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Surgical and endovascular treatments for cerebral aneurysm thrombosis. (A) Endovascular coiling of the aneurysm sac. (B) Surgical clipping of the aneurysm neck. (C) Endovascular treatment combining use of coils and a stent. (D) Endovascular treatment with a flow diverter. Taken from Perrone et al. (2015).
Source publication
Thrombosis is a condition closely related to cerebral aneurysms and controlled thrombosis is the main purpose of endovascular embolization treatment. The mechanisms governing thrombus initiation and evolution in cerebral aneurysms have not been fully elucidated and this presents challenges for interventional planning. Significant effort has been di...
Citations
... The defense mechanism is to form a clot at the site of injury to prevent potential bleeding. The clot may partially or completely fill the sac, reducing the risk of rupture by providing structural support to the weakened arterial wall [15]. We should also reiterate that our patient received dual antiplatelet therapy since the placement of flow-diverting stent was planned. ...
Despite growing evidence over the last few years of the efficacy and safety of direct thrombus aspiration using a large bore distal access catheter as a type of mechanical thrombectomy procedure in acute stroke large-vessel occlusion patients, the experience and evidence of this technique for managing thromboembolic complications in endovascular aneurysm treatment is still limited and little research is available regarding this topic. We present a case of a thromboembolic occlusion of the left middle cerebral artery during the preprocedural angiograms of a large and fusiform left internal carotid artery aneurysm. This complication was successfully managed by navigating an already-placed distal access catheter intended for support during the opening of the flow-diverting stent; therefore, the thrombus was manually aspirated for two minutes, and Thrombolysis in Cerebral Infarction (TICI) scale 3 flow was restored. This case should encourage the use of a distal access catheter, already placed for aneurysm treatment, to perform zero-delay direct thrombus aspiration as a rescue approach for thromboembolic complications during endovascular treatments.
... It is a volumetric occlusion technique, where the sack of an aneurysm is filled with a thin metal wire, usually platinum, that coils up therein. This causes a stagnation of the blood flow in the aneurysm which together with the intrinsic thrombogenicity of the metal wire leads to embolization (Ngoepe et al, 2018;Byrne et al, 1997). ...
Endovascular coil embolization is one of the primary treatment techniques for cerebral aneurysms. Although it is a well established and minimally invasive method, it bears the risk of sub-optimal coil placement which can lead to incomplete occlusion of the aneurysm possibly causing recurrence. One of the key features of coils is that they have an imprinted natural shape supporting the fixation within the aneurysm. For the spatial discretization our mathematical coil model is based on the Discrete Elastic Rod model which results in a dimension-reduced 1D system of differential equations. We include bending and twisting responses to account for the coils natural curvature. Collisions between coil segments and the aneurysm-wall are handled by an efficient contact algorithm that relies on an octree based collision detection. The numerical solution of the model is obtained by a symplectic semi-implicit Euler time stepping method. Our model can be easily incorporated into blood flow simulations of embolized aneurysms.In order to differentiate optimal from sub-optimal placements, we employ a suitable in silico Raymond-Roy type occlusion classification and measure the local packing density in the aneurysm at its neck, wall-region and core. We investigate the impact of uncertainties in the coil parameters and embolization procedure. To this end, we vary the position and the angle of insertion of the microcatheter, and approximate the local packing density distributions by evaluating sample statistics.
... Some place a heavy emphasis on the role of platelets, while others focus on the coagulation cascade and the eventual formation of fibrin (Guerrero-Hurtado et al., 2023;Tosenberger et al., 2016;Wu et al., 2014). In computational models of cerebral aneurysm thrombosis, sites of thrombus development and progression were correlated to specific flow features in thrombosis potential models (Ngoepe et al., 2018). The current generation of models can couple direct clot growth with complex, patient-specific haemodynamics during deployment of devices for endovascular treatment. ...
Thrombosis is an important contributor to cerebral aneurysm growth and progression. A number of sophisticated multiscale and multiphase in silico models have been developed with a view towards interventional planning. Many of these models are able to account for clotting outcomes, but do not provide detailed insight into the role of flow during clot development. In this study, we present idealised, two-dimensional in silico cerebral fibrin clot model based on computational fluid dynamics (CFD), biochemical modelling and variable porosity, permeability, and diffusivity. The model captures fibrin clot growth in cerebral aneurysms over a period at least 1000 s in five different geometries. The fibrin clot growth results were compared to an experiment presented in literature. The biochemistry was found to be more sensitive to mesh size compared to the haemodynamics, while larger timesteps overpredicted clot size in pulsatile flow. When variable diffusivity was used, the predicted clot size was 25.4% lesser than that with constant diffusivity. The predicted clot size in pulsatile flow was 14.6% greater than in plug flow. Different vortex modes were observed in plug and pulsatile flow; the latter presented smaller intermediate modes where the main vortex was smaller and less likely to disrupt the growing fibrin clot. Furthermore, smaller vortex modes were seen to support fibrin clot propagation across geometries. The model clearly demonstrates how the growing fibrin clot alters vortical structures within the aneurysm sac and how this changing flow, in turn, shapes the growing fibrin clot.
... To compare the multi-fidelity models MuFi-1 and MuFi-2 with the high-fidelity model based on the PDE system (1), we considered a simplified coagulation cascade model under pulsatile flow through an idealized two-dimensional geometry (Fig 1). This flow geometry broadly resembles a cerebral aneurysm or the left atrial appendage, two cardiovascular sites associated with thrombosis [36][37][38][39][40]. The parent vessel is modeled as a straight tube of diameter H, and the aneurysm is modeled as a circular cavity of radius 0.75H. ...
Clot formation is a crucial process that prevents bleeding, but can lead to severe disorders when imbalanced. This process is regulated by the coagulation cascade, a biochemical network that controls the enzyme thrombin, which converts soluble fibrinogen into the fibrin fibers that constitute clots. Coagulation cascade models are typically complex and involve dozens of partial differential equations (PDEs) representing various chemical species’ transport, reaction kinetics, and diffusion. Solving these PDE systems computationally is challenging, due to their large size and multi-scale nature. We propose a multi-fidelity strategy to increase the efficiency of coagulation cascade simulations. Leveraging the slower dynamics of molecular diffusion, we transform the governing PDEs into ordinary differential equations (ODEs) representing the evolution of species concentrations versus blood residence time. We then Taylor-expand the ODE solution around the zero-diffusivity limit to obtain spatiotemporal maps of species concentrations in terms of the statistical moments of residence time, t R p ¯ , and provide the governing PDEs for t R p ¯ . This strategy replaces a high-fidelity system of N PDEs representing the coagulation cascade of N chemical species by N ODEs and p PDEs governing the residence time statistical moments. The multi-fidelity order( p ) allows balancing accuracy and computational cost providing a speedup of over N / p compared to high-fidelity models. Moreover, this cost becomes independent of the number of chemical species in the large computational meshes typical of the arterial and cardiac chamber simulations. Using a coagulation network with N = 9 and an idealized aneurysm geometry with a pulsatile flow as a benchmark, we demonstrate favorable accuracy for low-order models of p = 1 and p = 2. The thrombin concentration in these models departs from the high-fidelity solution by under 20% ( p = 1) and 2% ( p = 2) after 20 cardiac cycles. These multi-fidelity models could enable new coagulation analyses in complex flow scenarios and extensive reaction networks. Furthermore, it could be generalized to advance our understanding of other reacting systems affected by flow.
... Recently, endovascular treatments have been developed that induce the formation of a stable thrombus filling the cavity, isolating its wall from blood flow mechanical stresses. Coils can be placed inside the aneurysm or a stent can be deployed along the parent vessel (Pierot & Wakhloo 2013), reducing flow into the cavity and increasing stasis, leading to the formation of a stable thrombus (Rayz et al. 2010;Ngoepe et al. 2018). Flow-diverting stents are high-porosity tubular meshes deployed along the parent artery wall, across the aneurysmal neck. ...
Characterizing the haemodynamics in intracranial aneurysms is of high interest as it impacts aneurysm growth, rupture and treatment, especially with flow-diverting stents (FDS). Flow in these geometries is known to depend on the Dean, Reynolds and Womersley numbers, $De$ , $Re$ , $Wo$ , but is also influenced by geometrical parameters such as the sac shape or the size of the opening. Via particle image velocimetry, this parametric study aimed at evaluating the combined effects of $Re$ , $De$ , $Wo$ and the geometry of the aneurysmal sac on the haemodynamics before and after treatment with FDS. Eight ellipsoidal idealized aneurysm models were created with two curvatures of the parent vessel, two aspect ratios of the sac and two neck sizes. Before treatment, a single counter-rotating vortex, whose strength increases with $Re$ and $De$ , as well as with the neck size and the aspect ratio, was observed in the sac for all but one geometry. After treatment with FDS, four different flow topologies were observed, depending on the geometry: no separation, separation for part of the cycle, two opposing vortices or a single counter-rotating vortex. A linear model with interaction revealed the predominant effect of $De$ and the curvature of the parent vessel on the haemodynamics before and after treatment. This work once more demonstrated the primary role of haemodynamics in the treatment of intracranial aneurysms with FDS. Future work will consider the complexity of patient-specific geometries, and their effects on both the haemodynamics in the sac and the porosity of the FDS.
... The calculated aneurysm TOT (table 1) is a measure of flow stasis and has been studied as a potential marker for thrombus formation, and subsequently IA occlusion. [33][34][35][36] The mean TOT in all models were significantly higher after Contour deployment, thus confirming the positive treatment effect of the Contour and increasing the chance of thrombus formation. These results are in accordance with the washout time calculations observed with DSA in the same aneurysm models. ...
Background
The novel Contour Neurovascular System (Contour) has been reported to be efficient and safe for the treatment of intracranial, wide-necked bifurcation aneurysms. Flow in the aneurysm and posterior cerebral arteries (PCAs) after Contour deployment has not been analyzed in detail yet. However, this information is crucial for predicting aneurysm treatment outcomes.
Methods
Time-resolved three-dimensional velocity maps in 14 combinations of patient-based basilar tip aneurysm models with and without Contour devices (sizes between 5 and 14 mm) were analyzed using four-dimensionsal (4D) flow MRI and numerical/image-based flow simulations. A complex virtual processing pipeline was developed to mimic the experimental shape and position of the Contour together with the simulations.
Results
On average, the Contour significantly reduced intra-aneurysmal flow velocity by 67% (mean w/ = 0.03m/s; mean w/o = 0.12m/s; p-value=0.002), and the time-averaged wall shear stress by more than 87% (mean w/ = 0.17Pa; mean w/o = 1.35Pa; p-value=0.002), as observed both by numerical simulations and 4D flow MRI. Furthermore, a significant reduction in flow (P<0.01) was confirmed by the neck inflow rate, kinetic energy, and inflow concentration index after Contour deployment. Notably, device size has a stronger effect on reducing flow than device positioning. However, positioning affected flow in the PCAs, while being robust in effectively reducing flow.
Conclusions
This study showed the high efficacy of the Contour device in reducing flow within aneurysms regardless of the exact position. However, we observed an effect on the flow in PCAs, which needs to be investigated further.
... 4 Similar to the wound-healing mechanism, the biotransformation and organization of the intrasaccular thrombus into fibrous scar tissue allow the aneurysmal structure to be reduced and eventually resorbed to some extent. 11 In the present case, we decided to implant an FD stent to stabilize the growing thrombosed aneurysm. In fact, FD stent implantation stopped aneurysmal enlargement and further reduced the size of the giant thrombosed BA aneurysm, which showed a tendency to increase in a short period, suggesting that the decrease in flow within the thrombosed aneurysm itself may have triggered the healing mechanism. ...
BACKGROUND
The effect of vessel wall magnetic resonance imaging (VW-MRI) enhancement in partially thrombosed aneurysms has previously indicated aneurysmal instability and a rupture risk. However, whether the contrast effect of the wall changes before or after flow diversion treatment is still under investigation.
OBSERVATIONS
The authors report a case of a partially thrombosed basilar artery aneurysm that increased in size over a short period, worsened brainstem compression symptoms, and was treated with a flow diverter stent with good results. In this case, VW-MRI after surgery showed a reduced contrast effect on the intraluminal thrombus within the aneurysm. The aneurysm thrombosed and markedly regressed over the next 5 months, with remarkable improvement in the brainstem compression symptoms.
LESSONS
This finding on VW-MRI may indicate an attenuation of neovascularization in the thrombus wall and be a sign of aneurysm stabilization.
... To compare the multi-fidelity models MuFi-1 and MuFi-2 with the high-fidelity model based on the PDE system (1), we considered a simplified coagulation cascade model under pulsatile flow through an idealized two-dimensional geometry (Fig 1). This flow geometry broadly resembles a cerebral aneurysm or the left atrial appendage, two cardiovascular sites associated with thrombosis [1,9,19,42,57]. The parent vessel is modeled as a straight tube of diameter H, and the aneurysm is modeled as a circular cavity of radius 0.75H. The center of the cavity is located such that the aneurysm neck size is H. ...
Clot formation is a crucial process that prevents bleeding, but can lead to severe disorders when imbalanced. This process is regulated by the coagulation cascade, a biochemical network that controls the enzyme thrombin, which converts soluble fibrinogen into the fibrin fibers that constitute clots. Coagulation cascade models are typically complex and involve dozens of partial differential equations (PDEs) representing various chemical species transport, reaction kinetics, and diffusion. Solving these PDE systems computationally is challenging, due to their large size and multi-scale nature.
We propose a multi-fidelity strategy to increase the efficiency of coagulation cascade simulations. Leveraging the slower dynamics of molecular diffusion, we transform the governing PDEs into ordinary differential equations (ODEs) representing the evolution of species concentrations versus blood residence time. We then Taylor-expand the ODE solution around the zero-diffusivity limit to obtain spatiotemporal maps of species concentrations in terms of the statistical moments of residence time, tpR, and provide the governing PDEs for tpR. This strategy replaces a high-fidelity system of N PDEs representing the coagulation cascade of N chemical species by N ODEs and p PDEs governing the residence time statistical moments. The multi-fidelity order(p) allows balancing accuracy and computational cost, providing a speedup of over N/p compared to high-fidelity models.
Using a simplified coagulation network and an idealized aneurysm geometry with a pulsatile flow as a benchmark, we demonstrate favorable accuracy for low-order models of p = 1 and p = 2. These models depart from the high-fidelity solution by under 16% (p = 1) and 5% (p = 2) after 20 cardiac cycles.
The favorable accuracy and low computational cost of multi-fidelity models could enable unprecedented coagulation analyses in complex flow scenarios and extensive reaction networks. Furthermore, it can be generalized to advance our understanding of other systems biology networks affected by blood flow.
... Hemodynamical quantities, such as wall shear stress (WSS), vorticity, recirculation and pressure fluctuations, are known to play an important role in the development of eventual complications, e.g. aneurysm rupture, regrowth and thrombogenesis [123,124]. Extensive in-vitro and in-silico studies have been conducted to describe the aneurysmal flow alternations after embolization [125][126][127][128][129][130] and the influence of stent structure [91,131] and coiling packing density and configuration [117,132,133]. Blood flow is introduced after and not during EVT structural simulations since the effect of drag forces on the device expansion is assumed to be negligible [88]. ...
... The incidence of thrombosis of small ruptured aneurysms has been shown to be 1%-2% [18]. In general, extremely small caliber aneurysms, such as basilar perforator aneurysms, are often characterized by reduced flow, facilitating partial or complete thrombosis [16,18,19]. This underscores the importance of close in-hospital observation of these patients and the utility of short-interval repeat DSA, especially if there is a considerable blood burden in the subarachnoid space. ...
Basilar perforating artery aneurysms are rare and underreported vascular anomalies in the cerebrovascular literature. Various open and endovascular treatment approaches can be employed to treat these aneurysms based on several patient- and aneurysm-specific factors. Some authors have even advocated for conservative, nonoperative management. Here, we report a case of a ruptured distal basilar perforating artery aneurysm secured by an open transpetrosal approach.
A 67-year-old male presented to our institution with a Hunt-Hess grade 2, modified Fisher grade 3 subarachnoid hemorrhage (SAH). Initial cerebral digital subtraction angiography (DSA) did not identify an intracranial aneurysm or other vascular lesions. However, the patient had a re-rupture event several days after presentation. DSA at this time revealed a posteriorly projecting distal basilar perforating artery aneurysm. Initial attempts with endovascular coil embolization were unsuccessful. Thus, an open transpetrosal approach was taken to gain access to the middle and distal basilar trunk to secure the aneurysm.
This case underscores the unpredictability of basilar perforating artery aneurysms and the challenges encountered when considering active treatment. We demonstrate an open surgical approach with an intraoperative video for definitive management after failed attempted endovascular treatment.
