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INFLUENCE OF STENT STRUT DISTRIBUTION ON LOCAL VESSEL STRESS
Presentation 1550 − Topic 03. Arterial biomechanics
S25
INFLUENCE OF STENT STRUT DISTRIBUTION ON LOCAL VESSEL STRESS Claudia Maria Amatruda, D Rod Hose, Patricia Lawford, Andrew Narracott
Dept of Cardiovascular Science, Medical Physics Group, University of Sheffield, UK
Introduction Obstructive coronary artery disease is a manifestation of ischemic heart disease, the most common cause of death in the world. At present, stents are used in more than 70% of percutaneous coronary interventions. A disadvantage of the technique is represented by in-stent restenosis, a common and difficult to treat re-narrowing of the artery [Gunn, 2002], which often occurs a few months after this intervention and may be linked to the local stress caused by the stent struts [Arjomand, 2003]. Evaluating the distribution and magnitude of stress within the vessel after stenting is important to study the stimuli for tissue growth. Stent-vessel interaction has been analyzed in literature, often using stent models with perfectly symmetric expansion. Uneven stent strut distribution has been observed in histological images from experimental animal models [Gunn, 2002]. This study considers the influence of uneven stent strut distribution in a coronary artery model.
the final struts configuration alone. An increased stress is particularly noticeable when a stent strut is very distant from its neighbour.
Figure 1: Radial stress after stent expansion in case of even and very uneven strut distribution.
Methods
Discussion
Models of a section of a coronary artery, with typical dimensions, were generated within ANSYS Mechanical APDL version 12.0 (ANSYS Inc.): the aim of such a model is to capture the stent expansion inside the vessel, in order to analyze the subsequent vessel stress. A hyperelastic material model has been assumed for the vessel, which is consistent with previous computational studies [Gijsen, 2008].
This study has examined the influence of the stent strut evenness on the stress distribution and stress magnitude. In addition to spatial distribution, timedependent effects at a number of timescales should also be considered, including: • pulsatile pressure from cardiac cycle (seconds), • viscoelastic properties of the vessels and stress relaxation after stent expansion (minutes), • mechano-biology of neointimal formation and in-stent restenosis (days/weeks), dependent on evolution of the stress distribution with time. Such data will be included to develop more accurate hypotheses to describe the mechanobiology of in-stent restenosis [Amatruda, 2011].
U = 0.04(I1 - 3) + 0.003(I2 - 3)2 + 0.085(I2 - 3)3 All the stent models were composed of 12 struts (diameter: 0.09 mm) and were expanded with the same radial displacement, 10% more than the diameter of the vessel (2.8 mm). Variation in the angular position of the struts was used to represent uneven expansion. The radial stress distribution has been considered, according to the correlation between compression and cell death in the literature, where it has been linked to neointima formation [Boyle, 2010].
Results Stent strut position noticeably influences both the stress distribution and the maximum compressive stress, which increases by ~10% due to changes in
References Amatruda et al, Int Conf on Advs of Med and Health Care through Tech 36: 276-279, 2011. Arjomand et al, Am Heart J 146(5): 787-796, 2003. Boyle et al, Phil Trans R Soc A 368:2919-35, 2010. Gijsen et al, Biomed Eng Online 7: 23, 2008. Gunn et al, Heart 88(4): 401-405, 2002. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 238113 (project MeDDiCA).
ESB2012: 18th Congress of the European Society of Biomechanics
Journal of Biomechanics 45(S1)
S25
INFLUENCE OF STENT STRUT DISTRIBUTION ON LOCAL VESSEL STRESS Claudia Maria Amatruda, D Rod Hose, Patricia Lawford, Andrew Narracott
Dept of Cardiovascular Science, Medical Physics Group, University of Sheffield, UK
Introduction Obstructive coronary artery disease is a manifestation of ischemic heart disease, the most common cause of death in the world. At present, stents are used in more than 70% of percutaneous coronary interventions. A disadvantage of the technique is represented by in-stent restenosis, a common and difficult to treat re-narrowing of the artery [Gunn, 2002], which often occurs a few months after this intervention and may be linked to the local stress caused by the stent struts [Arjomand, 2003]. Evaluating the distribution and magnitude of stress within the vessel after stenting is important to study the stimuli for tissue growth. Stent-vessel interaction has been analyzed in literature, often using stent models with perfectly symmetric expansion. Uneven stent strut distribution has been observed in histological images from experimental animal models [Gunn, 2002]. This study considers the influence of uneven stent strut distribution in a coronary artery model.
the final struts configuration alone. An increased stress is particularly noticeable when a stent strut is very distant from its neighbour.
Figure 1: Radial stress after stent expansion in case of even and very uneven strut distribution.
Methods
Discussion
Models of a section of a coronary artery, with typical dimensions, were generated within ANSYS Mechanical APDL version 12.0 (ANSYS Inc.): the aim of such a model is to capture the stent expansion inside the vessel, in order to analyze the subsequent vessel stress. A hyperelastic material model has been assumed for the vessel, which is consistent with previous computational studies [Gijsen, 2008].
This study has examined the influence of the stent strut evenness on the stress distribution and stress magnitude. In addition to spatial distribution, timedependent effects at a number of timescales should also be considered, including: • pulsatile pressure from cardiac cycle (seconds), • viscoelastic properties of the vessels and stress relaxation after stent expansion (minutes), • mechano-biology of neointimal formation and in-stent restenosis (days/weeks), dependent on evolution of the stress distribution with time. Such data will be included to develop more accurate hypotheses to describe the mechanobiology of in-stent restenosis [Amatruda, 2011].
U = 0.04(I1 - 3) + 0.003(I2 - 3)2 + 0.085(I2 - 3)3 All the stent models were composed of 12 struts (diameter: 0.09 mm) and were expanded with the same radial displacement, 10% more than the diameter of the vessel (2.8 mm). Variation in the angular position of the struts was used to represent uneven expansion. The radial stress distribution has been considered, according to the correlation between compression and cell death in the literature, where it has been linked to neointima formation [Boyle, 2010].
Results Stent strut position noticeably influences both the stress distribution and the maximum compressive stress, which increases by ~10% due to changes in
References Amatruda et al, Int Conf on Advs of Med and Health Care through Tech 36: 276-279, 2011. Arjomand et al, Am Heart J 146(5): 787-796, 2003. Boyle et al, Phil Trans R Soc A 368:2919-35, 2010. Gijsen et al, Biomed Eng Online 7: 23, 2008. Gunn et al, Heart 88(4): 401-405, 2002. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 238113 (project MeDDiCA).
ESB2012: 18th Congress of the European Society of Biomechanics
Journal of Biomechanics 45(S1)