular viewpoints of platelet pathline demonstrating high damage values while (a) traversing near leaflet surface, (b) corresponding vorticity field, (c) viscous shear stress field (units in dynes/cm2), and (d) damage accumulation over time

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Fig. 13

Platelet caught in recirculation near sinus expansion wall (a) 3D angled view, (b) cross-sectional view

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Fig. 14

Perpendicular viewpoints of platelet pathline demonstrating (a) platelet caught in recirculation near sinus expansion wall, (b) corresponding vorticity field, (c) viscous shear stress field (units in dynes/cm2), and (d) damage accumulation over time

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Fig. 15

2000 platelets at (a) beginning of simulation and (b) end diastole after 320 ms of mid-diastole simulation

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Fig. 16

Cluster of platelets leaking through b-datum gap (a) approaching b-datum line, (b) flowing through gap 2 ms later

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Fig. 17

(a) Cluster of platelets leaking through b-datum gap, (b) corresponding vorticity flow field, and (c) viscous shear stress field (units in dynes/cm2)

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Fig. 18

Platelet leaking through valve housing gap (a) approaching leaflet, (b) flowing through gap 2 ms later, and (c) on ventricular side after leakage

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Fig. 19

Near peak flow (Re = 5500) showing (a) disorganized vortex shedding past leaflet tips that incur mild damage, (b) corresponding shear stress field (units in dynes/cm2)

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Fig. 20

Rigid ellipsoid isolated in simple shear flow (Jeffery's orbit)

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Fig. 21

(a) Angular orientation and (b) angular velocity variation for simulations versus theory of Jeffery's orbit for platelet 0.07 × 0.07 × 0.031 radius, one-way FSI, Rep = 0.0218, G = 1/6000, τ = 5

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Fig. 22

Effect of particle size on orbital drift from Jeffery's orbit theory for two-way FSI modeling (maximum diameter given as major axis diameter in LB units)

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Fig. 23

Variation of rotation angle over time for an example platelet for (a) one-way FSI and (b) two-way FSI

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