Bioinspired polymeric heart valves: A combined in vitro and in silico approach

Figures

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  Bioinspired heart valve systolic performance: polymeric construct versus computational model.

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  Figure 1. Step-by-step diagram showing the design process of the bioinspired valve design with minimized commissural gaps. A, Side view of the valve; the green arrow indicates top view of the valve where the following steps are illustrated. B, Tri-leaflet valve developed from rotating the highlighted leaflet around a central axis with overlapping cusps. C, Original design created from pulling leaflets away from a central axis. D, Overlapping leaflet geometry with lines drawn from center of valve to each commissure used to redefine the free edges. E, Improved leaflet design defined by the new free edge and original equation-based curves derived from the micro-CT scan. F, Filleted leaflet geometry with smoother belly region. G, Full bioinspired trileaflet valve design with minimized commissural gaps.

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  Figure 2. A, Schematic of the manufacturing process. The heart valve mold is 3D-printed using polypropylene and then dipped in a polysiloxane urethane (PSU) solution. After evaporation of the solvent, the polymeric heart valve (PHV) can be lifted off the mold. B, A PHV, with red circles indicating the locations where thickness was measured. HV, Heart valve; THF, tetrahydrofuran.

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  Figure 3. Meshed geometry of the valve (leaflets connected with the conduit) with an element size of 0.75 mm. A, Top view. B, Side view at a cross-section.

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  Figure 4. A, Thickness in different locations of the valve in polymeric heart valves (PHVs) produced using polysiloxane urethane (PSU) 13 w/v%. Thickness decreases from the center of the leaflet free edge to the sides (toward the commissures) and downward (toward the belly). The box spans from the first to third quartile, whiskers indicate the minimum-maximum range, and the line indicates the median. B, Values of w1 for PHVs produced using different PSU concentrations. The box indicates the first to third quartile range, and the whiskers indicate the minimum to maximum range. C and D, The effect of thickness on the effective orifice area (EOA) and regurgitant fraction (RF); the shaded area in both graphs highlights the trend. E, Assessment of opening (top) and closing (bottom) performance of valves under normotensive conditions with increasing values of w1 thickness, from left to right: 110, 150, 180, and 200 μm.

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  Figure 5. Data comparison between the experiment (solid lines) and the simulation (dashed lines) with a leaflet thickness of 110 μm for both pressure difference profile (blue; left y-axis) and flow rate (red; right y-axis). The simulation lines cover only systole. The blue and red dotted lines represent the 0 for the left and right axes, respectively.

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  Figure 6. Displacement (left) and stress distribution (right) for fully opened valves from side and top views with different leaflet thicknesses: 110 μm (A), 150 μm (B), 180 μm (C), and 200 μm (D).

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  Figure 7. Comparison of the effect of leaflet thickness (w1) on effective orifice area between the simulation and experimental results. Note that the data points for simulation and experiment overlap for 180 μm. EOA, Effective orifice area.

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  Figure 8. Graphical abstract depicting study workflow, results, and implications. EOA, Effective orifice area; RF, regurgitant fraction; ALE, arbitrary Lagrangian-Eulerian; CT, computed tomography.

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  Figure E1. Dispersion of thickness at different points of the leaflet for all PSU concentrations tested. Note how the thickness follows a somewhat similar trend for all concentrations, being highest at the center of the leaflet free edge (w1) and thinnest at the base below the valve (w4). The thickness at w5 for the 14 w/v% PSU valves does not follow the trend and thus will be further investigated in future experiments. N.B. The process of dip coating produces 100% PSU layers after solvent evaporation (hence, material properties do not change). The thickness of this layer depends mainly on the viscosity (μ) and density (ρ) of the dipping solution, which depend on the concentration of PSU.

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  Figure E2. Effect of thickness of different locations on the leaflet—w1 (A), w2 (B), w3 (C), w4 (D), w5 (E), and w6 (F)—on the effective orifice area (EOA). Note that only w1 has a correlation between thickness and EOA (with EOA decreasing with increasing thickness). For all other values of thickness, there is no clear trend. This highlights the sensitivity of hydrodynamic performance on w1.