Design of Tissue-Engineered Leaflet Shape for the Ovine Pulmonary Valve Single Leaflet Replacement Surgery

Pulmonary valve (PV) replacement surgery is a treatment option for patients with a congenitally defective pulmonary outflow track. A tissue engineered pulmonary valve (TEPV) is a potential approach to serve as a replacement pediatric heart valve that has the potential for somatic growth. The single leaflet replacement surgical model can assist in assessing candidate biomaterials responses to in-vivo function. However, an empirically determined unloaded leaflet shape may result in abnormal valve function due to incomplete coaptation of leaflets and asymmetric stress distributions. Thus, to determine the final deformed shape of an engineered scaffold replacement PV leaflet under transvalvular pressure the following key factors must be determined: the scaffold anisotropic mechanical properties, optimal thickness, and the exact initial leaflet shape. We have used electrospun poly (ester urethane) ureas (ES-PEUU) scaffolds since they exhibit mechanical properties very similar to the native PV [1]. In this work we present a design framework of the optimal leaflet shape determination utilizing a single sheet of ES-PEUU for single leaflet replacement surgery via finite element (FE) simulation. The mechanical properties of ES-PEUU scaffold for leaflet replacement were obtained from biaxial in-plane tension and three-point bending flexural deformation experiments. Generalized Fung-type hyperelastic constitutive model [2] was implemented into a commercial FE software package to simulate the mechanical behavior of ES-PEUU scaffolds. By perturbing the initial shape of leaflet and simulating its quasi-static deformation under PV diastolic loading, the optimal shape of unloaded leaflet can be determined by comparing the deformed shape of leaflet obtained from FE simulation of TEPV with the one from microCT scan of a native ovine PV.