Porosity distribution upon the surface of a deployed flow diverter: an experimental and simulation study

Endovascular intervention using traditional neurovascular stents and densely braided flow diverters (FDs) have become the preferred treatment strategies for traditionally challenging intracranial aneurysms. Modeling stent and FD deployment in patient-specific aneurysms and its flow modification results prior to the actual intervention can potentially predict the patient outcome and treatment optimization. We present a clinically focused, streamlined virtual stenting workflow that efficiently simulates stent and FD treatment in patient-specific aneurysms based on expanding a simplex mesh structure. The simplex mesh is generated using an innovative vessel-specific initialization technique, which uses the patient’s parent artery diameter to identify the initial position of the simplex mesh inside the artery. A novel adaptive expansion algorithm enables the acceleration of deployment process by adjusting the expansion forces based on the distance of the simplex mesh from the parent vessel. The virtual stenting workflow was tested by modeling the treatment of two patient-specific aneurysms using the Enterprise stent and the Pipeline Embolization Device (commercial FD). Both devices were deployed in the aneurysm models in a few seconds. Computational fluid dynamics analyses of pre- and post-treatment aneurysmal hemodynamics show flow reduction in the aneurysmal sac in treated aneurysms, with the FD diverting more flow than the Enterprise stent. The test results show that this workflow can rapidly simulate clinical deployment of stents and FDs, hence paving the way for its future clinical implementation.

Background Placement of flow diverter (FD) is an endovascular technique where the flow to the aneurysm is directed away from the aneurysmal sac using a stent in the parent vessel. In this clinical report, the authors share their institutional experience pertaining to clinical course of patients with intracranial aneurysm requiring placement of FD. Materials and Methods After approval from institute ethics committee (IEC), the authors retrospectively studied all patients who underwent placement of FD for intracranial aneurysms from January 2014 to December 2017. Data regarding patient demographics, presenting complaints, aneurysm details, anesthesia technique, and intra- and postprocedural complications were noted. Duration of hospital stay, neurological outcome as measured by Glasgow outcome scale (GOS) at discharge and at 6 months was noted. Data are presented as median (range) or number (%). Results Over a period of 3 years, 22 patients underwent FD placement. Two patients had subarachnoid hemorrhage (SAH) at the time of presentation, and the rest had unruptured aneurysms. All patients received general anesthesia (GA) for the procedure, and intravenous propofol was used for induction of anesthesia. Majority of the patients received sevoflurane and nitrous oxide combination for maintenance of anesthesia (20/22 [91%]). Five patients were not extubated at the end of the procedure. The most common indication for mechanical ventilation was delayed reversal because of hypothermia. At 6 months of follow-up, GOS was 5 in 18 patients. None of the patients developed any delayed complications related to FD and were neurologically intact. Conclusions The use of FD for the treatment of aneurysms is a safe option. GA was used for carrying out procedure in all patients. The neurological outcome was good in all patients who were followed at 6 months.

Background/Purpose Flow diverter porosity directly influences the blood flow reduction at the aneurysm neck level and the anatomical result of the treatment. In this research, we present and compare three methodologies to determine the local porosity of deployed flow diverters. Method Three-dimensional rotational angiography was used to obtain computational vessel models of three patients. Different flow diverters were virtually deployed in the computational models and implanted in 3D-printed models of the vasculatures by interventional neuroradiologists. Experimental porosity determinations were conducted using 2D microscope photographs and 3D Dyna-CT images (i.e. cone-beam Computed Tomography angiographic images), while simulated porosity was computed using ANKYRAS software. Results No statistically significant differences were observed between the porosity distributions from the three methods (p > 0.01). When computing the differences point-by-point, narrow distributions centered on zero were obtained, revealing a good agreement in the determinations. Orthogonal regression analysis affirmed this equivalence. The lowest agreement between porosity measurement methods was observed to occur at curve segments with relatively low porosity. Conclusions The local porosity of deployed flow diverters can be accurately determined by the three methods presented in this work. Assessing FD porosity with 3D Dyna-CT images would allow the evaluation of real patient data, whereas simulations could determine local porosity before the treatment.

Flow diversion is a new endovascular technique developed for treatment of intracranial aneurysms. It is based on stent-induced modification of blood flow within and around an aneurysm inflow zone, leading to gradual intra-aneurysmal thrombosis and subsequent atrophy, while preserving flow into the parent vessel and perforating branches. Flow-diversion technique is well-suited for the treatment of large, giant, wide-necked, and fusiform intracranial aneurysms because it does not rely on endosaccular packing with coils but rather on the strategy of placing a stent across the aneurysm “neck” or across the diseased segment of a vessel in case of a fusiform aneurysm. Over time, neointimal endothelium covers the flow diverter such that it becomes incorporated into the parent vessel wall and occludes the aneurysm from the circulation, effectively repairing the diseased parent vessel segment. This report describes in detail the Pipeline embolization device (ev3-Covidien, Irvine, California, USA), its mechanism of action and deployment technique, and reviews the pertinent literature regarding safety, efficacy and potential risks and complications associated with the use of this flow diverter.

Background: Treatment of cerebral aneurysms using hemodynamic implants such as endosaccular flow disruptors and endoluminal flow diverters has gained significant momentum during recent years. The intended target zone of those devices is the immediate interface between aneurysm and parent vessel. The therapeutic success is based on the reduction of aneurysmal perfusion and the subsequent formation of a neointima along the surface of the implant. However, a subset of aneurysms–off-centered bifurcation aneurysms involving the origin of efferent branches and aneurysms arising from peripheral segments of small cerebral vessels–oftentimes cannot be treated via coiling or implanting a hemodynamic implant at the neck level for technical reasons. In those cases, indirect flow diversion–a flow diverter deployed in the main artery proximal to the parent vessel of the aneurysm–can be a viable treatment strategy, but clinical evidence is lacking in this regard.Materials and Methods: Five neurovascular centers contributed to this retrospective analysis of patients who were treated with indirect flow diversion. Clinical data, aneurysm characteristics, anti-platelet medication, and follow-up results, including procedural and post-procedural complications, were recorded.Results: Seventeen patients (mean age: 60.5 years, range: 35–77 years) with 17 target aneurysms (vertebrobasilar: n = 9) were treated with indirect flow diversion. The average distance between the flow-diverting stent and the aneurysm was 1.65 mm (range: 0.4–2.4 mm). In 15/17 patients (88.2%), perfusion of the aneurysm was reduced immediately after implantation. Follow-ups were available for 12 cases. Delayed opacification (OKM A3: 11.8%), reduction in size (OKM B1-3: 29.4%) and occlusion (D1: 47.1%) were observable at the latest investigation. Clinically relevant procedural complications and adverse events in the early phase and in the late subacute phase were not observed in any case.Conclusion: Our preliminary data suggest that indirect flow diversion is a safe, feasible, and effective approach to off-centered bifurcation aneurysms and distant small-vessel aneurysms. However, validation with larger studies, including long-term outcomes and optimized imaging, is warranted.

Background and Purpose Cavernous carotid aneurysms can cause pain and ophtalmoplegia from mass effect, but they rarely rupture or cause life threatening complications. Treatment options include observation, parent vessel occlusion, coil embolization, or in the last decade flow-diversion (FD). We aimed to compare the results of FD with more conventional treatments in patients with cavernous aneurysms recruited in the Flow Diverter in the Treatment of Aneurysms trial (FIAT). Materials and methods FIAT, conducted in 3 Canadian hospitals, proposed randomized allocation to flow diversion or standard management options (observation, coil embolization, parent vessel occlusion, or clip placement), and a registry of nonrandomized patients treated with flow diversion. The primary safety outcome was death or dependency (modified Rankin Scale score >2) at 3 months, to be determined for all patients who received flow diversion at any time. The primary efficacy outcome was angiographic occlusion at 3–12 months combined with an independent clinical outcome. Results Forty-two patients with cavernous aneurysms were included in the FIAT study. In 31 patients, treatment was randomly allocated: 17 were treated with FD, 14 using best standard treatment (BST). Eleven patients treated with FD were judged untreatable otherwise. An hemorrhagic complication occurred in 3/28 patients treated with FD (11%; 3.7%–27.2%), as compared to 0/14 with BST (0%–21.5%) Overall, we had a 3% mortality rate and a 7% major neurologic complication rate. Conclusion Flow diversion in CCAs was not safe as hypothesized. We observed unusual and potentially fatal hemorrhagic complications in patients treated with FD that need to be attentively analyzed, especially considered that CCAs hemorrhagic presentation is a rare event. More randomized trials are needed to determine the role of flow diversion in the management of cavernous carotid aneurysms. Disclosures L. Nico: 1; C; Medtronic-Covidien. A. Weill: None. D. Roy: None. J. Raymond: None.

IntroductionContrast usage for Cone Beam Angiographic Computed Tomography (CBCTA) performance has limited efficacy for simultaneous visualization of vasculature, implanted devices, and surrounding tissue. Optimal windowing of CBCTA images in order...

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.

Background: Intracranial aneurysms arising from small parent vessels (<2 mm) are challenging due to their fragile anatomy and distal locations. Flow diversion (FD) offers a promising treatment, but its safety and efficacy in small vessels remain underexplored. Objective: To evaluate angiographic occlusion rates and procedure-related morbidity associated with flow diversion for intracranial aneurysms arising from parent vessels <2 mm in diameter. Methods: A retrospective cohort study was conducted at Bicêtre Hospital, Paris, France, from January 2018 to December 2023, analyzing 50 patients undergoing 56 procedures for 55 aneurysms. FD devices (e.g., Silk Vista Baby, Pipeline Flex) were used. Follow-up at 6, 18, and 42 months assessed occlusion via digital subtraction angiography (DSA) using Raymond-Roy and O’Kelly-Marotta scales. Results: Complete occlusion was achieved in 70.9% (39/55) of aneurysms at a mean follow-up of 17.86 months. At 6, 18, and 42 months, occlusion rates were 56.4%, 55.6%, and 76.5%, respectively. Intraprocedural complications occurred in 28.6% (16/56) of procedures, with 19.6% (11/56) due to in-stent thrombosis. Symptomatic major complications were observed in 17.9% (10/56), including ischemic events and hemorrhage, and permanent FD-related morbidity was 8.0% (4/50). Conclusion: FD is effective for small vessel aneurysms, with high occlusion rates, but significant complications highlight the need for careful patient selection and refined techniques. Larger studies are needed to optimize outcomes.

Lessons Learned from Endovascular Coil Embolization of Pericallosal Artery Aneurysms and Adoption of Flow Diversion: A Retrospective Cohort Assessment of the Efficacy of Coiling and Flow Diversion

Introduction Flow diversion with the Pipeline Embolization Device (PED) provides a dramatic new tool for the treatment of intracranial aneurysms, though its use has been marked by technical nuances and challenges, particularly related to the delivery system. The Pipeline Flex provides a new delivery system, allowing more precise deployment. Here we report the use of the new PED Flex system in a child with a giant, symptomatic intracranial aneurysm. Materials and methods A 7 year-old boy with right eye vision loss was discovered to have a giant aneurysm of the right internal carotid artery (ICA) extending from the cavernous segment to the carotid terminus (Figure 1). The aneurysm was fusiform and measured 3.5 cm. He was treated with aspirin and clopidogrel and doses were adjusted based on VerifyNow assays. A 3D model of the aneurysm and parent vessel was created, and several Pipeline configurations were rehearsed prior to the procedure. A 6 French Shuttle Sheath (Cook) was used as the guide catheter. A multi-PED construct was created across the aneurysm, using a total of six devices (Figure 1). All devices were deployed without difficulty, and occasional device distortions were easily corrected with resheathing and redeployment. After the construct was complete, partial coil embolization of the aneurysm was performed. Results The patient awoke without new symptoms, but did have some vision loss of the contralateral eye over the ensuing three months related to aneurysmal thrombosis and inflammation. He was treated with multiple courses of steroids and his vision improved in the contralateral eye. Platelet inhibition was monitored and required frequent clopidogrel dose adjustments. Follow up angiography was performed at 6 months, and will be presented. Conclusion Flow diversion is a powerful tool for the treatment of large and giant aneurysms, and may also be used in children. This case demonstrates the utility of the PED Flex in creating a complex, multi-device construct in a 7-year-old child with a giant aneurysm, and provides a number of useful observations: a 6 French sheath may be used in a 7-year-old child if needed; the Pipeline Flex offers additional precision in deployment; rehearsal of comple procedures using a 3D model can be very useful; and clopidogrel dosing in children is often a moving target, and requires frequent laboratory monitoring of platelet inhibition and dose adjustment. Disclosures M. Froehler: None.

CFD modeling of blood flow following coil embolization of aneurysms

Background: In the last decade, flow diversion (FD) has been established as hemodynamic treatment for cerebral aneurysms arising from proximal and distal cerebral arteries. However, two significant limitations remain—the need for 0.027” microcatheters required for delivery of most flow diverting stents (FDS), and long-term dual anti-platelet therapy (DAPT) in order to prevent FDS-associated thromboembolism, at the cost of increasing the risk for hemorrhage. This study reports the experience of three neurovascular centers with the p64MW-HPC, a FDS with anti-thrombotic coating that is implantable via a 0.021” microcatheter.Materials and methods: Three neurovascular centers contributed to this retrospective analysis of patients that had been treated with the p64MW-HPC between March 2020 and March 2021. Clinical data, aneurysm characteristics, and follow-up results, including procedural and post-procedural complications, were recorded. The hemodynamic effect was assessed using the O'Kelly–Marotta Scale (OKM).Results: Thirty-two patients (22 female, mean age 57.1 years) with 33 aneurysms (27 anterior circulation and six posterior circulation) were successfully treated with the p64MW-HPC. In 30/32 patients (93.75%), aneurysmal perfusion was significantly reduced immediately post implantation. Follow-up imaging was available for 23 aneurysms. Delayed aneurysm perfusion (OKM A3: 8.7%), reduction in aneurysm size (OKM B1-3: 26.1%), or sufficient separation from the parent vessel (OKM C1-3 and D1: 65.2%) was demonstrated at the last available follow-up after a mean of 5.9 months. In two cases, device thrombosis after early discontinuation of DAPT occurred. One delayed rupture caused a caroticocavernous fistula. The complications were treated sufficiently and all patients recovered without permanent significant morbidity.Conclusion: Treatment with the p64MW-HPC is safe and feasible and achieves good early aneurysm occlusion rates in the proximal intracranial circulation, which are comparable to those of well-established FDS. Sudden interruption of DAPT in the early post-interventional phase can cause in-stent thrombosis despite the HPC surface modification. Deliverability via the 0.021” microcatheter facilitates treatment in challenging vascular anatomies.

Basilar trunk perforator (BTP) aneurysms are rare lesions that pose significant challenges to microsurgical clipping and endovascular coiling. We present the intriguing case of a ruptured BTP aneurysm that was successfully treated with the Pipeline Embolization Device (PED). An elderly woman presenting with subarachnoid hemorrhage was found to have a 1.5-mm aneurysm arising from the proximal portion of a thin midbasilar perforator. The decision was made to treat this aneurysm with flow diversion in an attempt to preserve the patency of the perforator and to avoid the hazards associated with parent vessel trapping. A 3 × 12-mm PED was successfully deployed in the basilar trunk across the neck of the aneurysm, causing stasis in the aneurysm, with continuous flow through the parent vessel. The procedure and postoperative course were uneventful. A follow-up angiogram 2 weeks later showed complete disappearance of the aneurysm with preservation of the patency of the perforator. At the 6-month follow-up, the patient was asymptomatic and remained neurologically intact. We present the first case of a BTP aneurysm treated with the PED. The aneurysm was successfully occluded, and the patency of the feeding vessel was preserved. In light of the limitations of coiling and the hazards associated with microsurgery and parent vessel trapping, the PED may be a valuable option for BTP aneurysms.

Introduction: Intracranial aneurysms are associated with local degradation of the vessel wall resulting in the formation of a blood-filled sac. Approximately 6 million people are estimated to have intercranial saccular aneurysms in the US alone. Most aneurysms remain undetected until rupture, resulting in hemorrhage which carries a high mortality rate (>50%). Flow diverters are placed across the aneurysm neck to divert blood flow away from the sac, preventing rupture once occluded. However, flow diverters carry significant risk for thromboembolism, which is a major cause of morbidity. The elevated risk of thromboembolism is likely due to endothelial injury of the parent artery at the neck of the aneurysm. We hypothesize that the bionanomatrix can promote faster endothelialization and aneurysm occlusion thereby reducing the risk of thromboembolism after flow diverter treatment. Methods: The bionanomatrix is composed of peptide amphiphiles containing endothelial cell adhesive ligand (YIGSR) and a nitric oxide (NO) donor (KKKKK), both components critical for recruiting and retaining endothelial cells on the device. The NO releasing bionanomatrix was coated onto the flow diverters using ultrasonic spray coating, and the NO effects on endothelial cell (EC) and smooth muscle cell (SMC) proliferation on the coated devices was assessed, in vitro, using calcien-AM staining. For the in vivo study, an elastase-induced rabbit aneurysm model was created. The bionanomatrix coated and uncoated flow diverters were implanted into the rabbit aneurysm model for 4 weeks. The coated and uncoated flow diverters were then analyzed for endothelialization, smooth muscle cell proliferation, and aneurysm occlusion by angiography, gross image, and immunohistochemistry analyses. Results: In vitro, the bionanomatrix coated flow diverters significantly enhanced endothelial cell proliferation as well as reduced smooth muscle cell proliferation on the flow diverters compared to the uncoated device. In vivo, after 4 weeks, the bionanomatrix coated flow diverters demonstrated enhanced neck coverage, more complete endothelialization, and reduced smooth muscle thickness on the coated flow diverters compared to the uncoated devices as seen by gross image analysis and histology. Conclusions: The bionanomatrix coated flow diverters can successfully promote faster endothelialization and brain aneurysm occlusion which is critical for reducing the risk of thromboembolism after neurointervention.