Figure 1.
Schematics of heart valve anatomy.
(A) The arrangement of the valves in the heart. (B) The structures and layers of an aortic valve leaflet.
Figure 2.
Schematics of a leaflet illustrating the structural parameters used to quantitatively describe the leaflet mesostructure, including 1) the length from the free edge along the root, Lr, 2) the distance along a fiber bundle to the first branching, Lb, 3) the width of the fiber bundle at the root, Wr, 4) the width of the fiber bundle before the first branching, Wb, and 5) the position of the fiber bundle from the free edge along the root, Nr.
Figure 3.
Polarized light images of three representative aortic valve leaflets.
Images of three representative leaflets (left) along with traces of the major fiber bundles (right) to clarify primary structures of the leaflets. Fiber bundles appear yellow-orange and membranes appear blue as a result of the use of transmitted elliptically polarized light imaging. Clear differences in the fiber bundle arrangement were shown in the three leaflets. The left leaflet was the most asymmetric, while the non-coronary and right leaflets were more symmetric. Fiber bundles were most distinct at the edge (root) and branched or spread out towards the belly of the leaflet. Overall, fiber bundles appeared to present a cross-hatched, overlapping structure with thin connecting membranes. The yellow boxes identify the regions presented in Figures 8 and 12.
Figure 4.
Figures of whole leaflet properties.
(A) Boxplot of aortic leaflet widths. The leaflet widths are significantly different with the right coronary leaflets being the widest, followed by the left coronary leaflets and the non-coronary leaflets being the least wide (*: p<0.001. via one-way ANOVA, n = 16). (B) Boxplot of aortic leaflet heights, where no significant difference was found between the heights of the leaflets (p>0.05 via one-way ANOVA). (C) Bar graphs of average fiber bundle counts (max of Nr) for each side of each leaflet (mean±SEM, *: p<0.05 via student’s t-test between each side of the coronary, n = 7). (D) Bar graphs of average fiber bundle width at the root (Wr) for each side of each leaflet. (mean±SEM, *: p<0.01 via student’s t-test between each side of the leaflet, n = 33).
Figure 5.
Polarized light image of the right aortic leaflet with trace highlighting the underlying fiber bundles (shown in light grey in the trace) that travel upwards from the nadir of the leaflet.
Figure 6.
Polarized light images of aortic valve mesostructure.
(A) Image of typical fiber bundle (orange) and membrane (blue, blue-green) structures showing the crimping patterns typical of collagen (arrows) and highly parallel fibril organization in the fiber bundles. (B) Image of complex overlapping fiber-membrane structures showing crimping patterns typical of collagen (arrow), as well as the fiber bundles branching and extending inwards from the root of the leaflet, interconnecting with membranes with fan-like and pinnate structures.
Figure 7.
Bar graphs of average fiber bundle root witdth (Wr) as a function of position from the free edge (Nr).
The fiber bundles toward the center of the leaflet (Nr = 3,4) tended to be the widest with the addition of the second fiber bundle on the right coronary leaflet. Error bars indicate the standard error.
Figure 8.
Bar graph of average distance between adjacent fiber bundles on each side (mean ±95% confidence intervals), calculated by least squared linear regression of Lr over Nr on each side of each leaflet (R2>0.81 for all regressions).
Figure 9.
Higher resolution polarized light images of fiber bundle branching patterns from Fig. 3.
Three branching mechanisms were shown: (A)Tree-like fiber bundle branching. (B) Pinnate fiber branching. (C) Fan-like fiber branching.
Figure 10.
Linear regression of branching measurements.
(A) Graph of the fiber bundle width at the first branch point (Wb) relative to the width at the root (Wr). The trendline has an R2 value of.68 suggesting some relationship between Wb and Wr. The slope of the trendline is close to 1 suggesting that the fiber bundles do not widen before the first branch point. (B) Graph of the length along fiber bundle to the first branch point (Lb) relative to the width at the root (Wr). The trendline has an R2 value of.02 suggesting no correspondence.
Figure 11.
Bar graphs of the relative widening (Wb/Wr) as a function of fiber bundle position position from the free edge (Nr) (mean ± SEM).
(*: p<0.05 via student’s t-test).
Figure 12.
Higher resolution optical image of the left coronary leaflet showing the anchoring structures of fiber bundles, with fibrils branching off into the connecting membrane.