Angiographic Safety and Efficacy of the ReSolv Flow-Diverting Stent in a Rabbit Model.

BACKGROUND: Bioresorbable polymer-based flow-diverting stents have potential benefits over existing metal devices. This study aimed to evaluate the safety and efficacy of the novel ReSolv device, which is a primarily polymer-based flow-diverting stent, using the in vivo rabbit sidewall saccular aneurysm model. METHODS: ReSolv stents were deployed in 14 New Zealand White rabbits that had undergone aneurysm creation procedures. Animals were allocated to follow-up time points of 1, 3, 6, 9, 12, 16, or 18 months. Angiographic images were evaluated by an independent neurointerventionalist blinded to follow-up time points for (1) in-stent stenosis, (2) parent vessel and jailed side branch patency, (3) wall apposition, and (4) aneurysm occlusion using the Raymond-Roy Occlusion Classification (RROC), O'Kelly Marotta grading scale, and the 4F flow diversion predictive score. Primary efficacy outcome was defined as RROC Class I or II. RESULTS: At a median follow-up time of 7.5 months, parent vessel (14/14) and jailed side (33/33) branches were patent in all cases. There was no development of thrombus on the stent or cases of significant in-stent stenosis, and all stents had good wall apposition. Adequate occlusion was found in 85.7% (n = 12) of animals, including an RROC Class I in 64.3% (n = 9) and RROC Class II in 21.4% (n = 3). CONCLUSIONS: The ReSolv stent shows encouraging angiographic safety and efficacy outcomes after placement in a rabbit sidewall saccular aneurysm model. Longer term studies are ongoing to determine eventual fate of the aneurysm, parent vessel, and jailed side branches after absorption of the polymer component of the stent.

Endovascular Pipeline Shield Treatment of Iatrogenic Internal Carotid Artery Pseudoaneurysm and Carotid-Cavernous Fistula.

Pseudoaneurysm (PA) and carotid cavernous fistula (CCF) of the internal carotid artery (ICA) is an uncommon complication of endoscopic endonasal surgery that occurs in 1% of cases. We report on the successful placement of flow-diverting stents (FDS) to ICA pseudoaneurysm and caroticocavernous fistula caused by iatrogenic ICA injury for a pituitary adenoma in a 37-year-old female. After placement of the pipeline shield given a certain time, dual antiplatelet agents (DAPT) and follow-up angiogram verified complete aneurysm obliteration and effective endoluminal reconstruction of the injured vessel. In managing ICA pseudoaneurysms, the placement of flow-diverting stents is a viable vessel-sparing technique.

Recurrent, Severe Coital Headaches Associated With Bilateral Carotid Artery Aneurysms and the Effect of Endovascular Treatment.

Headaches are one of the most common chief complaints in the outpatient setting. Distinguishing between benign and life-threatening headaches can be difficult, particularly in the setting of a pre-existing history of headaches. Here, we present a 41-year-old female with a past medical history of migraines and uterine leiomyoma status post hysterectomy about nine months ago who presented to the clinic for severe coital headaches and worsening migraines starting eight months ago. Computer tomography angiogram (CTA) head and neck demonstrated bilateral para-ophthalmic internal carotid artery (ICA) aneurysms (right, 7.5, left 6 mm). A diagnostic cerebral angiogram (DSA) was subsequently done and confirmed the CTA findings. The patient underwent left and right flow-diverting stent placement two and four months later, respectively. One week after the right ICA stent placement, her headaches had improved to one to two times per week. At six months after the stent placement, she resumed her normal sex life and her migraines returned to baseline. Our case suggests that recurrent severe coital headaches are associated with bilateral carotid artery aneurysms. Thus, while assessing a patient with recurrent coital headaches, it is important to have a wide arsenal of differentials to rule out possibly catastrophic causes.

Extracranial internal carotid artery-dissecting aneurysm having a re-entry tear and causing lower cranial nerve palsies treated with flow-diverting stent: A case report.

Background: Extracranial internal carotid artery (ICA)-dissecting aneurysms (DAs) rarely cause re-entry tears and lower cranial nerve palsies. The therapeutic strategies for these pathologies are not well established. This report presents a case of an extracranial ICA -DA with a re-entry tear that caused lower cranial nerve palsy. Case Description: A 60-year-old man presented with left neck pain, hoarseness, and dysphagia. Physical examination and laryngoscopy determined palsies of the left cranial nerves IX, X, and XII. Digital subtraction angiography (DSA) revealed a DA in the left extracranial ICA, and three-dimensional DSA showed entry and re-entry tears in the intimal flap. Flow-diverting stents (FDSs) were placed on the lesion that covered the entry and re-entry tears because the symptoms did not improve after five weeks of conservative treatment. A post-procedural angiogram indicated flow stagnation in the DA. Symptoms improved remarkably immediately after the procedure, and the aneurysm was almost completely occluded six months later. Conclusion: Herein, an extracranial ICA -DA with a re-entry tear that caused lower cranial nerve palsy did not improve after five weeks of conservative treatment. FDS placement promptly resolved the aneurysm and symptoms. Thus, FDS placement may be an effective treatment option for extracranial ICA-DAs with re-entry tears or lower cranial nerve palsies.

Fungal symptomatic intracranial aneurysm treated with a flow diverting stent: A case report.

Background: Intracranial infectious aneurysms (IIAs) are very rare, and fungal aneurysms are infrequently reported. We report a case of an unruptured IIA caused by fungal rhinosinusitis and treated with a flow-diverting stent. Case Description: An 81-year-old woman visited the ophthalmology department with impaired eye movement and ptosis and was placed under follow-up. A week later, she also developed a headache; magnetic resonance angiography revealed an aneurysm measuring 2 mm in the C4 portion of the right internal carotid artery. A 3-week follow-up with contrast-enhanced magnetic resonance imaging showed an increase in its size to 10 mm, and a contrast lesion was observed surrounding the right cavernous sinus. The patient started treatment with voriconazole and steroids on the same day. Ten weeks later, despite improvements in inflammation, the size of the aneurysm was unchanged; we, therefore, treated the aneurysm with a flow-diverting stent. Oculomotor nerve palsy improved, and the patient was discharged to a rehabilitation hospital 28 days after the placement, with a modified Rankin Scale of 4. A 1-year follow-up angiogram showed a partial decrease in the size of the aneurysm, with an O'Kelly-Marotta grading scale of B3. Conclusion: IIAs grow rapidly, and the risk of rupture is high due to the weakening of the aneurysmal wall. To reduce the risks of rupture and recurrence after treatment, the infection should be treated before inserting a flow-diverting stent. Flow-diverting stent placement may be an effective treatment for IIA once the original infection has been cured.

Determinants of Mortality and Mid-Term Outcomes After Transcarotid Artery Revascularization and Transfemoral Carotid Artery Stenting.

OBJECTIVES: The potential benefit of transcarotid artery revascularization (TCAR) over transfemoral carotid artery stenting (tfCAS) has been studied in the perioperative period with lower rates of stroke and death; however, data on mid-term outcomes are limited. We aimed to evaluate 3-year outcomes after TCAR and tfCAS and determine the primary predictors of 30-day and 1-year mortality following TCAR. METHODS: Data from the Vascular Quality Initiative for patients undergoing TCAR or tfCAS from January 2016 to December 2022 were analyzed. 1:1 propensity score matching using the nearest-neighbor method was used to adjust baseline demographics and clinical characteristics. Kaplan-Meier survival analysis and Cox Proportional Hazard Regression were used to evaluate long-term outcomes. Iterative stepwise multiple logistic regression analysis and Cox Proportional Hazard Regression were used to identify predictors of 30-day and 1-year mortality, respectively, based upon preoperative, intraoperative, and postoperative factors. RESULTS: A total of 70 237 patients were included in analysis (TCAR=58.7%, tfCAS=41.3%). Transcarotid artery revascularization patients were older and had higher rates of comorbid conditions and high-risk medical and anatomic features than tfCAS patients. Propensity score matching yielded 22 322 pairs with no major differences between groups except that TCAR patients were older (71.6 years vs 70.8 years). At 3 years, TCAR was associated with a 24% reduction in hazard of death compared with tfCAS (hazard ratio [HR]=0.76, 95% confidence interval [CI]=0.71-0.82, p<0.001), for both symptomatic and asymptomatic patients. This survival advantage was established in the first 6 months (HR=0.59, 95% CI=0.53-0.62, p<0.001), with no difference in mortality risk from 6 months to 36 months (HR=0.95, 95% CI=0.86-1.05, p=0.31). Transcarotid artery revascularization was also associated with decreased hazard for 3-year stroke (HR=0.81, 95% CI=0.66-0.99, p=0.04) and stroke or death (HR=0.81, 95% CI=0.76-0.87, p<0.001) compared with tfCAS. The top predictors for 30-day and 1-year mortality were postoperative complications. The primary independent predictor was the occurrence of postoperative stroke. CONCLUSIONS: Transcarotid artery revascularization had a sustained mid-term survival advantage associated over tfCAS, with the benefit being established primarily within the first 6 months. Notably, our findings highlight the importance of postoperative stroke as the primary independent predictor for 30-day and 1-year mortal. CLINICAL IMPACT: The ongoing debate over the superiority of TCAR compared to tfCAS and CEA has been limited by a lack of comparative studies examining the impact of pre-operative symptoms on outcomes. Furthermore, data are scarce on mid-term outcomes for TCAR beyond the perioperative period. As a result, it remains uncertain whether the initial benefits of stroke and death reduction observed with TCAR over tfCAS persist beyond one year. Our study addresses these gaps in the literature, offering evidence to enable clinicians to assess the efficacy of TCAR for up to three years. Additionally, our study seeks to identify risk factors for postoperative mortality following TCAR, facilitating optimal patient stratification.

Numerical simulation of flow-diverting stent: comparison between branches in bifurcation brain aneurysm.

The usage of flow-diverting stents in the treatment of intracranial aneurysms is widespread due to their high success and low complication rates. However, their use is still not officially recommended for bifurcation aneurysms, as there is a risk of generating ischemic complications due to the reduced blood flow to the jailed branch. Many works utilize computational fluid dynamics (CFD) to study how hemodynamic variables respond to flow diverter placement, but few seem to use it to verify flow variation between branches of bifurcation aneurysms and to aid in the choice of the best ramification for device placement. This investigation was performed in the present work, by comparing wall shear stress (WSS) and flowrates for a patient-specific scenario of a middle cerebral artery (MCA) aneurysm, considering device placement on each branch. A secondary objective was to follow a methodology that provides fast results, envisioning application to daily medical practice. The device was simplified as a homogeneous porous medium, and extreme porosity values were simulated for comparison. Results suggest that stent placement on either branch is both safe and effective, significantly reducing WSS and flow into the aneurysm while maintaining flow to the different ramifications within acceptable thresholds.

Effect on ophthalmic imaging findings of flow-diverting stent treatment covering the origin of the ophthalmic artery.

BACKGROUND: Flow-diverting stents are devices that are increasingly used in the treatment of intracranial aneurysms and expand the spectrum of endovascular treatment. The patency of side branches and perforators is a major concern about flow-diverting stent (FDS) treatment. METHODS: From 2011 to 2020, seventy-eight patients in whom the orifice of the ophthalmic artery was covered during FDS treatment were evaluated in this study. Bilateral retinal vascular parameters of study subjects were evaluated with OCT and OCTA. The FDS implanted-side eyes of the patients were defined as the procedure group, and the fellow eyes were considered as the control group. RESULTS: Twenty-seven patients who were treated with FDS covering the ostium of the ophthalmic artery and who could undergo full ophthalmologic examination were included in the study. There was no statistically significant difference found in terms of visual acuity, retinal vascular parameters, and choroidal thickness between the procedure group and the control group (p>0.05). However, in one case, recanalized retinal artery branch occlusion was detected on the side where the FDS was implanted. CONCLUSION: The orifice of the ophthalmic artery is often covered during FDS treatment for carotid-ophthalmic aneurysms; however, this treatment approach has no significant effect on ophthalmic vascular parameters.

Treatment of an acutely ruptured complex fusiform middle cerebral artery aneurysm with flow diverting stenting and adjunctive coil embolization.

This technical video demonstrates the treatment of an acutely ruptured, large, complex left fusiform middle cerebral artery (MCA) aneurysm with endovascular flow diversion with adjunctive coiling in a 27-year-old female. Two telescoping flow-diverting stents (Pipeline Flex) were placed, with partial coiling of a saccular portion of the aneurysm. Technical challenges, alternative treatment, intraoperative and postoperative antiplatelet management, vasospasm treatment, and clinical and radiographic follow-up are described. The video can be found here: https://stream.cadmore.media/r10.3171/2022.7.FOCVID2249.

Panhypopituitarism caused by an unruptured giant cavernous internal carotid artery aneurysm compressing the pituitary gland treated with a flow-diverting stent: A case report.

Background: Internal carotid artery (ICA) aneurysms extending into the intrasellar region that mimics pituitary tumors and leads to pituitary dysfunction are relatively rare. The treatment for aneurysms includes surgery and endovascular procedures. However, functional recovery of the pituitary gland is difficult. Case Description: We report a case of a 43-year-old woman who presented with severe headaches and generalized malaise. Magnetic resonance imaging (MRI) revealed a giant unruptured cavernous ICA aneurysm that pushed the pituitary stalk contralaterally. A baseline endocrinological examination suggested panhypopituitarism. Hypopituitarism was treated with hormone replacement therapy, which improved the patient's symptoms of headaches and malaise after 4 days. The aneurysm was treated using a pipeline flow-diverting stent. Two years later, the aneurysm had reduced to half of its maximum diameter, and the pituitary stalk was visible on MRI. Hormone loading tests 1 week postoperatively showed almost no response. At postoperative 6 months, there was a trend toward improvement. Conclusion: Flow-diverting stent deployment is useful for large or giant carotid artery aneurysms with pituitary gland compression.

How precise is PreSize Neurovascular? Accuracy evaluation of flow diverter deployed-length prediction.

OBJECTIVE: The use of flow-diverting stents has been increasingly important in intracranial aneurysm treatment. However, accurate sizing and landing zone prediction remain challenging. Inaccurate sizing can lead to suboptimal deployment, device waste, and complications. This study presents stent deployment length predictions offered in medical software (PreSize Neurovascular) that provides physicians with real-time planning support, allowing them to preoperatively "test" different devices in the patient's anatomy in a safe virtual environment. This study reports the software evaluation methodology and accuracy results when applied to real-world data from a wide range of cases and sources as a necessary step in demonstrating its reliability, prior to impact assessment in prospective clinical practice. METHODS: Imaging data from 138 consecutive stent cases using the Pipeline embolization device were collected from 5 interventional radiology centers in the United Kingdom and retrospectively analyzed. Prediction accuracy was calculated as the degree of agreement between stent deployed length measured intraoperatively and simulated in the software. RESULTS: The software predicted the deployed stent length with a mean accuracy of 95.61% (95% confidence interval [CI] 94.87%-96.35%), the highest reported accuracy in clinical stent simulations to date. By discounting 4 outlier cases, in which events such as interactions with coils and severe push/pull maneuvers impacted deployed length to an extent the software was not able to simulate or predict, the mean accuracy further increases to 96.13% (95% CI 95.58%-96.69%). A wide discrepancy was observed between labeled and measured deployed stent length, in some cases by more than double, with no demonstrable correlation between device dimensions and deployment elongation. These findings illustrate the complexity of stent behavior and need for simulation-assisted sizing for optimal surgical planning. CONCLUSIONS: The software predicts the deployed stent length with excellent accuracy and could provide physicians with real-time accurate device selection support.

The changing landscape of cerebral revascularization surgery: A United Kingdom experience.

Objective: We describe the chronological trends in cerebral revascularization surgery through a single-surgeon experience; and we review whether in the context of giant and fusiform cerebral aneurysms, flow-diverting stents have impacted on the use of cerebral revascularization surgery. Methods: We review our single institution prospectively collected database of cerebral revascularization procedures between 2006 and 2018. Comparing this to our database of flow-diverting endovascular stent procedures, we compare the treatment of fusiform and giant aneurysms. We describe patient demographics, procedural incidence, complications, and outcomes. Results: Between 2006 and 2018, 50 cerebral revascularization procedures were performed. The incidence of cerebral revascularization surgery is declining. In the context of giant/fusiform aneurysm treatment, the decline in cerebral revascularization is accompanied by a rise in the use of flow-diverting endovascular stents. Thirty cerebral revascularizations were performed for moyamoya disease and 11 for giant/fusiform aneurysm. Four (14%) direct bypass grafts occluded without neurological sequela. Other morbidity included hydrocephalus (2%), transient ischemic attacks (2%), and ischemic stroke (2%). There was one procedure-related mortality (2%). Flow-diverting stents were inserted for seven fusiform and seven giant aneurysms. Comparing the treatment of giant/fusiform aneurysms, there was no significant difference in morbidity and mortality between cerebral revascularization and flow-diverting endovascular stents. Conclusion: We conclude that with the decline in the incidence of cerebral revascularization surgery, there is a need for centralization of services to allow high standards and outcomes to be maintained.

Prediction of Cerebral Aneurysm Hemodynamics With Porous-Medium Models of Flow-Diverting Stents via Deep Learning.

The interventional treatment of cerebral aneurysm requires hemodynamics to provide proper guidance. Computational fluid dynamics (CFD) is gradually used in calculating cerebral aneurysm hemodynamics before and after flow-diverting (FD) stent placement. However, the complex operation (such as the construction and placement simulation of fully resolved or porous-medium FD stent) and high computational cost of CFD hinder its application. To solve these problems, we applied aneurysm hemodynamics point cloud data sets and a deep learning network with double input and sampling channels. The flexible point cloud format can represent the geometry and flow distribution of different aneurysms before and after FD stent (represented by porous medium layer) placement with high resolution. The proposed network can directly analyze the relationship between aneurysm geometry and internal hemodynamics, to further realize the flow field prediction and avoid the complex operation of CFD. Statistical analysis shows that the prediction results of hemodynamics by our deep learning method are consistent with the CFD method (error function <13%), but the calculation time is significantly reduced 1,800 times. This study develops a novel deep learning method that can accurately predict the hemodynamics of different cerebral aneurysms before and after FD stent placement with low computational cost and simple operation processes.

Visceral Artery Aneurysms Embolization and Other Interventional Options: State of the Art and New Perspectives.

Visceral artery aneurysms (VAAs) are rare, usually asymptomatic and incidentally discovered during a routine radiological examination. Shared guidelines suggest their treatment in the following conditions: VAAs with diameter larger than 2 cm, or 3 times exceeding the target artery; VAAs with a progressive growth of at least 0.5 cm per year; symptomatic or ruptured VAAs. Endovascular treatment, less burdened by morbidity and mortality than surgery, is generally the preferred option. Selection of the best strategy depends on the visceral artery involved, aneurysm characteristics, the clinical scenario and the operator's experience. Tortuosity of VAAs almost always makes embolization the only technically feasible option. The present narrative review reports state of the art and new perspectives on the main endovascular and other interventional options in the treatment of VAAs. Embolization techniques and materials, use of covered and flow-diverting stents and percutaneous approaches are accurately analyzed based on the current literature. Visceral artery-related considerations and targeted approaches are also provided and discussed.

Association Between Aneurysmal Haemodynamics and Device Microstructural Characteristics After Flow-Diversion Treatments With Dual Stents of Different Sizes: A Numerical Study.

OBJECTIVES: Treating intracranial aneurysms with flow-diverting stents sometimes requires deployment of a second device. Herein we quantify the sizing effects of devices in dual-stent treatments upon the final stent microstructure and the post-treatment aneurysmal haemodynamics. METHODS: Fifteen sidewall ICA aneurysm geometries were included. Using a virtual stenting technique, we implanted either one or two stents for each aneurysm treatment considered, with each stent specified as one of two different sizes, yielding a total of two single-stent and fouir dual-stent treatment scenarios for each aneurysm. Three stent microstructural parameters and nine aneurysmal haemodynamic parameters were quantified and systematically compared across the 90 treatment scenarios. RESULTS: Deployment of a second stent further reduced the aneurysmal inflow rate (IR) and energy loss (EL) by, respectively, 14 ± 11% (p = 0.001) and 9 ± 12% (p = 0.056), relative to the untreated condition. Sizing effects of the earlier-deployed stent led to largest differences of 6.9% for the final IR reduction and 11.1% for the EL, whereas sizing effects from the later-deployed stent were minor (≤2.1%). The change in stent pore size was the only microstructural parameter demonstrating a strong correlation with the reduction in the post-treatment aneurysmal haemodynamics, in terms of the IR (r = 0.50, p < 0.001) and pressure drop (r = 0.63, p < 0.001). CONCLUSION: Size of the earlier-deployed stent has substantial effects on the final haemodynamic outcomes after dual-stent treatment. The average pore size of stent wires at the aneurysm orifice shows promise as a potential index for predicting the efficacy of flow-diversion treatments.

Endovascular repair of a complex renal artery aneurysm using PipelineTM Embolization Device (PED) assisted coil embolization.

Background: We describe the treatment of a renal artery aneurysm with complex anatomy using coils and the PipelineTM Embolization Device (Medtronic, Irvine, CA), a flow-diverting stent typically used for the treatment of intracranial aneurysms. Methods: A 62-year-old female with history of an asymptomatic right renal artery aneurysm that was discovered incidentally 10 years ago was found to have enlargement of the aneurysm (1.9cm to 2.7cm) on a repeat surveillance CT scan. She was successfully treated with combined Pipeline Embolization Device and coil embolization of the aneurysm sac. Results: Post-procedural angiography showed complete occlusion of the aneurysm with maintenance of perfusion to the entire kidney. Conclusion: PipelineTM assisted coil embolization may be an option for parenchyma-sparing treatment of renal artery aneurysms with complex anatomy.

Flow-diverting stent and delayed intracranial bleeding: the case for discussing acquired von Willebrand disease.

A unique feature of the flow-diverting stent (FDS) has rendered it useful in the endovascular treatment of selected intracranial aneurysms for the last decade. Delayed aneurysmal rupture and intracranial parenchymal bleeding are two leading hemorrhagic complications after FDS. It has recently been shown for the first time that there is a relationship between FDS and reduced level of vWF activity in patients undergoing endovascular cerebral aneurysm treatment. Here, the current literature is reviewed in the context of this novel finding to propose an illustrative scenario that conceptually links implantation of FDS to delayed intracranial bleeding, through the mechanism of shear-induced activation of vWF. In this scenario, after FDS implantation, sustained release of activated vWF in association with platelets plays a pivotal role in the mechanisms of delayed intracranial hemorrhages.

Treatment of visceral artery aneurysms and pseudoaneurysms with the use of cerebral flow diverting stents: initial experience.

BACKGROUND: Flow-diverter stents (FDS) are designed to maintain laminar flow in the parent artery and sidebranches and to promote thrombosis of the aneurysm. Although these devices were developed for use in intracranial circulation, FDS could be employed to treat aneurysms regardless of their location, when anatomic factors may limit the efficacy of classic endovascular techniques. The objective of this study is to describe the initial experience of a single center in the treatment of visceral artery aneurysms and pseudoaneurysms (VAA-VAP) with cerebral FDS, analyzing safety, efficacy and 1-year outcome. Between 2016 and 2018 six patients (4 women, mean age 57.6) underwent treatment with FDS of 4 VAA and 2 VAP located in renal (4), hepatic (1) and splenic arteries (1). Mean aneurysm diameter was 14.3 mm (range 8-22). All the aneurysms had sidebranches arising from the neck or had an unfavorable dome-to-neck ratio. Technical success, safety, efficacy and 1-year outcome were analyzed. Follow-ups (FU) with Color-Doppler US and CTA ranged from 12 to 36 (mean 20) months. RESULTS: Technical success was achieved in all cases. There were no aneurysm rupture nor reperfusion after exclusion. Five out of six (83.3%) FDS were patent at each FU; all the aneurysms showed shrinkage with a mean dimensional reduction rate of 55.8%. Sac thrombosis was observed in 4 aneurysms at 1 (n = 3) and at 12-month FUs. There was one sidebranch occlusion with evidence of a small area of kidney hypoperfusion at the 12-month FU, which was asymptomatic. In one patient, a reintervention was needed because CTA showed a severe in-stent stenosis, which was symptomatic. Mean hospitalization was 4.1 days. CONCLUSIONS: Treatment of morphologically complex VAA and VAP with cerebral FDS proved to be safe and efficient. Stronger evidence from larger populations are required.

Evaluation of Two Fast Virtual Stenting Algorithms for Intracranial Aneurysm Flow Diversion.

BACKGROUND: Endovascular treatment of intracranial aneurysms (IAs) by flow diverter (FD) stents depends on flow modification. Patient-specific modeling of FD deployment and computational fluid dynamics (CFD) could enable a priori endovascular strategy optimization. We developed a fast, simplistic, expansion-free balls-weeping algorithm to model FDs in patientspecific aneurysm geometry. However, since such strong simplification could result in less accurate simulations, we also developed a fast virtual stenting workflow (VSW) that explicitly models stent expansion using pseudo-physical forces. METHODS: To test which of these two fast algorithms more accurately simulates real FDs, we applied them to virtually treat three representative patient-specific IAs. We deployed Pipeline Embolization Device into 3 patient-specific silicone aneurysm phantoms and simulated the treatments using both balls-weeping and VSW algorithms in computational aneurysm models. We then compared the virtually deployed FD stents against experimental results in terms of geometry and post-treatment flow fields. For stent geometry, we evaluated gross configurations and porosity. For post-treatment aneurysmal flow, we compared CFD results against experimental measurements by particle image velocimetry. RESULTS: We found that VSW created more realistic FD deployments than balls-weeping in terms of stent geometry, porosity and pore density. In particular, balls-weeping produced unrealistic FD bulging at the aneurysm neck, and this artifact drastically increased with neck size. Both FD deployment methods resulted in similar flow patterns, but the VSW had less error in flow velocity and inflow rate. CONCLUSION: In conclusion, modeling stent expansion is critical for preventing unrealistic bulging effects and thus should be considered in virtual FD deployment algorithms. Also endowed with its high computational efficiency and superior accuracy, the VSW algorithm is a better candidate for implementation into a bedside clinical tool for FD deployment simulation.

Complex cerebral aneurysms: intra-luminal reconstruction using Pipeline flow-diverting stent and the obliteration mechanism.

OBJECTIVES: Patients with complex cerebral aneurysms can now be treated intravascularly with the help of flow-diverting stents. The primary purpose of this article is to document the clinical and angiographic outcomes in 80 patients who were treated with the Pipeline flow-diverting stent (PFS; Medtronic, Dublin, Ireland) and the obliteration mechanism was discussed. PATIENTS AND METHODS: Between October 2015 and October 2019, 80 patients with 90 complex (undefined neck, large/giant, blood blister-like, and recurrent side-wall) cerebral aneurysms treated with the PFS were retrospectively reviewed. Forty-five patients were women and 35 were men, with a mean age of 52 years. Large or giant aneurysms were defined as 10 mm or larger and small aneurysms were defined as less than 10 mm at the largest diameter measured on angiogram. RESULTS: Forty-one aneurysms (45.6%) were large or giant, 41 (45.6%) were small, four (4.4%) were recurrent side-wall aneurysms and four (4.4%) were blood blister-like aneurysms. In total, 87 PFSs were placed in 80 patients with 90 aneurysms. In six patients, coexisting proximal stenosis of parent artery was also covered with PFS without balloon angioplasty. Adjunct coils were placed in 31 aneurysms (34%). One patient died of intracerebral hematoma after thrombolysis. There was one intrastent occlusion at six-month follow-up without any symptoms. The morbidity and the mortality rate is 0% and 1.3% (95% confidence interval (CI), 0%-3.7%). Control angiography was available in 74 (92.5%) patients with 83 aneurysms, and the aneurysm occlusion rate was 98.8% (95% CI, 96.5%-100%) in 6 to 12 months. CONCLUSION: For wide-necked saccular, large/giant, blood blister-like aneurysms and recurrent side-wall aneurysms, PFS is a valid and safe treatment option.