Metal coverage ratio of pipeline embolization device for treatment of unruptured aneurysms: Reality check

Jou, Liang Der; Chintalapani, Gouthami; Mawad, Michel E.

doi:10.1177/1591019915617315

Cited by 29 publications

(35 citation statements)

References 31 publications

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“…Since the literature data on FRED were not available, the diameter of the inner wires was calibrated based on the known outer braid diameter. The device crosssectional dimensions were also confirmed with the literature data [4,49,50] and are presented in Table 1. The table also lists the micro-CT derived porosity and pore density for each device.…”

Section: Cfd Model Constructionsupporting

confidence: 79%

“…As the plots show, the device oversizing can cause a maximal change (relative to designed values) in porosity and pore density of around 20-25% for most braided flow diverters. Whether this range effects aneurysm treatment efficacy is not yet clear, but a preliminary study [4] suggests that just a 3% absolute difference ($12% relative difference) in deployed device porosity can result in different aneurysm outcomes. The point of minimal efficacy (highest porosity and lower pore density) occurs when the angle between the wires is 90 deg.…”

Section: Device Mesh Structurementioning

confidence: 99%

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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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Section: Cfd Model Constructionsupporting

confidence: 79%

Section: Device Mesh Structurementioning

confidence: 99%

Hemodynamics of Flow Diverters

Dholakia

Sadasivan

Fiorella

et al. 2017

Journal of Biomechanical Engineering

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“…Lieber and coworkers extensively studied the aneurysmal flow circulation in the presence of a FDS, illustrating that the capability of diminishing the inflow is a function of the stent shape and strut diameter [9,10]. Studies on the stent effects on aneurysm circulation have also been carried out by using computational fluid dynamics (CFD) [1,7,8,[11][12][13][14]. For example, the effects of stent mesh shape were investigated by Aenis et al [11], Rhee et al [15] Bando and Berger [16], Stuhne and Steinman [17] and Cebral and Lohner [18].…”

Section: Introductionmentioning

confidence: 99%

CFD-Based Comparison Study of a New Flow Diverting Stent and Commercially-Available Ones for the Treatment of Cerebral Aneurysms

et al. 2019

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Flow-diverting stents (FDSs) show considerable promise for the treatment of cerebral aneurysms by diverting blood flow away from the aneurysmal sacs, however, post-treatment complications such as failure of occlusion and subarachnoid haemorrhaging remain and vary with the FDS used. Based on computational fluid dynamics (CFD), this study aimed to investigate the performance of a new biodegradable stent as compared to two metallic commercially available FDSs. CFD models were developed for an idealized cerebral artery with a sidewall aneurysmal sac treated by deploying the aforementioned stents of different porosities (90, 80, and 70 % ) respectively. By using these models, the simulation and analysis were performed, with a focus on comparing the local hemodynamics or the blood flow in the stented arteries as compared to the one without the stent deployment. For the comparison, we computed and compared the flow velocity, wall shear stress (WSS) and pressure distributions, as well as the WSS related indices, all of which are of important parameters for studying the occlusion and potential rupture of the aneurysm. Our results illustrate that the WSS decreases within the aneurysmal sac on the treated arteries, which is more significant for the stents with lower porosity or finer mesh. Our results also show that the maximum WSS near the aneurysmal neck increases regardless of the stents used. In addition, the WSS related indices including the time-average WSS, oscillatory shear index and relative residence time show different distributions, depending on the FDSs. Together, we found that the finer mesh stents provide more flow reduction and smaller region characterized by high oscillatory shear index, while the new stent has a higher relative residence time.

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“…For all the above reasons, the practical limit of safe % metal coverage is likely to be Ͼ30%. Furthermore, on the basis of known PED size/coverage relationships, 26 as well as of in vivo experience, 28 single PED coverage is likely to remain below 30%.…”

Section: )mentioning

confidence: 99%

Toward Better Understanding of Flow Diversion in Bifurcation Aneurysms

Shapiro¹,

Shapiro

Raz³

et al. 2018

AJNR Am J Neuroradiol

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BACKGROUND AND PURPOSE:Flow diversion is being increasingly used to treat bifurcation aneurysms. Empiric approaches have generally led to encouraging results, and a growing body of animal and ex vivo literature addresses the fate of target aneurysms and covered branches. Our prior investigations highlighted the dynamic nature of metal coverage provided by the Pipeline Embolization Device and suggested strategies for creating optimal single and multidevice constructs. We now address the geometric and hemodynamic aspects of jailing branch vessels and neighboring target aneurysms. MATERIALS AND METHODS:Fundamental electric and fluid dynamics principles were applied to generate equations describing the relationships between changes in flow and the degree of vessel coverage in settings of variable collateral support to the jailed territory. Given the high complexity of baseline and posttreatment fluid dynamics, in vivo, we studied a simplified hypothetic system with minimum assumptions to generate the most conservative outcomes. RESULTS:In the acute setting, Pipeline Embolization Devices modify flow in covered branches, principally dependent on the amount of coverage, the efficiency of collateral support, and intrinsic resistance of the covered parenchymal territory. Up to 30% metal coverage of any branch territory is very likely to be well-tolerated regardless of device or artery size or the availability of immediate collateral support, provided, however, that no acute thrombus forms to further reduce jailed territory perfusion. CONCLUSIONS:Basic hemodynamic principles support the safety of branch coverage during aneurysm treatment with the Pipeline Embolization Device. Rational strategies to build bifurcation constructs are feasible. ABBREVIATIONS: FD ϭ flow diverter; PcomA ϭ posterior communicating artery; PED ϭ Pipeline Embolization Device

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Metal coverage ratio of pipeline embolization device for treatment of unruptured aneurysms: Reality check

Cited by 29 publications

References 31 publications

Hemodynamics of Flow Diverters

Hemodynamics of Flow Diverters

CFD-Based Comparison Study of a New Flow Diverting Stent and Commercially-Available Ones for the Treatment of Cerebral Aneurysms

Toward Better Understanding of Flow Diversion in Bifurcation Aneurysms

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