Study of parameters for evaluating flow reduction with stents in a sidewall aneurysm phantom model

Yu, Chang Ho; Kwon, Tae Kyu

doi:10.3233/bme-141055

Cited by 10 publications

(10 citation statements)

References 15 publications

(12 reference statements)

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“…Raben et al observed that wider bifurcation angles increases area of low flow and recirculation [ 42 ], while Yu and Kwon observed that endovascular prosthesis’s design parameters such as number of strands, or strut angle have also significant influence on implant’s migration risk. They also observed that an ideal endovascular prosthesis should have higher strut angle [ 43 ].…”

Section: Discussionmentioning

confidence: 99%

Spatial Configuration of Abdominal Aortic Aneurysm Analysis as a Useful Tool for the Estimation of Stent-Graft Migration

et al. 2020

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The aim of this study was to prepare a self-made mathematical algorithm for the estimation of risk of stent-graft migration with the use of data on abdominal aortic aneurysm (AAA) size and geometry of blood flow through aneurysm sac before or after stent-graft implantation. AngioCT data from 20 patients aged 50–60 years, before and after stent-graft placement in the AAA was analyzed. In order to estimate the risk of stent-graft migration for each patient we prepared an opposite spatial configuration of virtually reconstructed stent-graft with long body or short body. Thus, three groups of 3D geometries were analyzed: 20 geometries representing 3D models of aneurysm, 20 geometries representing 3D models of long body stent-grafts, and 20 geometries representing 3D models of short body stent-graft. The proposed self-made algorithm demonstrated its efficiency and usefulness in estimating wall shear stress (WSS) values. Comparison of the long or short type of stent-graft with AAA geometries allowed to analyze the implants’ spatial configuration. Our study indicated that short stent-graft, after placement in the AAA sac, generated lower drug forces compare to the long stent-graft. Each time shape factor was higher for short stent-graft compare to long stent-graft.

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Section: Discussionmentioning

confidence: 99%

Spatial Configuration of Abdominal Aortic Aneurysm Analysis as a Useful Tool for the Estimation of Stent-Graft Migration

et al. 2020

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“…Flow diverter-equivalent porosities can induce near-stagnant flows in sidewall and/or low flow aneurysms, while the flow reductions in bifurcation and/or high-flow patient geometries are comparatively less. Increasing the device pore density while maintaining a constant porosity also results in reduced intraneurysmal flow activity [7,15,[40][41][42]. Again, there is a wide variation in the results thus far and a very loose extrapolation from these studies on simplified geometries suggests that doubling the pore density (at constant porosity) can result in reduction of flow activity ranging anywhere between 20% and 150%.…”

Section: Intra-aneurysmal Flow Alterationsmentioning

confidence: 99%

Hemodynamics of Flow Diverters

Dholakia

Sadasivan

Fiorella

et al. 2017

Journal of Biomechanical Engineering

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Cerebral aneurysms are pathological focal evaginations of the arterial wall at and around the junctions of the circle of Willis. Their tenuous walls predispose aneurysms to leak or rupture leading to hemorrhagic strokes with high morbidity and mortality rates. The endovascular treatment of cerebral aneurysms currently includes the implantation of fine-mesh stents, called flow diverters, within the parent artery bearing the aneurysm. By mitigating flow velocities within the aneurysmal sac, the devices preferentially induce thrombus formation in the aneurysm within hours to days. In response to the foreign implant, an endothelialized arterial layer covers the luminal surface of the device over a period of days to months. Organization of the intraneurysmal thrombus leads to resorption and shrinkage of the aneurysm wall and contents, eventually leading to beneficial remodeling of the pathological site to a near-physiological state. The devices' primary function of reducing flow activity within aneurysms is corollary to their mesh structure. Complete specification of the device mesh structure, or alternately device permeability, necessarily involves the quantification of two variables commonly used to characterize porous media-mesh porosity and mesh pore density. We evaluated the flow alteration induced by five commercial neurovascular devices of varying porosity and pore density (stents: Neuroform, Enterprise, and LVIS; flow diverters: Pipeline and FRED) in an idealized sidewall aneurysm model. As can be expected in such a model, all devices substantially reduced intraneurysmal kinetic energy as compared to the nonstented case with the coarse-mesh stents inducing a 65-80% reduction whereas the fine-mesh flow diverters induced a near-complete flow stagnation (∼98% reduction). We also note a trend toward greater device efficacy (lower intraneurysmal flow) with decreasing device porosity and increasing device pore density. Several such flow studies have been and are being conducted in idealized as well as patient-derived geometries with the overarching goals of improving device design, facilitating treatment planning (what is the optimal device for a specific aneurysm), and predicting treatment outcome (will a specific aneurysm treated with a specific device successfully occlude over the long term). While the results are generally encouraging, there is poor standardization of study variables between different research groups, and any consensus will only be reached after standardized studies are conducted on collectively large datasets. Biochemical variables may have to be incorporated into these studies to maximize predictive values.

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“…3,[9][10][11][12][13][14][15][16][17][18] In general, it is well established that lowering the device porosity and increasing the device pore density results in greater reduction of intraneurysmal flow activity. 11,13,16,[19][20][21][22][23][24][25][26] The primary clinical utility of all these studies is to be able to predict device efficacy (long-term aneurysm occlusion) based on intraneurysmal flow reduction quantities. Sample sizes are sparse, but several studies based on clinical data [27][28][29][30][31][32][33] collectively note that the reduction in intraneurysmal flow after flow diversion can be significantly different between aneurysms that remain patent at follow-up versus those that occlude at follow-up; the sensitivity and specificity of these parameters seem reasonably high at 75%-90%.…”

Section: Introductionmentioning

confidence: 99%

In vitro angiographic comparison of the flow-diversion performance of five neurovascular stents

et al. 2017

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Background and purpose Data differentiating flow diversion properties of commercially available low- and high-porosity stents are limited. This in vitro study applies angiographic analysis of intra-aneurysmal flow to compare the flow-diversion performance of five neurovascular devices in idealized sidewall and bifurcation aneurysm models. Methods Five commercial devices (Enterprise, Neuroform, LVIS, FRED, and Pipeline) were implanted in silicone sidewall and bifurcation aneurysm models under physiological average flow of blood analog fluid. High-speed angiographic images were acquired pre- and post-device implantation and contrast concentration-time curves within the aneurysm were recorded. The curves were quantified with five parameters to assess changes in contrast transport, and thus aneurysm hemodynamics, due to each device. Results Inter-device flow-diversion performance was more easily distinguished in the sidewall model than the bifurcation model. There were no obvious overall statistical trends in the bifurcation parameters but the Pipeline performed marginally better than the other devices. In the sidewall geometry, overall evidence suggests that the LVIS performed better than the Neuroform and Enterprise. The Pipeline and FRED devices were statistically superior to the three stents and Pipeline was superior to FRED in all sidewall parameters evaluated. Conclusions Based on this specific set of experiments, lower-porosity flow diverters perform significantly better in reducing intra-aneurysmal flow activity than higher-porosity stents in sidewall-type geometries. The LVIS device is potentially a better flow diverter than the Neuroform and Enterprise devices, while the Pipeline is potentially better than the FRED.

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Study of parameters for evaluating flow reduction with stents in a sidewall aneurysm phantom model

Cited by 10 publications

References 15 publications

Spatial Configuration of Abdominal Aortic Aneurysm Analysis as a Useful Tool for the Estimation of Stent-Graft Migration

Spatial Configuration of Abdominal Aortic Aneurysm Analysis as a Useful Tool for the Estimation of Stent-Graft Migration

Hemodynamics of Flow Diverters

In vitro angiographic comparison of the flow-diversion performance of five neurovascular stents

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