A Computational Modelling for Hemodynamic Conditions Following Flow-Diverting Treatment in Cerebral Aneurysms

2018 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
Average Velocity ◽  
Physiological State ◽  
Cerebral Aneurysms ◽  
Side Wall ◽  
Flow Diverter ◽  
Geometrical Parameters ◽  
Parent Artery ◽  
Flow Diverter Stent ◽  
Structure Of Flow ◽  
Flow Diverters

Cerebral aneurysms are abnormal dilations of blood vessels within the skull that, in some cases, may rupture and bleed. The rupture of an aneurysm can cause significant bleeding into or around the brain (a stroke). Flow diverters are specially designed low porosity stents that are deployed into the parent artery to cover the neck of the aneurysm. The dense mesh-like structure of flow diverters aims at redirecting flow from the aneurysm to the parent artery and vice versa, resulting in flow stasis in the aneurysm and promoting thrombus formation conditions. The thrombosed aneurysm is then resorbed by the body’s wound healing mechanisms-the end result of which is a remodeled vessel returned to its normal physiological state. Most previous studies have been focused on correlating the hemodynamic conditions with the outcome of the flow diverters. On the other hand, the effects of the location of the stents have not been addressed. In this study, a numerical simulation of an idealized side wall aneurysm model is used to predict the hemodynamic conditions for different flow diverter stent locations. The CFD model of the aneurysm is developed based on data from the literature and the geometrical parameters are set according to the test data. Pulsatile boundary conditions are chosen according to the normal physiological conditions. The entire stent geometry is used to model the effect of the stent on the flow characteristics. The hemodynamic conditions in the aneurysm corresponding to different stent locations are compared. The results show that the average velocity and vorticity are significantly different depending on different stent locations. Marked reduction in average velocity, average vorticity, and mean wall shear stress within the aneurysm sac have been observed even in malposition cases. The results of this study can be further used to guide the deployment of the flow diverter stent in clinical application.

Expanding Indications for Flow Diverters: Ruptured Aneurysms, Blister Aneurysms, and Dissecting Aneurysms

Neurosurgery ◽  
2019 ◽  
Vol 86 (Supplement_1) ◽  
pp. S96-S103 ◽  
Author(s):  
Peter Kan ◽  
Ahmad Sweid ◽  
Aditya Srivatsan ◽  
Pascal Jabbour
Keyword(s):  
Cerebral Aneurysms ◽  
Flow Diverter ◽  
Unruptured Aneurysms ◽  
Ruptured Aneurysms ◽  
Complex Aneurysms ◽  
Search Terms ◽  
Flow Diverter Stent ◽  
Acute Rupture ◽  
Flow Diverters ◽  
Dissecting Aneurysms

Abstract BACKGROUND The safety and efficacy of flow diversion (FD) in the treatment of cerebral aneurysms have been reported by many studies. FD has enabled the treatment of complex aneurysms and aneurysms that were previously untreatable by conventional means. It has achieved high rates of obliteration with essentially no recanalization, and its indications have continued to expand, now including ruptured aneurysms, blister aneurysms, and dissecting aneurysms. OBJECTIVE To provide a review on the outcomes of studies covering the use of FD in the settings of ruptured, blister, and dissecting aneurysms. In addition, to discuss dual antiplatelet therapy (DAPT) used in preparation for FD deployment in these scenarios, including associated complications with DAPT use in the acute rupture setting. METHODS References for this topical review were identified by PubMed searches between January 2000 and January 2019. The search terms “aneurysm”, “flow diverter”, “stent”, “pipeline”, “ruptured”, “blister”, and “dissecting aneurysms” were used. RESULTS FD carries a higher complication rate in the acute rupture setting than for unruptured aneurysms. Patient selection is of paramount importance for achieving good functional and angiographic outcomes. DAPT still remains challenging, especially in ruptured aneurysms. Advancements in surface modification of flow diverters can reduce the risk of thromboembolism and perhaps lead to a safer antiplatelet regimen. CONCLUSION In summary, FD shows promise to be an effective treatment for ruptured, blister, and dissecting aneurysms.

scholarly journals Treatment of Intracranial Aneurysms Using the New Silk Vista Flow Diverter: Safety Outcomes at Short-Term Follow-Up

2021 ◽  
Vol 12 ◽  
Author(s):  
José M. Pumar ◽  
Antonio Mosqueira ◽  
Jorge Olier ◽  
Claudio Rodriguez-Fernandez ◽  
Pedro Vega ◽  
...  
Keyword(s):  
Endovascular Treatment ◽  
Cerebral Aneurysms ◽  
Flow Diverter ◽  
Parent Artery ◽  
Short Term ◽  
Unruptured Aneurysms ◽  
Brain Aneurysms ◽  
New Generation ◽  
Flow Diverters

Background: Flow diverters are widely used as the first endovascular treatment option for complex brain aneurysms due to their high percentage of occlusion and low morbi-mortality. The Silk Vista device is a new generation of flow diverters designed to facilitate full visibility, improve apposition to the vessel wall, and enhance navigability. Indeed, its greatest advantage is that it enables the easier navigation of stents between 3.5 and 4.75 mm through a 0.021 microcatheter. The objective of this study was to evaluate the safety and effectiveness of Silk Vista systems for treating cerebral aneurysms.Methods: This prospective observational study included 25 consecutive patients with 27 wide-necked unruptured aneurysms treated with SILK Vista who were retrospectively analyzed for safety and efficacy.Results: Endovascular treatment was successfully performed in all patients. The final morbidity and mortality rates were both 0.0%. Short-term (3–5 months) angiographic follow-up revealed 21 complete occlusions and 6 near-complete occlusions. No significant parent artery stenosis was observed.Conclusions: This report demonstrates the efficacy of Silk Vista in treating brain aneurysms, although longer experiences should be carried out to confirm our results.

Hemodynamics of Flow Diverters

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Ronak Dholakia ◽  
Chander Sadasivan ◽  
David J. Fiorella ◽  
Henry H. Woo ◽  
Baruch B. Lieber
Keyword(s):  
Physiological State ◽  
Cerebral Aneurysms ◽  
Parent Artery ◽  
High Morbidity ◽  
Pore Density ◽  
Predictive Values ◽  
Mesh Structure ◽  
Fine Mesh ◽  
Flow Activity ◽  
Flow Diverters

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.

scholarly journals Comparison of the In Vitro Hemodynamic Performance of New Flow Diverters for Bypass of Brain Aneurysms

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Asher L. Trager ◽  
Chander Sadasivan ◽  
Baruch B. Lieber
Keyword(s):  
Cerebral Aneurysms ◽  
Flow Diverter ◽  
Parent Artery ◽  
New Device ◽  
Design Changes ◽  
Hemodynamic Performance ◽  
Braiding Angle ◽  
Treatment For Cerebral Aneurysms

One possible treatment for cerebral aneurysms is a porous tubular structure, similar to a stent, called a flow diverter. A flow diverter can be placed across the neck of a cerebral aneurysm to induce the cessation of flow and initiate the formation of an intra-aneurysmal thrombus. This excludes the aneurysm from the parent artery and returns the flow of blood to normal. Previous flow diverting devices have been analyzed to determine optimal characteristics, such as braiding angle and wire diameter. From this information, a new optimized device was designed to achieve equivalent hemodynamic performance to the previous best device, but with better longitudinal flexibility to preserve physiological arterial configuration. The new device was tested in vitro in an elastomeric replica of the rabbit elastase induced aneurysm model and is now in the process of being tested in vivo. Particle image velocimetry was utilized to determine the velocity field in the plane of symmetry of the model under pulsatile flow conditions. Device hemodynamic performance indices such as the hydrodynamic circulation were evaluated from the velocity fields. Comparison of these indices with the previous best device and a control shows that the significant design changes of the device did not change its hemodynamic attributes (p > 0.05).

scholarly journals Re-treatment of residual aneurysms after flow diversion: An experimental study

2018 ◽  
Vol 31 (3) ◽  
pp. 270-279 ◽  
Author(s):  
Robert Fahed ◽  
Tim E Darsaut ◽  
Marc Kotowski ◽  
Igor Salazkin ◽  
Jean Raymond
Keyword(s):  
Flow Diverter ◽  
Artery Occlusion ◽  
Flow Diversion ◽  
Embolic Agent ◽  
Parent Artery ◽  
Arterial Lumen ◽  
Parent Artery Occlusion ◽  
Liquid Embolic ◽  
Liquid Embolic Agent ◽  
Flow Diverters

Aim Flow diverters are increasingly used to treat aneurysms, but treatment is not always effective. The management of aneurysms that fail to occlude following flow diversion is problematic. We aimed to reproduce failures in an animal model and study re-treatment with additional flow diverters alone or with flow diverters and liquid embolic agent. Material and methods Twenty wide-necked aneurysms were created at the carotid-lingual bifurcation in 10 dogs, and were treated with flow diverters 4–6 weeks later. Follow-up angiography was performed at three months. Suitable residual aneurysms were randomly allocated: re-treatment with flow diverters alone ( n = 6), or with the injection of liquid embolic between two layers of flow diverters ( n = 4) or no re-treatment ( n = 2). Angiography was repeated three months later, followed by euthanasia, photography and pathology. Results Patent wide-necked aneurysms were produced in 17/20 attempts (85%); three months after flow diversion there were 15/17 (88%) residual aneurysms. In three cases, re-treatment was not possible because the flow diverter had prolapsed into the aneurysm, leaving 12 aneurysms to study. Re-treated aneurysms showed improved angiographic results at six months (median score of 2; P = 0.03), but residual aneurysms were present in all cases. Parent artery occlusion occurred in two aneurysms treated with flow diverter plus liquid embolic. At pathology, aneurysms were only partially filled with thrombus; leaks through the flow diverters were found in the neointima connecting the arterial lumen to residual aneurysms. Conclusion Re-treatment of residual flow-diverted experimental aneurysms with additional flow diverters did not lead to aneurysm occlusion.

Abstract 1122‐000152: Flow Diverter Use in Acutely Presented Dissecting Aneurysms, 2 Years Follow Up of 53 Cases

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Ossama Y Mansour ◽  
Aser Goma
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Clinical Outcome ◽  
Flow Diverter ◽  
Parent Artery ◽  
Modified Rankin Scale ◽  
Alternative Treatment Option ◽  
Increased Risk ◽  
Flow Diverters ◽  
Dissecting Aneurysms

Introduction : Acute dissecting aneurysms are among the uncommon causes of subarachnoid hemorrhage. Established endovascular treatment options include parent artery occlusion and stent‐assisted coiling, but appear to be associated with an increased risk of ischemic stroke. reconstruction of the vessels with flow diverters is an alternative therapeutic option. Methods : This is a retrospective analysis of 53 consecutive acutely ruptured dissecting aneurysms treated with flow diverters. The primary end point was favorable aneurysm occlusion, defined as OKM C1‐3 and D . Secondary end points were procedure‐related complications and clinical outcome. Results : 23 aneurysms (43.4%%) arose from the intradural portion of the vertebral artery, 10 (18.8%) were located on the posterior inferior cerebellar artery and 3 (5.6%) posterior cerebral artery, 7 (13.2%) MCA, (18.8%) ICA . 45 aneurysms presented by SAH while 8 presented by Ischemic manifestation. Flow diverter placement was technically successful in all cases . immediate postoperative rerupture occurred in two case (3.7%), thromboembolic complications in 3 cases (5.7%). Median clinical follow‐up was 640 days and median angiographic follow‐up was 690 days. ten patients (18.9%) with poor‐grade subarachnoid hemorrhage died in the acute phase. Favorable clinical outcome (modified Rankin scale ≤2) was observed in 27 of 53 patients (51%) and a moderate outcome (modified Rankin scale 3/4) was observed in 12 of 53 patients (22.6%). All aneurysms showed complete occlusion at follow‐up. Conclusions : Flow diverters might be a feasible, alternative treatment option for acutely symptomatic dissecting aneurysms and may effectively prevent rebleeding in ruptured aneurysms.

scholarly journals Mechanism of Action and Biology of Flow Diverters in the Treatment of Intracranial Aneurysms

Neurosurgery ◽  
2019 ◽  
Vol 86 (Supplement_1) ◽  
pp. S13-S19 ◽  
Author(s):  
Krishnan Ravindran ◽  
Amanda M Casabella ◽  
Juan Cebral ◽  
Waleed Brinjikji ◽  
David F Kallmes ◽  
...  
Keyword(s):  
Mechanism Of Action ◽  
Flow Diverter ◽  
Parent Artery ◽  
First Line ◽  
Aneurysm Neck ◽  
First Line Therapy ◽  
Preclinical Animal Models ◽  
Computational Analyses ◽  
Flow Diverters ◽  
Present Understanding

Abstract Flow diverters have drastically changed the landscape of intracranial aneurysm treatment and are now considered first-line therapy for select lesions. Their mechanism of action relies on intrinsic alteration in hemodynamic parameters, both at the parent artery and within the aneurysm sac. Moreover, the device struts act as a nidus for endothelial cell growth across the aneurysm neck ultimately leading to aneurysm exclusion from the circulation. In silico computational analyses and investigations in preclinical animal models have provided valuable insights into the underlying biological basis for flow diverter therapy. Here, we review the present understanding pertaining to flow diverter biology and mechanisms of action, focusing on stent design, induction of intra-aneurysmal thrombosis, endothelialization, and alterations in hemodynamics.

Optimization of Strut Placement in Flow Diverter Stents for Four Different Aneurysm Configurations

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Hitomi Anzai ◽  
Jean-Luc Falcone ◽  
Bastien Chopard ◽  
Toshiyuki Hayase ◽  
Makoto Ohta
Keyword(s):  
Arterial Occlusion ◽  
Flow Simulation ◽  
Flow Diverter ◽  
Optimal Placement ◽  
Parent Artery ◽  
High Porosity ◽  
Mesh Structure ◽  
Flow Reduction ◽  
Fine Mesh ◽  
Flow Diverter Stent

A modern technique for the treatment of cerebral aneurysms involves insertion of a flow diverter stent. Flow stagnation, produced by the fine mesh structure of the diverter, is thought to promote blood clotting in an aneurysm. However, apart from its effect on flow reduction, the insertion of the metal device poses the risk of occlusion of a parent artery. One strategy for avoiding the risk of arterial occlusion is the use of a device with a higher porosity. To aid the development of optimal stents in the view point of flow reduction maintaining a high porosity, we used lattice Boltzmann flow simulations and simulated annealing optimization to investigate the optimal placement of stent struts. We constructed four idealized aneurysm geometries that resulted in four different inflow characteristics and employed a stent model with 36 unconnected struts corresponding to the porosity of 80%. Assuming intracranial flow, steady flow simulation with Reynolds number of 200 was applied for each aneurysm. Optimization of strut position was performed to minimize the average velocity in an aneurysm while maintaining the porosity. As the results of optimization, we obtained nonuniformed structure as optimized stent for each aneurysm geometry. And all optimized stents were characterized by denser struts in the inflow area. The variety of inflow patterns that resulted from differing aneurysm geometries led to unique strut placements for each aneurysm type.

A Novel Method for Excluding Aneurysms From the Cerebral Circulation: Preliminary Results in Rabbits

2009 ◽  
Author(s):  
Baruch B. Lieber ◽  
Mohammad Ali-Aziz Sultan ◽  
Chander Sadasivan ◽  
Brant D. Watson ◽  
Liliana Cesar ◽  
...  
Keyword(s):  
Clinical Evidence ◽  
Thrombus Formation ◽  
Cerebral Aneurysms ◽  
Parent Artery ◽  
Momentum Exchange ◽  
Aneurysm Neck ◽  
Novel Method ◽  
Flow Stasis ◽  
Intracranial Circulation ◽  
Flow Diverters

Despite many advances in the treatment of cerebral aneurysms in the last few decades, none of the available methods provide an unequivocal solution for all aneurysm sizes and morphologies. The feasibility of successfully treating aneurysms solely by the placement of an intravascular flow-diverting mesh across the aneurysm neck was established more than a decade ago [1]. Flow diverters disrupt the momentum exchange between the parent artery and aneurysm and significantly reduce intraaneurysmal hydrodynamic vorticity and kinetic energy. The resultant flow stasis promotes thrombus formation within the aneurysm sac, which eventually matures into fibrotic tissue, leading to exclusion of the aneurysm from the circulation. With the increased use of stents in the intracranial circulation, cases where coiling is not feasible, or is staged as a secondary procedure, are providing clinical evidence of the successful treatment of aneurysms with stents alone [2,3]. Methodological evidence of the performance of appropriately designed flow diverters in treating cerebral aneurysms has recently become available in the literature [4,5].

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