Flow diverters for treatment of intracranial aneurysms: Current status and ongoing clinical trials

Clinical Outcomes On Tubridge Flow Diverter in Treatmenting Intracranial Aneurysms: a Retrospective Multicenter Registry Study

PURPOSE

In China, the application of nitinol Tubridge flow diverter (TFD) has become popular for treating intracranial aneurysms (IAs). In this study, we investigated the safety outcomes of the application of TFD for treating IAs in real-world scenarios.

METHODS

We retrospectively analyzed aneurysms treated with TFD in 235 centers throughout China between April 2018 and April 2020. The primary endpoint was the event-free survival rate at 12 months, defined as the occurrence of morbidity (spontaneous rupture, intraparenchymal hemorrhage (IPH), ischemic stroke, and permanent cranial neuropathy) or death. Univariate and multivariate analyses were performed to assess the risk factors. A good outcome was defined as a modified Rankin Score (mRS) of 0-2.

RESULTS

We included 1281 unruptured aneurysms treated with TFD. The overall neurological morbidity and death rates after 12 months were 5.4 and 2.8%, respectively. Ischemic strokes were the most common complication (4.2%, P < 0.001). Cranial neuropathy, IPH, and spontaneous rupture occurred in 0.3%, 0.3%, and 0.5% of aneurysms, respectively. Univariate and multivariate analyses indicated that the male gender, older age, larger aneurysm diameter, and aneurysm located on BA were the independent risk factors for neurologic events. Aneurysm located on BA was the independent risk factor for ischemic strokes. Most patients (1222) had access to the mRS, and 93.2% of them achieved good outcomes.

CONCLUSION

Treatment of IAs with TFD was associated with low morbidity and mortality, most of which were ischemic events. Large posterior aneurysms might be associated with a higher complication rate.

TRIAL REGISTRATION

Retrospectively registered.

Endoluminal flow diversion as a primary treatment strategy for pediatric traumatic intracranial aneurysms: a case-based review of literature

BACKGROUND

Traumatic intracranial aneurysms (TICAs) constitute a notable portion of pediatric intracranial aneurysms. Their unstable structure dictates a high incidence of rupture or mass effect from enlarging unruptured aneurysms, necessitating prompt diagnosis and treatment. TICAs often lack a true neck or are wide-necked, making them unsuitable for coil embolization and surgical clipping, and their fragile nature poses a risk of rupture during surgical and intrasaccular interventions. Endoluminal flow diverters (FD), deployed without requiring direct access to the aneurysmal sac, have emerged as an appealing sole treatment modality for TICAs. However, the clinical experience with this technique remains limited in the pediatric population.

METHOD

We describe the successful treatment of a paraclinoid TICA in a 4-year-old female using an endoluminal FD alone. Additionally, we conducted a literature review to assess the safety and effectiveness of this treatment modality in pediatric TICAs.

RESULTS

Endoluminal flow diversion led to complete aneurysm obliteration in our case, with no observed complication, at the 9-month follow-up. Our review of the previously reported pediatric TICAs managed by standalone flow diversion highlights this technique as safe, efficient, and promising as a sole treatment modality, particularly in the anterior circulation, with a high rate of persistent total obliteration and a low rate of complications. However, the requirement for long-term antiplatelet therapy with the possibility of frequent dose monitoring and adjustments warrants special attention when using endoluminal FDs. Until guidelines specifically addressing optimal antiplatelet therapy in children with intracranial FDs are formulated, adherence to existing protocols is imperative to avoid in-stent thrombosis.

CONCLUSION

Our literature review and personal experience indicate that endoluminal flow diversion can be a viable treatment approach for pediatric TICAs. However, prospective studies with extensive follow-ups are required to assess the durability of endoluminal FDs in treating pediatric TICAs, considering the long life expectancy of this demographic.

The Safety and Efficacy of eCLIPs for Treatment of Wide-Necked Bifurcation Aneurysms: A Systematic Review and Meta-Analysis

BACKGROUND

Wide-necked bifurcation aneurysms (WNBAs) are challenging intracranial aneurysms. Several device and treatment approaches have been proposed for the treatment of WNBAs. The endovascular clip system (eCLIPs) is a newly developed endovascular device with flow diverter and flow disruptor features. This study aims to investigate the safety and efficacy of the eCLIPs for treatment of patients with WNBAs.

METHODS

This is a systematic review and meta-analysis study conducted in accordance with the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. The electronic databases of PubMed, Embase, Scopus, and Web of Science were systematically reviewed from inception to June 19, 2023. The rate of complete and near-complete occlusion, successful device implantation, and serious adverse events were pooled using STATA, version 17.

RESULTS

A total of 5 studies with 110 patients with WNBAs were systematically investigated. Our findings show that the immediate successful implantation rate of eCLIPs was 0.93 (95% confidence interval [CI], 0.88-0.97). Moreover, the immediate postoperative complete occlusion rate was 0.34 (95% CI, 0.10-0.58), and the immediate postoperative near-complete occlusion rate was 0.35 (95% CI, 0.24-0.45). Also, the near-complete occlusion rate at the latest follow-up was 0.3 (95% CI, 0.16-0.44). The serious adverse event rate was 0.14 (95% CI, 0.05-0.22). Stroke was also reported in 2 studies, with 1 study reporting 1 patient who experienced stroke within the first 24 hours and 1 study reporting no patients with stroke.

CONCLUSIONS

Our findings document that the eCLIPs is a safe and effective device for treating patients with WNBAs and associated with favorable outcomes.

Surface modification of neurovascular stents: from bench to patient

Flow-diverting stents (FDs) for the treatment of cerebrovascular aneurysms are revolutionary. However, these devices require systemic dual antiplatelet therapy (DAPT) to reduce thromboembolic complications. Given the risk of ischemic complications as well as morbidity and contraindications associated with DAPT, demonstrating safety and efficacy for FDs either without DAPT or reducing the duration of DAPT is a priority. The former may be achieved by surface modifications that decrease device thrombogenicity, and the latter by using coatings that expedite endothelial growth. Biomimetics, commonly achieved by grafting hydrophilic and non-interacting polymers to surfaces, can mask the device surface with nature-derived coatings from circulating factors that normally activate coagulation and inflammation. One strategy is to mimic the surfaces of innocuous circulatory system components. Phosphorylcholine and glycan coatings are naturally inspired and present on the surface of all eukaryotic cell membranes. Another strategy involves linking synthetic biocompatible polymer brushes to the surface of a device that disrupts normal interaction with circulating proteins and cells. Finally, drug immobilization can also impart antithrombotic effects that counteract normal foreign body reactions in the circulatory system without systemic effects. Heparin coatings have been explored since the 1960s and used on a variety of blood contacting surfaces. This concept is now being explored for neurovascular devices. Coatings that improve endothelialization are not as clinically mature as anti-thrombogenic coatings. Coronary stents have used an anti-CD34 antibody coating to capture circulating endothelial progenitor cells on the surface, potentially accelerating endothelial integration. Similarly, coatings with CD31 analogs are being explored for neurovascular implants.

Safety and effect of pipeline flex embolization device for complex unruptured intracranial aneurysms

To investigate the safety and short-term effect of Pipeline Flex devices in the treatment of complex unruptured intracranial aneurysms, a retrospective study was performed for patients with complex unruptured intracranial aneurysms who were treated with the Pipeline Flex embolization device (PED Flex device) combined with or without coiling. The clinical, endovascular, and follow-up data were analyzed. One hundred and thirty-one patients with 159 complex unruptured cerebral aneurysms were treated with the PED Flex device, with 144 Flex devices deployed. Periprocedural complications occurred in four patients, resulting in the complication rate of 3.1%, including ischemic complications in three patients (2.3%) and hemorrhagic complication in one (0.8%). At discharge, the mRS was 0 in 101 (77.1%) patients, 1 in 25 (19.1%), 2 in four (3.1%), and 4 in one (0.8%), with the good prognosis rate (mRS 0-2) of 99.2%. Clinical follow-up was carried out in 87 (66.4%) patients 3-42 months after the procedure, with the mRS of 0 in 78 (89.7%), 1 in five (5.7%), 2 in three (3.4%), and 4 in one (1.1%). No significant (P = 0.16) difference existed in the mRS at discharge compared with that at clinical follow-up. Angiographic follow-up was performed in 61 (46.7%) patients with 80 (50.3%) aneurysms at 3-40 months, with the OKM grade of D in 57 (71.3%) aneurysms, C in eight (10%), and B in 15 (18.8%). Asymptomatic instent stenosis occurred in four patients (6.6%). In conclusion: The treatment of complex intracranial aneurysms with the Pipeline Flex embolization device may be safe and effective, with a high complete occlusion rate, a decreased complication rate, and a good prognosis rate at medium follow-up.

Volume embolization ratio of coiled cerebral aneurysms, does awake technique affect the results?

Background

Despite the great innovations in the neuroendovascular techniques and related materials, there are still notable percentages of recurrent cerebral aneurysms after aneurysm coiling. Aneurysm packing density is well known to affect the initial angiographic result of aneurysm embolization and has a crucial role in the stability of aneurysm obliteration. Although aneurysm coiling is commonly performed under general anesthesia, it could be performed under local anesthesia in certain circumstances.

Objective

The purpose of this study is to compare the volume embolization ratio (VER) and angiographic results of cerebral aneurysm embolization performed under local and general anesthesia.

Materials and methods

This is a retrospective cohort analysis of 20 consecutive cases of coiled cerebral aneurysms that were coiled under LA. Further, 15 cerebral aneurysm coil embolization cases have been collected from our data as matched control group.

Results

Embolization was performed under local anesthesia (Group A) in 20 patients (57.1%) and under general anesthesia (Group B) in 15 patients (42.9%). At the end of the procedure, control angiogram revealed complete obliteration in 13 patients (37.1%), while incomplete obliteration was detected in 22 patients (62.9%). The mean VER 27.9 ± 11.8 without a significant difference between both groups of the study as the VER of Group (A) was 26.05 ± 8.4 and that of Group B was 30.44 ± 15.2. Follow-up angiography at 1 year revealed complete obliteration in 17 (48.6%) of the coiled aneurysms, while incomplete obliteration was detected in 18 patients (51.4%).

Conclusions

Endovascular coiling of cerebral aneurysms under local anesthesia is a safe and feasible procedure without significant effects on the VER.

Technical nuances and approach-related morbidity of anterolateral and posterolateral lumbar corpectomy approaches-a systematic review of the literature

Purpose

Approaches for lumbar corpectomies can be roughly categorized into anterolateral (AL) and posterolateral (PL) approaches. It remains controversial to date whether one approach is superior to the other, and no comparative studies exist for the two approaches for lumbar corpectomies.

Methods

A systematic review of the literature was performed through a MEDLINE/PubMed search. Studies and case reports describing technique plus outcomes and possible complications were included. Thereafter, estimated blood loss (EBL), length of operation (LOO), utilized implants, neurological outcomes, complication rates, and reoperation rates were analyzed.

Results

A total of 64 articles reporting on 702 patients including 513 AL and 189 PL corpectomies were included in this paper. All patients in the PL group were instrumented via the same approach used for corpectomy, while in the AL group the majority (68.3%) of authors described the use of an additional approach for instrumentation. The EBL was higher in the AL group (1393 ± 1341 ml vs. 982 ± 567 ml). The LOO also was higher in the AL group (317 ± 178 min vs. 258 ± 93 min). The complication rate (20.5% vs. 29.1%, p = 0.048) and the revision rate (3.1% vs. 9.5%, p = 0.004) were higher in the PL group. Neurological improvement rates were 43.8% (AL) vs. 39.2% (PL), and deterioration was only noted in the AL group (6.0%), while 50.2% (AL) and 60.8% (PL) showed no change from initial presentation to the last follow-up.

Conclusion

While neurological outcomes of both approaches are comparable, the results of the present review demonstrated lower complication and revision rates in anterolateral corpectomies. Nevertheless, individual patient characteristics must be considered in decision-making.

CFD to Quantify Idealized Intra-Aneurysmal Blood Flow in Response to Regular and Flow Diverter Stent Treatment

Cerebral aneurysms are pathological dilatations of the vessels supplying the brain. They carry a certain risk of rupture, which in turn, results in a high risk of mortality and morbidity. Flow diverters (FDs) are high-density meshed stents which are implanted in the vessel segment harboring an intracranial aneurysm to cover the entrance of the aneurysm, thus reducing the blood flow into the aneurysm, promoting thrombosis formation and stable occlusion, which prevents rupture or growth of the aneurysm. In the present study, the blood flow in an idealized aneurysm, treated with an FD stent and a regular stent (RS), were modeled and analyzed considering their design, surface area porosity, and flow reduction to investigate the quantitative and qualitative effect of the stent on intra-aneurysmal hemodynamics. CFD simulations were conducted before and after treatment. Significant reductions were observed for most hemodynamic variables with the use of stents, during both the peak systolic and late diastolic cardiac cycles. FD reduces the intra-aneurysmal wall shear stress (WSS), inflow, and aneurysmal flow velocity, and increases the turnover time when compared to the RS; therefore, the possibility of aneurysm thrombotic occlusion is likely to increase, reducing the risk of rupture in cerebral aneurysms.

Cerebral Aneurysm Occlusion at 12-Month Follow-Up After Flow-Diverter Treatment: Statistical Modeling for V&V With Real-World Data

Background: Flow-Diverter (FD) porosity has been pointed as a critical factor in the occlusion of cerebral aneurysms after treatment.

Objective: Verification and Validation of computational models in terms of predictive capacity, relating FD porosity and occlusion after cerebral aneurysms treatment.

Methods: Sixty-four aneurysms, with pre-treatment and follow-up images, were considered. Patient demographics and aneurysm morphological information were collected. The computational simulation provided by ANKYRAS provided FD porosity, expansion, and mesh angle. FD occlusion was assessed and recorded from follow-up images. Multiple regression Logit and analysis of covariance (ANCOVA) models were used to model the data with both categorical and continuous models.

Results: Occlusion of the aneurysm after 12 months was affected by aneurysm morphology but not by FD mesh morphology. A Time-To-Occlusion (TTO) of 6.92 months on average was observed with an SE of 0.24 months in the aneurysm population surveyed. TTO was estimated with statistical significance from the resulting model for the data examined and was capable of explaining 92% of the data variation.

Conclusions: Porosity was found to have the most correction power when assessing TTO, proving its importance in the process of aneurysm occlusion. Still, further Verification and Validation (V&V) of treatment simulation in more extensive, multi-center, and randomized databases is required.

Stent-in-stent technique for the management of blood blister-like basilar apex aneurysms

Blood blister-like basilar apex aneurysms are rare thin-walled vascular lesions with a poorly defined aneurysmal neck. We present two patients with ruptured blister aneurysms of the basilar apex who were treated using the stent-in-stent technique. Long-term follow-up showed persistent and complete occlusion of the aneurysms without radiographically or neurological complications. There is no optimal treatment of choice for the basilar apex blood blister-like aneurysms. Double- or triple-stent placement using the stent-in-stent technique can be a safe and feasible option for these uncommon and challenging intracranial aneurysms.

Preservation of Posterior Tibial Artery Flow Following Dissection With Associated Aneurysmal Degeneration in Ehlers-Danlos Syndrome Type IV Treated With Flow-Diverting Stent

Ehlers-Danlos syndrome type IV (EDS-IV), the vascular type, is a rare genetic disorder affects the large and medium size arteries resulting in dissections, often with aneurysmal degeneration, intramural hematomas and pseudoaneurysms. Embolization or ligation is standard management for aneurysm formation. We present a case of an EDS-IV patient with a posterior tibial artery dissection with associated aneurysm successfully treated with Flow Diversion stent (FDS) preserving vessel patency and excluding the aneurysm. FDS technology allows for low profile, micro-catheter deliverable treatment options to exclude aneurysms in EDS-IV patients that are may be prone to spasm and dissection using more conventional stent graft technology.

Particle Image Velocimetry Measurements of the Flow-Diverting Effects of a New Generation of the eCLIPs Implant for the Treatment of Intracranial Bifurcation Aneurysms

Flow diverters (FDs) for the endovascular treatment of intracranial aneurysms are effective for sidewall aneurysms, but their use at a bifurcation is problematic because FDs only partially cover the aneurysm neck and impede flow into a daughter branch; they are thus not employed routinely in this anatomy. eCLIPs was developed as a non-tubular implant to completely cover the neck of an aneurysm and serve as a coil retention device necessary for the adequate treatment of wide-neck bifurcation aneurysms. eCLIPs has shown some flow diversion effects in bifurcation anatomy but not equal to those exhibited by clinically accepted flow diverters in sidewall anatomy. A new generation of eCLIPs implant, the eCLIPs bifurcation flow diverter (eBFD), with higher metal coverage, was developed to achieve a similar flow diversion as a Pipeline Embolization Device (PED), a prototypical FD. Particle image velocimetry was used to capture the fluid dynamics and velocity reduction within silicone aneurysm replicas. A circulatory mimicking loop was developed to circulate the flow through the silicone models. All generations of eCLIPs implants had some flow-diverting effect, with increasing metal coverage density of the implant proportionately increasing the flow diversion effect. The eBFD, with a metal density of 35%, showed greater flow diversion than PED, with 30% metal density, for bifurcation anatomy. The eBFD showed similar reduction of flow in a bifurcation anatomy to PED in a sidewall, both sufficient to permit early thrombosis of the aneurysm. Thus, the eBFD can potentially provide sufficient flow diversion for the treatment of bifurcation aneurysms to avoid adjunctive coiling.

Super-resolution and denoising of 4D-Flow MRI using physics-Informed deep neural nets

BACKGROUND AND OBJECTIVE

Time resolved three-dimensional phase contrast magnetic resonance imaging (4D-Flow MRI) has been used to non-invasively measure blood velocities in the human vascular system. However, issues such as low spatio-temporal resolution, acquisition noise, velocity aliasing, and phase-offset artifacts have hampered its clinical application. In this research, we developed a purely data-driven method for super-resolution and denoising of 4D-Flow MRI.

METHODS

The flow velocities, pressure, and the MRI image magnitude are modeled as a patient-specific deep neural net (DNN). For training, 4D-Flow MRI images in the complex Cartesian space are used to impose data-fidelity. Physics of fluid flow is imposed through regularization. Creative loss function terms have been introduced to handle noise and super-resolution. The trained patient-specific DNN can be sampled to generate noise-free high-resolution flow images. The proposed method has been implemented using the TensorFlow DNN library and tested on numerical phantoms and validated in-vitro using high-resolution particle image velocitmetry (PIV) and 4D-Flow MRI experiments on transparent models subjected to pulsatile flow conditions.

RESULTS

In case of numerical phantoms, we were able to increase spatial resolution by a factor of 100 and temporal resolution by a factor of 5 compared to the simulated 4D-Flow MRI. There is an order of magnitude reduction of velocity normalized root mean square error (vNRMSE). In case of the in-vitro validation tests with PIV as reference, there is similar improvement in spatio-temporal resolution. Although the vNRMSE is reduced by 50%, the method is unable to negate a systematic bias with respect to the reference PIV that is introduced by the 4D-Flow MRI measurement.

CONCLUSIONS

This work has demonstrated the feasibility of using the readily available machinery of deep learning to enhance 4D-Flow MRI using a purely data-driven method. Unlike current state-of-the-art methods, the proposed method is agnostic to geometry and boundary conditions and therefore eliminates the need for tedious tasks such as accurate image segmentation for geometry, image registration, and estimation of boundary flow conditions. Arbitrary regions of interest can be selected for processing. This work will lead to user-friendly analysis tools that will enable quantitative hemodynamic analysis of vascular diseases in a clinical setting.

Periprocedural to 1-year safety and efficacy outcomes with the Pipeline Embolization Device with Shield technology for intracranial aneurysms: a prospective, post-market, multi-center study

Background

The first and second generations of the Pipeline Embolization Device (PED) have been widely adopted for the treatment of intracranial aneurysms (IAs) due to their high associated occlusion rates and low morbidity and mortality. The objective of this study was to evaluate the safety and effectiveness of the third- generation Pipeline Shield device (PED-Shield) for the treatment of IAs.

Methods

The SHIELD study was a prospective, single-arm, multicenter, post-market, observational study evaluating the PED-Shield device for the treatment of IAs. The primary efficacy endpoint was complete aneurysm occlusion without significant parent artery stenosis or retreatment at 1-year post-procedure and the primary safety endpoint was major stroke in the territory supplied by the treated artery or neurological death.

Results

Of 205 subjects who consented across 21 sites, 204 subjects with 204 target aneurysms were ultimately treated (mean age 54.8±12.81 years, 81.4% [166/204] female). Technical success (ie, deployment of the PED-Shield) was achieved in 98.0% (200/204) of subjects with a mean number of 1.1±0.34 devices per subject and a single device used in 86.8% (177/204) of subjects. The primary effectiveness endpoint was met in 71.7% (143/200) of subjects while the primary safety endpoint occurred in six (2.9%) subjects, two (1.0%) of which led to neurological death.

Conclusions

The findings of the SHIELD study support the safety and effectiveness of the PED-Shield for IA treatment, evidenced by high occlusion rates and low rates of neurological complications in the study population.

Clinical trial registration-URL

http://www.clinicaltrials.gov. Unique identifier: NCT02719522.

Flow diversion for treatment of intracranial aneurysms: Mechanism and implications

Flow diverters are new generation stents that have recently garnered a large amount of interest for use in treatment of intracranial aneurysms. Flow diverters reduce blood flow into the aneurysm, with redirection along the path of the parent vessel. Flow stagnation into the aneurysm and neck coverage with subsequent endothelialization are the important synergistic mechanisms by which the therapy acts. Several studies have examined the mechanisms by which flow diverters subsequently lead to aneurysm occlusion. This review aims to provide a general overview of the flow diverters and their mechanism of action and potential implications. ANN NEUROL 2019;85:793-800.

A Virtual Comparison of the eCLIPs Device and Conventional Flow-Diverters as Treatment for Cerebral Bifurcation Aneurysms

PURPOSE

Effective, consistent, and complication-free treatment of cerebral bifurcation aneurysms remains elusive despite a pressing need, with the majority of lesions presenting in such locations. Current treatment options focus either on aneurysm coil retention, supported by a stent-like device positioned in the parent vessel lumen, or intrasaccular devices that disrupt flow within the aneurysm dome. A third alternative, i.e., the use of conventional (intraluminal) flow-diverters to treat such bifurcation aneurysms raises the problem that at least one daughter vessel needs to be jailed in such a deployment. The eCLIPs is a stent-like device that offers the possibility of flow-diversion at the aneurysm neck, without the drawbacks of daughter vessel occlusion or those of intrasaccular deployment.

METHODS

In this study the eCLIPs device was virtually deployed in five cerebral bifurcation aneurysms and compared with a conventional tubular flow-diverter device. Computational fluid dynamics (CFD) simulations of the aneurysm haemodynamic environment pre- and post-implantation were conducted, and focussed on metrics associated with successful aneurysm occlusion. Absolute and relative reductions in aneurysm inflow rate (Q) and time-averaged wall shear stress (TAWSS) were recorded.

RESULTS

The eCLIPs device was found to perform in a similar qualitative fashion to tubular flow-diverters, with overall reduction of metrics being somewhat more modest however, when compared to such devices. Aneurysm inflow reduction and TAWSS reduction were typically 10-20% lower for the eCLIPs, when compared to a generic flow diverter (FD_BRAIDED) similar to devices currently in clinical use. The eCLIPs was less effective at diffusing inflow jets and at reducing the overall velocity of the flow, when compared to these devices. This result is likely due to the larger device pore size in the eCLIPs. Notably, it was found that the eCLIPs provided approximately equal resistance to flow entering and exiting the aneurysm, which was not true for the FD_BRAIDED device, where high-speed concentrations of outflow were seen at the aneurysm neck along with local TAWSS elevation. The clinical implications of such behaviour are not examined in detail here but could be significant.

CONCLUSIONS

Our findings indicate that the eCLIPs device acts as a flow-diverter for bifurcation aneurysms, with somewhat diminished occlusion properties comparing to tubular flow diverters but without the jailing and diminished flow evident in a daughter vessel associated with use of conventional devices.

Effect of different stent configurations using Lattice Boltzmann method and particles image velocimetry on artery bifurcation aneurysm problem

Proper design of stent for application at specific aneurysm effect arteries could help to reduce the issues with thrombosis and aneurysm. In this paper, four types of stent configuration namely half-Y (6 mm), half-Y (4 mm), cross-bar, and full-Y configuration will implanted on real 3D artery bifurcation aneurysm effected arteries. Comparisons were then conducted based on the flow patterns after stent placement using both LBM-based solver and PIV experimental findings. According to the data obtained from all 4 stent designs, the flow profiles and the computed velocity from both methods were in agreement with each other. Both methods found that half-Y (6 mm) stent configuration is by far the best configuration in reducing the blood velocity at the vicinity of the aneurysm sac. The analysis also show that the half-Y (6 mm) stent configuration recorded the highest percentage of velocity reduction and managed to substantially reduce the pressure at the bifurcation region. This high flow velocity reduction through the use of half-Y stent could consequently promote the formation of thrombus thereby reducing the risk of rupture in the aneurysm sac.

Sensitivity study on modelling a flow-diverting stent as a porous medium using computational fluid dynamics

The flow-diverting (FD) stent has become a commonly used endovascular device to treat cerebral aneurysms. This discourages blood from entering the aneurysm, thereby reducing the likelihood of aneurysm rupture. Using computational fluid dynamics (CFD) to simulate the aneurysmal haemodynamics after FD treatment could help clinicians predict the stent effectiveness prior to the real procedure in the patient. As an alternative to modelling the stent as a fine wire mesh, modelling the FD stent as a porous medium was established to save computational time, and has also been proved capable of predicting the same haemodynamics as obtained using the real FD stent geometry. The flow resistance effect of a porous-medium stent may differ with respect to its morphology or permeability; however, the flow resistance effect after adjusting these parameters had not been clarified. In this study, we analysed the haemodynamic changes caused by alterations of porous-medium thickness and permeability, thereby providing future porous-medium stent simulations with important information on the respective parametric sensitivities. We found significant sensitivity to permeability. Results were insensitive to thickness when permeability was adjusted beforehand to compensate. We also compared our results with observations from an in-vitro model, and found good agreement. This supports adoption of porous-medium models in future work.

Large Basilar Apex Aneurysms Treated with Flow-Diverter Stents

BACKGROUND AND PURPOSE

The treatment of wide-neck, large basilar apex aneurysms is challenging with either an endovascular or a surgical approach. The aim of the present study was to report our experience treating basilar apex aneurysms with flow-diverter stents and to evaluate their efficacy and safety profile in this specific anatomic condition.

MATERIALS AND METHODS

We retrospectively analyzed data from all consecutive patients treated with flow-diverter stents at our institution between January 2011 and January 2015. Patients with large basilar apex aneurysms treated with a flow-diverter stent were included in the study. Clinical presentations, technical details, intra- and perioperative complications, and clinical and angiographic outcomes were recorded, with a midterm follow-up.

RESULTS

Of the 175 aneurysms treated with flow-diverter stents at our institution, 5 patients (2 women and 3 men; age range, 44-58 years) received flow-diverter stent for basilar apex aneurysms. The mean follow-up after stent deployment was 21 months (range, 15-24 months). One patient died on day 31 from an early postprocedural midbrain hemorrhage. One patient had a right cerebellar hemispheric ischemic lesion with a transient cerebellar syndrome resolved within 24 hours without neurologic sequelae at the latest follow-up. The mRS was 0 in 4 patients and 6 in 1 patient at last follow-up.

CONCLUSIONS

Flow diversion is a feasible technique with an efficacy demonstrated at a midterm follow-up, especially in the case of basilar apex aneurysm recurrences after previous endovascular treatments. Concern about its safety profile still exists.

Endovascular Treatment of Complex Distal Posterior Cerebral Artery Aneurysms with the Pipeline Embolization Device

OBJECTIVE

To assess the safety and efficacy of the Pipeline Embolization Device (PED) for endovascular treatment of complex, distal posterior cerebral artery (PCA) aneurysms.

METHODS

We conducted a retrospective review of patients who underwent endovascular treatment of complex PCA aneurysms with PED from November 2012 to December 2015. A total of 4 patients were identified and treated. Twelve-month angiographic and clinical follow-up was available for all patients.

RESULTS

Mean aneurysm size (largest diameter) was 10.0 mm, and all aneurysms originated at the P2 segment or beyond. Technical success was achieved in all patients. All patients were treated with a single PED; adjunctive intrasaccular coil was also placed in one patient. All patients achieved a favorable postprocedural outcome (modified Rankin Scale score = 0) with no new neurologic deficits. No patients experienced neurologic complications or perforator infarction, and presenting symptoms resolved in all patients. Follow-up cerebral angiography at 12 months in 3 patients showed complete occlusion (Raymond-Roy Occlusion Classification class 1) and minimal residual aneurysm filling (Raymond-Roy Occlusion Classification class 2) in 1 patient. A small degree of focal stenosis was present in 2 patients within the PED at 12-month follow-up that was associated with mild decrease in flow within the distal PCA branches.

CONCLUSIONS

PED use provides a practical and viable treatment option for complex, distal PCA aneurysms. Based on our limited institutional experience, PED use for treatment of complex, distal PCA aneurysms in select patients appears safe and effective.

Patency of the posterior communicating artery following treatment with the Pipeline Embolization Device

OBJECTIVE

The Pipeline Embolization Device (PED) has become an effective treatment strategy for some cerebral aneurysms. Concerns regarding the patency of branch arteries have been raised. The objective of this study was to assess the patency of the posterior communicating artery (PCoA) following treatment of PCoA aneurysms using the PED.

METHODS

All patients with PCoA aneurysms treated with the PED who had angiographic follow-up were retrospectively identified. The patency of the PCoA at follow-up was evaluated by 2 authors who were not involved in the intervention. Univariate and multivariate analyses were performed to identify factors associated with the following: 1) PCoA patency versus no or diminished flow, and 2) PCoA patency and diminished flow versus PCoA occlusion.

RESULTS

Thirty patients with an angiographic follow-up of 6 months were included. Aneurysm obliteration was achieved in 25 patients (83.3%). The PCoA was patent in 7 patients (23.3%), had diminished flow in 7 patients (23.3%), and was occluded in 16 patients (53.3%). In the univariate analysis of outcome, there was a trend for aneurysms with incomplete occlusion, aneurysms not previously treated, those with presence of a fetal PCoA, and those with an artery coming from the aneurysm to have higher odds of the PCoA remaining patent. In univariate and multivariate analyses of factors associated with outcome, fetal PCoA and presence of an artery coming from the aneurysm were associated with the PCoA remaining open with or without diminished flow. No patients had symptoms related to PCoA occlusion.

CONCLUSIONS

Occlusion and diminished flow through the PCoA is common following PED treatment of PCoA aneurysms. However, it is clinically insignificant in most cases.

The pressure reduction coefficient: A new parameter to assess aneurysmal blood stasis induced by flow diverters/disruptors

Background and purpose Pore density (PD), surface metal coverage (SMC) and the number of wires are all different parameters which can influence the efficacy of a flow disruptor/diverter. Nevertheless, the relative importance of a parameter to induce intra-aneurysmal blood stasis is still poorly evaluated. Therefore, comparison between devices based on a unique value is not reliable. The aim of this study was to propose a new bench top parameter (the pressure reduction coefficient (PRC; ξ)) in order to assess the global haemodynamic effect of each flow diverter/disruptor to slow flow. Methods Eight devices were tested in vitro during three different flow conditions. For the eight devices, the PRC was computed at different volumetric flow rates to characterise flow reduction. Comparison was made with SMC, PD and the number of wires. Results The PRC obtained for flow disruptors was on average 1.5 times more efficient in reducing flow compared to flow diverters. PD (mm²) ranged from 24 to 38 for flow diverters and did not independently correlate with the PRC. The SMC of flow diverters ranged from 25% to 70%, and ranged from 20% to 100% for flow disruptors, without independent correlation to the PRC. The number of wires ranged from 48 to 96 for the flow diverters and did not correlate independently to the PRC. Conclusion There were no direct correlations between individual device characteristics and the PRC, suggesting a multifaceted and interrelating association of the overall design of each implant. Hence, the PRC could be used as a simple, reliable parameter to assess the overall capacity of flow disruptors/diverters to induce intra-aneurysmal blood stasis.

When flow diverters fail: short review and a case illustration of a device failure

The ultimate aims of treatment of the intracranial aneurysms are reconstruction the vessel wall and correcting the hemodynamic disturbance. A flow diverter (FD) is a stent placed inside lumen of the parent artery with aim to blood flow reduction into the aneurysms sac to the extent of almost stagnation leading to gradual onset of progressive thrombosis and neointimal lining of arterial wall remodeling to maintain blood outflow into perforators the side and branches. Flow diverter is considered as an effective treatment for fusiform, wide-necked, large and giant intracranial unruptured aneurysms. However, FD implantation may also be associated with growth and rupture of residual aneurysms. The most frequent complication of endovascular aneurysms management is thromboembolic events and less common are intra and postoperative hemorrhagic aneurysmal rupture. Authors report a case where a lack of operation of the device as illustration is presented to demonstrate the shortcomings of this new type of devices.

Virtual flow-diverter treatment planning: The effect of device placement on bifurcation aneurysm haemodynamics

Bifurcation aneurysms account for a large fraction of cerebral aneurysms and often present morphologies that render traditional endovascular treatments, such as coiling, challenging and problematic. Flow-diverter stents offer a potentially elegant treatment option for such aneurysms, but clinical use of these devices remains controversial. Specifically, the deployment of a flow-diverter device in a bifurcation entails jailing one or more potentially vital vessels with a low-porosity mesh designed to restrict the flow. When multiple device placement configurations exist, the most appropriate clinical decision becomes increasingly opaque. In this study, three bifurcation aneurysm geometries were virtually treated by flow-diverter device. Each aneurysm was selected to offer two possible device deployment positions. Flow-diverters similar to commercially available designs were deployed with a fast-deployment algorithm before transient and steady state computational fluid dynamics simulations were performed. Reductions in aneurysm inflow, mean wall shear stress and maximum wall shear stress, all factors often linked with aneurysm treatment outcome, were compared for different device configurations in each aneurysm. In each of the three aneurysms modelled, a particular preferential device placement was shown to offer superior performance with the greatest reduction in the flow metrics considered. In all the three aneurysm geometries, substantial variations in inflow reduction (up to 25.3%), mean wall shear stress reduction (up to 14.6%) and maximum wall shear stress reduction (up to 12.1%) were seen, which were all attributed to device placement alone. Optimal device placement was found to be non-trivial and highly aneurysm specific; in only one-third of the simulated geometries, the best overall performance was achieved by deploying a device in the daughter vessel with the highest flow rate. Good correspondence was seen between transient results and steady state computations that offered a significant reduction in simulation run time. If accurate steady state computations are combined with the fast-deployment algorithm used, the modest run time and corresponding hardware make a virtual treatment pipeline in the clinical setting a meaningful possibility.

In Vitro Investigation of a New Thin Film Nitinol-Based Neurovascular Flow Diverter

Fusiform and wide-neck cerebral aneurysms (CAs) can be challenging to treat with conventional endovascular or surgical approaches. Recently, flow diverters have been developed to treat these cases by diverting flow away from the aneurysm rather than occluding it. The pipeline embolization device (PED), which embodies a single-layer braided design, is best known among available flow diverters. While the device has demonstrated success in recent trials, late aneurysmal rupture after PED treatment has been a concern. More recently, a new generation of dual-layer devices has emerged that includes a novel hyperelastic thin film nitinol (HE-TFN)-covered design. In this study, we compare fluid dynamic performance between the PED and HE-TFN devices using particle image velocimetry (PIV). The PED has a pore density of 12.5–20 pores/mm2 and a porosity of 65–70%. The two HE-TFN flow diverters have pore densities of 14.75 pores/mm2 and 40 pores/mm2, and porosities of 82% and 77%, respectively. Conventional wisdom suggests that the lower porosity PED would decrease intra-aneurysmal flow to the greatest degree. However, under physiologically realistic pulsatile flow conditions, average drops in root-mean-square (RMS) velocity (VRMS) within the aneurysm of an idealized physical flow model were 42.8–73.7% for the PED and 68.9–82.7% for the HE-TFN device with the highest pore density. Interestingly, examination of collateral vessel flows in the same model also showed that the HE-TFN design allowed for greater collateral perfusion than the PED. Similar trends were observed under steady flow conditions in the idealized model. In a more clinically realistic scenario wherein an anatomical aneurysm model was investigated, the PED affected intra-aneurysmal VRMS reductions of 64.3% and 56.3% under steady and pulsatile flow conditions, respectively. In comparison, the high pore density HE-TFN device reduced intra-aneurysmal VRMS by 88% and 71.3% under steady and pulsatile flow conditions, respectively. We attribute the superior performance of the HE-TFN device to higher pore density, which may play a more important role in modifying aneurysmal fluid dynamics than the conventional flow diverter design parameter of greatest general interest, absolute porosity. Finally, the PED led to more elevated intra-aneurysmal pressures after deployment, which provides insight into a potential mechanism for late rupture following treatment with the device.

Flow Diversion for Intracranial Aneurysm Management: A New Standard of Care

Endovascular treatment of intracranial aneurysms with complex morphologies such as giant, wide-necked, or fusiform aneurysms is challenging. Stent-assisted coiling and balloon-assisted coiling are alternative techniques to treat such complex aneurysms, but studies have shown less-than-expected efficacy, as suggested by their high rate of recanalization. The management of complex aneurysms via microsurgery or conventional neuroendovascular strategies has traditionally been poor. However, over the last few years, flow-diverting stents (FDS) have revolutionized the treatment of such aneurysms. FDS are implanted within the parent artery rather than the aneurysm sac. By modifying intra-aneurysmal and parent-vessel flow dynamics at the aneurysm/parent vessel interface, FDS trigger a cascade of gradual intra-aneurysmal thrombosis. As endothelialization of the FDS is complete, the parent vessel reconstructs while preserving the patency of normal perforators and side branch vessels. As with any intervention, the practice and application of flow-diversion technology is inherent, with risks that include vessel rupture or perforation, in-stent thrombosis, perforator occlusion, procedural and delayed hemorrhages, and perianeurysmal edema. Herein, we review the devices, their mechanisms of actions, clinical applications, complications, and ongoing studies.

Tirofiban as treatment for acute retinal artery occlusion following internal carotid artery flow diverter implantation

PURPOSE

To report a favorable outcome of branch retinal artery occlusion (BRAO) treated by means of early administration of tirofiban, a glycoprotein IIb-IIIa platelet receptor inhibitor.

METHODS

Case report.

RESULTS

A 65-year-old woman developed dramatic visual impairment in her left eye secondary to BRAO after left internal carotid artery endovascular reconstruction with flow diverter stent implant; visual acuity was hand motion. A dose of intravenous tirofiban was injected 10 minutes after symptoms onset. Fourteen hours after drug infusion, retinal fluorescein angiography revealed a well-perfused macula with a partial reperfusion of the inferior temporal branch of the central retinal artery; visual acuity was 20/20 in both eyes.

CONCLUSIONS

This case supports the effectiveness of tirofiban in secondary BRAO in neurosurgery and may open its usage to further research.

Microstructured Thin Film Nitinol for a Neurovascular Flow-Diverter

A cerebral aneurysm occurs as a result of a weakened blood vessel, which allows blood to flow into a sac or a ballooned section. Recent advancement shows that a new device, ‘flow-diverter’, can divert blood flow away from the aneurysm sac. People found that a flow-diverter based on thin film nitinol (TFN), works very effectively, however there are no studies proving the mechanical safety in irregular, curved blood vessels. Here, we study the mechanical behaviors and structural safety of a novel microstructured TFN membrane through the computational and experimental studies, which establish the fundamental aspects of stretching and bending mechanics of the structure. The result shows a hyper-elastic behavior of the TFN with a negligible strain change up to 180° in bending and over 500% in radial stretching, which is ideal in the use in neurovascular curved arteries. The simulation determines the optimal joint locations between the TFN and stent frame. In vitro experimental test qualitatively demonstrates the mechanical flexibility of the flow-diverter with multi-modal bending. In vivo micro X-ray and histopathology study demonstrate that the TFN can be conformally deployed in the curved blood vessel of a swine model without any significant complications or abnormalities.

Morphologic and Clinical Outcome of Intracranial Aneurysms after Treatment Using Flow Diverter Devices: Mid-Term Follow-Up

Flow diverters (FDs) are designed for the endovascular treatment of complex intracranial aneurysm configurations. From February 2009 to March 2013 28 patients (22 females, 6 males) were treated with FD; mean age was 57 years. Data, including aneurysm features, clinical presentation, history of previous bleeding, treatment, and follow-up results, are presented. Early postinterventional neurological deficits (transient: n = 3/enduring: n = 1) appeared in 4/28 patients (14%), and early improvement of neurological symptoms was observed in 7 patients with previous restriction of cranial nerve function. The overall occlusion rate was 20/26 (77%; 59% after 3 months). 77% achieved best results according to O'Kelly-Marotta score grade D with no contrast material filling (70% of those after 3 months). In 4/6 patients who did not achieve grade D, proximal and/or distal stent overlapping ≥5 mm was not guaranteed sufficiently. During follow-up we did not detect any aneurysm recurrence or haemorrhage. In-stent stenosis emerged as the most frequent complication (4/27; 15%) followed by 2 cases of vascular obliteration (AICA/VA). In conclusion endovascular reconstruction using a FD represents a modern and effective treatment in those aneurysms that are not suitable for conventional interventional or surgical treatment. The appearance of severe complications was rare.

Treatment of Intracranial Aneurysms With Pipeline Embolization Device: Newer Applications and Technical Advances

OPINION STATEMENT

Pipeline embolization device (PED) is a flow diverter used in the endovascular treatment of intracranial aneurysms, particularly those with unfavorable configurations. It works by causing progressive flow redirection leading to thrombosis within the aneurysm. PED was initially approved for adults with large or giant wide-necked (≥4 mm or no discernible neck) aneurysms of the internal carotid artery (ICA) from the petrous to the superior hypophyseal segments. Studies have shown a superior aneurysm occlusion rate of 85 % at 6 months for the PED and mortality ranging from 2.6 to 4 %. There appears to be a knowledge gap in terms of the duration of dual antiplatelet therapy and efficacy of assessing platelet inhibition. However, increasing operator experience and favorable longer-term outcome data have led to the exploration of PED for a wide array of off-label uses. Given the paucity of good-quality studies comparing PED with other endovascular/surgical treatment options, several multicenter randomized trials are currently underway to answer these important questions.

Feasibility, Safety, and Efficacy of Flow-Diverting Stent-Assisted Microsphere Embolization of Fusiform and Sidewall Aneurysms

BACKGROUND

Treatment of wide-necked internal carotid artery aneurysms is frequently associated with incomplete occlusion and high recurrence rates. Furthermore, platinum coils cause strong beam-hardening artifacts, hampering subsequent image analyses.

OBJECTIVE

To assess the feasibility, safety, and efficacy of flow-diverting, stent-assisted microsphere embolization of fusiform and sidewall aneurysms in vitro and in vivo.

METHODS

Using a recirculating pulsatile in vitro flow model, 5 different aneurysm geometries (inner/outer curve, narrow/wide neck, and fusiform) were treated (each n = 1) by flow-diverting stent (FDS) implantation and subsequent embolization through a jailed microcatheter using calibrated microspheres (500-900 μm) larger than the pores of the FDS mesh. Treatment effects were analyzed angiographically and by micro computed tomography. The fluid of the in vitro model was filtered to ensure that no microspheres evaded the aneurysm. The experiment was repeated once in vivo.

RESULTS

In vitro, all 5 aneurysms were safely and completely occluded by FDS-assisted microsphere embolization. Virtually complete aneurysm occlusion was confirmed by angiography and micro computed tomography. No microspheres escaped into the circulation. The experiment was successfully repeated in 1 pig with a sidewall aneurysm generated by vessel occlusion. An embolic protection system placed distally of the FDS in vitro and in vivo (each n = 1) contained no microspheres after the embolization. Thus, no microspheres were lost in the circulation, and the use of an embolic protection system seems feasible to provide additional safety.

CONCLUSION

FDS-assisted microsphere embolization of fusiform and sidewall aneurysms is feasible and yields virtually complete aneurysm occlusion while avoiding coil-associated beam-hardening artifacts.

The expanding realm of endovascular neurosurgery: flow diversion for cerebral aneurysm management

The worldwide prevalence of intracranial aneurysms is estimated to be between 5% and 10%, with some demographic variance. Subarachnoid hemorrhage secondary to ruptured intracranial aneurysm results in devastating neurological outcomes, leaving the majority of victims dead or disabled. Surgical clipping of intracranial aneurysms remained the definitive mode of treatment until Guglielmi detachable coils were introduced in the 1990s. This revolutionary innovation led to the recognition of neurointervention/neuroendovascular surgery as a bona fide option for intracranial aneurysms. Constant evolution of endovascular devices and techniques supported by several prospective randomized trials has catapulted the endovascular treatment of intracranial aneurysms to its current status as the preferred treatment modality for most ruptured and unruptured intracranial aneurysms. We are slowly transitioning from the era of coils to the era of flow diverters. Flow-diversion technology and techniques have revolutionized the treatment of wide-necked, giant, and fusiform aneurysms, where the results of microsurgery or conventional neuroendovascular strategies have traditionally been dismal. Although the Pipeline Embolization Device (ev3-Covidien, Irvine, CA) is the only flow-diversion device approved by the Food and Drug Administration for use in the United States, others are commercially available in Europe and South America, including the Silk (Balt Extrusion, Montmorency, France), Flow-Redirection Endoluminal Device (FRED; MicroVention, Tustin, CA), Surpass (Stryker, Kalamazoo, MI), and p64 (Phenox, Bochum, Germany). Improvements in technology and operator experience and the encouraging results of clinical trials have led to broader acceptance for the use of these devices in cerebral aneurysm management. Continued innovation and refinement of endovascular devices and techniques will inevitably improve technical success rates, reduce procedure-related complications, and broaden the endovascular therapeutic spectrum for varied aneurysm morphology.

Towards Predicting Patient-Specific Flow-Diverter Treatment Outcomes for Bifurcation Aneurysms: From Implantation Rehearsal to Virtual Angiograms

Despite accounting for the majority of all cerebral aneurysm cases, bifurcation aneurysms present many challenges to standard endovascular treatment techniques. This study examines the treatment of bifurcation aneurysms endovascularly with flow-diverting stents and presents an integrative computational modeling suite allowing for rehearsing all aspects of the treatment. Six bifurcation aneurysms are virtually treated with 70% porosity flow-diverters. Substantial reduction (>50%) in aneurysm inflow due to device deployment is predicted in addition to reductions in peak and average aneurysm wall shear stress to values considered physiologically normal. The subsequent impact of flow-diverter deployment on daughter vessels that are jailed by the device is investigated further, with a number of simulations conducted with increased outlet pressure conditions at jailed vessels. Increased outlet pressures at jailed daughter vessels are found to have little effect on device-induced aneurysm inflow reduction, but large variation (13–86%) is seen in the resulting reduction in daughter vessel flow rate. Finally, we propose a potentially powerful approach for validation of such models, by introducing an angiographic contrast model, with contrast transport modeled both before and after virtual treatment. Virtual angiograms and contrast residence curves are created, which offer unique clinical relevance and the potential for future in vivo verification of simulated results.

Incidence and clinical implications of carotid branch occlusion following treatment of internal carotid artery aneurysms with the pipeline embolization device

BACKGROUND

The use of flow diverters such as the pipeline embolization device (PED) for treatment of intracranial aneurysms carries the risk of side branch occlusion.

OBJECTIVE

To determine the incidence and clinical outcomes associated with supraclinoid internal carotid artery (ICA) branch occlusion after deployment of PEDs for ICA aneurysms.

METHODS

We reviewed patients who underwent endovascular treatment with PEDs for ICA aneurysms between June 2011 and March 2013. Forty-nine patients (43 women, mean age 56.3±1.8 years, 68 aneurysms) in whom PEDs traversed the origin of supraclinoid ICA branches (ophthalmic [OA], posterior communicating [PcommA], and anterior choroidal artery [AChA]) were selected for this study. Follow-up angiograms (mean follow-up, 12.8±0.8 months) were studied to determine the location of PEDs and the patency of ICA branches.

RESULTS

PEDs were placed across the ostia of 49 OAs, 14 PcommAs, and 11 AChAs. Multiple PEDs were deployed in 16 patients. Rate of branch occlusion was 4% (2/49) for the OA, 7.1% (1/14) for the PcommA, and 0% for the AChA. Patients with branch occlusion did not endure new neurological deficits. ICA branch occlusion was not associated with the number of PEDs covering the ostia (P=.76) or the origin of ICA branches from the aneurysm (P=.24).

CONCLUSION

The incidence of major supraclinoid ICA branch occlusion after treatment with PEDs was low. These events were not associated with new neurological deficits nor were they related to the number of PEDs deployed or the origin of ICA branches from the aneurysm.

Computation of the change in length of a braided device when deployed in realistic vessel models

PURPOSE

An important issue in the deployment of braided stents, such as flow diverters, is the change in length, also known as foreshortening, underwent by the device when is released from the catheter into a blood vessel. The position of the distal end is controlled by the interventionist, but knowing a priori the position of the proximal end of the device is not trivial. In this work, we assess and validate a novel computer method to predict the length that a braided stent will adopt inside a silicon model of an anatomically accurate vessel.

METHODS

Three-dimensional rotational angiography images of aneurysmatic patients were used to generate surface models of the vessels (3D meshes) and then create accurate silicon models from them. A braided stent was deployed into each silicon model to measure its length. The same stents deployed on the silicon models were virtually deployed on the 3D meshes using the method being evaluated.

RESULTS

The method was applied to five stent placements on three different silicon models. The length adopted by the real braided device in the silicon models varies between 15 and 30% from the stent length specified by the manufacturer. The final length predicted by the method was within the estimated error of the measured real stent length.

CONCLUSIONS

The method provides, in a few seconds, the length of a braided stent deployed inside a vessel, showing an accurate estimation of the final length for the cases studied. This technique could provide useful information for planning the intervention and improve endovascular treatment of intracranial aneurysms in the future.

Long-term occlusion results with SILK flow diversion in 28 aneurysms: Do recanalizations occur during follow-up?

BACKGROUND AND PURPOSE

The purpose of this article is to report on the long-term success rates of Silk flow-diverter (FD) treatment in a multicenter prospective study for the treatment of complex aneurysms.

METHODS

Between May 2008 and January 2011, all consecutive patients featuring complex intracranial aneurysms eligible for FD treatment with the Silk in three neurovascular centers were included. Clinical and imaging data were assessed during hospitalization and follow-up.

RESULTS

Five patients were initially asymptomatic, 20 patients showed various neurological symptoms. Twenty-eight FDs were implanted in 25 patients treating 28 aneurysms. The immediate procedure-related morbidity was 8% (two of 25), mortality 0%. One procedure-related death was observed during follow-up (in-stent thrombosis). Compared to the immediate result nearly two of three aneurysms improved during follow-up; all angiographically confirmed inflow changes took place within six months after treatment. Final anatomic outcome in 24 aneurysms of 22 patients comprised 14 (59%) with complete occlusion, seven (29%) with a neck remnant, two (8%) with residual filling <50%, none with residual filling >50% and one (4%) unchanged in comparison to its pretreatment status. Postinterventional recanalizations were seen in three of 13 (23%) aneurysms treated with FD alone; none were observed in 15 aneurysms treated with adjunctive coiling.

CONCLUSION

Anatomic presentation and location are key for successful FD treatment. The rate of successful occlusion increases during follow-up. Postinterventional monitoring for at least six months is paramount, as anatomic outcome is not reliably predictable and recanalizations may occur in initially completely occluded aneurysms.

Management of complicated aortic aneurysms using multiple overlapping uncovered stents: mid-term outcome from a cohort study

This study sought to report the mid-term outcome of a modified flow-diverting strategy in the treatment of complicated aortic aneurysms of different morphology. Historical data suggested aortic aneurysm expansion and rupture after endovascular treatment with current commercial flow-diverters, indicating the essentiality of further investigation of this technique prior to its large-scale clinical application. An alternative flow-diverting strategy using layer-by-layer assembled multiple overlapping uncovered stents was employed in this study. The treatment outcome in aneurysms of different morphology (saccular, fusiform, and dissecting) was assessed during a mid-term follow-up period.Of 42 patients enrolled in this study (30 male, mean age: 63.3 years), technical success was achieved in 40 cases. During an average follow-up period of 20.9 months, mean aneurysm diameter shrunk from 53.4 ± 13.6 mm to 48.8 ± 13.9 mm (P < 0.001), while stent-induced sac thrombosis ratio increased significantly (18.1 ± 14.9% to 93.6 ± 9.5%, P < 0.001). The majority of side branches (74/76 major visceral branches, 237/244 minor segmental arteries), covered by 3.3 stents on average, maintained their patency after stenting. Saccular aneurysms manifested the highest thrombus deposition speed (18/20 were totally thrombosed within 12 months) and most significant shrinkage (51.4 ± 13.3 mm pre-operatively vs 43.5 ± 10.2 mm during follow-up, P < 0.001) compared with fusiform and dissecting aneurysms. This modified flow-diverting strategy could be a feasible alternative in the management of complicated aortic aneurysms where vital branches need to be preserved. The treatment outcome may depend on the aneurysm type. Further studies with larger patient cohort and longer follow-up are required to substantiate these results.

Relationship between aneurysm occlusion and flow diverting device oversizing in a rabbit model

BACKGROUND AND PURPOSE

Implanted, actual flow diverter pore density is thought to be strongly influenced by proper matching between the device size and parent artery diameter. The objective of this study was to characterize the correlation between device sizing, metal coverage, and the resultant occlusion of aneurysms following flow diverter treatment in a rabbit model.

METHODS

Rabbit saccular aneurysms were treated with flow diverters (iso-sized to proximal parent artery, 0.5 mm oversized, or 1.0 mm oversized, respectively, n=6 for each group). Eight weeks after implantation, the angiographic degree of aneurysm occlusion was graded (complete, near-complete, or incomplete). The ostium of the explanted aneurysm covered with the flow diverter struts was photographed. Based on gross anatomic findings, the metal coverage and pore density at the ostium of the aneurysm were calculated and correlated with the degree of aneurysm occlusion.

RESULTS

Angiographic results showed there were no statistically significant differences in aneurysm geometry and occlusion among groups. The mean parent artery diameter to flow diverter diameter ratio was higher in the 1.0 mm oversized group than in the other groups. Neither the percentage metal coverage nor the pore density showed statistically significant differences among groups. Aneurysm occlusion was inversely correlated with the ostium diameter, irrespective of the size of the device implanted.

CONCLUSIONS

Device sizing alone does not predict resultant pore density or metal coverage following flow diverter implantation in the rabbit aneurysm model. Aneurysm occlusion was not impacted by either metal coverage or pore density, but was inversely correlated with the diameter of the ostium.

International retrospective study of the pipeline embolization device: a multicenter aneurysm treatment study

BACKGROUND AND PURPOSE

Flow diverters are increasingly used in the endovascular treatment of intracranial aneurysms. Our aim was to determine neurologic complication rates following Pipeline Embolization Device placement for intracranial aneurysm treatment in a real-world setting.

MATERIALS AND METHODS

We retrospectively evaluated all patients with intracranial aneurysms treated with the Pipeline Embolization Device between July 2008 and February 2013 in 17 centers worldwide. We defined 4 subgroups: internal carotid artery aneurysms of ≥10 mm, ICA aneurysms of <10 mm, other anterior circulation aneurysms, and posterior circulation aneurysms. Neurologic complications included spontaneous rupture, intracranial hemorrhage, ischemic stroke, permanent cranial neuropathy, and mortality. Comparisons were made with t tests or ANOVAs for continuous variables and the Pearson χ(2) or Fisher exact test for categoric variables.

RESULTS

In total, 793 patients with 906 aneurysms were included. The neurologic morbidity and mortality rate was 8.4% (67/793), highest in the posterior circulation group (16.4%, 9/55) and lowest in the ICA <10-mm group (4.8%, 14/294) (P = .01). The spontaneous rupture rate was 0.6% (5/793). The intracranial hemorrhage rate was 2.4% (19/793). Ischemic stroke rates were 4.7% (37/793), highest in patients with posterior circulation aneurysms (7.3%, 4/55) and lowest in the ICA <10-mm group (2.7%, 8/294) (P = .16). Neurologic mortality was 3.8% (30/793), highest in the posterior circulation group (10.9%, 6/55) and lowest in the anterior circulation ICA <10-mm group (1.4%, 4/294) (P < .01).

CONCLUSIONS

Aneurysm treatment with the Pipeline Embolization Device is associated with the lowest complication rates when used to treat small ICA aneurysms. Procedure-related morbidity and mortality are higher in the treatment of posterior circulation and giant aneurysms.