Vascular stents are medical devices used to treat stenoses blockages in arteries
that restrict blood flow. Most commonly, stents are made out of stainless steel or nitinol,
and are delivered to the afflicted sites via catheter-based delivery systems. Usually, stents
are balloon-expandable or self-expanding. In order for the treated vessel to remain
patent, it is necessary that the stents be oversized to prevent flow-induced or pressureinduced
stent migration. Furthermore, stents must be rigid enough to prevent the collapse
of the vessel, allowing the free passage of blood. However, it has been observed that the
presence of the stent in the artery triggers adverse biological responses such as neointinal
hyperplasia, often times culminating in restenosis. Extensive research external to this
investigation has elucidated evidence to suggest that the abnormally high stresses
imparted to the arterial wall as a result of stenting are an important factor in the treatment
and development of cardiovascular diseases. Furthermore, normal physiologic diameter
flcutuations between systole and diastole produce beneficial biological responses in the
artery wall. The primary purpose of this study was to investigate specific stent design
criteria that minimize the stress field in the arterial wall to mitigate the impact of
restenosis. Commerically available finite element software was used to design the stents parametrically, and perform the stress analysis on a hyperelastic arterial model, including
the effects of contact between the artery and stent. Seven stent geometries were uniquely
defined by varying strut-spacing, ring amplitude, and crown radii of curvature. Stent
designs with large strut spacing, large ring amplitude and a greater than zero radius of
curvature imparted the less severe stress field in the arterial wall as well as maximizing
vessel deflection between systole and diastole. In contrast, stents with small strut
spacing, small amplitudes and zero radius of curvature at the crowns imparted
significantly higher stresses. The small strut spacing and small amplitude created stiffer
stents, prventing the artery from experiencing physiologic diameter fluctuations between
systole and diastole. Evidence presented herein suggests that strut spacing should be as
wide as possible without causing pillowing of the arterial wall into the stent.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/5812 |
| Date | 17 September 2007 |
| Creators | Bedoya Cervera, Jose Julian |
| Contributors | Moore, James E., Jr. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 5919976 bytes, electronic, application/pdf, born digital |
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