Design of an aortic polymeric valve with asymmetric leaflets and evaluation of its performance by finite element method

• Published in: Computers in biology and medicine 2022-06, Vol.145, p.105440-105440, Article 105440
• Main Authors: Sarrafzadeh-Ghadimi, Nima, Ghalichi, Farzan, Niroomand-Oscuii, Hanieh, Fatouraee, Nasser
• Format: Article
• Language: English
• Subjects: Aorta; Asymmetric leaflet; Asymmetry; Coaptation; Eccentricity; Finite element method; Geometric design; Geometric orifice area; Geometry; Heart valves; Hypotheses; Low level; Material properties; Orifices; Parameters; Performance evaluation; Polyethylene; Polyethylenes; Polymeric valve; Polymers; Polypropylene; Polystyrene; Polystyrene resins; Prostheses; Prosthetic valves; Radial curve; Sinuses; Straight lines; Surface area; Systole
• ISSN: 0010-4825; 1879-0534
• DOI: 10.1016/j.compbiomed.2022.105440

The geometry of leaflets plays a significant role in prosthetic valves’ (PVs) performance. Typically, natural aortic valves have three unequal leaflets, which differ in size. The present study aims to design an asymmetric tri-leaflet polymeric valve with one large and two small leaflets based on commissure lengths and leaflet eccentricities. Eccentricity was related to commissure lengths based on the deformation of the free margins for the fully-opened state of leaflets. The polystyrene-block-polyethylene-polypropylene-block-polystyrene polymer characterized the material properties of the leaflets. The Finite Element Method (FEM) was used to evaluate performance parameters, including maximum geometric orifice area (GOA), average GOA, maximum von Mises stress, and leaflet's coaptation surface area (CSA). Asymmetric valves with no eccentricity provided a low level of GOA because the asymmetric form of small leaflets caused them to close faster than the large leaflet, leading to a sudden drop in the GOA during systole. As the radial curve tends towards a straight line, an undesirable coaptation occurs, and peak stress increases despite higher GOAs. A new radial curve consisting of two straight lines connected by an arc that provided 25.64 mm2 coaptation surface area (CAS) and 117.54 mm2 average GOA, was proposed to improve coaptation and GOA. The radial curve of leaflets affects the valve's performance more than other geometric parameters. The combination of straight lines and arcs for radial curves was selected as the reference model for asymmetric valves with one large and two small leaflets. •Aortic valve leaflets are asymmetric and unequal in their sizes.•Asymmetry of leaflets has not been taken into account in designing prosthetic valves.•Radial curve of leaflets has an strong effect on geometric orifice area and coaptation.•A good performance was recorded for a proposed radial curve with two lines and an arc between them.•The corresponding valve with proposed curve could be improved and take a step forward to understand asymmetry of leaflets.