Fluoroscopy, CT, and MR imaging characteristics of a novel primarily bioresorbable flow-diverting stent for aneurysms

Background Five to ten percent of the global population have unruptured intracranial aneurysms, and ruptured brain aneurysms cause approximately 500,000 deaths a year. Flow-diverting stent treatment is a less invasive intracranial aneurysm treatment that induces aneurysm thrombosis. The imaging characteristics of a novel primarily bioresorbable flow-diverting stent (BFDS) are assessed in comparison to the leading metal stent using fluoroscopy, CT, and MRI. Methods X-ray/fluoroscopic images of stents were taken using a human cadaveric skull model. CT and MRI were acquired using silicone flow models of residual aneurysms. Images were analyzed with Likert scales in anonymous surveys by neurointerventionalists. Quantitative measurements of radiographic density (CT) and artifact boundary size (CT & MRI) were also obtained. Results Visibility of the BFDS on X-ray was less than the metal stent but deemed adequate for deployment and intraprocedural assessment. The metal stent was more radiopaque than the BFDS on CT, but qualitative assessment was not significantly different for the two stents. MRI imaging was significantly better using the BFDS in terms of overall artifact and intraluminal assessment. Conclusions The BFDS has adequate visualization on X-ray/fluoroscopy and should be clinically acceptable for fluoroscopic deployment. On MRI, there is less quantitative artifact as well as overall improved qualitative assessment that will allow for more detailed non-invasive imaging follow-up of treated aneurysms, potentially reducing the need for digital subtraction catheter angiography.

Design and Analysis of a Biodegradable Polycaprolactone Flow Diverting Stent for Brain Aneurysms

The flow diverting stent (FDS) has become a promising endovascular device for the treatment of aneurysms. This research presents a novel biodegradable and non-braided Polycaprolactone (PCL) FDS. The PCL FDS was designed and developed using an in-house fabrication unit and coated on two ends with BaSO4 for angiographic visibility. The mechanical flexibility and quality of FDS surfaces were examined with the UniVert testing machine, scanning electron microscope (SEM), and 3D profilometer. Human umbilical vein endothelial cell (HUVEC) adhesion, proliferation, and cell morphology studies on PCL FDS were performed. The cytotoxicity and NO production by HUVECs with PCL FDS were also conducted. The longitudinal tensile, radial, and bending flexibility were found to be 1.20 ± 0.19 N/mm, 0.56 ± 0.11 N/mm, and 0.34 ± 0.03 N/mm, respectively. The FDS was returned to the original shape and diameter after repeated compression and bending without compromising mechanical integrity. Results also showed that the proliferation and adhesion of HUVECs on the FDS surface increased over time compared to control without FDS. Lactate dehydrogenase (LDH) release and NO production showed that PCL FDS were non-toxic and satisfactory. Cell morphology studies showed that HUVECs were elongated to cover the FD surface and developed an endothelial monolayer. This study is a step forward toward the development and clinical use of biodegradable flow diverting stents for endovascular treatment of the aneurysm.

Determinants of intracranial aneurysm retreatment following embolization with a single flow-diverting stent

Purpose Flow diverting stents have revolutionized the treatment of intracranial aneurysms through endoluminal reconstruction of the parent vessel. Despite this, certain aneurysms require retreatment. The purpose of this study was to identify clinical and radiologic determinants of aneurysm retreatment following flow diversion. Methods A multicenter flow diversion database was evaluated to identify patients presenting with an unruptured, previously untreated aneurysm with a minimum of 12 months’ clinical and angiographic follow-up. Univariate and multivariate logistic regression modeling was performed to identify determinants of retreatment. Results We identified 189 aneurysms treated in 189 patients with a single flow-diverting stent. Mean age was 54 years, and 89% were female. Complete occlusion was achieved in 70.3% and 83.6% of patients at six and 12 months, respectively. Aneurysm retreatment with additional flow-diverting stents occurred in 5.8% of cases. Univariate analysis revealed that dome diameter [Formula: see text]10 mm ( p = 0.012), pre-clinoid internal carotid artery location ( p = 0.012), distal > proximal parent vessel diameter ( p = 0.042), and later dual antiplatelet therapy (DAPT) discontinuation ( p < 0.001) were predictive of retreatment. Multivariate analysis identified discontinuation of DAPT [Formula: see text]12 months ( p = 0.003) as a strong determinant of retreatment with dome diameter [Formula: see text]10 mm trending toward statistical significance ( p = 0.064). Large aneurysm neck diameter, presence of aneurysm branch vessels, patient age, smoking history, and hypertension were not determinant of retreatment on multivariate analysis. Conclusions Prolonged DAPT is the most important determinant of aneurysm retreatment following single-device flow diversion. Abbreviating DAPT duration to only six months should be a consideration in this population, especially for patients with a large aneurysm dome diameter.

Abstract 1122‐000218: Flow Reversal After Stent Diversion Causes In‐Stent Thrombosis and Anemia‐Driven Ischemia

Introduction : Large symptomatic ICA aneurysms are rare, but present a life threatening risk of rupture that increases with size, female sex, and age >50 at the time of diagnosis, among other risk factors. Historically, large carotid aneurysms have been treated with intentional carotid sacrifice, requiring recruitment of contralateral, posterior, and ECA‐supplied collaterals to provide flow to the anterior circulation previously supplied by the sacrificed ICA, lest the patient experience an iatrogenic stroke. While still a viable option in some cases, flow diverting stents provide an attractive alternative to vessel sacrifice. By providing a channel for blood to bypass the aneurysm, the stent can effectively exclude the aneurism from active circulation while preserving a path for blood to travel to the anterior cerebral circulation it currently provides. Methods : Here, we present a case of a 1.3 cm symptomatic left cavernous ICA aneurysm treated with such a flow diverting stent. Results : The patient presented to the emergency department with left sided ptosis. CTA head and neck revealed the 1.3 cm left sided cavernous ICA aneurysm. She was treated endovascularly under general anesthesia with continuous intra‐operative monitoring. The procedure was complicated by iatrogenic flow reversal through the Circle of Willis at the time of stent deployment and resultant in situ thrombosis of the stent without alteration in electrical signals recorded at the scalp – thus creating a de facto carotid sacrifice without intra‐operative complication. Follow up doppler study revealed a loss of flow through the left ICA and reversal of flow through the ophthalmic artery on the left side, thus confirming ECA collateral supply to the area. Post‐op course was complicated by extensive bleeding from the scalp electrode sites used for intraoperative monitoring due to hyper‐response to aspirin‐ticagrelor dual‐antiplatelet therapy. This gave rise to a symptomatic anemia that manifested as pressure‐dependent left‐sided circulatory failure on exam – specifically hemiparesis and aphasia. The symptoms ultimately resolved with pressure augmentation, blood transfusion, and supportive care in the Neuro ICU. The patient was successfully transitioned to a general neurology floor with subsequent resolution of the anemia and, correspondingly, the symptoms. Conclusions : The patient was discharged to rehab and at 4‐month follow‐up is again living independently with no residual deficits. This case has significance for pre‐operative anti‐platelet optimization for flow diverting stents, management of post‐operative complications of flow‐diverting stent placement including thrombosis and bleeding, and optimal critical care support for patients with pressure‐dependent ischemia. Specifically, the course of the patient’s symptoms and anemia raise the question of optimal hemoglobin targets in the subset of patients with pressure‐dependent ischemia, and how to best reach those targets.

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

Background: We describe the treatment of a renal artery aneurysm with complex anatomy using coils and the Pipeline (TM) 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: Pipeline (TM) assisted coil embolization may be an option for parenchyma-sparing treatment of renal artery aneurysms with complex anatomy.

In-silico trial of intracranial flow diverters replicates and expands insights from conventional clinical trials

The cost of clinical trials is ever-increasing. In-silico trials rely on virtual populations and interventions simulated using patient-specific models and may offer a solution to lower these costs. We present the flow diverter performance assessment (FD-PASS) in-silico trial, which models the treatment of intracranial aneurysms in 164 virtual patients with 82 distinct anatomies with a flow-diverting stent, using computational fluid dynamics to quantify post-treatment flow reduction. The predicted FD-PASS flow-diversion success rates replicate the values previously reported in three clinical trials. The in-silico approach allows broader investigation of factors associated with insufficient flow reduction than feasible in a conventional trial. Our findings demonstrate that in-silico trials of endovascular medical devices can: (i) replicate findings of conventional clinical trials, and (ii) perform virtual experiments and sub-group analyses that are difficult or impossible in conventional trials to discover new insights on treatment failure, e.g. in the presence of side-branches or hypertension.

Silk Vista Baby Is a Safe and Technically Feasible Flow Diverting Stent for Distal Aneurysm Treatment

Background and Purpose: Flow diverting stents are designed to divert blood flow from the aneurysm sac, allowing for eventual occlusion following endovascular therapy. This case series reports clinical experience using the Silk Vista Baby (SVB, Balt Extrusion, Montmorency, France), a flow diverter (FD) designed to treat intracranial aneurysms in small, distal vessels.Methods: All patients who underwent treatment with SVB at the University Hospital “Santa Maria della Misericordia” of Udine between July 2018 and September 2020 were retrospectively identified. Baseline patient and aneurysm characteristics, intraprocedural technical outcomes, periprocedural complications, modified Rankin Scale (mRS) at discharge, magnetic resonance imaging (MRI) results at 3-month follow-up, and angiographic results at 6-month follow-up were collected.Results: A total of 18 patients (55.6% [10/18] male; mean age 62.6 years, range: 42–77 years) were retrospectively identified, receiving treatment for 22 aneurysms. Most patients were symptomatic (14/18, 77.8%) and approximately half had subarachnoid hemorrhage (10/18, 55.6%). Sufficient aneurysm coverage was achieved in 88.9% (16/18) of patients with a single device. Mortality did not occur (0/18, 0%); adverse device-related events included side branch occlusion (1/18, 5.6%) and in-stent thrombosis (1/18, 5.6%). At discharge, 77.8% (14/18) had an mRS of 0. In most cases, patients showed complete occlusion (10/15, 66.7%) or a small aneurysmal remnant (3/15, 20.0%) upon MRI; upon angiography, most showed complete occlusion (10/13, 76.9%) or only a small aneurysmal remnant (2/13, 15.4%).Conclusion: This case series showed that the SVB FD is safe and feasible to use in patients with aneurysms in small, distal vessels. Additional randomized, prospective studies with larger cohorts are needed for the SVB.

In-silico trial of intracranial flow diverters replicates and expands insights from conventional clinical trials

Although the cost of clinical trials is ever-increasing, in-silico trials, which rely on virtual populations and interventions simulated using patient-specificc models, may offer a solution to contain these costs. However, in-silico trial endpoints need to be compared to those available from conventional clinical trials to ensure that the predictions of safety or effcacy from the in-silico approach are valid. Here, we present the flow diverter performance assessment (FDPASS) in-silico trial, which modelled the treatment of intracranial aneurysms in 82 virtual patients with a flow-diverting stent, using computational fluid dynamics (CFD) to quantify post-treatment flow reduction in the aneurysm sac. The predicted FD-PASS flow-diversion success rate replicated the values previously reported in three reference clinical trials. The in-silico approach allowed broader investigation of factors associated with insuficient flow reduction and increased stroke risk after flow diversion than would be feasible in a conventional trial. These ndings demonstrate for the rst time that in-silico trials of medical devices can (i) replicate ndings of conventional clinical trials and (ii) incorporate virtual experiments that are impossible in conventional trials.

In-silico trial of intracranial flow diverters confirms and expands insights from conventional clinical trials

Although the cost of clinical trials is ever-increasing, in-silico trials, which rely on virtual populations and interventions simulated using patient-specificc models, may offer a solution to contain these costs. However, in-silico trial endpoints need to be compared to those available from conventional clinical trials to ensure that the predictions of safety or effcacy from the in-silico approach are valid. Here, we present the flow diverter performance assessment (FDPASS) in-silico trial, which modelled the treatment of intracranial aneurysms in 82 virtual patients with a flow-diverting stent, using computational fluid dynamics (CFD) to quantify post-treatment flow reduction in the aneurysm sac. The predicted FD-PASS flow-diversion success rate replicated the values previously reported in three reference clinical trials. The in-silico approach allowed broader investigation of factors associated with insuficient flow reduction and increased stroke risk after flow diversion than would be feasible in a conventional trial. These ndings demonstrate for the rst time that in-silico trials of medical devices can (i) replicate ndings of conventional clinical trials and (ii) incorporate virtual experiments that are impossible in conventional trials.