Comparative Study of the Effect of Structural Parameters on the Flexibility of Endovascular Stent Grafts

Abstract

The complication of stent graft-induced new entry (SINE) after thoracic endovascular aortic repair (TEVAR) may be caused by the spring-back force of both ends of the stent grafts. Spring-back force, which is exerted by the curvature and ends of stent grafts on the greater wall of the aorta, suggests poor flexibility. Research on stent graft flexibility via design optimization has been widely disregarded. Thus, this study investigates the relationship between stent graft structure and flexibility by measuring bending and spring-back forces. Stent spacing (5, 10, and 15 mm), apex angle (30° and 45°), and strut configuration (Z- and M-stented) were considered for the structural parameters. The overall tendency of spring-back and bending forces was similar. The stent graft with 15 mm spacing attained the lowest force level. The force difference between samples with 30° and 45° apex angles became prominent as the curving angle increased. The sample with 45° stent apex attained low force value. The Z-stented graft obtained a lower force than the M-stented graft with the same number of struts per hoop. Consequently, optimal flexibility was obtained when the structural design was characterized by long stent spacing, big stent apex angle, and Z-type strut configuration.

Computational Comparison of the Mechanical Behavior of Aortic Stent-Grafts Derived from Auxetic Unit Cells

“…A different approach examining the link between SG microstructure and flexibility based on its effect on stent graft-induced new entry (SINE) after thoracic endovascular aortic repair (TEVAR) was conducted by Guan et al [ 23 ], where stent spacing, apex angle, and strut configuration (Z- and M-shaped) were selected as structural parameters to investigate their effect on bending and spring-back forces. According to [ 23 ], optimizing SG flexibility can be achieved through enhanced stent spacing, a larger stent apex angle, and usage of z-stent shape over m-stent shape. Yan et al [ 24 ] suggested non-equal-strut stent hoops to improve radial support force and longitudinal flexibility, which were proven through numerical and experimental testing.…”

A modeling framework for computational simulations of thoracic endovascular aortic repair

“…A smaller aortic arch angle requires larger bending in the proximal stent graft to conform to the arch curvature. Spring back force, defined as the force applied by the stent graft to the greater wall of the aorta 42 increases in the smaller aortic arch angles. This leads to stent graft straightening and enlargement of the bird‐beak size.…”

Mechanical characterizations of braided composite stents made of helical polyethylene terephthalate strips and NiTi wires

“…The BCS was braided by 8 NiTi wires and 24 PET strips. The thickness of the PET strip was 0.12mm [12]. The width of the PET strip (w) was 0.57 mm, which could be calculated as following:…”

“…The BCS was braided by 8 NiTi wires and 24 PET strips. The thickness of the PET strip was 0.12mm [ 12 ]. The width of the PET strip ( w) was 0.57 mm, which could be calculated as following: where L is the distance of the two crossover points along the circumferential direction ( Figure 1a ).…”