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Research Papers

The Effect of Implantation Orientation of a Bileaflet Mechanical Heart Valve on Kinematics and Hemodynamics in an Anatomic Aorta

[+] Author and Article Information
Iman Borazjani

St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414iman@buffalo.edu

Fotis Sotiropoulos

St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414fotis@umn.edu

J Biomech Eng 132(11), 111005 (Oct 15, 2010) (8 pages) doi:10.1115/1.4002491 History: Received July 22, 2010; Revised August 09, 2010; Posted September 01, 2010; Published October 15, 2010; Online October 15, 2010

We carry out three-dimensional high-resolution numerical simulations of a bileaflet mechanical heart valve under physiologic pulsatile flow conditions implanted at different orientations in an anatomic aorta obtained from magnetic resonance imaging (MRI) of a volunteer. We use the extensively validated for heart valve flow curvilinear-immersed boundary (CURVIB) fluid-structure interaction (FSI) solver in which the empty aorta is discretized with a curvilinear, aorta-conforming grid while the valve is handled as an immersed boundary. The motion of the valve leaflets are calculated through a strongly coupled FSI algorithm implemented in conjunction with the Aitken convergence acceleration technique. We perform simulations for three valve orientations, which differ from each other by 45 deg and compare the results in terms of leaflet motion and flow field. We show that the valve implanted symmetrically relative to the symmetry plane of the ascending aorta curvature exhibits the smallest overall asymmetry in the motion of its two leaflets and lowest rebound during closure. Consequently, we hypothesize that this orientation is beneficial to reduce the chance of intermittent regurgitation. Furthermore, we find that the valve orientation does not significantly affect the shear stress distribution in the aortic lumen, which is in agreement with previous studies.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) A typical bileaflet mechanical heart valve meshed with triangular elements, as required by the CURVIB method. (b) The anatomy of the left side of the heart. The ascending aorta has a curvature different from that of the aortic arch; LV: left ventricle; NCA: noncoronary artery; RCA: right coronary artery; LCA: left coronary artery.

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Figure 2

(a) The anatomically realistic aorta geometry reconstructed from MRI data with the straight inlet and outlet additions as in Ref. 33 and the placement of the valves at different orientations inside it. The ascending aorta is almost symmetric about its plane of curvature (dash-double-dot line). (b) The placement of the valves inside the sinus from top view. The original orientation of the leaflet (vertical leaflets) (33) was parallel to the plane of curvature of the ascending aorta. The 90 deg orientation (horizontal leaflets) are perpendicular to this plane of curvature while the 45 deg orientation (inclined leaflets) is in between.

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Figure 3

Physiological incoming flow waveform specified at the inlet and the leaflet kinematics for the BMHV in an anatomic aorta at different orientations. The time instants in the cardiac cycle in which the flow is visualized are marked with thick vertical lines a, b, c, and d.

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Figure 4

Comparison of instantaneous out-of-plane nondimensional vorticity (ΩD/U) contours for 0 deg (left), 45 deg (middle), and 90 deg (right) orientations on the midplane of the valve. a, b, c, etc., correspond to the time instant marked in Fig. 3 within the cardiac cycle.

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Figure 5

Comparison of vortical structures visualized by the isosurface of q-criteria for 0 deg (left), 45 deg (middle), and 90 deg (right) orientations. a, b, c, etc., correspond to the time instant marked in Fig. 3 within the cardiac cycle.

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Figure 8

Comparison of instantaneous isosurfaces of local maximum shear τloc=6.4 Pa for 0 deg (left), 45 deg (middle), and 90 deg (right) orientations. a, b, c, etc., correspond to the time instant marked in Fig. 3 within the cardiac cycle.

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Figure 7

Histograms of local maximum shear τloc in the anatomic aorta for 0 deg (dotted lines), 45 deg (solid lines), and 90 deg (dashed lines) orientations. f is the percentile of the number of occurrences of a shear value τloc values in intervals with the width Δτloc=0.064 Pa to the total number of occurrences. a, b, c, etc., correspond to the time instant marked in Fig. 3 within the cardiac cycle.

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Figure 6

Instantaneous nondimensional pressure (p/ρU2) contours for 0 deg (left), 45 deg (middle), and 90 deg (right) orientations on the midplane of the valve corresponding to the time instant d marked in Fig. 3.

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