Finite Element Analysis and Bench Testing of Ventricular Septal Defect Occluder

Abstract

The mechanical behavior of the ventricular septal defect (VSD) occluder is strongly linked to complications following transcatheter closure of the VSD. Methods: A mechanical model of the VSD occluder was constructed by theoretical modeling of the braiding structure. The mechanical properties of the VSD occluders with different braiding angles (30 deg, 45 deg, 60 deg), materials (nitinol (NiTi), polydioxanone (PDO)), and waist-heights (3 mm, 4 mm) were studied by finite element analysis and validated by bench tests. Under 1 mm radial shrinkage, the bending angles at the waist of the 30 deg NiTi, 45 deg NiTi, 60 deg NiTi and 45 deg PDO occluders were 112 deg, 121 deg, 155 deg and 155 deg, respectively. The maximum principal strains at the waist were 16.62%, 8.19%, 1.20%, and 0.66%, respectively. With 0.5 rad axial bending, the maximum radial deformations at the waist were 1.73, 1.44, 0.41 and 1.68 mm, respectively. When the occluders were implanted into VSD with the mean thickness of 3.5 mm, considerable stress developed at the hole's margin and the contact area. The area with the 3 mm occluder was much bigger than that with the 4 mm occluder. Conclusions: the 60 deg NiTi occluder showed better ability to fit the deformation of the defect than the other NiTi occluders, and the 45 deg PDO occluder performed better under compression conditions but poorly under bending conditions than the 45 deg NiTi occluder. The choice of the appropriate waist-height is beneficial to eliminate associative complication by reducing the contact stress.