Impact of Variation in Commissural Angle between Fused Leaflets in the Functionally Bicuspid Aortic Valve on Hemodynamics and Tissue Biomechanics

Figures

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  Figure 1. Computed tomographic 3D reconstructions of two patients with functionally bileaflet aortic valves with fusion between the coronary leaflets and trisinuate aortic roots are demonstrated (Patient 1 = Panels (A,C); Patient 2 = Panels (B,D)). Panels (A,B) demonstrate a short axis view of the aortic valve with the angle between the two commissures measured to be symmetrical and very asymmetrical, respectively. Prominent raphes are visualized at the zone of fusion between the coronary leaflets for both valves. Panels (C,D) demonstrate the blood-filled trisinuate aortic roots, both with similar commissural heights (11 mm) of the hypoplastic interleaflet triangle under the zone of fusion between the coronary leaflets. The sinutubular junction is marked with a blue line. L, left coronary sinus; LCA, left coronary artery; N, non-coronary sinus; R, right coronary artery; RCA, right coronary artery.

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  Figure 2. (a) Reconstructed geometry of the thoracic aorta is shown to the left, complete with specified boundary conditions (transparent grey color), and with the aortic valvar leaflets: left coronary (L), non-coronary (N), and right coronary (R). (b) Graphs in this section depict the flow rate during the cardiac cycle, both at the inlet and outlet (in the descending aorta). The pressure boundary conditions at the head and neck vessels across the cardiac cycle are established using the three-parameter Windkessel model. The solid surfaces of the leaflets that intersect with the aortic root are fixed, whereas all other solid surfaces are free.

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  Figure 3. Within the blue hashed box, we have short-axis and long-axis reconstructed geometry of the normal trileaflet aortic valve, and with two variations in the extent of the zone of fusion, one with 2/3rd commissural height (comH) and partial fusion between the coronary leaflets, and the other with 1/3rd commissural height and complete fusion between the coronary leaflets. With decreasing commissural height, there is increased fusion and angle of the apex of the interleaflet triangle (inta). Within the green hashed box, there is a variation of the commissural angle, i.e., 120∘, 150∘, and 180∘ deg. This increases the surface area of the unfused non-coronary leaflet. Within the red hashed box, there is a variation in the fusion orientation with the RN and rare LN leaflet fusion phenotypes.

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  Figure 4. Blood flow visualization using velocity vectors at different time instants during the cardiac cycle for the TAV case and the BAV cases with fully fused coronary leaflets. The velocity vectors are presented on a vertical plane, coronally oriented.

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  Figure 5. Velocity and streamline distribution shown on the short-axis cut plane. The plane is located 1.5×comH proximally of the sinutubular junction as shown with the white dashed line in Figure 4. The keys are the same as those in Figure 4.

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  Figure 6. (a) Streamwise velocity profile (W) and (b) cross-flow velocity profile (V) distribution along the white dashed line that is located proximal to the sinutubular junction, see annotated white dashed line in Figure 5. The x-axis of the profile is normalized with the total length, where x/X=0 is towards the convex side and x/X=1 is towards the concave side of the ascending aorta. All cases are for peak systole. The 4D Flow MRI data for the normal TAV cases are shown with black dots.

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  Figure 7. (a) Aortic opening area as a function of the cardiac cycle for the TAV and BAV cases. (b) Radial displacement of the non-coronary leaflet at the mid-point location of the free edge. (c) Radial displacement of the right leaflet at the mid-point location of the free edge.

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  Figure 8. Isometric views showing the von Mises stress distribution during opening and closing for the TAV case and the BAV cases during the cardiac cycle.

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  Figure 9. Isometric views showing the Frobenius norm of the strain tensor during opening and closing for the TAV case and the BAV cases with full coronary leaflet fusion during the cardiac cycle. Same keys as in Figure 8.

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  Figure 10. Variation of (a) von Mises stress and (b) Frobenius norm of the strain tensor along the mid of the non-coronary leaflet between the intersection with the aortic root (s=0) up to the free edge (s=1). Data are presented for the TAV case and the BAV cases.