Performance of Self-Expanding Nitinol Stent in a Curved Artery: Impact of Stent Length and Deployment Orientation

Abstract

The primary aim of this work was to investigate the performance of self-expanding Nitinol stents in a curved artery through finite element analysis. The interaction between a PROTÉGÉ™ GPS™ self-expanding Nitinol stent and a stenosed artery, as well as a sheath, was characterized in terms of acute lumen gain, stent underexpansion, incomplete stent apposition, and tissue prolapse. The clinical implications of these parameters were discussed. The impact of stent deployment orientation and the stent length on the arterial wall stress distribution were evaluated. It was found that the maximum principal stress increased by 17.46%, when the deployment orientation of stent was varied at a 5 deg angle. A longer stent led to an increased contact pressure between stent and underlying tissue, which might alleviate the stent migration. However, it also caused a severe hinge effect and arterial stress concentration correspondingly, which might aggravate neointimal hyperplasia. The fundamental understanding of the behavior of a self-expanding stent and its clinical implications will facilitate a better device design.

Balloon-Expandable Stents Expansion in Tapered Vessels and Their Interactions

“…9,10 The stent became bent and curved when it was expanded in a curved vessel. [11][12][13] The results of this study showed that an originally straight stent will become tapered when it is expanded in a tapered vessel. This is a very interesting phenomenon, and it should be noted in stent design and clinical stent selection processes because it will affect the conformity of the stent.…”

“…7,8 A number of studies have utilized the finite element method (FEM) to investigate the structural properties of stents and their biomechanical impacts on the coronary artery during stent expansion. [9][10][11][12][13][14] These studies mainly focus on research in which arterial tapering was not a factor, either through simplifying assumptions or by modeling specific, nontapered arteries. However, the diameter varies along the length of a vessel and is sometimes significant.…”

Migration resistance of esophageal stents: The role of stent design

“…The anatomical details of the esophagus including the stellate appearance of the inner esophageal layer [14] was simplified as an esophagus tube with a friction coefficient. A range of friction coefficients were used depending on relative movement between the stent and the esophageal wall [22]. A larger friction coefficient was commonly associated with the less migration risk.…”

“…The stent was made of nitinol which underwent phase transformation between austenite and martensite during one loading cycle [22]. The superelastic behavior of shape memory alloys can be simply understood as the phase transformation of austenite and martensite under stress.…”

Tissue Stresses in Stented Coronary Arteries with Different Geometries: Effect of the Relation Between Stent Length and Lesion Length

“…The factors that influence stent implantation involve the stent loading method (Imani et al 2014), the stent structural design (Hara et al 2006;Lally et al 2005;Hsiao et al 2012;Imani et al 2013bImani et al , 2015, the wire stent fabrication technique (Zhao et al 2012a), the material of the stent (Schiavone et al 2014), and the plaque and vessel geometry (Dottori et al 2016;Shen et al 2014;Wei et al 2016). A few researchers have used FEA to study the effect of these factors on stent and vascular mechanical properties (Gu et al 2010;Hyre and Pulliam 2008;Cui et al 2010;Zhao et al 2012b). For example, Gu et al (2010) used a computational model in which the length of the stent was longer than the lesion length to study the effect of stent structure and the level of stenosis on ISR.…”