Rethinking mechanical heart valves in the aortic position: new paradigms in design and testing

Figures

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  Figure 1. Schematic of a native aortic valve and a bileaflet mechanical heart valve in open and closed positions.

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  Figure 2. Schematic of the flow features of a bileaflet MHV. (A) Side view of the main forward flow at peak systole. Velocity and vorticity scales are qualitative. The vorticity map illustrates the shedding of pairs of counter-rotating vortices. The inset illustrates the flow separation region on the medial surface of the leaflet. (B) Side view of the regurgitant jets that develop at the edges of the leaflets and in the hinge gaps during diastole. (C) Top view of the valve during peak systolic flow. The fully open leaflets allow the development of three main jets. (D) Top view of the valve during diastole. The inset illustrates the streamlines and flow separation in the hinge gap between the leaflet peg and the butterfly-shaped recess in the valve housing. To keep the illustration simple, the hinge gap flow in the inset is seen from a different point of view than the top view image (right-to-left corresponds to the aorta-to-ventricle orientation).

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  Figure 3. Simplified sketch of the SJM bileaflet valve. In subsequent iterations (from the original Masters design to Masters HP and finally to Regent), the sewing cuff has been shrunk and mover from intra-annular to supra-annular position, resulting in an increase of the orifice-to-annulus diameter ratio. The ratio values reported in the figure are specific to the 19 mm version of the SJM valve.

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  Figure 4. Bileaflet valves in open position (A) On-X valve design. Reproduced with permission from “0n-X@ Aortic Heart Valve” by Artivion, Inc. Used with the Permission of Artivion, Inc. (B) Newly proposed iValve design. Adapted with permission from “Rendered isometric views of the iValve are shown in the A) closed and B) open positions. Both the housing and leaflets are identifiable” by Dylan Goode, Lawrence Scotten, Rolland Siegel and Hadi Mohammadi, licensed under CC BY-NC 4.0.

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  Figure 5. Time-averaged streamwise velocity contours in the monitor plane: (a) control: without VGs; (b) with co-rotating VGs; and (c) with counter-rotating VGs. Reprinted with permission from “Time-averaged streamwise velocity contours in the monitor plane: (a) control: without VGs; (b) with co-rotating VGs; and (c) with counter-rotating VGs” by Zhenyu Wang, Lakshmi Prasad Dasi and Hoda Hatoum, licensed under CC-BY.

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  Figure 6. Principles of 2D-2C PIV. A high-speed camera captures images of the seeding particles in the plane illuminated by a thin laser sheet (pulsed). Each image is divided into a grid of interrogation windows. Pairs of single-exposure images (delayed by Δt) are analyzed using cross-correlation algorithms to determine the particle displacement Δx (in the plane of the laser sheet) for each interrogation window. The result is a vector map of the two components of the fluid velocity in the plane of the laser sheet. The delay Δt affects the temporal resolution of the velocity maps, while the distance between the center points of the interrogation window affects the spatial resolution.