Comparison of techniques for stent assisted coil embolization of aneurysms.
Spiotta Alejandro M,Wheeler Anne Marie,Smithason Saksith,Hui Ferdinand,Moskowitz Shaye
Journal of neurointerventional surgery
INTRODUCTION:Stent assisted coiling (SAC) of aneurysms has been adopted with potential mechanical, hemodynamic and biologic properties imparting an advantage over coil embolization alone. The purpose of this investigation is to compare the various techniques of SAC at a single institution with regards to clinical, technical and angiographic complications and success. METHODS:Patients who underwent SAC between 2003 and 2010 were identified. Clinical charts, procedures, angiographic and non-invasive radiological images were analyzed to determine the anatomical and procedural details and adverse events. Immediate post-procedural angiograms as well as follow-up imaging were studied to assess the degree of aneurysm occlusion. RESULTS:260 aneurysms were identified. The 'coil through' technique was employed in 37.3%, 'balloon stent' in 36.2%, 'jailing' in 10.8% and the 'coil stent' technique in 7.7%. Overall rate of adverse events was higher with the 'coil stent' and 'jailing' techniques compared with the 'balloon stent' technique. The 'coil through' technique was associated with a significantly lower packing density (31.4±20%) than all other techniques ('coil stent' 45.4±22%, 'jailing' 42.2±20%, 'balloon stent' 44.3±22%). Among 'coil stent' patients, an initial Raymond class 1 was achieved in 40%, compared with 57% of 'jailing', 28% of 'coil through' and 63% of 'balloon stent' cases. CONCLUSION:Balloon assisted coil embolization followed by adjunctive stent deployment across the aneurysm neck appears to be the superior technique among stent assisted coiling methods at our institution. It combines a lower rate of thrombotic and coil related complications with a high rate of complete occlusion on initial and follow-up imaging.
10.1136/neurintsurg-2011-010055
Role of distal cerebral vasculature in vessel constriction after aneurysm treatment with flow diverter stents.
Narata Ana Paula,Moura Fernando,Larrabide Ignacio,Chapot René,Cognard Christophe,Januel Anne-Christine,Velasco Stéphane,Bouakaz Ayache,Patat Frederic,Marzo Alberto
Journal of neurointerventional surgery
BACKGROUND:Treatment of intracranial aneurysms with flow diverter stent (FDS) procedures can lead to caliber changes of jailed vessels. The reason some branches remain unchanged and others are affected by narrowing remains unknown. OBJECTIVE:To investigate the influence of resistance to flow from distal vasculature on stent-induced hemodynamic modifications affecting bifurcating vessels. MATERIALS AND METHODS:Radiological images and demographic data were acquired for 142 aneurysms treated with a FDS. Vascular resistance was estimated from patient-specific anatomic data. Correlation analysis was used to identify correspondence between anatomic data and clinical outcome. Computational Fluid Dynamics was performed on a typical patient-specific model to evaluate the influence of FDS on flow. Relevant hemodynamic variables along the bifurcating vessels were quantitatively analyzed and validated with in vitro data obtained using power Doppler ultrasound. RESULTS:Statistical analysis showed a correlation between clinical outcome and FDS resistance to flow considering overall jailed vessel vascular resistance (r=0.5, P<0.001). Computational predictions of blood flow showed that hemodynamics is minimally affected by FDS treatment in the ophthalmic artery. CONCLUSIONS:Jailed vessels are affected by narrowing when resistance to flow from the FDS constitutes a larger proportion of the overall vessel resistance to flow. This knowledge may contribute to better understanding of intracranial hemodynamics after a FDS procedure and reinforce indications for flow diversion in the treatment of intracranial aneurysms.
10.1136/neurintsurg-2019-015447
Association between hemodynamic conditions and occlusion times after flow diversion in cerebral aneurysms.
Mut Fernando,Raschi Marcelo,Scrivano Esteban,Bleise Carlos,Chudyk Jorge,Ceratto Rosana,Lylyk Pedro,Cebral Juan R
Journal of neurointerventional surgery
BACKGROUND:Evaluation of flow diversion treatment of intracranial aneurysms is difficult owing to lack of knowledge of the target hemodynamic environment. OBJECTIVE:To identify hemodynamic conditions created after flow diversion that induce fast aneurysm occlusion. METHODS:Two groups of aneurysms treated with flow diverters alone were selected: (a) aneurysms completely occluded at 3 months (fast occlusion), and (b) aneurysms patent or incompletely occluded at 6 months (slow occlusion). A total of 23 aneurysms were included in the study. Patient-specific computational fluid dynamics models were constructed and used to characterize the hemodynamic environment immediately before and after treatment. Average post-treatment hemodynamic conditions between the fast and slow occlusion groups were statistically compared. RESULTS:Aneurysms in the fast occlusion group had significantly lower post-treatment mean velocity (fast=1.13 cm/s, slow=3.11 cm/s, p=0.02), inflow rate (fast=0.47 mL/s, slow=1.89 mL/s, p=0.004) and shear rate (fast=20.52 1/s, slow=32.37 1/s, p=0.02) than aneurysms in the slow occlusion group. Receiver operating characteristics analysis showed that mean post-treatment velocity, inflow rate, and shear rate below a certain threshold could discriminate between aneurysms of the fast and slow occlusion groups with good accuracy (84%, 77%, and 76%, respectively). CONCLUSIONS:The occlusion time of cerebral aneurysms treated with flow diverters can be predicted by the hemodynamic conditions created immediately after device implantation. Specifically, low post-implantation flow velocity, inflow rate, and shear rate are associated with fast occlusion times.
10.1136/neurintsurg-2013-011080
Impact of image reconstruction parameters when using 3D DSA reconstructions to measure intracranial aneurysms.
Journal of neurointerventional surgery
BACKGROUND AND PURPOSE:Safe and effective use of newly developed devices for aneurysm treatment requires the ability to make accurate measurements in the angiographic suite. Our purpose was to determine the parameters that optimize the geometric accuracy of three-dimensional (3D) vascular reconstructions. METHODS:An in vitro flow model consisting of a peristaltic pump, plastic tubing, and 3D printed patient-specific aneurysm models was used to simulate blood flow in an intracranial aneurysm. Flow rates were adjusted to match values reported in the literature for the internal carotid artery. 3D digital subtraction angiography acquisitions were obtained using a commercially available biplane angiographic system. Reconstructions were done using Edge Enhancement (EE) or Hounsfield Unit (HU) kernels and a Normal or Smooth image characteristic. Reconstructed images were analyzed using the vendor's aneurysm analysis tool. Ground truth measurements were derived from metrological scans of the models with a microCT. Aneurysm volume, surface area, dome height, minimum and maximum ostium diameter were determined for the five models. RESULTS:In all cases, measurements made with the EE kernel most closely matched ground truth values. Differences in values derived from reconstructions displayed with Smooth or Normal image characteristics were small and had only little impact on the geometric parameters considered. CONCLUSIONS:Reconstruction parameters impact the accuracy of measurements made using the aneurysm analysis tool of a commercially available angiographic system. Absolute differences between measurements made using reconstruction parameters determined as optimal in this study were, overall, very small. The significance of these differences, if any, will depend on the details of each individual case.
10.1136/neurintsurg-2017-013080
Assessment of intra-aneurysmal flow modification after flow diverter stent placement with four-dimensional flow MRI: a feasibility study.
Pereira Vitor Mendes,Brina Olivier,Delattre Benedicte M A,Ouared Rafik,Bouillot Pierre,Erceg Gorislav,Schaller Karl,Lovblad Karl-Olof,Vargas Maria-Isabel
Journal of neurointerventional surgery
BACKGROUND:Flow diverter stents (FDS) have been effectively used for the endovascular treatment of sidewall intracranial aneurysms (IAs). Unlike standard endovascular treatments used to exclude directly the aneurysm bulge from the parent vessel, FDS induce reduction in the intra-aneurysmal flow and promote progressive and stable thrombosis therein. The advent of FDS has therefore increased the need for understanding of IA hemodynamics. METHODS:We proposed the use of the most recently evolved four-dimensional (4D) flow MRI technique to evaluate qualitatively and quantitatively post-FDS flow modification in 10 patients. We report intra-aneurysmal velocity measurements and the influence of metal artifacts induced by the stent. RESULTS:An index was defined to quantitatively measure flow changes-namely, the proportional velocity reduction ratio (PVRR)-with ranges from 34.6% to 71.1%. Furthermore, we could compare streamlines characterizing the post-stent flow patterns in five patients in whom the intra-aneurysmal velocity was beyond the visualization threshold of 7.69 cm/s. CONCLUSIONS:Despite metal artifacts and the low velocities involved, 4D flow MRI could be of interest to measure qualitatively and quantitatively flow changes in stented aneurysms. However, further enhancements are required together with further validation work before it can be considered for clinical use.
10.1136/neurintsurg-2014-011348
Computational fluid dynamics analysis of flow reduction induced by flow-diverting stents in intracranial aneurysms: a patient-unspecific hemodynamics change perspective.
Ouared Rafik,Larrabide Ignacio,Brina Olivier,Bouillot Pierre,Erceg Gorislav,Yilmaz Hasan,Lovblad Karl-Olof,Mendes Pereira Vitor
Journal of neurointerventional surgery
BACKGROUND AND PURPOSE:Flow-diverter stents (FDSs) have been used effectively to treat large neck and complex saccular aneurysms on the anterior carotid circulation. Intra-aneurysmal flow reduction induces progressive aneurysm thrombosis in most patients. Understanding the degree of flow modification necessary to induce complete aneurysm occlusion among patients with considerable hemodynamics variability may be important for treatment planning. MATERIALS AND METHODS:Patients with incidental intracranial saccular aneurysms who underwent FDS endovascular procedures were included and studied for a 12 months' follow-up period. We used computational fluid dynamics on patient-specific geometries from 3D rotational angiography without and with virtual stent placement and thus compared intra-aneurysmal hemodynamic problems. Receiver operating characteristic analysis was used to estimate the stent:no-stent minimum hemodynamic ratio thresholds that significantly (p≤0.05) determined the condition necessary for long-term (12 months) aneurysm occlusion. RESULTS:We included 12 consecutive patients with sidewall aneurysms located in the internal carotid or vertebral artery. The measured porosity of the 12 deployed virtual FDSs was 83±3% (mean±SD). Nine aneurysms were occluded during the 12 months' follow-up, whereas three were not. A significant (p=0.05) area under the curve (AUC) was found for spatiotemporal mean velocity reduction in the aneurysms: AUC=0.889±0.113 (mean±SD) corresponding to a minimum velocity reduction threshold of 0.353 for occlusion to occur. The 95% CI of the AUC was 0.66 to 1.00. The sensitivity and specificity of the method were ∼99% and ∼67%, respectively. For both wall shear stress and pressure reductions in aneurysms no thresholds could be determined: AUC=0.63±0.16 (p=0.518) and 0.67±0.165 (p=0.405), respectively. CONCLUSIONS:For successful FDS treatment the post-stent average velocity in sidewall intracranial aneurysms must be reduced by at least one-third from the initial pre-stent conditions.
10.1136/neurintsurg-2015-012154
Determination of a shear rate threshold for thrombus formation in intracranial aneurysms.
Ribeiro de Sousa Daniel,Vallecilla Carolina,Chodzynski Kamil,Corredor Jerez Ricardo,Malaspinas Orestis,Eker Omer Faruk,Ouared Rafik,Vanhamme Luc,Legrand Alexandre,Chopard Bastien,Courbebaisse Guy,Zouaoui Boudjeltia Karim
Journal of neurointerventional surgery
BACKGROUND:Particular intra-aneurysmal blood flow conditions, created naturally by the growth of an aneurysm or induced artificially by implantation of a flow diverter stent (FDS), can potentiate intra-aneurysmal thrombosis. The aim of this study was to identify hemodynamic indicators, relevant to this process, which could be used as a prediction of the success of a preventive endovascular treatment. METHOD:A cross sectional study on 21 patients was carried out to investigate the possible association between intra-aneurysmal spontaneous thrombus volume and the dome to neck aspect ratio (AR) of the aneurysm. The mechanistic link between these two parameters was further investigated through a Fourier analysis of the intra-aneurysmal shear rate (SR) obtained by computational fluid dynamics (CFD). This analysis was first applied to 10 additional patients (4 with and 6 without spontaneous thrombosis) and later to 3 patients whose intracranial aneurysms only thrombosed after FDS implantation. RESULTS:The cross sectional study revealed an association between intra-aneurysmal spontaneous thrombus volume and the AR of the aneurysm (R(2)=0.67, p<0.001). Fourier analysis revealed that in cases where thrombosis occurred, the SR harmonics 0, 1, and 2 were always less than 25/s, 10/s, and 5/s, respectively, and always greater than these values where spontaneous thrombosis was not observed. CONCLUSIONS:Our study suggests the existence of an SR threshold below which thrombosis will occur. Therefore, by analyzing the SR on patient specific data with CFD techniques, it may be potentially possible to predict whether or the intra-aneurysmal flow conditions, after FDS implantation, will become prothrombotic.
10.1136/neurintsurg-2015-011737
Hemodynamic analysis of fast and slow aneurysm occlusions by flow diversion in rabbits.
Chung Bongjae,Mut Fernando,Kadirvel Ramanathan,Lingineni Ravi,Kallmes David F,Cebral Juan R
Journal of neurointerventional surgery
PURPOSE:To assess hemodynamic differences between aneurysms that occlude rapidly and those occluding in delayed fashion after flow diversion in rabbits. METHODS:Thirty-six elastase-induced aneurysms in rabbits were treated with flow diverting devices. Aneurysm occlusion was assessed angiographically immediately before they were sacrificed at 1 (n=6), 2 (n=4), 4 (n=8) or 8 weeks (n=18) after treatment. The aneurysms were classified into a fast occlusion group if they were completely or near completely occluded at 4 weeks or earlier and a slow occlusion group if they remained incompletely occluded at 8 weeks. The immediate post-treatment flow conditions in aneurysms of each group were quantified using subject-specific computational fluid dynamics and statistically compared. RESULTS:Nine aneurysms were classified into the fast occlusion group and six into the slow occlusion group. Aneurysms in the fast occlusion group were on average significantly smaller (fast=0.9 cm, slow=1.393 cm, p=0.024) and had smaller ostia (fast=0.144 cm2, slow=0.365 cm2, p=0.015) than aneurysms in the slow occlusion group. They also had a lower mean post-treatment inflow rate (fast=0.047 mL/s, slow=0.155 mL/s, p=0.0239), kinetic energy (fast=0.519 erg, slow=1.283 erg, p=0.0468), and velocity (fast=0.221 cm/s, slow=0.506 cm/s, p=0.0582). However, the differences in the latter two variables were only marginally significant. CONCLUSIONS:Hemodynamic conditions after flow diversion treatment of cerebral aneurysms in rabbits are associated with the subsequent aneurysm occlusion time. Specifically, smaller inflow rate, kinetic energy, and velocity seem to promote faster occlusions, especially in smaller and small-necked aneurysms. These results are consistent with previous studies based on clinical series.
10.1136/neurintsurg-2014-011412
Neurovascular stent artifacts in 3D-TOF and 3D-PCMRI: Influence of stent design on flow measurement.
Bouillot Pierre,Brina Olivier,Delattre Bénédicte M A,Ouared Rafik,Pellaton Alain,Yilmaz Hasan,Machi Paolo,Lovblad Karl-Olof,Farhat Mohamed,Pereira Vitor Mendes,Vargas Maria Isabel
Magnetic resonance in medicine
PURPOSE:The morphological and hemodynamic evaluations of neurovascular diseases treated with stents would benefit from noninvasive imaging techniques such as 3D time-of-flight MRI (3D-TOF) and 3D phase contrast MRI (3D-PCMRI). For this purpose, a comprehensive evaluation of the stent artifacts and their impact on the flow measurement is critical. METHODS:The artifacts of a representative sample of neurovascular stents were evaluated in vitro with 3D-TOF and 3D-PCMRI sequences. The dependency of the artifacts with respect to the orientation was analyzed for each stent design as well as the impact on the flow measurement accuracy. Furthermore, the 3D-PCMRI data of four patients carrying intracranial aneurysms treated with flow diverter stents were analyzed as illustrative examples. RESULTS:The stent artifacts were mainly confined to the stent lumen therefore indicating the leading role of shielding effect. The influence of the stent design and its orientation with respect to the transmitting MR coils were highlighted. The artifacts impacted the 3D-PCMRI velocities mainly in the low magnitude domains, which were discarded from the analysis ensuring reliable near-stent velocities. The feasibility of in-stent flow measurements was confirmed in vivo on two patients who showed strong correlation between flow and geometric features. In two other patients, the consistency of out-of-stent velocities was verified qualitatively through intra-aneurysmal streamlines except when susceptibility artifacts occurred. CONCLUSION:The present results motivate the conception of low inductance or nonconductive stent design. Furthermore, the feasibility of near-stent 3D-PCMRI measurements opens the door to clinical applications like the post-treatment follow-up of stenoses or intracranial aneurysms.
10.1002/mrm.27352
Intra-aneurysmal hemodynamic alterations by a self-expandable intracranial stent and flow diversion stent: high intra-aneurysmal pressure remains regardless of flow velocity reduction.
Shobayashi Yasuhiro,Tateshima Satoshi,Kakizaki Ryuichi,Sudo Ryo,Tanishita Kazuo,Viñuela Fernando
Journal of neurointerventional surgery
OBJECT:Little is known about how much protection a flow diversion stent provides to a non-thrombosed aneurysm without the adjunctive use of coils. METHODS:A three-dimensional anatomically realistic computation aneurysm model was created from the digital subtraction angiogram of a large internal carotid artery-ophthalmic artery aneurysm which could have been treated with either a neck bridging stent or a flow diversion stent. Three-dimensional computational models of the Neuroform EZ neck bridging stent and Pipeline embolization device were created based on measurements with a stereo-microscope. Each stent was placed in the computational aneurysm model and intra-aneurysmal flow structures were compared before and after placement of the stents. Computational fluid dynamics were performed by numerically solving the continuity and Navier-Stokes momentum equations for a steady blood flow based on the finite volume method. Blood was assumed as an incompressible Newtonian fluid. Vessel walls were assumed to be rigid, and no-slip boundary conditions were applied at the lumens. To estimate the change in the intra-aneurysmal pressures we assumed that, at the inlets, the intra-arterial pressure at peak systole was 120 mm Hg both before and after stent placement RESULTS:Without any stent, the blood flow entered into the aneurysm dome from the mid to proximal neck area and ascended along the distal wall of the aneurysm. The flow then changed its direction anteriorly and moved along the proximal wall of the aneurysm dome. In addition to the primary intra-aneurysmal circulation pattern, a counterclockwise vortex was observed in the aneurysm dome. The placement of a Neuroform EZ stent induced a mean reduction in flow velocity of 14% and a small change in the overall intra-aneurysmal flow pattern. The placement of a Pipeline device induced a mean reduction in flow velocity of 74% and a significant change in flow pattern. Despite the flow velocity changes, Neuroform EZ and Pipeline devices induced reductions in intra-aneurysmal pressure of only 4 mm Hg and 8 mm Hg, respectively. CONCLUSIONS:The flow diversion effects of both stents were limited to flow velocity reduction. In a non-thrombosed aneurysm or an aneurysm with delayed thrombosis, the intra-aneurysmal pressure remains essentially unchanged regardless of the level of the intra-aneurysmal flow velocity reduction induced by the stents.
10.1136/neurintsurg-2012-010488
Intra-aneurysmal hemodynamics: evaluation of pCONus and pCANvas bifurcation aneurysm devices using DSA optical flow imaging.
Pérez Marta Aguilar,Henkes Hans,Bouillot Pierre,Brina Olivier,Slater Lee-Anne,Pereira Vitor Mendes
Journal of neurointerventional surgery
BACKGROUND:Implantation of self-expanding stents from the parent artery into the sac of a bifurcation aneurysm is regularly used to facilitate endovascular coil occlusion with the so-called waffle cone technique (WCT). Self-expanding aneurysm bridging stents like Solitaire AB, can be used; however, bifurcation devices like pCONus and pCANvas are especially designed for WCT. These devices provide additional support for coil implantation owing to intraluminal nylon fibers (pCONus) or membranes (pCANvas) covering the intracranial aneurysm neck. OBJECTIVE:Assessment of the intra-aneurysmal hemodynamic impact of these three devices: a regular intracranial stent (Solitaire AB) and two bifurcation devices (pCONus and pCANvas). MATERIAL AND METHODS:An in vitro experiment was set up using a silicone model of a basilar tip aneurysm filled with blood mimicking fluid under a pulsatile circulation. Solitaire AB, pCONus, and pCANvas were successively implanted in the model for hemodynamic evaluation. High frame rate DSA series were acquired under various conditions. Intra-aneurysmal flow changes, including mean aneurysm flow amplitude ratio (R), were subsequently assessed by the optical flow method, measuring the detector velocity field before and after device implantations. RESULTS:pCONus and Solitaire minimally reduced the intra-aneurysmal flow (R=0.96, p=0.17 and R=0.91, p=0.01, respectively), whereas pCANvas strongly diminished the intra-aneurysmal flow (R=0.41, p=5×10). CONCLUSIONS:Waffle cone deployment of stents and technique-specific devices had no undesirable effect on the intra-aneurysmal flow. In particular, no increased flow was redirected into the aneurysm sac. The intraluminal membrane of the pCANvas strongly reduced the intra-aneurysmal flow, potentially preventing recanalization problems.
10.1136/neurintsurg-2015-011927
Hemodynamic differences between Pipeline and coil-adjunctive intracranial stents.
Jankowitz Brian Thomas,Gross Bradley A,Seshadhri Santhosh,Girdhar Gaurav,Jadhav Ashutosh,Jovin Tudor G,Wainwright John Michael
Journal of neurointerventional surgery
INTRODUCTION:Modern coil-adjunctive intracranial stent designs have increased metal surface coverage to construct putative 'flow diverter lights.' This is rooted in the assumption that flow diversion is linearly correlated with metal surface coverage rather than being a threshold to be reached by device porosity and design. OBJECTIVE:To evaluate this assumption, by performing computational flow analysis on three aneurysm models treated with low metal surface coverage stents (ATLAS and Enterprise), a Pipeline flow diverter, and the LVIS Blue stent. METHODS:Computational flow analysis was performed on virtual deployment models entailing deployment of an ATLAS, Enterprise, LVIS Blue, or Pipeline. The impact of device deployment on velocity vectors at the neck, maximum wall shear stress, inflow rate into the aneurysm, and turnover time was determined. RESULTS:Velocity vector plots demonstrated low magnitude, localized inflow jets for Pipeline only; asymmetric, selectively high inflow jets were seen for LVIS Blue, and broader velocity vector clusters were seen for Atlas and Enterprise. Reduction in wall shear stress as compared with baseline was significant for all devices and greatest for the Pipeline. Mean peak wall shear stress was significantly lower for LVIS Blue in comparison with ATLAS or Enterprise but significantly lower for Pipeline than for LVIS Blue. Reduction of inflow rate into the aneurysm was significant for LVIS Blue and Pipeline but significantly lower for Pipeline than for LVIS Blue. Turnover time was statistically similar for ATLAS, Enterprise, and LVIS Blue, but significantly increased for Pipeline. CONCLUSION:Considerable differences in peak wall shear stress, inflow rates, and turnover time between flow diverters, moderate- and low-porosity stents reinforce the assumption that effective flow diversion represents a threshold in device design, encompassing metal surface coverage only in part.
10.1136/neurintsurg-2018-014439
A virtual coiling technique for image-based aneurysm models by dynamic path planning.
Morales Hernán G,Larrabide Ignacio,Geers Arjan J,San Román Luis,Blasco Jordi,Macho Juan M,Frangi Alejandro F
IEEE transactions on medical imaging
Computational algorithms modeling the insertion of endovascular devices, such as coil or stents, have gained an increasing interest in recent years. This scientific enthusiasm is due to the potential impact that these techniques have to support clinicians by understanding the intravascular hemodynamics and predicting treatment outcomes. In this work, a virtual coiling technique for treating image-based aneurysm models is proposed. A dynamic path planning was used to mimic the structure and distribution of coils inside aneurysm cavities, and to reach high packing densities, which is desirable by clinicians when treating with coils. Several tests were done to evaluate the performance on idealized and image-based aneurysm models. The proposed technique was validated using clinical information of real coiled aneurysms. The virtual coiling technique reproduces the macroscopic behavior of inserted coils and properly captures the densities, shapes and coil distributions inside aneurysm cavities. A practical application was performed by assessing the local hemodynamic after coiling using computational fluid dynamics (CFD). Wall shear stress and intra-aneurysmal velocities were reduced after coiling. Additionally, CFD simulations show that coils decrease the amount of contrast entering the aneurysm and increase its residence time.
10.1109/TMI.2012.2219626
Stretchable, Implantable, Nanostructured Flow-Diverter System for Quantification of Intra-aneurysmal Hemodynamics.
Howe Connor,Mishra Saswat,Kim Yun-Soung,Chen Yanfei,Ye Sang-Ho,Wagner William R,Jeong Jae-Woong,Byun Hun-Soo,Kim Jong-Hoon,Chun Youngjae,Yeo Woon-Hong
ACS nano
Random weakening of an intracranial blood vessel results in abnormal blood flow into an aneurysmal sac. Recent advancements show that an implantable flow diverter, integrated with a medical stent, enables a highly effective treatment of cerebral aneurysms by guiding blood flow into the normal vessel path. None of such treatment systems, however, offers post-treatment monitoring to assess the progress of sac occlusion. Therefore, physicians rely heavily on either angiography or magnetic resonance imaging. Both methods require a dedicated facility with sophisticated equipment settings and time-consuming, cumbersome procedures. In this paper, we introduce an implantable, stretchable, nanostructured flow-sensor system for quantification of intra-aneurysmal hemodynamics. The open-mesh membrane device is capable of effective implantation in complex neurovascular vessels with extreme stretchability (500% radial stretching) and bendability (180° with 0.75 mm radius of curvature) for monitoring of the treatment progress. A collection of quantitative mechanics, fluid dynamics, and experimental studies establish the fundamental aspects of design criteria for a highly compliant, implantable device. Hemocompatibility study using fresh ovine blood captures the device feasibility for long-term insertion in a blood vessel, showing less platelet deposition compared to that in existing implantable materials. In vitro demonstrations of three types of flow sensors show quantification of intra-aneurysmal blood flow in a pig aorta and the capability of observation of aneurysm treatment with a great sensitivity (detection limit as small as 0.032 m/s). Overall, this work describes a mechanically soft flow-diverter system that offers an effective treatment of aneurysms with an active monitoring of intra-aneurysmal hemodynamics.
10.1021/acsnano.8b04689
Geometrical deployment for braided stent.
Bouillot Pierre,Brina Olivier,Ouared Rafik,Yilmaz Hasan,Farhat Mohamed,Erceg Gorislav,Lovblad Karl-Olof,Vargas Maria Isabel,Kulcsar Zsolt,Pereira Vitor Mendes
Medical image analysis
The prediction of flow diverter stent (FDS) implantation for the treatment of intracranial aneurysms (IAs) is being increasingly required for hemodynamic simulations and procedural planning. In this paper, a deployment model was developed based on geometrical properties of braided stents. The proposed mathematical description is first applied on idealized toroidal vessels demonstrating the stent shortening in curved vessels. It is subsequently generalized to patient specific vasculature predicting the position of the filaments along with the length and local porosity of the stent. In parallel, in-vitro and in-vivo FDS deployments were measured by contrast-enhanced cone beam CT (CBCT) in idealized and patient-specific geometries. These measurements showed a very good qualitative and quantitative agreement with the virtual deployments and provided experimental validations of the underlying geometrical assumptions. In particular, they highlighted the importance of the stent radius assessment in the accuracy of the deployment prediction. Thanks to its low computational cost, the proposed model is potentially implementable in clinical practice providing critical information for patient safety and treatment outcome assessment.
10.1016/j.media.2016.01.006
The effect of shear stress on neointimal response following sirolimus- and paclitaxel-eluting stent implantation compared with bare-metal stents in humans.
Papafaklis Michail I,Bourantas Christos V,Theodorakis Panagiotis E,Katsouras Christos S,Naka Katerina K,Fotiadis Dimitrios I,Michalis Lampros K
JACC. Cardiovascular interventions
OBJECTIVES:We aimed to explore the relationship of neointimal thickness (NT) to shear stress (SS) after implantation of sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES) compared with bare-metal stents (BMS). We then tested the hypothesis that drug elution attenuates the SS effect. BACKGROUND:Neointimal thickness after BMS implantation has been associated with SS; pertinent data for drug-eluting stents (DES) are limited. METHODS:Three-dimensional coronary artery and stent reconstruction was performed in 30 patients at 6-month follow-up after SES (n = 10), PES (n = 10), or BMS (n = 10) implantation. Baseline SS at the stent surface was calculated using computational fluid dynamics and NT at follow-up was computed in 3-dimensional space. RESULTS:Neointimal thickness was lower in DES versus BMS (0.03 ± 0.07 mm vs. 0.16 ± 0.08 mm, p < 0.001) and maximum NT was reduced in SES versus PES (0.33 ± 0.13 mm vs. 0.46 ± 0.13 mm, p = 0.025). In the total population, both SS (slope: -0.05 mm/Pa, p < 0.001) and DES (coefficient for DES vs. BMS: -0.17 mm, p = 0.003) were independent predictors of NT. Subgroup analysis demonstrated a significant negative relationship of NT to SS in PES (slope: -0.05 mm/Pa, p = 0.016) and BMS (slope: -0.05 mm/Pa, p = 0.001). Sirolimus elution significantly attenuated the effect of SS on NT (interaction coefficient for SES vs. BMS: 0.04 mm/Pa, p = 0.023), whereas the SS effect remained unchanged in PES (interaction coefficient for PES vs. BMS: 0.01 mm/Pa, p = 0.71). CONCLUSIONS:Neointimal thickness is significantly correlated (inversely) to SS in PES as in BMS. Sirolimus elution abrogates the SS effect on the neointimal response following stent implantation, whereas the SS effect is unchanged in PES.
10.1016/j.jcin.2010.08.018
Hemodynamics study of a multilayer stent for the treatment of aneurysms.
Xiong Yan,Wang Xuhong,Jiang Wentao,Tian Xiaobao,Wang Qingyuan,Fan Yubo,Chen Yu
Biomedical engineering online
BACKGROUND:The changes of hemodynamics caused by the implantation of multilayer stent (MS) have significant effects for aneurysm sac. METHODS:Comparisons of 3D numerical models with/without a MS in an abdominal aortic aneurysm with a 90° branch vessel were numerically studied from the viewpoint of hemodynamics. RESULTS:The results showed that: (1) The flow fields and Wall Shear Stress (WSS) are changed dramatically after MS implantation. The velocity of the blood flow in aneurysm sac decreases significantly and the regions of low-WSS increase. These help thrombus formation; (2) The pressure in aneurysm slightly decreases and keeps close to the normal level of blood pressure, however the risk of aneurysm enlargement or even rupture still exists; (3) The flux and the velocity in branch artery are reduced by about half after MS implantation. Due to the implantation of MS, the changes in the flow field causes the decrease of pressure/WSS in aneurysm sac and the blood flow in branch vessel. CONCLUSIONS:The implantation of MS into abdominal artery results in more low-WSS regions inside aneurysm which induces thrombus formation. The pressure is reduced slightly means the risk of aneurysm rupture exists.
10.1186/s12938-016-0248-0
Comparative Analysis of Long-Term Effect of Stent-Assisted Coiling in Unruptured Sidewall-Type and Terminal-Type Aneurysms.
Teramoto Shinichiro,Oishi Hidenori,Arai Hajime
World neurosurgery
BACKGROUND:Stent-assisted coiling is recognized as effective to induce progressive occlusion and prevent recurrence of aneurysm. The long-term effects of stent-assisted coiling of sidewall-type and terminal-type aneurysms were comparatively analyzed focusing on the different hemodynamic characteristics. METHODS:Retrospective analysis included a total of 120 unruptured aneurysms in 116 consecutive patients who underwent stent-assisted coiling and completed 2-year follow-up. The stent systems, baseline characteristics, and postcoiling occlusion status of sidewall-type and terminal-type aneurysms were assessed. RESULTS:Sidewall-type aneurysms had a significantly larger dome size (P = 0.02) and greater diameter of the parent vessel (P < 0.001) than terminal-type aneurysms. Initial occlusion status of the aneurysms was significantly maintained for 2 years in both sidewall-type and terminal-type aneurysms as follows: sidewall-type aneurysms showed that complete occlusion (CO), neck remnants (NRs), and body filling (BF) immediately posttreatment were significantly correlated with CO (P < 0.05), NRs (P < 0.01), and BF (P < 0.05) at 2-year follow-up, respectively, and terminal-type aneurysms showed that CO, NRs, and BF immediately posttreatment were significantly correlated with CO (P < 0.05), NRs (P < 0.05), and BF (P < 0.05) at 2-year follow-up, respectively. In addition, sidewall-type aneurysms with CO immediately posttreatment were significantly correlated with non-NRs (P < 0.01) and non-BF (P < 0.01) at 2-year follow-up. CONCLUSIONS:Stent-assisted coiling allows higher coil packing for sidewall-type aneurysms, but the indication should be carefully considered for terminal-type aneurysms.
10.1016/j.wneu.2019.02.145
Alteration of intra-aneurysmal hemodynamics for flow diversion using enterprise and vision stents.
Tremmel Markus,Xiang Jianping,Natarajan Sabareesh K,Hopkins L Nelson,Siddiqui Adnan H,Levy Elad I,Meng Hui
World neurosurgery
OBJECTIVE:Flow diversion is a novel concept for intracranial aneurysm treatment. The recently developed Enterprise Vascular Reconstruction Device (Codman Neurovascular, Raynham MA) provides easy delivery and repositioning. Although designed specifically for restraining coils within an aneurysm, this stent has theoretical effects on modifying flow dynamics, which have not been studied. The goal of this study was to quantify the effect of single and multiple self-expanding Enterprise stents alone or in combination with balloon-mounted stents on aneurysm hemodynamics using computational fluid dynamics (CFD). METHODS:The geometry of a wide-necked, saccular, basilar trunk aneurysm was reconstructed from computed tomographic angiography images. Various combinations of 1-3 stents were "virtually" conformed to fit into the vessel lumen and placed across the aneurysm orifice. CFD analysis was performed to calculate hemodynamic parameters considered important in aneurysm pathogenesis and thrombosis for each model. RESULTS:The complex aneurysmal flow pattern was suppressed by stenting. Stent placement lowered average flow velocity in the aneurysm; further reduction was achieved by additional stent deployment. Aneurysmal flow turnover time, an indicator of stasis, was increased to 114-117% for single-stent, 127-128% for double-stent, and 141% for triple-stent deployment. Furthermore, aneurysmal wall shear stress (WSS) decreased with increasing number of deployed stents. CONCLUSION:This is the first study analyzing flow modifications associated with placement of Enterprise stents for aneurysm occlusion. Placement of 2-3 stents significantly reduced intra-aneurysmal hemodynamic activities, thereby increasing the likelihood of inducing aneurysm thrombotic occlusion.
10.1016/j.wneu.2010.05.008
Stent-induced vessel deformation after intracranial aneurysm treatment - A hemodynamic pilot study.
Voß Samuel,Beuing Oliver,Janiga Gábor,Berg Philipp
Computers in biology and medicine
BACKGROUND:Stent-assisted coiling has become an important treatment option for intracranial aneurysms. However, studies have shown that this procedure can lead to the deformation of the local vasculature. Its effect on intra-aneurysmal hemodynamics still remains unclear. METHODS:Pre- and post-interventional image data of three representative middle cerebral artery aneurysms are considered in this study. This includes virtually deployed stents and coils. To evaluate the proportional effect of a) vessel deformation, b) stent deployment, and c) coil placement, 24 unsteady blood flow simulations were carried out focusing on the separated effects related to intra-aneurysmal hemodynamics. Four flow parameters (velocity within the aneurysm sac, aneurysm neck inflow rate, inflow concentration index, and ostium inflow area) and four shear parameters (wall shear stress, normalized wall shear stress, shear concentration index, and high shear area) were quantified. RESULTS:All of the considered flow and shear parameters, except for the shear concentration index, were clearly reduced due to treatment. Coiling and stenting caused a distinct and smaller neck inflow rate, respectively, while the impact of deformation was inconsistent among the aneurysms. Overall, coiling appears to have the strongest impact on local hemodynamics. CONCLUSION:Stent-induced vessel deformation has a clear impact on intra-aneurysmal hemodynamics. This effect is neglected by the majority of previous studies, which consider the pre-interventional state for investigating the relation of stents and hemodynamics. The findings of this pilot study suggest that while stent-assisted coiling can lead to an improved hemodynamic situation, undesired flow conditions may occur in response to treatment.
10.1016/j.compbiomed.2019.103338
Comparison among different high porosity stent configurations: hemodynamic effects of treatment in a large cerebral aneurysm.
Roszelle Breigh N,Nair Priya,Gonzalez L Fernando,Haithem Babiker M,Ryan Justin,Frakes David
Journal of biomechanical engineering
Whether treated surgically or with endovascular techniques, large and giant cerebral aneurysms are particularly difficult to treat. Nevertheless, high porosity stents can be used to accomplish stent-assisted coiling and even standalone stent-based treatments that have been shown to improve the occlusion of such aneurysms. Further, stent assisted coiling can reduce the incidence of complications that sometimes result from embolic coiling (e.g., neck remnants and thromboembolism). However, in treating cerebral aneurysms at bifurcation termini, it remains unclear which configuration of high porosity stents will result in the most advantageous hemodynamic environment. The goal of this study was to compare how three different stent configurations affected fluid dynamics in a large patient-specific aneurysm model. Three common stent configurations were deployed into the model: a half-Y, a full-Y, and a crossbar configuration. Particle image velocimetry was used to examine post-treatment flow patterns and quantify root-mean-squared velocity magnitude (VRMS) within the aneurysmal sac. While each configuration did reduce VRMS within the aneurysm, the full-Y configuration resulted in the greatest reduction across all flow conditions (an average of 56% with respect to the untreated case). The experimental results agreed well with clinical follow up after treatment with the full-Y configuration; there was evidence of thrombosis within the sac from the stents alone before coil embolization was performed. A computational simulation of the full-Y configuration aligned well with the experimental and in vivo findings, indicating potential for clinically useful prediction of post-treatment hemodynamics. This study found that applying different stent configurations resulted in considerably different fluid dynamics in an anatomically accurate aneurysm model and that the full-Y configuration performed best. The study indicates that knowledge of how stent configurations will affect post-treatment hemodynamics could be important in interventional planning and demonstrates the capability for such planning based on novel computational tools.
10.1115/1.4026257
Changes in hemodynamics after placing intracranial stents.
Tanemura Hiroshi,Ishida Fujimaro,Miura Yoichi,Umeda Yasuyuki,Fukazawa Keiji,Suzuki Hidenori,Sakaida Hiroshi,Matsushima Satoshi,Shimosaka Shinichi,Taki Waro
Neurologia medico-chirurgica
Stent-assisted coil embolization has enabled the endovascular treatment of wide-necked cerebral aneurysms. Moreover, recent reports demonstrated that stent-assisted coil embolization was associated with a significant decrease in angiographic recurrences of coiled cerebral aneurysms. One of the possible explanations for this adjunctive effect of stent-assisted coil embolization is changes in the local hemodynamics caused by placing intracranial stents. This study investigated the hemodynamic effect of intracranial stents using computational fluid dynamics (CFD) analysis. The geometry of the intracranial stent, Enterprise(TM) VRD, was acquired by using micro computed tomography and virtually placed across the aneurysm orifice of a saccular aneurysm model (saccular model) and a blister-like aneurysm model (blister-like model) constructed from patient-specific three-dimensional (3D) rotational angiography data. Transient CFD analysis was performed with these models with and without stents. Stent placement induced no significant changes in the 3D streamline in the saccular model and slight changes in the blister-like model. Both saccular and blister-like models with stents had lower wall shear stress (WSS) and flow velocity, and higher oscillatory shear index, WSS gradient, and relative residence time than the equivalent models without stents, indicating the possibility that stent placement induced stagnant and disturbed blood flow. Cross-sectional vector velocity around the stent strut revealed complex blood flow patterns with variable direction and velocity. Although this study was a simulation under limited conditions, similar hemodynamic changes might be induced in the neck remnants treated with stent-assisted coil embolization.
10.2176/nmc.53.171
Numerical study of hemodynamics in brain aneurysms treated with flow diverter stents using porous medium theory.
Yadollahi-Farsani Hooman,Scougal Erik,Herrmann Marcus,Wei Wei,Frakes David,Chong Brian
Computer methods in biomechanics and biomedical engineering
Conventional approaches of implementing computational fluid dynamics to study aneurysmal hemodynamics after treatment with a flow diverter stent are computationally expensive. Cumbersome meshing and lengthy simulation runtimes are common. To address these issues, we present a novel volume penalization method that considers flow diverters as heterogeneous porous media. The proposed model requires a considerably smaller number of mesh elements, leading to faster simulation runtimes. Three patient-specific aneurysms were virtually treated with flow diverters and aneurysmal hemodynamics were simulated. The results of the virtual deployments including aneurysmal hemodynamics were compared to corresponding results from conventional approaches. The comparisons showed that the proposed approach led to 9.12 times increase in the speed of simulations on average. Further, aneurysmal kinetic energy and inflow rate metrics for the proposed approach were consistent with those from conventional approaches, differing on average by 3.52% and 3.78%, respectively.
10.1080/10255842.2019.1609457
Hemodynamic effects of stent struts versus straightening of vessels in stent-assisted coil embolization for sidewall cerebral aneurysms.
Kono Kenichi,Shintani Aki,Terada Tomoaki
PloS one
BACKGROUND:Recent clinical studies have shown that recanalization rates are lower in stent-assisted coil embolization than in coiling alone in the treatment of cerebral aneurysms. OBJECTIVE:This study aimed to assess and compare the hemodynamic effect of stent struts and straightening of vessels by stent placement on reducing flow velocity in sidewall aneurysms, with the goal of reducing recanalization rates. METHODS:We evaluated 16 sidewall aneurysms treated with Enterprise stents. We performed computational fluid dynamics simulations using patient-specific geometries before and after treatment, with or without stent struts. RESULTS:Stent placement straightened vessels by a mean (±standard deviation) of 12.9° ± 13.1° 6 months after treatment. Placement of stent struts in the initial vessel geometries reduced flow velocity in aneurysms by 23.1% ± 6.3%. Straightening of vessels without stent struts reduced flow velocity by 9.6% ± 12.6%. Stent struts had significantly stronger effects on reducing flow velocity than straightening (P = 0.004, Wilcoxon test). Deviation of the effects was larger by straightening than by stent struts (P = 0.01, F-test). The combination of stent struts and straightening reduced flow velocity by 32.6% ± 12.2%. There was a trend that larger inflow angles produced a larger reduction in flow velocity by straightening of vessels (P = 0.16). CONCLUSION:In sidewall aneurysms, stent struts have stronger effects (approximately 2 times) on reduction in flow velocity than straightening of vessels. Hemodynamic effects by straightening vary in each case and can be predicted by inflow angles of pre-operative vessel geometry. These results may be useful to design a treatment strategy for reducing recanalization rates.
10.1371/journal.pone.0108033
Successful Retreatment of Recurrent Intracranial Vertebral Artery Dissecting Aneurysms After Stent-Assisted Coil Embolization: A Self-Controlled Hemodynamic Analysis.
Liu Jian,Jing Linkai,Zhang Ying,Song Ying,Wang Yang,Li Chuanhui,Wang Yanmin,Mu Shiqing,Paliwal Nikhil,Meng Hui,Linfante Italo,Yang Xinjian
World neurosurgery
BACKGROUND:Intracranial vertebral artery dissecting aneurysms (VADAs) tend to recur despite successful stent-assisted coil embolization (SACE). Hemodynamics is useful in evaluating aneurysmal formation, growth, and rupture. Our aim was to evaluate the hemodynamic patterns of the recurrence of VADA. METHODS:Between September 2009 and November 2013, all consecutive patients with recurrent VADAs after SACE in our institutions were enrolled. Recurrence was defined as recanalization and/or regrowth. We assessed the hemodynamic alterations in wall shear stress (WSS) and velocity after the initial SACE and subsequently after retreatment of the aneurysms that recurred. RESULTS:Five patients were included. After the initial treatment, 3 patients showed recanalization and 2 showed regrowth. In the 2 patients with regrowth, the 2 original aneurysms maintained complete occlusion; however, de novo aneurysm regrowth was confirmed near the previous site. Compared with 3 recanalized aneurysms, the completely occluded aneurysms showed high mean reductions in velocity and WSS after initial treatment (velocity, 77.6% vs. 57.7%; WSS, 74.2% vs. 52.4%); however, WSS remained high at the region near the previous lesion where the new aneurysm originated. After the second retreatment, there was no recurrence in any patient. Compared with the 3 aneurysms that recanalized, the 4 aneurysms that maintained complete occlusion showed higher reductions in velocity (62.9%) and WSS (71.1%). CONCLUSIONS:Our series indicated that hemodynamics might have an important role in recurrence of VADAs. After endovascular treatment, sufficient hemodynamic reduction in aneurysm dome, orifice, and parent vessel may be one of the key factors for preventing recurrence in VADAs.
10.1016/j.wneu.2016.10.003
Hemodynamic alterations after stent implantation in 15 cases of intracranial aneurysm.
Wang Chao,Tian Zhongbin,Liu Jian,Jing Linkai,Paliwal Nikhil,Wang Shengzhang,Zhang Ying,Xiang Jianping,Siddiqui Adnan H,Meng Hui,Yang Xinjian
Acta neurochirurgica
BACKGROUND:Stent-assisted coiling technology has been widely used in the treatment of intracranial aneurysms. In the current study, we investigated the intra-aneurysmal hemodynamic alterations after stent implantation and their association with the aneurysm location. METHODS:We first retrospectively studied 15 aneurysm cases [8 internal carotid artery-ophthalmic artery (ICA-OphA) aneurysms and 7 posterior communicating artery (PcoA) aneurysms] treated with Enterprise stents and coils. Then, based on the patient-specific geometries before and after stenting, we built virtual stenting computational fluid dynamics (CFD) simulation models. RESULTS:Before and after the stent deployment, the average wall shear stress (WSS) on the aneurysmal sac at systolic peak changed from 7.04 Pa (4.14 Pa, 15.77 Pa) to 6.04 Pa (3.86 Pa, 11.13 Pa), P = 0.001; the spatially averaged flow velocity in the perpendicular plane of the aneurysm dropped from 0.5 m/s (0.28 m/s, 0.7 m/s) to 0.33 m/s (0.25 m/s, 0.49 m/s), P = 0.001, respectively. Post stent implantation, the WSS in ICA-OphA aneurysms and PcoA aneurysms decreased by 14.4 % (P = 0.012) and 16.6 % (P = 0.018), respectively, and the flow velocity also reduced by 10.3 % (P = 0.029) and 10.5 % (P = 0.013), respectively. Changes in the WSS, flow velocity, and pressure were not significantly different between ICA-OphA and PcoA aneurysms (P > 0.05). Stent implantation did not significantly change the peak systolic pressure in either aneurysm type. CONCLUSION:After the stent implantation, both the intra-aneurysmal flow velocity and WSS decreased independently of aneurysm type (ICA-OphA and PcoA). Little change was observed in peak systolic pressure.
10.1007/s00701-015-2696-x
The hemodynamic alterations induced by the vascular angular deformation in stent-assisted coiling of bifurcation aneurysms.
Jeong W,Han M H,Rhee K
Computers in biology and medicine
The hemodynamic changes induced by stent deployment and vascular remodeling in bifurcation aneurysms were investigated using computational fluid dynamics. The stent deployment reduced the intra-aneurysmal flow activity by decreasing the mean velocity, mean kinetic energy, mean wall shear stress, and mean vorticity. These hemodynamic parameters increased with an increase in the branching angle because of the vessel deformation caused by stent straightening. The maximum wall shear stress and its spatial gradient occurred near the neck of the aneurysm in the stented left daughter vessel, whereas a maximum oscillatory shear index was detected near the neck of the right aneurysm of the right daughter vessel. Theses parameters, which might be related to the recurrence of aneurysms, were also increased by stent-induced vessel deformation.
10.1016/j.compbiomed.2014.07.006
Effect of hemodynamics on outcome of subtotally occluded paraclinoid aneurysms after stent-assisted coil embolization.
Liu Jian,Jing Linkai,Wang Chao,Paliwal Nikhil,Wang Shengzhang,Zhang Ying,Xiang Jianping,Siddiqui Adnan H,Meng Hui,Yang Xinjian
Journal of neurointerventional surgery
BACKGROUND:Endovascular treatment of paraclinoid aneurysms is preferred in clinical practice. Flow alterations caused by stents and coils may affect treatment outcome. OBJECTIVE:To assess hemodynamic changes following stent-assisted coil embolization (SACE) in subtotally embolized paraclinoid aneurysms with residual necks that were predisposed to recanalization. METHODS:We studied 27 paraclinoid aneurysms (seven recanalized and 20 stable) treated with coils and Enterprise stents. Computational fluid dynamic simulations were performed on patient-specific aneurysm geometries using virtual stenting and porous media technology. RESULTS:After stent placement in 27 cases, aneurysm flow velocity decreased significantly, the reduction gradually increasing from the neck plane (11.9%), to the residual neck (12.3%), to the aneurysm dome (16.3%). Subsequent coil embolization was performed after stent placement and the hemodynamic factors decreased further and significantly at all aneurysm regions except the neck plane. In a comparison of recanalized and stable cases, univariate analysis showed no significant differences in any parameter before treatment. After stent-assisted coiling, only the reduction in area-averaged velocity at the neck plane differed significantly between recanalized (8.1%) and stable cases (20.5%) (p=0.016). CONCLUSIONS:Aneurysm flow velocity can be significantly decreased by stent placement and coil embolization. However, hemodynamics at the aneurysm neck plane is less sensitive to coils. Significant reduction in flow velocity at the neck plane may be an important factor in preventing recanalization of paraclinoid aneurysms after subtotal SACE.
10.1136/neurintsurg-2015-012050
Flow diverter effect of LVIS stent on cerebral aneurysm hemodynamics: a comparison with Enterprise stents and the Pipeline device.
Wang Chao,Tian Zhongbin,Liu Jian,Jing Linkai,Paliwal Nikhil,Wang Shengzhang,Zhang Ying,Xiang Jianping,Siddiqui Adnan H,Meng Hui,Yang Xinjian
Journal of translational medicine
BACKGROUND:The aim of this study was to quantify the effect of the new Low-profile Visualized Intraluminal Support (LVIS®D) device and the difference of fluid diverting effect compared with the Pipeline device and the Enterprise stent using computational fluid dynamics (CFD). METHODS:In this research, we simulated three aneurysms constructed from 3D digital subtraction angiography (DSA). The Enterprise, LVIS and the Pipeline device were virtually conformed to fit into the vessel lumen and placed across the aneurysm orifice. Computational fluid dynamics analysis was performed to compare the hemodynamic differences such as WSS, Velocity and Pressure among these stents. RESULTS:Control referred to the unstented model, the percentage of hemodynamic changes were all compared to Control. A single LVIS stent caused more wall shear stress reduction than double Enterprise stents (39.96 vs. 30.51 %) and velocity (23.13 vs. 18.64 %). Significant reduction in wall shear stress (63.88 %) and velocity (46.05 %) was observed in the double-LVIS stents. A single Pipeline showed less reduction in WSS (51.08 %) and velocity (37.87 %) compared with double-LVIS stent. The double-Pipeline stents resulted in the most reduction in WSS (72.37 %) and velocity (54.26 %). Moreover, the pressure increased with minuscule extent after stenting, compared with the unstented model. CONCLUSIONS:This is the first study analyzing flow modifications associated with LVIS stents. We found that the LVIS stent has certain hemodynamic effects on cerebral aneurysms: a single LVIS stent caused more flow reductions than the double-Enterprise stent but less than a Pipeline device. Nevertheless, the double-LVIS stent resulted in a better flow diverting effect than a Pipeline device.
10.1186/s12967-016-0959-9