Determination of the influence of stent strut thickness using the finite element method: implications for vascular injury and in-stent restenosis

Abstract

Many clinical studies, including the ISAR-STEREO trial, have identified stent strut thickness as an independent predictor of in-stent restenosis where thinner struts result in lower restenosis than thicker struts. The aim of this study was to more conclusively identify the mechanical stimulus for in-stent restenosis using results from such clinical trials as the ISAR-STEREO trial. The mechanical environment in arteries stented with thin and thicker strut stents was investigated using numerical modelling techniques. Finite element models of the stents used in the ISAR-STEREO clinical trial were developed and the stents were deployed in idealised stenosed vessel geometries in order to compare the mechanical environment of the vessel for each stent. The stresses induced within the stented vessels by these stents were compared to determine the level of vascular injury caused to the artery by the stents with different strut thickness. The study found that when both stents were expanded to achieve the same initial maximum stent diameter that the thinner strut stent recoiled to a greater extent resulting in lower luminal gain but also lower stresses in the vessel wall, which is hypothesised to be responsible for the lower restenosis outcome. This study supports the hypothesis that arteries develop restenosis in response to injury, where high vessel stresses are a good measure of that injury. This study points to a critical stress level in arteries, above which an aggressive healing response leads to in-stent restenosis in stented vessels. Stents can be designed to reduce stresses in this range in arteries using preclinical tools such as numerical modelling.

CCN4 Regulates Vascular Smooth Muscle Cell Migration and Proliferation

“…Excessive proliferation of SMCs with the deposition of ECM proteins at the arterial anastomotic site is a critical problem during cardiovascular diseases (Janssens et al, 1998;Zahedmanesh and Lally, 2009). In this study, the direct contribution of CCN4 to VSMCs proliferation was examined using RNA interference.…”

Computational analysis of mechanical stress–strain interaction of a bioresorbable scaffold with blood vessel

“…Hardening was implemented in ABAQUS by considering the increase of yield stress with the plastic strain. The hypocellular plaque was modelled as an isotropic hyperelastic material using the Ogden strain energy potential, with parameters given in Zahedmanesh and Lally (2009). While the balloon was modelled as linear elastic, with a density of 1.1×10 6 kg/mm 3 , Young's modulus of 900 MPa and Poisson's ratio of 0.3 (Gervaso et al, 2008).…”

Effects of material, coating, design and plaque composition on stent deployment inside a stenotic artery—Finite element simulation

“…Both the blood vessel and stenotic plaque were described by Ogden hyperelastic strain energy potential (Zahedmanesh and Lally, 2009;Zahedmanesh et al, 2010):…”

“…The values of the coefficients in Eq (2) are given in Table 3 (Zahedmanesh and Lally, 2009). Physically,  I and  i describe the shear behaviour of the material and D i represents the compressibility (Ali et al, 2010).…”

“…The model parameters were fitted by Zahedmanesh and Lally (2009) Mooney-Rivlin model has also been widely used to describe the constitutive behaviour of blood vessel. The difference between Mooney-Rivlin and Ogden models is just the type of formulation for strain energy potential (Prendergast et al, 2003;Gastaldi et al, 2010; Zahedmanesh and Lally, 2009; Karimi et al, 2014).…”