Flow-diverting Stents Research Articles

Safety and efficacy of flow diverter stents in the treatment of bifurcation cerebral aneurysms: single-center experience.

The use of flow diverter (FD) stents is continually expanding. Aneurysms on arterial bifurcation typically have an undesirable anatomical form, are frequently wide-necked, and include one or more side-branch arteries. In recent years, the off-label use of flow diversion in treating intracranial aneurysms beyond the internal carotid artery has become increasingly popular. This study reports our center's initial experience treating bifurcation aneurysms with FD devices, documenting occlusion outcomes using the O'Kelly-Marotta and modified Cekirge-Saatci scales, as well as the safety of FD usage in bifurcation locations. This retrospective, single-center study analyzed a prospectively maintained database of patients with cerebral aneurysms treated endovascularly. The study identified bifurcation aneurysms that were treated between January 2019 and May 2022 by placing an FD device covering the neck of the aneurysm. Our short series suggests that flow diversion is a viable therapeutic option for bifurcation aneurysms with favorable angiographic outcomes. In highly selective cases, flow diversion may be considered for treating bifurcation aneurysms in patients who will undergo follow-up examinations in the future. Flow diversion has emerged as a valuable technique in the management of bifurcation aneurysms, offering the potential for satisfactory occlusion and long-term outcomes.

Effect of the Effective Metal Surface Area of Two Different Flow Diverter Stents on the Stagnation Region Formation Inside the Aneurysm Sac

Abstract Objective Flow diversion (FD) is a relatively new technique for treating large, wide-necked, or fusiform aneurysms. Although FD is a more preferred option than coiling or clipping techniques in neurosurgery and neuroradiology clinics, the blood flow mechanism inside the aneurysm sac is not fully understood after the treatment. Besides, effective metal surface area (EMSA), a property of an FD related to porosity, shows variation at the patient's aneurysm neck by providing more or less blood flow inside an aneurysm sac than planned, causing nonstagnant or stagnant fluid region formation in the sac, respectively. Thus, the change in FD's EMSA can significantly affect the treatment's effectiveness, making even operation unsuccessful when variation in FD's EMSA at the aneurysm neck is overlooked. Materials and Methods In this study, a large aneurysm of a 52-year-old female patient was numerically investigated by virtually placing two commercially available FDs with different EMSA values one by one into the aneurysm-carrying artery. Results While FD stents at the aneurysm site substantially reduced the blood flow into the aneurysm, an FD with a 15.6% EMSA caused blood to flow in the aneurysm sac to have six times more kinetic energy than that of FD with a 29.5% EMSA. Conclusion Although FD's EMSA value demonstrated nearly up to 20% reduction at the patient's aneurysm neck based on a product catalog value, numerical model results revealed that the stagnated region's formation inside the aneurysm sac could be determined within a 9% difference based on digital subtraction angiography reformat image.

Evaluating the Safety of Stent-Assisted Endovascular Treatment for Unruptured Cerebral Aneurysms in Older Adults: Emphasizing the Role of Antiplatelet Therapy

Introduction: This study aimed to compare the outcomes and safety in patients aged ≥75 years and those aged <75 years who underwent stent-assisted endovascular treatment for unruptured cerebral aneurysms, specifically focusing on perioperative antiplatelet therapy (APT). Methods: This multicenter retrospective study comprised patients who underwent stent-assisted coiling (SAC) or flow diverter stent (FDS) placement for unruptured cerebral aneurysms. The primary outcome was defined as the composite outcomes of perioperative thromboembolic events, bleeding events, or death. Results: Among 632 patients, 533 (84.3%) were aged <75 years and 99 (15.6%) were aged ≥75 years. No significant differences were observed in the dual APT duration. The primary outcome occurred in 14.3% of patients aged <75 years and in 14.1% of those aged ≥75 years, with no significant difference (p = 1.0). The composites of the primary outcome, including thromboembolic events, bleeding events, and death differed insignificantly. Similar findings were observed when the primary outcomes for SAC (12.7% vs. 11.5%, p = 0.95) and FDS (17.5% vs. 18.4%, p = 1.0) were analyzed. The 30-day, 1-year, and 2-year cumulative event-free survival rates for the primary outcome were 89.5, 87.2%, and 85.2%, respectively, in patients aged <75 years, and 90.9%, 88.7%, and 87.0%, respectively, in those aged ≥75 years. These trends were similar (log-rank test, p = 0.92). Conclusion: No significant differences were observed in the rates of the primary outcomes between patients aged <75 years and those aged ≥75 years. Therefore, refraining from stent-assisted treatment for unruptured aneurysms based solely on age might be inappropriate.

Real-world evaluation of CYP2C19 guided antiplatelet therapy in patients undergoing intracranial aneurysm repair.

Aim: To evaluate the feasibility and impact of using CYP2C19 genotype to guide selection of antiplatelet therapy in patients undergoing intracranial aneurysm treatment with a flow diversion stent in a real-world clinical setting.Patients & methods: A single-center, retrospective, observational cohort study was conducted in 112 patients undergoing intracranial aneurysm repair with flow-diversion stenting from 2014 to2021. Data were abstracted from health records. The frequency of clopidogrel or alternative therapy (ticagrelor or prasugrel) use was compared across CYP2C19 status (intermediate or poor metabolizer [IM/PM] vs. normal, rapid, or ultrarapid metabolizer [NM/RM/UM]).Results: In the study population, CYP2C19 genotype testing was performed on 110 (98.2%) patients; of these, 106 (97.2%) had results available prior to the stent procedure and 28 (25.5%) were IM/PMs. Alternative therapy was used more frequently in IM/PMs compared with NM/RM/UMs (57.1 vs. 8.5%, respectively, p<0.0001). The frequency of thromboembolic events over 12months did not significantly differ across clopidogrel-treated IM/PMs, clopidogrel-treated NM/RM/UMs and patients on alternative therapy (p=0.352); although, event numbers were low.Conclusion: A pre-emptive CYP2C19 genotyping strategy to guide antiplatelet therapy selection in intracranial aneurysm repair patients is feasible in a real-world clinical setting. Larger studies are needed to assess the impact on clinical outcomes.

Advancements in Endovascular Treatment of Extracranial Carotid Artery Aneurysms

Traditionally, extracranial carotid artery aneurysms or pseudoaneurysms (ECCAs) have been managed through open surgical repair. Recent literature highlights the increasing success of endovascular techniques in treating ECCAs. Our study explores our center's experience with endovascular management of ECCAs, including the innovative use of Transcarotid Artery Revascularization (TCAR) at a tertiary care center. We performed a retrospective analysis of patients with ECCAs who underwent endovascular intervention at a single institution. We examined our database from the period of 2010 to 2024. Our treatment modalities have expanded to include covered stenting, stent-assisted coil embolization, braided stents, overlapping closed-cell stents, and most recently Transcarotid Artery Revascularization (TCAR). There were 29 extracranial carotid artery aneurysms in 27 patients treated with various endovascular modalities. The average age was 67.6 years, with 17 (63.0%) males and 10 (37.0%) females. 8 (29.6%) patients had prior ipsilateral carotid intervention. 9 (31.0%) aneurysms were symptomatic. The most common etiology was idiopathic, with 16 (55.2%) aneurysms being spontaneous. Treatment modalities included: 2 (6.9%) treated with covered stents, 2 (6.9%) with stent-assisted embolization, 3 (10.3%) with flow-diverting braided stents, 3 (10.3%) with embolization or ligation alone, 17 (58.6%) with overlapping bare metal stents via femoral or radial access, and 2 (6.9%) with overlapping bare metal stents via TCAR. Technical success was achieved in all patients. The mean follow-up duration was 236 days (range: 2 to 3039 days). No perioperative or post-operative complications occurred, including no neurological deficits or embolic events. All patients were discharged on post-operative day 1 or 2. All 29 (100%) stents maintained vessel patency on follow-up imaging, and exclusion of ECCAs was confirmed on post-procedure surveillance imaging. Our study highlights that endovascular therapy is effective in managing ECCAs, with high patency rates and a favorable procedural safety profile.

Arterial spin labeling detects trapped labeled spins in flow-diverted aneurysms and it reflects intra-aneurysmal flow stasis.

This study evaluated arterial spin labeling (ASL) imaging findings in flow-diverted aneurysms (FD-ANs). Twenty-one patients with internal carotid artery aneurysms treated with flow-diverter stent (FDS) were included. Time-of-flight magnetic resonance angiography (TOF-MRA) and ASL were performed before and after follow-up digital subtraction angiography (DSA) on the day, 6 months, and/or 1 year after treatment. Two radiologists rated the clarity of the depiction of FD-ANs for MRA on a 3-point scale and the ASL signal intensity of the aneurysm as negative or positive. A neurosurgeon assessed DSA findings using the O'Kelly-Marotta (OKM) grading scale, categorizing them into filling and stasis grades. The 23 examinations were classified according to the OKM grading scale, and the proportion of ASL-positive cases and the proportion of cases with MRA scores of 1-2 (detectable) were calculated for each grade. The relationship between the OKM grading scale and ASL positivity or MRA detectable was examined using Fisher's exact test. Of seven examinations where the statis grade was 1 or 2, no examinations showed ASL positivity. However, among the 16 examinations in which the stasis grade was 3, 9 examinations showed ASL positivity. A significant association was observed between stasis grade and ASL positivity (p = 0.035). In contrast, no significant relationship was observed between the OKM grading scale and the MRA 3-point scale. High-signal ASL in FD-ANs could reflect stasis within the aneurysm; therefore, noninvasive ASL can indicate reduction in intra-aneurysmal blood flow after treatment and reperfusion during posttreatment observation.

Treatment of Acute Iatrogenic Cerebrovascular Injury Using Flow Diverter Stents

BACKGROUND AND OBJECTIVES: Iatrogenic cerebrovascular injury can cause intracranial hemorrhage and pseudoaneurysm formation, putting patients at high risk for postoperative bleeding. No consensus for management exists. This study describes endovascular treatment of these acute injuries with flow diverter stents. METHODS: Electronic medical records were retrospectively reviewed for injury type and etiology, timing of diagnosis, and endovascular management, including antiplatelet regimens, embolization results, and clinical outcome. RESULTS: Six patients were included. Three suffered an injury to the internal carotid artery, 1 suffered an injury to the left anterior cerebral artery, 1 suffered an injury to the right posterior cerebral artery, and 1 suffered an injury to the basilar artery. Four of the 6 injuries occurred during attempted tumor resection, 1 occurred during cerebrospinal fluid leak repair, and 1 occurred during an ophthalmic artery aneurysm clipping. All injuries resulted in pseudoaneurysm formation. Four were immediately detected on angiography; 2 were initially negative on imaging. Five were treated with a pipeline embolization device, and 1 was treated with a Silk Vista Baby. Two were treated with 2 pipeline embolization devices telescopically overlapped across the pseudoaneurysm. All devices deployed successfully. No pseudoaneurysm recurrence or rebleeding occurred. No parent artery occlusion or stenosis was observed, and complete pseudoaneurysm occlusion was observed in 4 patients (in 2 patients, follow-up imaging could not be obtained). CONCLUSION: With proper antiplatelet regimens, flow diverter stents can be used safely to successfully treat complex acute iatrogenic injuries. Early repeat angiogram is needed when immediate postinjury imaging does not discover the point of vessel injury.

Efficacy and safety of flow diverters in retreatment of recurrent intracranial aneurysms-A systematic review and meta-analysis.

Treatment of recurrent intracranial aneurysms after their initial therapy has been a significant challenge in the field of neurointervention. Recently flow diverters stents are widely used for treating intracranial aneurysms. In this systematic review and meta-analysis, we assessed the safety and efficacy of flow diverter in treating recurrent or recanalized intracranial aneurysms. This meta-analysis is reported following the PRISMA 2020 guidelines. We conducted a systematic review of literature in the PubMed, Embase, Web of Sciences, and Scopus databases. Pooled prevalence and the corresponding 95% are calculated from extracted data using a random-effect model. The systematic literature search included 21 studies involving 411 patients, with 135 (32.8%) being male and 276 (67.2%) being females with a total number of 447 aneurysms. The overall rate of adequate occlusion was 90.67% (95% CI: 84.23%-94.65%), and the rates were comparable between the surgery (93.48%), coiling (91.78%), and stenting (85.77%) groups. The overall pooled rate of complete occlusion was 81.80 (95% CI: 71.14%-89.13%). On doing a subgroup analysis, the complete occlusion rates were 89.68%, 84.39%, and 73.47% for the surgery, coiling, and stenting groups, respectively. The overall mortality rate and achieving modified Rankin scale score of 0-2 was 1.28% (95% CI: 0.45%-3.64%) and (95% CI: 89.92%-97.84%), respectively. No significant heterogeneity is noted in the included studies. Flow diverter stents are an effective and safe method for retreating recurrent or residual intracranial aneurysms with a high rate of complete and adequate occlusion. The rate of mortality, intracerebral hemorrhage, and overall and procedural complications following using flow diverters for intracranial aneurysms is low.

Radiation dose analysis in interventional neuroradiology of unruptured aneurysm cases

This study aimed to evaluate the radiation doses (peak skin dose (PSD) and bilateral lens dose) for each interventional neuroradiology procedure. A direct measurement system consisting of small radiophotoluminescence glass dosimeter chips and a dosimetry cap made of thin stretchable polyester was used for radiation dosimetry. The mean PSDs for each procedure were 1565 ± 590 mGy (simple technique coil embolization (STCE) cases), 1851 ± 825 mGy (balloon-assisted coil embolization (BACE) cases), 2583 ± 967 mGy (stent-assisted coil embolization (SACE) cases), 1690 ± 597 mGy (simple flow-diverter stenting (FDS) cases), and 2214 ± 726 mGy (FDS + coiling cases). The mean PSD was higher in SACE cases than in STCE, BACE, and simple FDS cases. Moreover, the PSD exceeded 2000 mGy and 3000 mGy in 46 (67.6%) and 19 (27.9%) SACE cases, respectively. The left lens doses for each procedure were 126 ± 111 mGy (STCE cases), 163 ± 152 mGy (BACE cases), 184 ± 148 mGy (SACE cases), 144 ± 60 mGy (simple FDS cases), and 242 ± 178 mGy (FDS + coiling cases). The left lens dose in SACE cases was higher than that in STCE cases and exceeded 500 mGy in 3 (4.4%) patients. In FDS + coiling cases, the mean PSD and left lens dose were 2214 ± 726 mGy and 242 ± 178 mGy, respectively. The left lens dose was higher than that in the STCE and BACE cases, with two (15.4%) patients receiving doses >500 mGy in FDS + coiling cases. The detailed data obtained in this study are expected to contribute to the promotion of radiation dose optimization.

Multimodal Management of Ruptured Internal Carotid Artery Blood Blister-like Aneurysm: Technical Notes and Case Series of Surgical Muscle Wrapping and Fenestration Clipping Combined with Flow-Diverter Embolization

To evaluate the effects of a multimodal management technique combining surgical muscle wrapping, clipping, and flow-diverter stent (FDS) placement in patients with ruptured blood blister-like aneurysms (BBAs) in the internal carotid artery (ICA). In a retrospective case series review from 2020 to 2023, 3 patients with ruptured ICA BBAs underwent multimodal management, an approach combining muscle wrapping, surgical clipping, and FDS embolization. The aneurysm sac was initially packed and wrapped with multiple tailored temporalis muscle grafts and then secured using fenestration clips, with good preservation of the ICA branches. The FDS was placed 2-3weeks after the clipping. All 3 patients had right ICA BBAs (mean age, 52years). The modified Hunt and Hess grades ranged from 2 to 3, and the Fisher grades ranged from 3 to 4. The mean angiography follow-up time was 27.7months (15, 31, and 37months). There were no instances of symptomatic vasospasm or visible ischemic stroke during follow-up computed tomography. No patient required cerebrospinal fluid shunt implantation, and all achieved favorable neurological outcomes (modified Rankin scale 0-1). Follow-up digital subtraction angiography revealed no evidence of aneurysm recurrence or significant ICA stenosis. We discuss a promising multimodal management approach for ruptured ICA BBAs combining muscle wrapping, surgical clipping, and FDS embolization. This technique was safe and effective in preventing re-rupture, achieving positive short-term clinical outcomes. Further research and more extensive studies are required to validate the long-term efficacy of this approach.

Robust optimization of geometrical properties of flow diverter stents for treating cerebral aneurysm: A proof-of-concept study

This study presents a novel approach to optimize the design of flow diverter (FD) stents for cerebral aneurysm (CA) treatment. By addressing sources of uncertainty in cardiovascular simulations, including geometrical and physical properties and boundary conditions, we aim to assess the applicability of robust optimization techniques to the FD design, establishing a foundation for acquiring robust FDs that are capable of operating consistently under various real-world scenarios. Blood flow in a simplified 2-dimensional CA and FD model was simulated through computational fluid dynamics (CFD). A design space exploration method, incorporating Latin hypercube sampling and Kriging surrogate models, was employed to obtain the optimal solution. The objective was to maximize the reduction in velocity and vorticity within the CA sac. This study used non-intrusive polynomial chaos expansion (PCE) to quantify and propagate the input uncertainties through the computational model and compute the statistical moments of velocity and vorticity reductions. To assess the effect of uncertain sources on objective functions, a sensitivity analysis method based on Sobol indices was applied. Robust optimization involved simultaneously optimizing the mean and standard deviation of velocity reduction. Additionally, we accounted for patients’ specific conditions and repeated the robust optimization. The results indicate that blood Hematocrit and inlet velocity are the most impactful uncertain sources in FD optimization. Moreover, the obtained Pareto front shows that in robust designs, FD struts are concentrated in the distal region of the CA neck, while optimal designs have more struts in the proximal region. This study proposes an FD that compromises robustness and optimality with a velocity reduction of 72.31 % and a standard deviation of 0.00343.

Predicting the O'Kelly-Marotta scale score after flow-diverter stent placement using silent MRA.

Flow-diverter (FD) stents were developed to treat aneurysms that are difficult to treat with conventional coiling or surgery. This study aimed to compare usefulness of Silent MRA and TOF (time of flight) -MRA in patients with aneurysms after FD placement. We retrospectively collected images from 22 patients with 23 internal carotid artery aneurysms treated with FD. Two radiologists conducted MRA and DSA experiments. In the first reading experiment, the radiologists evaluated the aneurysm filling by employing Silent MRA and TOF-MRA and utilizing the modified O'Kelly-Marotta (OKM) scale, a four-class classification system for aneurysms after FD placement. We then calculated the agreement between the modified OKM scale on MRA and the original OKM scale on DSA. In the second reading experiment, the radiologists rated blood flow within the FD using a five-point scale. The weighted kappa value of the OKM scale between DSA and TOF-MRA was 0.436 (moderate agreement), and that between DSA and Silent MRA was 0.943 (almost perfect agreement). The accuracies for the four-class classification were 0.435 and 0.870 for TOF-MRA and Silent MRA, respectively. The mean score of blood flow within FD for TOF-MRA was 2.43 ± 0.90 and that for Silent MRA was 3.04 ± 1.02 (P < 0.001). Silent MRA showed a higher degree of agreement than TOF-MRA in aneurysm filling with DSA. In addition, Silent MRA was significantly superior to TOF-MRA in depicting blood flow within the FD. Therefore, Silent MRA is clinically useful for the follow-up of patients after FD placement.

Virtual flow diverter deployment and embedding for hemodynamic simulations

Flow-diverter stents offer clinicians an effective solution for treating intracranial aneurysms, especially in cases where other devices may be unsuitable. However, strongly deviating success rates among different centres, manufacturers, and aneurysm phenotypes highlight the need for better in-situ studies of these devices. To support research in this area, virtual stenting algorithms have been proposed that, combined with computational fluid dynamics, provide insights into the hemodynamic alterations induced by the device. Yet, many existing algorithms rely on uncertain parameters, such as the forces applied during operation, fail to predict the length of the device after deployment, or lack robust validation steps, raising concerns about their reliability. Therefore, we developed a robust deployment technique that builds upon the geometrical features of the vessel and includes advancements from previous works. The algorithm is detailed and validated against literature examples, in-vitro experiments, and patient data, achieving a mean angular error below 5° in the latter. Furthermore, we describe and demonstrate how the deployed device can be embedded in a computational mesh using open-source tools and anisotropic meshing routines.

Flow diversion for unruptured MCA bifurcation aneurysms: comparison of p64 classic, p64 MW HPC, and p48 MW HPC flow diverter stents.

MCA bifurcation aneurysms pose treatment challenges because of the complex hemodynamics at the bifurcation and the risk of rupture. FDS implantation has been controversial and there are only limited reports. Therefore, the aim of this study was to assess the efficacy and safety of this treatment strategy using p64 MW HPC and p48 MW HPC FDSs for MCA bifurcation aneurysms, compared with the p64 classic FDS. We retrospectively analyzed our institutional database and identified all patients with saccular, non-ruptured MCA bifurcation aneurysms treated with p64 MW HPC, p48 MW HPC, or p64 classic FDS implantation alone. Aneurysms with implantation of additional devices in the same session, previous treatments, and acutely ruptured and fusiform aneurysms were excluded. A total of 79 aneurysms met the inclusion criteria: 23 receiving a p64 MW HPC, 34 receiving a p48 MW HPC, and 22 receiving a p64 classic FDS. The occlusion rate was highest for the p48 MW HPC 2 mm FDS, at 88.9% at FU2, compared with 72.2% for the p64 MW HPC and 70.6% for the p64 classic. The time to aneurysm occlusion was shortest with the p64 MW HPC, at 178.31 days. The highest retreatment rate was observed with the p48 MW HPC 3 mm. Treatment of MCA bifurcation aneurysms with a p48 MW HPC 2 mm or p64 MW HPC FDS is a safe and reliable strategy achieving high aneurysm occlusion rates - attributable to their lower porosity in relation to the parent vessel diameter as compared to the p48 MW HPC 3 mm FDS-, with reasonable morbidity and mortality.

Pure arterial malformation of the fetal PCA treated with flow diverter stent-case report and literature review.

Thirty-three-year-old female underwent diagnostic work-up for chronic headaches. Cerebral DSA on the right side showed fetal posterior cerebral artery (PCA) with unusually shaped arterial malformation on its proximal part. Malformation was formed by multiple convolutions and loops with no arteriovenous shunting. During endovascular procedure, flow diverter stent was placed in the right C6 segment. Patient was put on double antiaggregation therapy. Four weeks after procedure, patient was admitted to ER with signs of dyphasia. No recent ischemic lesions were detected on emergent magnetic resonance. Dyphasia resolved spontaneously. On follow-up magnetic resonance angiography 5 years after the procedure, main portion of malformation has diminished with slightly filling of posterior part supplied by right P1. Here, reported finding is consistent with previously described pure arterial malformation (PAM). Main intention of our treatment was to induce malformation remodeling with flow diverter placement. Two main risks arise when using flow diverters on fetal PCA region. Firstly, there is possibility of occluding fetal PCA alongside malformation. On the contrary, high flow through fetal PCA could hinder malformation thrombosis. Some case series reported high rate of fetal PCA occlusion without ischemic sequelae in the PCA teritory. Others consider flow diverters highly ineffective treatment for the fetal PCA aneurysms due to low rate of complete aneurysm occlusion. We presented first reported case in which flow diverter was used to treat PAM. Slow malformation thrombosis leaves enough time for collateral circulation to recruit and supply territory of the vessel affected by the malformation.

Changes in blood biochemistry thrombosis parameters 24 hours after stent-assisted endovascular treatment of intracranial aneurysms.

This study aims to elucidate the early changes in blood biochemistry thrombosis parameters following stent-assisted endovascular treatment of intracranial aneurysms. Consecutive patients with unruptured aneurysms undergoing stent implantation during endovascular treatment were included in this prospective study with approval from the local ethics committee. Blood samples were collected immediately before and 24 h after the procedure for biochemical analysis, including basic thrombosis indicators, bleeding tests, and a complete blood count. The study included 80 patients (60 women, 20 men) with 134 aneurysms. A total of 135 stents (110 flow-diverting, 25 standard) were used. Additionally, intrasaccular coiling was utilized in 28 aneurysms among 27 patients. Following the procedure, there was a significant decrease in activated partial thromboplastin time, fibrinogen, hemoglobin, and platelet levels, and a significant increase in prothrombin time, D-dimer, von Willebrand factor (vWF) activity/antigen ratio, and leukocyte levels in all patients. Correlation analyses revealed significant positive associations between platelet and fibrinogen levels, and a negative association between D-dimer and fibrinogen levels in the coil (-) group. Additionally, there was a significant negative correlation between aneurysm volume and vWF activity/antigen ratio, and procedure duration and thrombocyte count, while a positive association was found between aneurysm number and leukocyte count in the coil (-) group. Analysis of blood chemistry alterations indicates that intravascular thrombosis occurs in the intracranial circulation following stent-assisted endovascular treatment of intracranial aneurysms. This thrombotic process is more pronounced in patients whose aneurysms were left open (i.e. flow-diverting stent alone).

Neurological outcomes of flow-diverter stent placement for middle cerebral artery aneurysms, with reference to the effects of argatroban on ischemic events: patient series.

A systematic review and meta-analysis of flow-diverter stents (FDSs) for the treatment of middle cerebral artery (MCA) aneurysms reported concerns about ischemic complications during treatment. The authors report on the intraoperative and postoperative complications of unruptured MCA aneurysms and their control strategies at their hospital, with detailed information on the aneurysms and a review of the previous literature. Intraoperative and perioperative in-stent thrombus occlusion occurred in 3 (37.5%) of the 8 patients evaluated. In cases with in-stent thrombus formation, rapid administration of 10 mg argatroban led to improvement in blood flow, as seen on angiography. Only 1 patient (12.5%) had a symptomatic stroke postoperatively. This patient was admitted for rehabilitation and drug therapy but was discharged from the hospital 10 days postoperatively with a modified Rankin Scale (mRS) score of 1. The patient had an mRS score of 0 at 90 days after surgery and at the last observation. Ischemic complications require attention during FDS treatment for MCA aneurysms. The use of argatroban in cases of in-stent thrombosis may contribute to a good neurological prognosis. https://thejns.org/doi/10.3171/CASE24237.

Endothelial Cell Transcription Modulation in Cerebral Aneurysms After Endovascular Flow Diversion.

Flow diverting stents (FDS) are used to treat cerebral aneurysms, by promoting thrombosis and occlusion of the aneurysm sac. However, retreatment is required in some cases, and the biologic basis behind treatment outcome is not known. The goal of this study was to understand how changes in hemodynamic flow after FDS placement affect aneurysmal endothelial cell (EC) activity. Three-dimensional models of patient-specific aneurysms were created to quantify the EC response to FDS placement. Computational fluid dynamic simulations were used to determine the hemodynamic impact of FDS. Two identical models were created for each patient; into one a FDS was inserted. Each model was then populated with human carotid ECs and subjected to patient-specific pulsatile flow for 24 h. ECs were isolated from aneurysm dome from each model and bulk RNA sequencing was performed. Paired untreated and treated models were created for four patients. Aneurysm dome EC analysis revealed 366 (2.6%) significant gene changes between the untreated and FDS conditions, out of 13909 total expressed genes. Gene set enrichment analysis of the untreated models demonstrated enriched gene ontology terms related to cell adhesion, growth/tensile activity, cytoskeletal organization, and calcium ion binding. In the FDS models, enriched terms were related to cellular proliferation, ribosomal activity, RNA splicing, and protein folding. Treatment of cerebral aneurysms with FDS induces significant EC gene transcription changes related to aneurysm hemodynamics in patient-specific in vitro 3D-printed models subjected to pulsatile flow. Further investigation is needed into the relationship between transcriptional change and treatment outcome.

Review: Flow Diversion for the Treatment of Middle Cerebral Artery Aneurysms.

The invention of flow diverting stents (FDS) is a novel milestone in the field of endovascular aneurysm therapy, promoting physiological healing of the vessel segment contrary to prior deconstructive treatment strategies, such as coiling. The effects of FDS are based on changes in flow patterns, segmental wall stabilization, and the growth of a neointima. Although flow diversion is already well established for cerebral aneurysms in proximal segments, peripheral locations remain challenging. Especially the middle cerebral artery (MCA) with its predominance of non-collateralized perforators and functional end arteries that supply the eloquent areas of the brain is of major concern.The literature was reviewed for flow diversion of the MCA and antiplatelet therapy.Resulting from the special anatomical characteristics of the MCA, FDS implantation in this territory is completely different from the proximal vessel segments. Still, flow diversion represents an effective endovascular strategy, especially in otherwise non-accessible or sufficiently treatable lesions. However, the risk of ischemic adverse events might be increased. Special attention to the individual decision regarding device selection, antiplatelet regimen, and exact definition of the proximal and distal landing zone considering the jailed side branches is essential for a good angiographic and clinical outcome. · MCA aneurysms can be sufficiently treated by FDS.. · The anatomic and hemodynamic characteristics of the MCA result in an increased risk of thromboembolism.. · Individual device selection and antiplatelet regimen are essential for treatment success.. · Schüngel M, Wohlgemuth WA, Elolf E et al. Review: Flow Diversion for the Treatment of Middle Cerebral Artery Aneurysms. Fortschr Röntgenstr 2024; DOI 10.1055/a-2343-0046.

In vitro evaluation of flow diverter performance using a human fibrinogen-based flow model.

Fibrin deposition represents a key step in aneurysm occlusion, promoting endothelization of implants and connective tissue organization as part of the aneurysm-healing mechanism. In this study, the authors introduce a novel in vitro testing platform for flow diverters based on human fibrinogen. A flow diverter was deployed in 4 different glass models. The glass models had the same internal parent artery (4 mm) and aneurysm (8 mm) diameters with varying parent artery angulations (paraophthalmic, sidewall, bifurcation, and slightly curved models). The neck size and area were 4 mm and 25 mm2, respectively. Human fibrinogen (330 mg/dl) was circulated within the glass models at varying flow rates (0, 3, 4, and 5 ml/sec) with or without heparin, calcium chloride, and thrombin for as long as 6 hours or until complete fibrin coverage of the flow diverter's neck was achieved. Aneurysm neck coverage was defined as macroscopic fibrin deposition occluding the flow diverters' pores. Flow characteristics after flow diverter deployment were assessed with computational fluid dynamics analysis. The effects of flow rates, heparin, calcium chloride, and thrombin on fibrin deposition rates were tested using 1-way ANOVA and the Tukey test. A total of 84 replicates were performed. Human fibrin did not accumulate on the flow diverter stents under static conditions. The fibrin deposition rate on the aneurysm neck was significantly greater with the 5 ml/sec flow rate as compared to 3 ml/sec for all models. The paraophthalmic model had the highest inflow velocity of 48.7 cm/sec. The bifurcation model had the highest maximum shear stress (SS) and maximum normalized shear stress values at the device cells at 843.3 dyne/cm2 and 35.1 SS/SSinflow, respectively. The fibrin deposition rates of the paraophthalmic and bifurcation models were significantly higher than those of sidewall and slightly curved models for all additive or flow rate comparisons (p = 0.001 for all comparisons). The incorporation of thrombin significantly increased the fibrin deposition rates across all models (p = 0.001 for all models). Rates of fibrin deposition varied widely across different configurations and additive conditions in this novel in vitro model system. Fibrin accumulation started at the aneurysm inflow zone where flow velocity and shear stress were the highest. The primary factors influencing fibrin deposition included flow velocities, shear stress, and the addition of thrombin at a physiological concentration. Further research is needed to test the clinical utility of fibrinogen-based models for patient-specific aneurysms.