Finite Element Analysis and Bench Testing of Ventricular Septal Defect Occluder

Abstract

Complications after transcatheter closure of the ventricular septal defect (VSD) is significantly associated with the mechanical behaviour of the VSD occluder. This study aims to investigate the effect of structural parameters of the VSD occluder. A mechanical model of the VSD occluder was constructed by theoretical modelling. The mechanical properties of the VSD occluders with different braiding angles (30°, 45°, 60°), materials (nitinol (NiTi), polydioxanone (PDO)) and waist-heights (3 mm, 4 mm) were analysed and validated by bench tests. For the 30°NiTi, 45°NiTi, 60°NiTi and 45°PDO occluders, the bending angles at the waist under 1 mm radial shrinkage were 112°, 121°, 155° and 155°, respectively. And the maximum principal strains at the waist were 16.62%, 8.19%, 1.20%, and 0.66%, respectively. The maximum radial deformations with 0.5 rad axial bending 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, high stress appeared at the margin and the contact area, and the area with the 3-mm-occluder was much larger. In conclusion, the 60°NiTi occluder showed better ability to fit the deformation of the defect than the other NiTi occluders, and the 45°PDO occluder performed better under compression conditions but poorly under bending conditions than the 45°NiTi occluder. The choice of the appropriate waist-height is beneficial to eliminate associative complication by reducing the contact stress.