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Introduction EXCELLENT (NCT03685578) is a prospective, single-arm, multicenter, real-world international registry of mechanical thrombectomy (MT) for stroke with the EmboTrap device as first line treatment. The study entails thrombus analysis of specimens collected with each MT pass. Aim of the Study To compare rates of mRS 0–2 at 90 days and clot characteristics in subjects with and without first pass effect (FPE). Methods FPE was defined as mTICI 2c/3 after one pass and non-FPE as mTICI 2c/3 after >1 pass as adjudicated by an independent core lab. Clot analysis was performed by independent central labs blinded to clinical data. mRS at 90 days was scored by investigators blinded to procedural data. Results Overall mTICI2c/3 rates were 63.7% (326/512). FPE was achieved in 37.1% (190/512) and non-FPE in 26.6% (136/512) subjects. 90 day mRS 0–2 or equal to pre-stroke was achieved in 47.2% (75/159) with FPE and in 42.1% (51/121) non-FPE patients. All-cause 90-day mortality was 19.1% (34/178) in subjects with FPE and 26.4% (34/129) in subjects with non-FPE. Major thrombus components (mean% ±SD) were as follows: RBC: FPE 45.88±20.54, non-FPE 39.08±18.23, and first pass mTICI Conclusions The high rate of ‘real-world’ FPE observed in EXCELLENT was associated with improved clinical outcomes. Clots retrieved with FPE had higher RBC and lower fibrin content compared to non FPE and to first pass mTICI Disclosure EXCELLENT is sponsored by Cerenovus. Dr. Jovin is a consultant for Neuravi, Codman Neurovascular, Stryker (PI DAWN; unpaid), Fundacio Ictus (PI REVASCAT; unpaid), and holds stock in Anaconda, Silk Road, and Blockade Medical.

Purpose To evaluate the effectiveness and safety of image-guided percutaneous bleomycin sclerotherapy as a minimally invasive treatment approach for craniofacial (veno)lymphatic malformations in children and adolescents. Material and Methods We retrospectively reviewed our prospectively maintained Neuro IR database between January 2018 and June 2020 and identified all children and adolescents (1 to 19 years) who underwent percutaneous fluoroscopy guided bleomycin sclerotherapy for craniofacial (veno)lymphatic malformations. Patient clinical and imaging follow up data was collected. Results We identified 4 patients (2 female patients) between 20 months and 12 years old who presented with clinical and radiographic craniofacial (veno)lymphatic malformations. Two lesions were macrocystic, 1 microcystic and 1 mixed. No procedural complications ensued. On first follow up examination 2 patients report obvious decrease in size of the malformation which is confirmed with ultrasound and/or visual inspection. One patient subjectively reported minimal decrease in size with the ultrasound evaluation not showing any change from prior to the procedure. One patient who showed initial decrease in size of the lesion already underwent a second sclerotherapy session and is awaiting his next follow up appointment. The other 2 patients are scheduled to undergo their next sclerotherapy session as well. One patient did not reach the first follow up time point yet. Conclusion Sclerotherapy should be considered in selected patients with craniofacial (veno)lymphatic malformations as it represents a safe and successful treatment option, especially if surgical excision is considered challenging, with a high risk of complication and postoperative recurrence. Patients and parents have to be aware that sclerotherapy may require several sessions to achieve results. Generally, patients and parents are satisfied with sclerotherapy treatment outcomes, specifically the cosmetic results. Disclosures A. Kuhn: None. A. Puri: 1; C; NIH, Stryker Neurovascular, Medtronic, Cerenovus. 2; C; Microvention, QApel, Perfuze Medical, Arsenal Medical, Merit Medical, Stryker Neurovascular, Medtronic, Cerenovus. 4; C; InNeuroCo Inc, Galaxy therapeutics, Agile Medical, Perfuze medical and NTI. C. Zoppo: None. K. de Macedo Rodrigues: None. F. Massari: None. M. Gounis: 1; C; National Institutes of Health (NIH), the United States – Israel Binational Science Foundation, Anaconda, ApicBio, Axovant, Cerenovus, Cook Medical, Gentuity, Imperative Care, InNeuroCo, Magneto. 2; C; Cerenovus, Imperative Care, phenox, Medtronic Neurovascular, Route 92 Medical, Stryker Neurovascular. 4; C; Imperative Care, InNeuroCo and Neurogami. J. Singh: None.

Purpose To report the feasibility and safety of anatomical snuffbox access (distal radial artery, dRA) for carotid artery stenting (CAS). Methods We performed a retrospective review of our prospectively maintained neurointerventional database of CAS cases between May 2019 and February 2021. All CAS cases via the anatomical snuffbox were identified. Patient demographics, clinical information, procedural and radiographic data was collected. Results 24 CAS procedures in 22 patients via the anatomical snuffbox were identified. Patients‘ mean age was 69.5 years (range 53-87 years). 4 patients were female. Mean radial artery diameter was 2.1 mm (range 1.6-2.8 mm). Snuffbox access was achieved in all cases. Sixteen procedures involved the right carotid artery. In 19 cases a Carotid Wallstent (Boston Scientific) was used. In 2 cases a Viabahn stent graft (Gore) was placed and a Precise stent (Cordis) was deployed in 1 case. Conversion to femoral access was required in 2 cases (8.3%) due to persistent radial artery vasospasm resulting in patient discomfort despite multiple additional doses of intraarterial vasodilators and added intravenous sedation as well as tortuous vessel anatomy and limited support of the catheters in a type 3 aortic arch for left CAS. In our cases, dRA access was mainly obtained with a 6F Prelude Ideal hydrophilic sheath introducer (Merit Medical) and procedures were mainly performed using a Benchmark catheter (Penumbra). In 3 cases a Fubuki guide catheter (Asahi Intecc) was directly inserted into the dRA over the exchange length wire (sheath-less or bareback catheter use) after removal of the sheath. In one case, a 6F Benchmark guide catheter was used to gain direct access to the dRA. We did not observe any peri- or postprocedural access site complications. No access site complications were noted. A cerebral protection device was used in all cases. There was no morbidity or mortality associated with any of the CAS interventions. Conclusion Our preliminary experience with anatomical snuffbox access for CAS suggests this approach to be feasible and safe for patients. Preprocedural planning and technical considerations are both important for a successful procedure.Nevertheless, catheter systems and devices specifically designed for radial access are needed and will likely enable more interventionalists to safely perform such procedures via hand/wrist access. Disclosures A. Kuhn: None. J. Singh: None. S. Satti: 2; C; Balt, Stryker Neuromuscular, Cerenovus, Medtronic, Microvention, Terumo. T. Eden: None. V. Moholkar: None. K. de Macedo Rodrigues: None. F. Massari: None. V. Naragum: None. V. Anagnostakou: None. M. Gounis: 1; C; National Institutes of Health (NIH), the United States – Israel Binational Science Foundation, Anaconda, ApicBio, Axovant, Cerenovus, Cook Medical, Gentuity, Imperative Care, InNeuroCo, Magneto. 2; C; Cerenovus, Imperative Care, phenox, Medtronic Neurovascular, Route 92 Medical, Stryker Neurovascular. 4; C; Imperative Care, InNeuroCo and Neurogami. A. Puri: 1; C; NIH, Stryker Neurovascular, Medtronic, Cerenovus. 2; C; Microvention, QApel, Perfuze Medical, Arsenal Medical, Merit Medical, Stryker Neurovascular, Medtronic, Cerenovus. 4; C; InNeuroCo Inc, Galaxy therapeutics, Agile Medical, Perfuze medical and NTI.

Purpose To report the feasibility, safety and efficacy of the large bore catheters with matching Tenzing inserts for first pass efficacy in stroke thrombectomy without need for crossing the clot. Methods We performed a retrospective review of our prospectively maintained neurointerventional database of mechanical thrombectomy for stroke. Patient demographics, clinical information, procedural and radiographic data was collected. Results The most widely used techniques for stroke thrombectomy are aspiration, stent-retrievers or combination of these. The Mount Everest Technique (MET) has been designed combining innovative technology and the “Law of Conservation of Matter”, taking advantage of not needing to cross the clot with the bigger catheters to “ingest” the clot with very high first pass success. The Mount Everest Technique (MET) entails a triaxial assembly with an 8 Fr 0.106” Guiding Catheter (Base Camp), a 088” HiPoint “catheter on a stick/wire” with matching self-centering Tenzing insert catheter. The Tenzing catheter is used to climb up to the clot then, while pulling this insert out, the 088” catheter is capable to progress into the clot “ingesting” it, thanks to the “Law of Conservation of Matter”. The aspiration force is applied from the Base Camp catheter with the 088” HiPoint within the clot as a single assembly, thus taking the advantage of the super large bore distal catheter and the stable 0.106” Base Camp, resulting in the capability of physically “ingest” the clot. At the time of the abstract submission, we have utilized this novel Mount Everest Technique (MET) in 6 patients with large vessel occlusions involving the anterior circulation (ICA T-terminus and MCA M1 occlusions), with single pass (5) and 2 passes (1) complete vascular reperfusion of the occluded vessel in all the cases (TICI 3). No embolization in previously unaffected vascular territories or post procedure SAH has been observed. Conclusion The Mount Everest Technique (MET) combines the technological novelty of the 0.106” Base Camp, 088” HiPoint and matching self-centering Tenzing insert catheters to navigate these super large bore catheters to the face of the clot without needing to cross them with large microcatheters or wires. Thereafter based on the “Law of Conservation of Matter”, the retraction of the Tenzing insert while applying a suction force at the HiPoint catheter results in the “ingestion” of the clot in toto. This technique and catheter combination have led to 100% TICI 3 recanalization with 80% first pass success in our initial experience. Disclosures F. Massari: None. J. Singh: None. A. Kuhn: None. V. Naragum: None. V. Anagnostakou: None. M. Gounis: None. A. Puri: None.

Background Aneurysmal persistence after flow-diversion (FD) occurs in 5–25% of aneurysms which might necessitate further treatment. A frequently used retreatment paradigm utilizes the deployment of another flow-diverting device (FDD) in a telescoping fashion within the existing device. There are no current data evaluating this strategy. Methods A retrospective review of patients undergoing FD retreatment from 15 centers was performed, with inclusion criteria being repeat FD occurring for the same aneurysm at least 6 months after initial treatment, with minimum of 6 months of imaging follow-up after retreatment. Primary outcome was aneurysmal occlusion, and secondary outcomes were safety and complications. A multivariable logistic regression model was constructed to identify predictors of persistence/occlusion after retreatment. Comparative Kaplan-Meier curves were developed to assess the effect of early (6–12 months since initial treatment) vs late retreatment (>12 months since initial treatment) on the cumulative incidence of aneurysm occlusion over time. Results Ninety-five patients (median age 57, 81% females) harboring 95 aneurysms underwent 198 treatment procedures. In our cohort, 87.4% of aneurysms were unruptured; 74.7% were saccular and 79% were located in the internal carotid artery (median maximal diameter 9-mm), with 87 patients treated twice and 8 patients treated thrice. Median elapsed-time between first and second treatment was 12.2 months. Last available follow-up was performed at median of 12.8 months after retreatment, and median of 30.6 months after initial treatment, showing complete occlusion in 46.2%, and near-complete occlusion (90–99%) in 20.4% of aneurysms. No difference in ischemic complications following initial treatment and retreatment (4.2% vs 4.2; p>0.99). On multivariable logistic regression, fusiform morphology was associated with higher odds of non-occlusion after retreatment (OR 7.2; p=0.003), with history of hypertension and incorporated branch into aneurysms trending toward incomplete occlusion (p=0.055 and p=0.054; respectively). Family history of aneurysms and positive smoking history were associated with higher odds of complete occlusion (p=0.019 and p=0.026; respectively). Kaplan-Meier curves comparative estimators showed no significant difference in time-to-occlusion between the two groups (log rank test, p=0.48). Conclusion Repeat flow diversion for persistent aneurysms is safe and effective. Fusiform morphology is the strongest predictor of aneurysmal persistence after repeat flow diversion. Disclosures M. Salem: None. A. Sweid: None. A. Kuhn: None. A. Dmytriw: None. S. Gomez-Paz: None. G. Maragkos: None. M. Waqas: None. C. Parra-Farinas: None. A. Salehani: None. N. Adeeb: None. P. Brouwer: None. G. Pickett: None. M. Ghuman: None. V. Yang: None. A. Weill: None. C. Cognard: None. L. Renieri: None. P. Kan: None. N. Limbucci: None. V. Mendes Pereira: None. M. Harrigan: None. A. Puri: None. E. Levy: None. J. Moore: None. C. Ogilvy: None. T. Marotta: None. P. Jabbour: None. A. Thomas: None.

Introduction High Frequency Optical Coherence Tomography (HF-OCT)1 is an intra-vascular imaging technique to assess device-vessel interactions and neointimal tissue growth at unprecedented spatial resolution (~10µm). In this study, we tested the hypothesis that an adequately deployed (as visualized by HF-OCT) Woven EndoBridge (WEB, Microvention, Aliso Viejo, CA) will lead to a higher aneurysm occlusion rate at 12-week follow-up in an animal model of aneurysms. Methods Elastase-induced rabbit aneurysms (n=24) were treated with the WEB device. HF-OCT (Vis-M; Gentuity LLC, Sudbury MA) and DSA were performed after WEB deployment and repeated at 4, 8, and 12 weeks. Protrusion and malapposition were binary coded (0- present, 1- absent; 0- malapposed, 1- neck apposition >50%), respectively, on HF-OCT and DSA. A device was considered adequately deployed if it was scored as 1 on both metrics. Aneurysm healing on DSA was interpreted using the 4-point WEB occlusion score (WOS)2; with A-B considered a positive outcome. HF-OCT images acquired at 12 weeks were analyzed and neointimal coverage quantified. Scanning electron microscopy (SEM) was performed of the explanted specimens. Results Discrepancy between HF-OCT and DSA was found: HF-OCT classified as adequately deployed a total of 5 cases, whereas 8 cases were classified as adequately deployed by DSA images. Acceptable WOS grade at 12 weeks was seen in 21% of cases (n=5): 80% of those cases (n=4) were classified as adequately deployed based by HF-OCT; whereas only 60% of those cases (n=3) classified adequate by DSA. A significant interaction between adequate deployment on HF-OCT and positive outcome was confirmed (p=0.007). However, there was no statistically significant relationship between good outcome and adequate deployment based on DSA images (p=0.289). Based on HF-OCT images, the absence of the protrusion was related with a positive outcome (p=0.006); however, malapposition had no significant interaction with positive outcome (p=0.19). The area of neointimal tissue quantified by HF-OCT showed a strong correlation with SEM assessment (R²=0.96; p Conclusion HF-OCT may be valuable prognosticate adequate aneurysm occlusion with the WEB and can be used to monitor aneurysm healing longitudinally. Absence of protrusion was associated with subsequent aneurysm occlusion; however, malapposition alone did not show an effect on the rate of aneurysm healing. Reference Stroke. 2018:Nov29:STROKEAHA118022315 2. AJNR 2014;35:432–8. Disclosures Z. Vardar: None. R. King: None. A. Kraitem: None. E. Langan: None. L. Peterson: None. B. Duncan: None. C. Raskett: None. V. Anagnostakou: None. M. Gounis: None. A. Puri: None. G. Ughi: None.

Introduction A new method of intravascular imaging is introduced, high-frequency optical coherence tomography (HF-OCT), with resolution unprecedented for in vivo imaging (~10µm). Here we describe the first preclinical observations of cerebrovascular imaging with this new technology. Methods Two dogs were imaged using HF-OCT. A 6F straight guiding catheter was initially positioned into the right vertebral artery up to the origin of the right lateral spinal ramus anastomoticus and the basilar artery was accessed with an SL-10 microcatheter. In the first dog access was achieved through the main lumen of the vertebral artery coursing along the vertebral column around the C1 vertebral body and finally the vertebrobasilar junction and the basilar artery. In the second dog access was achieved through the right lateral spinal ramus and the anterior spinal artery, the diamond shaped confluence of anastomotic channels between vertebral arteries and spinal rami into the basilar artery. In both animals the microcatheter was advanced up to the P1-P2 segment of the left PCA in order to facilitate positioning of the HF-OCT wire which was unsheathed from the microcatheter. Using contrast at a flow rate of 4 ml/sec to wash out the blood in the vessels imaging of the basilar artery from distal to proximal was performed. Results Detailed images of the basilar artery, lower cerebellar arteries, basilar perforators, vertebrobasilar junction, spinal perforators were obtained (figure 1). Due to the high resolution of the method, the layers of the vessel wall were imaged. What was even more interesting was the ability to image beyond the artery into the structural components of the subarachnoid space with the arachnoid membranes and what we believe to be the arachnoid trabeculae. Venous structures and nerve root origins were also recognized. Conclusion HF-OCT imaging can offer detailed visualization not only of the vessel wall, the branching pattern of basilar and spinal perforators but also of structures of the subarachnoid space impossible to study with other imaging modalities due to inadequate resolution. The clinical implication of such an analysis is yet to be discovered. Disclosures V. Anagnostakou: None. Z. Vardar: None. A. Puri: None. G. Ughi: None. M. Gounis: None.

Introduction The NAPA study was a prospective, multicenter, single-arm IDE trial of the PulseRider device as an adjunctive treatment in conjunction with coil embolization of unruptured wide-neck bifurcation aneurysms which was electively discontinued for reasons not related to the safety or performance of the device. We report on the available enrollments in NAPA and their available follow up. Methods The PulseRider device was implanted in 18/21 enrollments. Available core-lab adjudicated data from the first 18 implants is presented. Of those, 5 have one year follow up data available. Of the 3 device implantation failures, the locations included basilar (1), carotid terminus (1), and ACOMM (1). Results For the 18 patients with PulseRider implanted as a coil-adjunct device, the mean age was 60.7± 8.9 yrs and 16 were female. The mean aneurysm diameter was 6.6± 2.2 mm, height 5.3±1.7 mm and neck 4.8 ±1.5 mm. Locations included the basilar apex (11), MCA bifurcation (4) and ACOMM (3). Thirteen of 18 were de novo aneurysms while the remainder (5) were treated in the setting of aneurysmal recurrence. The most common PulseRider placement was extra-aneurysmal (12/18), followed by intra-aneurysmal (4/18) and hybrid (2/18). Immediate angiographic occlusions were 66.6% RR-I, 16.7% RR-II, 16.7% RR-III. There were no device related adverse events. There were 3 (16.7%) procedure-related adverse events which did not result in neurological changes. Seven enrollments have 6 month follow up and all are RRI-II. Only 1 has one year angiographic follow up (RRI) adjudicated by the core lab, and 4 have clinical follow up (4/4 mRS 0–2). None of the target aneurysms have required retreatment. Conclusions The results of the discontinued NAPA provide high quality data on the occlusion rates and safety profile for the PulseRider device. Further one year angiographic and clinical follow up will be reported when available. Disclosures A. Spiotta: 1; C; Microvention. 2; C; Minnetronix, Penumbra, Cerenovus. 6; C; Cerenovus, Penumbra, Pulsar Vascular, Stryker, Microvention. K. Ebersole: None. J. Lena: None. R. Starke: 2; C; Medtronic Neurovascular, Penumbra, Cerenovus, Abbott. R. De Leacy: 6; C; Penumbra, Cerenovus, Siemens. A. Puri: 1; C; Stryker Neurovascular, Medtronic Neurovascular. 2; C; Stryker Neurovascular, Medtronic Neurovascular. D. Yavagal: 2; C; Medtronic Neurovascular, Rapid Medical, Steering Committee, Neuralanalytics. 6; C; Medtronic, Cerenovus/Johnson & Johnson, Rapid Medical, Neuralanalytics. B. Bohnstedt: 2; C; Penumbra, Stryker, Medtronic. L. Rangel-Castilla: None. A. Cheema: None. J. Davies: 1; C; National Center for Advancing Translational Sciences of the National Institutes of Health under award number KL2TR001413 to the University of Buffalo. 2; C; Medtronic, Neurotrauma Science, LLC. 4; C; RIST Neurovascular. K. de Macedo Rodrigues: None. J. Grossberg: None. B. Howard: None. C. Kellner: 1; C; Penumbra, Siemens Corp. G. Lanzino: None. S. Tateshima: 2; C; Cerenovus, Medtronic, Neurovasc, Stryker. 4; C; Neurovasc.

Introduction Advances in pump design make aspiration patterns programmable, producing an infinite combination of cyclical aspiration profiles for clot removal during treatment of acute ischemic stroke (AIS). However, little is known about how clots respond to different aspiration patterns. The goal of this study is to assess the structural and mechanical changes of the clot under aspiration. It is our hypothesis that a decreased fibrin pore size correlates to a higher aspiration efficacy. Materials and methods A fibrin-rich bovine clot was used to create an MCA occlusion in a patient-specific silicone model and underwent thromboaspiration via a 6F Sofia Plus catheter (MicroVention, Tustin, CA). Three sets of the retrieved clots were prepared for scanning electron microscopy (SEM) analysis, including clots lodged at the MCA without aspiration (control) as well as clots subjected to static (28 mmHg) or cyclic aspiration (amplitude: 18 to 27 mmHg) for 2 minutes (CLEARTM Aspiration System, Insera Therapeutics, LLC, Sacramento, CA). All the clot samples were fixed, dehydrated and frozen fractured. Surfaces of the fractured clots were imaged at 20 Kx at four different locations to obtain pore-size estimates of fibrin networks using ImageJ. Dynamic mechanical analysis (DMA) was conducted to understand the viscoelastic behavior of the clots obtained from patients with AIS under cyclic loading conditions. Results The fibrin-rich clot was corked in the distal tip of the aspiration catheter during clot retrieval. The average clot diameter measured proximally was 3.5 mm, 2.3 mm and 1.8 mm for the control, static and cyclic groups, respectively. Mechanical loading-unloading-reloading on the clot resulted in clot deformations; however, the changes in the clot dimension were less pronounced as the mechanical stimulus continued during the DMA tests. Clot deformation during aspiration was accompanied by a reduction in the average pore size in the fibrin-rich clot. The figure 1 demonstrates that the fibrin pore size measured from the proximal end of the clot was significantly reduced after aspiration when compared to the control clot (control: 857µm2, cyclic: 434µm2, static: 420 µm2). No significant differences in fibrin pore size were observed between the cyclic and static groups; however, it should be noted that the smallest pore size measurement was found in the cyclic group. Conclusion Applying cyclic or static aspiration to the fibrin-rich clot forms a denser fibrin mesh and results in clot stiffening. A comprehensive study is ongoing to study the structural changes of different clot models under aspiration at various frequencies and amplitudes. Disclosures M. Marosfoi: 2; C; Stryker Neurovascular and InNeuroCo Inc. L. Strittmatter: None. R. Arslanian: None. C. Raskett: None. M. Gounis: 1; C; the National Institutes of Health, Israel Binational Science Foundation, Anaconda, Cerenovus, Cook Medical, Gentuity, Imperative Care, InNeuroCo, Magneto, Microvention, Medtronic Neurovascular, MIVI Neurosciences, Neuravi, Neurogami, Philips Healthcare, Rapid Medical, Route 92 Medical, Stryker Neurovascular, Syntheon, and the Wyss Institute. 2; C; Cerenovus, Imperative Care, MIVI Neurosciences, phenox, Route 92 Medical, Stryker Neurovascular. 4; C; Imperative Care and Neurogami. A. Puri: 1; C; Medtronic Neurovascular and Stryker Neurovascular. 2; C; Medtronic Neurovascular and Stryker Neurovascular. F. Massari: None. K. De Macedo Rodrigues: None. J. Singh: None. J. Chueh: 2; C; Stryker Neurovascular and InNeuroCo Inc.

Introduction Recent studies have demonstrated that a direct aspiration first pass technique (ADAPT) for the treatment of acute ischemic stroke may be effective and safe. In this study, we sought to optimize the ADAPT technique by incorporating an adjunctive device such as a balloon guide catheter (BGC). The impact of diameter of the aspiration catheter as well as use of BGC on risk of distal embolization and rate of first pass success was evaluated. Methods Mechanical thrombectomy was simulated in an in-vitro Circle of Willis model. To create a challenging occlusive burden in the MCA, a 20 mm long clot analog was prepared. Direct aspiration was applied via an 0.068 distal access catheter (DAC, Cat 7, Stryker Neurovascular, group: ADAPT068), a large 0.074’ DAC (AXS Vecta 074, Stryker Neurovascular, group: ADAPT074) or 0.068’ DAC with a BGC (FlowGate 2 Balloon Guide Catheter) placed at the cervical ICA (group: ADAPT068-BGC). In both the ADAPT068 and 074 groups, a long 0.091’ sheath was used in conjunction with the DAC. The pump was turned on before the aspiration catheter was advanced proximal to the clot. Each run was assigned a TICI score to assess degree of recanalization. Ten replicates were performed per group, and the maximum thrombectomy attempt was limited to three per run. Distal emboli greater than 200μm were collected and measured using the Coulter Principle. Results The lowest number of distal emboli was observed when BGC was used in the ADAPT068 group. Collection of visible emboli greater than 1000μm yielded one particle from both the ADAPT068 and ADAPT068-BGC treatment groups, while ADAPT074 followed with four particles (average size 2.25 mm). A total of 34 emboli sized between 200–1000μm were collected from the ADAPT068 group, and the number of emboli was reduced by more than 50% when a BGC was employed in the ADAPT068-BGC group (P>0.05). The highest rate of first pass recanalization was observed in the ADAPT074 treatment group with the largest bore catheter; where 80% of runs scored a TICI 3 after one attempt (see figure 1). Complete ingestion was observed in 90% of cases with the ADAPT074 technique, while the ADAPT068-BGC and ADAPT068 groups achieved rates of 70% and 60% respectively. Conclusion BGC protected thrombectomy has been shown to reduce distal emboli for stent-retrievers previously. These preliminary data show that BGC protected thrombectomy also imparts benefit for ADAPT. The larger bore aspiration (ADAPT074) achieved the highest rate of first pass recanalization and complete clot ingestion. Disclosures R. Arslanian: None. M. Marosfoi: 2; C; Stryker Neurovascular, InNeuroCo. Inc., ThrombX. C. Raskett: None. M. J. Gounis: 1; C; Cerenovus, Imperative Care, MIVI Neurosciences, Stryker Neurovascular, National Institute of Health (NIH), US-Israel Binational Science Foundation, Anaconda, Cook Medical, Gentuity, InNeuroCo, Magneto, Microvention, Medtronic Neurovascular, Neuravi, Neurogami, Philips Healthcare, Rapid Medical, Route 92 Medical, Syntheon, Wyss Institute. 2; C; Cerenovus, Imperative Care, MIVI, Phenox, Route 92 Medical, Stryker Neurovascular. 4; C; Imperative Care, Neurogami. A. S. Puri: 1; C; Medtronic Neurovascular, Stryker Neurovascular. 2; C; Medtronic Neurovascular, Stryker Neurovascular. J. Chueh: 2; C; Stryker Neurovascular, InNeuroCo. Inc.

Background and objective The first pass effect (FPE) has become a novel measure for neurointerventionalists, achieving a complete recanalization with a single thrombectomy device pass, which has been shown to be associated with higher rates of good clinical outcomes. We describe and expand the FPE to one of a large US post-marketing registry (TRACK, Trevo Stent-Retriever Acute Stroke) to elucidate the effect of a single device pass and clinical outcome. Methods TRACK was a core-laboratory adjudicated multicenter registry of 634 patients from 23 centers aimed to evaluate the use of the Trevo device in everyday clinical practice. The TRACK registry was utilized to identify an FPE subgroup (n=140). Baseline features including demographics and clinical data were compared with the non-FPE patients (n=469). Clinical outcome measures included modified Rankin Scale score (mRS) at 30 and 90 days, National Institutes of Health Stroke Scale (NIHSS) score, symptomatic intracranial hemorrhage (sICH), and mortality. FPE was defined as a single pass/use of a device with TICI 2c/3 recanalization, and no use of rescue therapy. Results 609 patients were included in the FPE (140/609, 23%) vs non-FPE (469/609, 77%) subgroup analysis from the TRACK registry. There was no association between patient demographics and FPE group, including age (p=0.36), sex (p=0.50), race (p=0.49), location of occlusion (p=0.26), baseline NIHSS (p=0.61) past medical history including hypertension (p=0.57), atrial fibrillation (p=0.55), diabetes mellitus (p=0.74), hyperlipidemia (p=0.28), coronary artery disease (p=0.27), or history of smoking (p=0.12). The non-FPE group was associated with higher use of intraarterial tPA (FPE: 11% vs non-FPE: 23%). The onset to puncture time in minutes was not significantly different between groups (p=0.31); however, the total procedural time, total fluoroscopic time, and puncture to reperfusion time had significantly shorter mean time in FPE group (p Conclusion The achievement of complete revascularization from a single Trevo Stent-Retriever device pass is associated with higher rates of good clinical outcomes. Additionally, FPE in our subgroup registry analysis was associated with shorter procedural times, lower NIHSS at discharge, and significantly lower rates of EDT. Our analysis was not able to identify any patient demographics that would be associated to achieve first pass effect. Further research is warranted to confirm findings and identify additional factors achieving good clinical outcome after thrombectomy. Disclosures M. Mokin: 2; C; Claret Medical, Nogueira-Stryker Neurovascular (Trevo-2 Trial Principal Investigator; DAWN Trial Principal Investigator, TREVO Registry Steering Committee), Medtronic (SWIFT Trial Steering Committee; SWIFT-Prime Trial Steering Committee ; STAR Trial Angiographic Core Lab), Penumbra (3D Separator Trial Executive Committee), Neuravi (ARISE-2 Steering Committee), Genentech (Physician Advisory Board), Allm Inc (Physician Advisory Board). C. Primiani: None. A. Castonguay: None. R. Nogueira: None. D. Haussen: None. J. English: None. S. Satti: 2; C; Stryker Neurovascular. J. Chen: None. H. Farid: None. C. Borders: None. E. Veznedaroglu: None. M. Binning: None. A. Puri: None. N. Vora: None. R. Budzik: None. G. Dabus: None. I. Linfante: 2; C; Metronic, Stryker, Penumbra, and Cordis. V. Janardhan: None. A. Alshekhlee: None. M. Abraham: None. R. Edgell: None. M. Taqi: None. R. El Khoury: None. A. Majjhoo: None. M. Kabbani: None. M. Froehler: None. I. Finch: None. S. Ansari: None. R. Novakovic: None. T. Nguyen: None. O. Zaidat: 6; C; overall PI for TRACK, Arise II, Co-PI Therapy Trial, Steering committee STRATIS registry.

Introduction The use of flow diverters has emerged as an effective treatment of aneurysm. One of the major limitations of flow diverters is the need to put patients on dual anti-platelet therapy (DAPT). The exposure of bare metal struts leads to platelet activation. A method to assess the degree of neointimal tissue ingrowth over the surface of the device could permit patient-specific tailoring of DAPT. Currently, the standard of follow-up for flow diverter patients is digital subtraction angiography (DSA); however, it has been previously reported DSA appearance of complete aneurysm occlusion is not always reliable with continued aneurysm growth.1 There have been reported cases of very delayed complications after DAPT has been stopped,2 although rare, such complications can be catastrophic. High Frequency Optical Coherence Tomography (HF-OCT) is a novel intravascular imaging technique designed for use in cerebrovascular anatomy with a spatial resolution approaching 10 microns. In this study, we sought to compare HF-OCT with state-of-the-art DSA for the in vivo evaluation of complete aneurysm occlusion. Methods Flow diverters were implanted in 15 rabbits, at least 21 days after a standard elastase aneurysm creation. Six of the rabbits were imaged at 15 days post implant, including both DSA and HF-OCT to assess healing of the aneurysm. The remaining 9 rabbits were allowed to heal for 60 days, at which point they also received HF-OCT. Finally, the rabbits were euthanized, perfused with formalin, and the aneurysms were explanted for histological analysis. Results Fifteen days following implant, one aneurysm was seen to be fully occluded on DSA, but HF-OCT demonstrated an aneurysm remnant, and the struts remained uncovered (figure 1D-E). At 60 days post-implant, another aneurysm appeared fully healed on DSA, yet HF-OCT demonstrated that the aneurysm remained in communication with the parent artery (figure 1A-B). This observation was later confirmed on SEM (figure C). Conclusions Preliminary evidence is presented showing that DSA alone is insufficient to confirm complete aneurysm occlusion. HF-OCT may reliably show parent artery remodeling and inform patient-specific decisions regarding duration of DAPT. References AJNR June 2012;33(6):1150–1155. J Neurosurg 2016;125:929–935. Disclosures R. King: None. M. Marsofoi: None. E. Langan: None. M. Shazeeb: None. G. Ughi: 4; C; Gentuity LLC. 5; C; Gentuity LLC. C. Raskett: None. A. Puri: None. M. Gounis: None.

Introduction The development of High Frequency OCT1 (HF-OCT) allows for higher resolution intra-arterial imaging, such that vascular remodeling in response to stents and next generation intrasaccular devices (NGID) can be interrogated. We hypothesize that imperfections or gaps in the neck coverage of an aneurysm after treatment with a NGID will be predictive of failed aneurysm occlusion. Materials and methods Two aneurysms were made in each of six dogs, one sidewall aneurysm on the distal right common carotid artery (CCA), and a bifurcation aneurysm proximally at the apex of an anastomosis between the left and right CCAs. One aneurysm was excluded due to thrombosis at the time of treatment. Each aneurysm was treated with either detachable coils, or NGID, with a 7:4 randomization NGID:COIL. At implant, HF-OCT was obtained after each aneurysm was successfully packed. At 180 days, animals were assessed for final aneurysm occlusion by DSA. Separately, the HF-OCT data sets were automatically segmented such that gaps in the coverage of the aneurysm neck could be identified and used to predict if the aneurysm occlusion at 180 days. Results The overall rate of occlusion was not seen to be different between the NGID and COIL group (p=0.45) on the Raymond-Roy scale.2 All of the NGID constructs were successfully segmented, and the associated larges gap in the neck coverage for each was determined. A gap in the NGID construct at the level of the neck greater than 1 mm2 predicted failed aneurysm occlusion at 180-days (p = 0.047). This threshold correctly classified all aneurysms. Conclusions HF-OCT allows not only for the imaging and segmentation of intra-arterial devices in vivo, but showed great potential as a robust diagnostic tool. Preliminary evidence collected in this study showed that HF-OCT can prognosticate aneurysm treatment success at the time of treatment. References Stroke. 2018:Nov29:STROKEAHA118022315 Stroke. 2003;34(6):1398–1403. Disclosures R. King: None. M. Marosfoi: None. J. Caroff: None. G. Ughi: 4; C; Gentuity LLC. 5; C; Gentuity LLC. D. Groth: None. M. Gounis: None. A. Puri: None.

Mechanical Thrombectomy has been associated with improved neurological outcome in large vessel occlusion (LVO) acute ischemic stroke (AIS) patients. To better understand the relationship of LVO clot composition with vessel recanalization, we analyzed individual clots from 94 retrieval passes in 43 AIS patients (65.4±12.7 years, 17 (39.5%) female) who underwent intra-arterial mechanical thrombectomy procedures over a 2-year period. Rates of successful vessel recanalization (TICI 2B - 3) for each trial and final result were analyzed. Clot composition was analyzed histologically, and the area occupied primarily by red blood cells (RBC), fibrin, or mixed was quantified. Fibrin (44%) occupied the greatest area in retrieved clots, followed by mixed type (34%) and RBCs (22%). Clot composition was compared to recanalization success, first pass efficacy, patient comorbidities, devices or technique used, and carotid tortuosity score. In 43 patients, there were 94 passes (mean 2.14, range 1–6), 20 patients (47%) had first pass successful revascularization, 41 (95%) achieved successful revascularization, and 19 (48%) had a good outcome at 3 months (mRS 0–2). In the univariate analysis, first pass efficacy was associated with RBC composition and Atrial Fibrillation but not with fibrin composition, mixed composition, type of first pass technique employed, distal emboli, good outcome, or carotid tortuosity score. In the multivariate analysis, first pass efficacy was significantly correlated with RBC composition (p=.05) but not with atrial fibrillation (p=0.07) or other factors. Dense MCA sign on initial CT was correlated with mixed clot composition (p=0.025). RBC clot composition is associated with first pass efficacy in patients undergoing mechanical thrombectomy for LVO. Disclosures J. Johnson: None. A. Srivatsan: None. J. Chueh: None. M. Gounis: 1; C; NIH, NIH NINDS, Various Biomedical Device Industry Grants. A. Puri: None. V. Srinivasan: None. S. Chen: None. J. Burkhardt: None. P. Kan: 1; C; NIH, McDonald Foundation. 2; C; Stryker Neurovascular, Cerenovus, Medtronic.

Introduction Intravascular optical coherence tomography (OCT) has an established role in the diagnosis and image guided treatment of coronary artery disease. However, due to the profile and design of the catheter, these devices are not suitable for routine application in neurointerventional surgery. We aim to demonstrate that new generation high frequency OCT (HF-OCT) can image stents and flow diverters used to treat intracranial aneurysms with acceptable workflow deployed in neurointerventional surgery. Materials and methods An HF-OCT prototype was built (Gentuity, Sudbury MA) that is compatible with standard microcatheters (0.017’). An in vitro flow loop consisting of a patient-specific vascular replica and using porcine blood as a working fluid was deployed to test contrast infusion protocols necessary to remove blood from the target vascular section. Subsequently, eight pigs were implanted bilaterally with flow diverters and stents. The presence of acute platelet aggregation on the surface of the devices and malapposition of the device to the vessel wall was assessed by 3 raters reviewing digital subtraction angiography (DSA), high resolution cone beam CT (CBCT), and HF-OCT. Finally, using the tortuous porcine brachial artery, HF-OCT was performed, and image quality assessed. Results In the in vitro experiment, the optimized contrast infusion protocol was delivery of contrast through the intermediate catheter (0.058’ Navien, Medtronic Neurovascular, Irvine CA) delivering the HF-OCT device at a rate of 5 ml/s for 20–25 ml of contrast. This protocol resulted in complete clearing of highly attenuating erythrocytes for an optically clear field. In the pig study, the agreement by the reviewers (Fleiss kappa) regarding clot formation at 3 distinct locations along the flow diverter was 0.49, 0.67 and 0.90 for DSA, CBCT and HF-OCT, respectively. The agreement for diagnosing malapposition at these locations was 0.18, 0.67 and 0.87 for DSA, CBCT, and HF-OCT, respectively. In the porcine tortuosity model, in all cases, navigation and imaging was performed with uniform illumination and free from artifact. Conclusion An HF-OCT device has been built that is compatible with neurointerventional surgery workflow and cerebrovascular anatomy. Preclinical data demonstrate consistent improvement to diagnose acute platelet aggregation and malapposition of flow diverters as compared to existing imaging modalities (figure 1). Disclosures A. Puri: 1; C; NIH. M. Marosfoi: None. G. Ughi: 4; C; Gentuity. 5; C; Gentuity. R. King: None. E. Langan: None. J. Chueh: None. M. Gounis: 1; C; NIH.

Introduction/purpose Vascular closure devices have been designed to provide immediate sealing of the arterial puncture site after catheter-based angiography. The Celt ACD (Vasorum, Dubline, Ireland) is a novel stainless-steal arterial closure device which received FDA approval in 2016. The device is available in 3 sizes (5, 6 and 7 French) and is delivered by a disposable, single-use unit through the femoral sheath. We prospectively evaluated safety and efficacy of this new vascular closure device in our neurointerventional patient population. Materials and methods A total of 37 patients were included in our study between December 2017 and January 2018. All interventionalists have familiarized themselves with the device prior to usage. We evaluated device deployment feasibility, patient discomfort during deployment, device safety and efficacy in patients undergoing a variety of neurointerventional procedures. Results A total of 37 patients (20 females) with a mean age of 60 years (range 23–90 years) were included. The sheath was placed in the common femoral artery in the majority of cases (36/38). Femoral access ranged from 5 to 8 French. There were 24 elective diagnostic angiograms, 4 angiographic evaluations for SAH, 6 stroke interventions and 4 stenting/flow diverter placement procedures. Two of the stroke patients had received tPA. Twelve patients were on aspirin 81 mg or 325 mg daily and 8 patients were on dual antiplatelet therapy (aspirin 81 mg and Plavix 75 mg). Eleven patient were not on any form of anticoagulation/platelet inhibition. The remainder of the patients was either on Coumadin (therapeutic to sub-therapeutic levels), other anticoagulants such as Eliquis or a combination thereof with aspirin. Device deployment was successful in 33/38 cases (86.8%) and immediate hemostasis was achieved. Patients did not complain of pain or unusual discomfort with device deployment or during the recovery period. Inability to deploy the device occurred in a total of 4 cases (10.5%) due to operator failure (n=3) and in one case because the patient moved during release of the device. Major complication post device deployment was seen in one patient who was seen for a diagnostic angiogram prior to intervention. A Celt ACD device was used for closure after each procedure. This patient developed a large femoral hematoma and pseudoaneurysm likely due to vessel laceration which did not require surgical repair. Conclusion The Celt ACD vascular closure device is a good alternative to previously available closure devices. Disclosures A. Kuhn: None. K. de Macedo Rodrigues: None. D. Rex: None. F. Massari: None. A. Wakhloo: 1; C; Philips Healthcare. 2; C; Stryker Neurovascular. 3; C; Harvard Postgraduate Course, Miami Cardiovascular Institute. 4; C; NeuroIncCo. A. Puri: 1; C; Stryker Neurovascular. 2; C; Cadman Neurovascular, Stryker Neurovascular, Covidien. 3; C; Miami Cardiovascular Institute. 4; C; NeuroIncCo.

Purpose To demonstrate a novel use of the pipeline embolization device (PED) for reconstruction of a dissected cervical internal carotid artery (ICA) bridging the true arterial lumen through its false lumen. Case report 50-year-old male with daily right periorbital and frontal headaches with associated rhinorrhea, lacrimation and right eye ptosis for 3 months started 2 days after motor vehicle collision. Neurological exam was otherwise unremarkable. He was initially diagnosed as having cluster headaches. Imaging findings To exclude organic causes of headache, an MRI and MR angiogram of the brain were obtained and a cervical right ICA dissection was partially visualized. CT angiogram demonstrated a dissection of the cervical right ICA at the level of a vessel kinking with associated pseudoaneurysm compressing the true arterial lumen which appeared severely stenotic. Patient was then started on dual antiplatelet regimen. DSA confirmed CTA findings and showed insufficient collateral flow to the right ICA territory on balloon test occlusion. Given the vessel loop, probability of successful navigation of a carotid artery stent or balloon mounted coronary stent was deemed low considering its characteristic stiff construct. Decision was made to utilize a PED given flexibility, diameter compatibility and better conformation to vessel curvature. Gentle angioplasty was performed at the entry and reentry point prior to and after stent deployment. Two partially overlapped PED and one Precise Pro RX carotid stent were used to bridge the proximal and distal healthy lumen through the false lumen. Headaches resolved after endovascular treatment. Follow-up angiogram performed at 7 month showed complete occlusion of the excluded lumen with excellent flow through the stent construct. Summary Successful and uncomplicated reconstruction of a dissected cervical ICA demonstrated with the use of a PED bridging the proximal and distal true lumen via false lumen. Disclosures K. de Macedo Rodrigues: None. A. Kuhn: None. D. Rex: None. F. Massari: None. A. Puri: 1; C; Stryker Neurovascular, Covidien. 2; C; Codman Neurovascular, Covidien. 4; C; InNeuroCo. A. Wakhloo: 1; C; Philips Healthcare. 2; C; Stryker Neurovascular. 3; C; Harvard Postgraduate Course, Miami Cardiovascular Institute. 4; C; InNeuroCo.

Introduction/purpose Mechanical thrombectomy is an effective treatment for acute MCA occlusions. The goal is to achieve the best possible recanalization result in the least amount of thrombectomy passes. However, in some cases late or only incomplete MCA territory recanalization is achieved.We hypothesize that positioning of the thrombectomy device may play a role in regards to technical success of the procedure. Materials and methods We retrospectively reviewed our institutional stroke database and identified 50 patients with distal M1 occlusions (MCA occlusions with bifurcation involved based on CTA) from January 2013 to February 2018. We then divided the patients into 3 groups depending on the distal position of the thrombectomy device and passes performed: group 1- superior M2 division only, group 2- inferior M2 division only and group 3- mixed passes. Our evaluation included first pass TICI 2C/3 success, overall TICI 2C/3 results within the groups and median number of passes needed until completion of the procedure with acceptable recanalization result (TICI 2B-3). Procedure-related complications such as SAH were recorded. Results A total of 50 patients (29 females) were included with a mean age of 73 years (age range 32–96 years).10 patients were included in-group 1 (superior division only). First pass TICI 2C/3 result was achieved in 3 patients (30%). Overall TICI 2C/3 recanalization independent of number of passes needed was seen in 6/10 patients (60%). The median number of passes required for an acceptable TICI result were 1.5 in this group. Only one patient who required 2 passes for a TICI 2B result was found to have an asymptomatic SAH on post-procedural CT scan. 23 patients were included in-group 2 (inferior division only). First pass TICI 2C/3 result was achieved in 8 patients (57%). Overall TICI 2C/3 recanalization independent of number of passes needed was seen in 11/23 patients (48%). The median number of passes required for an acceptable TICI result were 1 in this group. In 2 patients, additional devices (aspiration and stent) were required. The patient requiring stent placement achieved a TICI score of 2A. In this group, one asymptomatic (TICI 2B result after single pass) and one symptomatic SAH (TICI 2B result after 3 passes) were observed. 14 patients were included in-group 3 (mixed passes). A 2-pass TICI 2C/3 result was achieved in 3 patients (21%). Overall TICI 2C/3 recanalization independent op number of passes needed was seen in 7 patients (50%). The median number of passes required for an acceptable TICI result were 3 in this group. SAH-complication post-procedure was seen in 6 patients (3 symptomatic). Conclusion Successful first pass TICI 2C/3 result was most commonly achieved with a thrombectomy pass from the inferior M2 division. The least amount of thrombectomy passes needed to achieve an acceptable TICI result was seen in group 2 (inferior division only). The most SAH-related complications and highest number of passes required to achieve at least a TICI 2B result was seen in group 3 (mixed passes). A larger cohort study will be required to validate our results. Disclosures A. Kuhn: None. K. de Macedo Rodrigues: None. D. Rex: None. F. Massari: None. A. Wakhloo: 1; C; Philips Healthcare. 2; C; Stryker Neurovascular. 3; C; Harvard Postgraduate Course, Miami Cardiovascular Institute. 4; C; InNeuroCo. A. Puri: 1; C; Stryker Neurovascular, Covidien. 2; C; Codman Neurovascular, Covidien. 4; C; InNeuroCo.

Purpose To show a two-centers initial post market experience with the use of a new intracranial stent specially designed for wide neck bifurcation aneurysm. Materials and methods We retrospectively reviewed 6 consecutive cases of elective endovascular treatment of bifurcation aneurysms with the use of the PulseRider nitinol implant (Pulsar Vascular, Los Gatos, California) in addition to bare platinum embolization coils. A total of 6 patients (5 females) with 6 aneurysms (4 basilar, 2 anterior communicating artery) with age ranging from 51–67 years old were included. Dual anti-platelet therapy was started 5 days prior to the procedure. Three ‘Y’ shape and 3 ‘T’ shape devices were utilized. Angiogram post device placement and coil placement were analyzed. A 6 month post procedure diagnostic cerebral angiogram was available for 2 patients. Results Implant placement and subsequent aneurysm sac coil embolization successfully performed for all patients. Two patients had the resheatable implant retrieved for shape exchange. A 28% mean packing density was achieved. No periprocedural or immediate post procedural complications encountered. Two patients had a 6 month follow-up angiogram showing complete aneurysm occlusion. Conclusion/summary Technical feasibility of the use of the PulseRider intracranial stent demonstrated in all 6 cases for endovascular embolization of wide neck bifurcation aneurysms. Limitations of this case series include small sample size, only 2 patients with a follow-up angiogram available and lack of long term clinical follow-up. Disclosures K. de Macedo Rodrigues: None. P. Kan: 2; C; Stryker, Medtronic. A. Kuhn: None. D. Rex: None. F. Massari: None. A. Wakhloo: 1; C; Philips Healthcare. 2; C; Stryker Neurovascular. 3; C; Harvard Postgraduate Course, Miami Cardiovascular Institute. 4; C; InNeuroCo. A. Puri: 1; C; Stryker Neurovascular, Covidien. 2; C; Codman Neurovascular, Covidien. 4; C; InNeuroCo.

Introduction Pipeline Embolization Device (PED) has proven to be an effective treatment for intracranial aneurysm with high rates of long-term complete occlusion.1,2 However, some aneurysms either do not achieve complete occlusion3–6 or heal in a delayed fashion7 during which the aneurysm is not protected from rupture. Recent scientific reports from animal models show that poor wall apposition of PED devices can lead to delayed occlusion of aneurysms.8,9 The purpose of this study was to compare the mid-term occlusion rates with or without balloon angioplasty (BA) after PED delivery. Materials and methods From October 2011 to September 2016 all consecutive patients treated with a PED and with an available angiographic follow-up performed between 6 and 24 months were included in this study. BA was performed at the operator’s discretion based on imaging findings. Aneurysms with previous history of stenting or cases where a non flow-diverter stent was associated with the PED were excluded from analysis. Clinical presentations, technical details, intra- and perioperative complications, and clinical and angiographic outcomes were recorded in a prospectively maintained database. Results 158 aneurysms were included and angioplasty was performed in 49% of cases. Average follow-up interval was 12 months for both groups (p=0.6). Patients’ demographics and aneurysm characteristics were not different between the two groups (table 1). The number of PED per case was slightly greater in the control group. Complete occlusion rate was significantly higher in the angioplasty group (88%) than in the control group (73%); p=0.017. No BA related hemorrhagic complication was reported. Angioplasty was not associated with a more frequent use of anti GPIIb/IIIa inhibitors (p=0.2), a marker of intra-operative thrombotic event. No increase in baseline mRS score was found during follow-up in the BA group. Conclusions Balloon angioplasty appears to be a safe technique to improve the midterm angiographic outcome after Pipeline Embolization Device treatment. References Becske, et al. Neurosurgery 2017. Brinjikji, et al. Stroke 2013. Shapiro, et al. Journal of Neurosurgery 2016. Brasiliense, et al. WNEU 2017. Adeeb, et al. AJNR 2017. Gressot, et al. WNEU 2016. Walcott, et al. JAMA Neurol 2016. King, et al. JNIS 2017. Rouchaud al. AJNR 2016. Disclosures J. Caroff: None. K. de Macedo Rodrigues: None. M. Howk: None. D. Rex: None. F. Massari: None. A. Kuhn: None. A. Wakhloo: 1; C; Philips Med (research and equipment support and MAB); Medtronic Consultant: Stryker Neurovascular. 2; C; Stryker Neurovascular. 3; C; Harvard Postgraduate Course; Baptist Health, Jacksonville, FL. 4; C; EpiEP; Neural Analytics; 4L Analytics; InNeuroCo. 5; C; Co-founder, CMO and Board member InNeuroCo. R. King: None. M. Gounis: 1; C; Medtronic Neurovascular, Stryker Neurovascular, Cerenovus Neurovascular. 2; C; Cerenovus Neurovascular, Medtronic Neurovascular, Phenox, Stryker Neurovascular. A. Puri: 1; C; Medtronic Neurovascular, Stryker Neurovascular. 2; C; Cerenovus Neurovascular, Medtronic Neurovascular, Stryker Neurovascular.

Introduction/Purpose In-stent stenosis and intimal hyperplasia (IH) occur in 9% and 35%, respectively, after flow diverter treatment1. Although this phenomenon is not rare, severe, symptomatic flow limiting narrowing is rarely observed. Recently FD have been used in several cases in small vessels (off-label indication), which can potentially result in a higher rate of symptomatic in-stent stenosis or stent thrombosis. We sought to determine the patterns of intimal hyperplasia after flow diversion treatment using a high resolution intravascular imaging technique (optical coherence tomography). Furthermore, we assessed the effect of phosphoryl-choline surface modified FDs in preventing in-stent stenosis. Materials and methods Forty New-Zealand white rabbits with elastase induced aneurysm were treated with classic Pipeline (C-PED) or with Pipeline-Flex with Shield Technology (S-PED). Four treatment groups were created, based on device type and the usage of dual anti-platelet therapy (DAPT). Ten animals per group were randomized for the following treatment: C-PED-no-DAPT, C-PED-with-DAPT, S-PED-no-DAPT, S-PED-with-DAPT. Optical coherence tomography was used in order to determine the location, thickness and the vessel involvement of intimal hyperplasia. Intimal hyperplasia was considered when the newly formed intraluminal tissue exceeded 0.1 mm in thickness and in stent stenosis when the lumen narrowing was >20%. Results Intimal hyperplasia developed at two specific locations: at the mid-segment of FD (at the inner curve of the innominate artery), presented as a focal IH with a mean thickness of 0.11–0.16 mm. And at the distal end of FD, where the mean device/vessel ratio >1.8, presented as circumferential hyperplasia with mean IH: 0.14–0.22 mm. Mild in-stent stenosis (20%–50%) was only seen distal to the vertebral artery. In stent stenosis was identified in 5 cases (50%) in C-PED group with and without DAPT, in 33% in S-PED-no-DAPT and in 0% in S-PED-with-DAPT. Phosphoryl-choline surface modified FD with DAPT showed a significant (Fisher’s exact, p Conclusions Our preliminary study suggests that the distal end of the FD (landed in small vessel) and the area of high metal density (mid-portion of FD) are more prone to develop intimal hyperplasia. Furthermore, using phosphoryl-choline surface modified flow diverters can be beneficial in preventing in-stent stenosis in small vessels. Reference . Neurosurgery. 2016;78:862–867 Disclosures M. Marosfoi: None. F. Clarencon: None. E. Langan: None. R. King: None. O. Brooks: None. T. Tamura: None. J. Wainwright: 5; C; Medtronic Neurovascular. M. Gounis: 1; C; Medtronic Neurovascular. A. Puri: 1; C; Medtronic Neurovascular.

Introduction/Purpose Malapposition has a negative correlation to aneurysm healing 1 . We examine the influence of malapposition communicating into the aneurysm, and the effect of malapposition incidence at any position along the parent artery on healing. We define communicating malapposition (CM) as any malapposition along the aneurysm neck (figure 1). We hypothesize that CM seen on optical coherence tomography (OCT) results in lower aneurysm occlusion rates after 30 days, and that malapposition at any other point along the parent artery has no effect. Materials and Methods Fifty New Zealand White rabbits underwent elastase-induced aneurysm creation. 2 After 21 days, animals were randomly implanted with: Pipeline Embolization Device (PED; n=20); Pipeline Embolization Device with Shield technology (SHIELD; n=20); or, Flow Reduction Endoluminal Device (FRED; n=10). Five days prior to implantation, 10 animals from each group began dual antiplatelet therapy (DAPT; aspirin/clopidogrel 10 mg/kg each) which was continued daily until the 30 day terminal endpoint. All animals were used for statistical analysis in this study since the influence of DAPT yielded no significant impact on rates of aneurysm occlusion. All animals underwent post-deployment OCT to assess device/vessel apposition. At 30 days, DSA and OCT were acquired to assess aneurysm healing. The incidence of CM was assessed on a binary scoring system: 0 CM present; 1 CM absent. Aneurysm healing on DSA was measured using a previously developed 5-point scale 3 – a score of 3 or 4 (neck remnant or complete occlusion) was considered a positive outcome. Separately, the presence of malapposition distal to the aneurysm neck was measured on a similar binary scale: 0- malapposition seen distal to aneurysm; 1 – no malapposition observed. A Fisher’s exact test was used to show significance. Results Overall positive aneurysm outcome at 30 days was seen in 50% of cases (n=25), with no CM seen in 80% of those cases (n=20). Significant interaction between no CM and positive outcome was confirmed by a Fisher exact test, p=0.0014. When malapposition incidence along the parent artery distal to the aneurysm was compared to positive outcome, no significant interaction was found, p=0.776. Conclusion OCT shows potential in serving as an indicator of poor outcome in the presence of CM during device implant. From these data, absence of communicating malapposition is strongly associated with early aneurysm occlusion, whereas malapposition distal to the aneurysm showed no effect on rates of aneurysm healing. References . AJNR 2016;37(11):2087–91. 2. AJR . 2000;174:349–354. . AJNR 2012;33(10):2004–9. Disclosures R. King: None. O. Brooks: None. E. Langan: None. M. Marosfoi: None. F. Clarencon: None. T. Tamaura: None. J. Wainwright: 5; C; Medtronic Neurovascular. M. Gounis: 1; C; Medtronic Neurovascular. A. Puri: 1; C; Medtronic Neurovascular.

Introduction A growing body of research has suggested the benefits of mechanical thrombectomy in large vessel occlusion with the use of newer generation of thrombectomy devices. Different device designs may influence the rate of procedural-related embolic events, which is a modifiable risk. The EmboTrap thrombectomy system features an inner stent channel with an outer stent trap design that may potentially reduce the risk of distal clot fragmentation. The objective of this study is the analysis of embolic potential during EmboTrap thrombectomy as compared with existing, FDA-cleared technology for the treatment of acute ischemic stroke. Materials and Methods A hard, inelastic clot was injected into a patient-specific circle of Willis replica to form a middle cerebral artery occlusion. A guide catheter was placed in the cervical ICA, and delivered the guidewire which was then softly advanced through the clot. A microcatheter was navigated over the wire across the occlusive clot. The guidewire was withdrawn followed by device (EmboTrap or Solitaire 2) deployment for mechanical thrombectomy. During retriever retraction, continuous aspiration was applied through an aspiration pump. Twenty experiments were carried out for each device. The maximum number of thrombectomy attempts was limited to 3. Emboli greater than 1000μm were measured with calipers. The Coulter Principle was used to characterize emboli with size between 200µm to 1000µm. Results EmboTrap thrombectomy resulted in a significant reduction in the frequency of large clot fragment (>1000μm) dislodgement as compared to Solitaire thrombectomy (p=0.031, Fisher’s exact test). Formation of emboli greater than 1000μm in size occurred in 3 out of 20 cases in the EmboTrap group, versus 11 of 20 experiments with the Solitaire group. Approximately 80% of >1000μm emboli were found in the MCA, regardless of device type. There was no significant difference in average clot size between EmboTrap and Solitaire groups (size ranging from 1000 to 4000μm) in the >1000μm size range. In the size range between 200 to 1000μm, a broader size distribution of emboli was observed with the Solitaire device (200- 770μm) compared to the EmboTrap device (200–325μm). There was no significant difference between the EmboTrap and Solitaire in 200 to 1000μm emboli formation (p=0.89, Mann-Whitney test). When combining all emboli in the most dangerous range (>200μm), EmboTrap offered size reduction of emboli (p=0.022). A complete flow restoration after a single pass was observed in all cases except for 1 experiment in the EmboTrap group, whereas 2 out 20 cases in the Solitaire group required more than 2 passes to achieve full recanalization. Conclusion Based on this preliminary study, it is our conclusion that stent retriever design can be optimized to alter the particle size distribution of distal emboli. When encountering friable hard clots, the use of the EmboTrap device may provide a reduction in distal emboli to both affected and unaffected territories and should be considered. Disclosures: J. Chueh: None. M. Marosfoi: None. R. King: None. O. Brooks: None. A. Puri: None. M. Gounis: 1; C; research grant. 6; C; Travel Support.

Introduction/Purpose Major ipsilateral ischemic stroke have been reported to range between 1.6%–4.3%1,2 after flow diverter treatment. Patient-specific contributors to peri-procedural thromboembolic complications remain under investigation. Beyond understanding and correcting patient-specific factors, we seek device technology to decrease these unpredictable complications. By using high resolution intravascular imaging tool (optical coherence tomography – OCT) we sought to determine the rate of acute micro-clot formation on the surface of different flow diverters. Furthermore, we assessed the consequences of angioplasty (after FD implant) with respect to acute clot formation. We hypothesize that a new generation phosphoryl-choline surface modified flow diverter may reduce acute clot formation on the surface of the device. Materials and methods Thirty elastase induced aneurysms were created in rabbits and treated with 3 different types of flow diverters. Classic Pipeline (C-PED), Pipeline-Flex with Shield Technology (S-PED) and FRED devices were implanted in 10 animals in each group. Four days prior to implant animals received dual anti-platelet therapy (DAPT: 10 mg/kg aspirin and clopidogrel) and that was continued until the end of the study (30 days). OCT (Dragonfly, St Jude) was used to assess the acute clot formation on the surface of devices, after deployment, and repeated 20 min after angioplasty (Figure). Thrombus formation was analyzed and scored by looking at 3 different locations along the implant. In addition, clot formation at the origins of covered side branches (OSB) was separately scored. Results At the origin of side branches, the S-PED showed a significantly less amount of clot formation both pre- and post-angioplasty (10% and 20%, versus C-PED: 40% and 60% and FRED: 60% and 90%, respectively, p=0.0065). At the 3 other locations (OSB not included): the distal end of the device, proximal end (including the level of the aneurysm) and the location between the aneurysm and the vertebral artery there was no difference in clot formation between the 3 devices immediately after deployment. However, following angioplasty of the devices, a decrease of clot formation was seen only in the S-PED group versus an increase as expected with the other devices (S-PED: 20% decrease, C-PED: 30% increase, FRED: 20% increase). Conclusion Our preliminary study supported our hypothesis that using phosphoryl-choline surface modified flow diverter can be useful to decrease the occurrence of micro-clot formation, especially post-angioplasty. Importantly, S-PED reduced clot formation at the origin of covered side-branches. References . AJNR 2015;36:98–107. . J. Neurosurg 2016;1–6. Disclosures M. Marosfoi: None. F. Clarencon: None. E. Langan: None. R. King: None. O. Brooks: None. T. Tamura: None. M. Gounis: 1; C; Medtronic Neurovascular. A. Puri: 1; C; Medtronic Neurovascular.

Introduction Recent meta-analysis of randomized clinical trials has shown that endovascular intervention yields higher rates of revascularization and superior functional outcomes as compared to standard medical therapy in the setting of emergent large vessel occlusion causing stroke. However, there remained approximately 20% patients in whom successful revascularization (mTICI score, 2b or 3) was not achieved after stent-retriever thrombectomy [1, 2]. Revascularization achieved with thrombectomy devices depends in part upon the integration of the thrombus material into the retrieval device. The histologic composition and mechanical properties of thrombi are key determinants of effective thrombus-device interaction. We hypothesize that calcified and fibrin-rich thrombi are stiffer than erythrocyte-rich thrombi; therefore, they may serve as the challenging thrombus models to evaluate thrombus-device interactions, and further aid the design and development of future generations of stent retrievers. The goal of this study is to 1) characterization of thromboemboli retrieved from patients with AIS, and 2) development of thrombus analogs with histologic and mechanical characteristics similar to those of challenging clinical thrombi for thrombectomy device testing. Materials and methods Thrombi were retrieved from patients with AIS using stent retriever devices. Several technical metrics of the thrombectomy procedure such as number of pass attempts and occurrence of embolic complication were collected. Fifty clinical thrombi collected from twenty nine AIS patients underwent histologic analysis, and nine clinical thrombi were subjected to dynamic mechanical analysis (DMA). Thrombus histology was determined by staining specimens for erythrocytes and fibrin content using the Martius Scarlet Blue technique and performing computerized segmentation and quantitative analysis. During the DMA tests, thrombus stiffness was defined as a function of stress variation over strain. The average stress variation at low strain (E1: 0 to 75% strain) and high strain (E2: 75 to 100% strain) was recorded. The results generated from the clinical samples were used to determine the key components of the challenging thrombus analogs, calcium apatite-rich and fibrin-rich thrombus analogs. Results Of the twenty nine AIS cases analyzed, fifteen cases required multiple pass attempts. The average histologic composition of the clinical thrombi obtained from cases with more than 1 thrombectomy pass was 26% erythrocyte, 54% fibrin, and 20% mixed, whereas the average histologic composition of all the fifty clinical thrombi analyzed was 33% erythrocyte, 47% fibrin, and 20% mixed. The DMA results demonstrated that the stiffness of the challenging clinical thrombi (E1: 0.00011±0.000076MPa, E2: 0.015±0.0083MPa) was similar to that of the fibrin-rich thrombus analogs (E1: 0.00013±0.000002MPa, E2: 0.011±0.0007MPa). Compared to the fibrin-rich thrombus analogs, addition of calcium apatite increased the stiffness of the thrombus analogs by approximately 5 times. Conclusion Thrombus analogs with mechanical characteristics similar to those of challenging clinical thrombi were successfully developed. The calcium apatite thrombus analog was found to be stiffer than the fibrin-rich thrombus analog. References . Saver JL et al: Stent-retriever thrombectomy after intravenous t-PA vs. t-PA alone in stroke. N Engl J Med 2015, 372(24):2285–2295. . Dorn F et al: Endovascular treatment of acute intracerebral artery occlusions with the solitaire stent: single-centre experience with 108 recanalization procedures. Cerebrovasc Dis 2012, 34(1):70–77. Disclosures: J. Chueh: None. J. Litchman: None. R. Arslanian: None. S. Carniato: 5; C; Principal Preclinical Research Associate at Stryker Neurovascular. D. Rex: None. M. Howk: None. M. Gounis: 1; C; research grant supported by Stryker Neurovascular. 2; C; consultant for Stryker Neurovascular. A. Puri: 1; C; research grant suppported by Stryker Neurovascular. 2; C; consultant for Stryker Neurovascular.