Impact of the Design of Aortic Bioprostheses on Valve Function: A Parametric Study

Structural valve deterioration of aortic bioprosthetic heart valves (BHV) is influenced by leaflet mechanical stress, dependent on design parameters. This study provides a mathematical description of BHV geometry based on these geometric parameters and investigates their influence on valve function.

Ten BHV models with variations in geometric parameters were tested under controlled conditions in a cardiac simulator. The Trifecta valve TF-25 (Abbott) was used as a reference geometry to define the "normal" mathematical valve design and was also experimentally tested. The valves were made of silicone using 3D-printed molds. Hemodynamic performance was assessed by Doppler echocardiography. Leaflet motion and strain fields were analyzed with stereophotogrammetry and digital image correlation.

There was no significant difference in hemodynamic performance between the Trifecta valve and the "normal" silicone valve (p > 0.05). Increased leaflet thickness, smaller diameters, and greater belly curvature reduced significantly (p < 0.01) the hemodynamic performance, while taller leaflets and greater free-edge angle relative to the commissural plane improved the valve performance. Strains during diastole were highest near the commissures. Increased leaflet thickness reduced leaflets deformation, whereas smaller diameters resulted in localized deformation peaks. A greater free-edge angle minimized deformation and increased spacing between leaflets caused inward pulling near stent posts. Excess leaflet height promoted leaflet pinwheeling.

The in vitro analysis reveals the differences between various geometries, emphasizing the importance of valve design for BHV function and durability. The development of new BHVs could be improved through in vitro testing. Furthermore, these in vitro experiments can be replicated to evaluate the geometry of native valves.