Mechanics Post-TAVR for Trileaflet vs Bicuspid Aortic Valves

Figures

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  Figure 1. Case Processing Workflow Anatomical reconstruction was performed using threshold based techniques to capture the aortic root, left ventricle, ascending aorta, aortic valve leaflets, and calcium nodules (left), TAVR was then simulated deploying a BE THV stent inside the native aortic valve anatomy (middle), and the mechanics of the leaflets were simulated through cardiac pressurization to analyze the systolic GOA and diastolic stress (right). BE = balloon-expandable; GOA = geometric orifice area; TAVR = transcatheter aortic valve replacement; THV = transcatheter heart valve.

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  Figure 2. Example Trileaflet and Bicuspid Aortic Valve Stent Expansion Simulation Result Results are displaying the stent expansion and leaflet diastolic pressurization of the bioprosthetic leaflets in the native valve anatomy following simulated TAVR. The BAV result showed a lower aspect ratio and waist underexpansion profile. AR = aspect ratio; BAV = bicuspid aortic valve; other abbreviations as in Figure 1.

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  Figure 3. Population Comparison of the Stent Waist The waist ER (top) and AR (bottom) between the trileaflet and bicuspid groups with the trileaflet group having a larger waist ER (P = 0.01) and a larger waist AR (P < 0.001). Continuous variables were compared using a 2 sided t-test for equal variances or a 2 sided Welch’s t-test for unequal variances, statistical results are indicated by ∗P < 0.05, ∗∗P < 0.01 and ∗∗∗P < 0.001. ER = expansion ratio; other abbreviations as in Figure 2.

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  Figure 4. Example Trileaflet and Bicuspid Aortic Valve Bioprosthetic Leaflet Simulation Result Stress contours in diastole (left) and the valve opening in systole (right) for an example trileaflet (top) and a bicuspid (bottom) case with the bicuspid showing elevated stress, leaflet overlap, and an elliptical opening.

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  Figure 5. Population Comparison of Bioprosthetic Leaflet Geometric Orifice Area and Stress Comparison of the normalized GOA (top) and the maximum stress (bottom) of the bioprosthetic leaflets between the trileaflet and bicuspid groups with the trileaflet group having a larger normalized GOA (P < 0.01) and a smaller stress (P < 0.001). Continuous variables were compared using a 2 sided t-test for equal variances or a 2 sided Welch’s t-test for unequal variances, statistical results are indicated by ∗P < 0.05, ∗∗P < 0.01 and ∗∗∗P < 0.001. GOA = geometric orifice area.

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  Figure 6. Example Comparison of Low and High Calcium Bicuspid Aortic Valves Simulation results of a bicuspid case with low calcium volume resulting in a circular stent profile (left) and with high calcium volume resulting in a deformed stent profile and elevated stress, overlap, and folding in the bioprosthetic leaflets (right).

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  Figure 7. Example Simulation Result With a Large Radially Facing Calcium Nodule A native valve with a large radially facing calcium nodule causing adverse stent waist underexpansion due to the resistance of the calcium nodule. This demonstrates the importance of not only calcium volume but shape and distribution on its impact on stent expansion in the model.

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  Figure 8. Native Valve With Additional Cusp Fusion of the Fused Leaflets The additional fusion makes the native valve opening relatively small causing significant underexpansion of the stent in the simulation.

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  Central Illustration. Simulated Transcatheter Aortic Valve Mechanical Metrics in Trileaflet vs Bicuspid Aortic Valves and Anatomical Correlations within the Bicuspid Group BE TAVR for BAV has worse simulated mechanical metrics compared to BE TAVR for trileaflet aortic valve patients and is associated with high calcium volume. Clinical studies are required to further investigate TAV durability differences in trileaflet vs BAV patients. AR = aspect ratio; BAV = bicuspid aortic valve; BE = balloon-expandable; ER = expansion ratio; GOA = geometric orifice area; TAV = transcatheter aortic valve; TAVR = transcatheter aortic valve replacement.