ABSTRACTS Platform 1 RNA Expression Identifying Ischemic Stroke In Acute Hospital Setting: Interim Analysis From BASE Clinical Trial Daniel J Miller, MD1 1Department of Neurology, Henry Ford Hospital, Detroit, Michigan, United States of America Introduction: Blood testing panels in the acute setting to determine (i) if a stroke occurred, (ii) differentiation cause between cardioembolic stroke (CES) or large artery atherosclerosis stroke (LAA), and (iii) separately detect the presence of atrial fibrillation (AF) would be of significant clinical utility. Using the Biomarkers of Acute Stroke Etiology (BASE) trial (NCT02014896) dataset, our purpose was to utilize blood gene expression signatures as a panel approach for accurately identifying if a stroke occurred compared to a control subject, differentiating LAS from CES acute stroke etiologies, and separately identify AF. Methods: The BASE trial enrolled suspected stroke patients presenting to 20 hospitals within 24 hrs of symptom onset and age, race, gender, smoking, comorbidity match controls. Final gold standard diagnosis and stroke etiology were determined by an adjudication committee using all hospital data but blinded to RNA test results. Whole blood, obtained in PAX tubes, was frozen at -20C within 72 hrs and analyzed at a core lab (Ischemia Care, Dayton, OH) using Affymetrix HTA microarrays. Genes on the HTA microarray were filtered to eliminate genes with low expression or high CV (> 10%) when run on replicate samples leaving 9,513 potential signature genes. A two-way random forest classifier was built through cross validation of the training data resulting in three distinct diagnostic signatures based upon 23 genes for a panel of three separate tests. Results: This is a planned interim cohort study of the 1700 patients enrolled in the BASE trial that does not include lacunar strokes, cryptogenic strokes, TIA, or stroke mimics. Overall, 224 patients were enrolled with NIHSS>=5, 59 (26%) with LAS, 165 (74%) with CES, and 66 control subjects; 56% were male, and median (IQR) age was 72.9 yrs (63.7, 82.9). Median (IQR) time from symptom onset to blood collection was 487 (321, 1129) minutes. Coexistent pathology at presentation included atrial fibrillation 120 (54%), hypertension 186 (83%), hyperlipidemia 186 (48%), diabetes 74 (33%), and coronary artery disease 78 (35%). Patients were randomly divided into training (132) and validation (92). The diagnostic 12 gene signature results distinguished stroke from control; C-statistic 0.86, sensitivity of 0.91, specificity of .61. The diagnostic 3 gene signature results distinguished CES from LAA C-statistic 0.70, sensitivity of 0.85, specificity of 0.49. The diagnostic 8 gene signature results distinguished AF from (a) cardioembolic stroke not due to atrial fibrillation and (b) LAA, C-statistic 0.69, sensitivity of 0.70, specificity of 0.59. Conclusions: Targeted panels of RNA expression markers may be used together or separately to determine if a stroke occurred, stratification into CE and LAA causes, and presence of AF, and may have triage, interventional, therapeutic, and secondary prevention implications. Keywords: Acute Stroke, Ischemic Stroke, Acute Ischemic Stroke Intervention, New Innovation, Inflammation Financial Disclosures: The authors had no disclosures. Grant Support: None. Platform 2 Closely Sizing the Catheter to Vessel Enables Flow-Arrest and Flow-Reversal During Aspiration in the MCA Raul G Nogueira, Professor1, David Ryan, Mr2, Liam Mullins, PhD3, John Thornton, FFR RCSI4, Sean G Fitzgerald, PhD2 1Grady Memorial Hospital and Emory University, Atlanta, Georgia, United States of America; 2National University of Ireland Galway, Galway, Ireland; 3Perfuze Ltd, Galway, Ireland; 4Beaumont Hospital, Dublin, Ireland Introduction: Delgado Almandoz et al. established catheter size as an independent predictor of successful revascularization (mTICI 2b/3) when using A Direct Aspiration First-Pass Thrombectomy (ADAPT) technique1. Several studies have also demonstrated a trend towards higher rates of successful reperfusion with larger bore catheters and with larger catheter-to-vessel diameter ratio,2, 3. While Balloon Guide Catheters (BGCs) are used to achieve flow control and larger bore catheters are known to increase aspiration force, little is known about distal flow a patterns during aspiration. Our objective was to establish flow patterns in terms of distal flow control using various aspiration catheter sizes, with and without the use of BGCs, in a representative in-vitro Circle of Willis model. Methods: The in-vitro model comprised a peristaltic pump, aortic arch and Circle of Willis (Vascular Simulations Inc). Pulse rate (72BPM), flow rate (720mL/min), and temperature (37°C) were controlled to replicate in- vivo conditions. Flow was measured continuously in the distal middle cerebral artery (MCA), 15cm distal to the catheter tip placed in the MCA-M1, using ultrasonic flow sensors (SONOFLOW CO.55/060, SONOTEC GmbH). Four aspiration catheters with increasing lumen size were evaluated; ACE 060 & ACE 064 (Penumbra), Sofia Plus (Microvention) and Millipede 088 (Perfuze). Results: Flow Control: The Millipede 088 device results in a significantly larger reduction in MCA flow than all other aspiration catheters, even when they used with a BGC (Fig 1A). The use of a BGC leads to moderate reduction in the amount of flow in the MCA using the ACE 060, ACE 064 and Sofia Plus devices (Fig 1A). Aspiration: Smaller catheters (ACE 060, ACE 064 and Sofia Plus) were unable to cause flow reversal in the distal MCA during aspiration (Fig 1 B&C). This means that there is still forward flow in the distal MCA during aspiration. Millipede 088 achieved complete flow reversal (-150ml/min) in the distal MCA during aspiration (Fig 1 D). Conclusions: Two key behaviours were observed. First, closely matching the catheter size to the vessel size allows the physician to control the degree of local flow arrest upon catheter insertion potentially negating the need for a BGC. Second, an 088 ID catheter enables significant flow reversal in the distal MCA during aspiration meaning that fluid is drawn from distal regions (distal aspiration) of the vasculature potentially enabling removal of distal clot emboli. Keywords: Endovascular, New Technique, Balloon Guide Catheter, Neurointerventional Education, Financial Disclosures: Perfuze Ltd - Stock Holder Grant Support: This work was supported by the European Regional Development Enterprise Ireland grant number IP-2019-0865. Platform 3 Long-term sided branch and perforator patency following Surpass flow diverter treatment in the SCENT Trial Miklos Marosfoi, MD1, Joost de Vries, MD2, Peter T Kan, MD3, Ricardo A Hanel, MD4, Alexander L Coon, MD5, Philip M Meyers, MD6, Ajay K Wakhloo, MD1 1Department of Neurointerventional Radiology, Beth Israel Lahey Health, LHMC, Burlington, Massachusetts, United States of America; 2Department of Neurosurgery, Radboud University Medical Center, Nijmegen, Netherlands; 3Department of Neurosurgery Baylor College of Medicine, Houston, Texas, United States of America; 4Department of Neurosurgery, Jacksonville Baptist, Jacksonville, Florida, United States of America; 5Carondelet Neurological Institute, St. Joseph's Hospital, Tucson, Arizona, United States of America; 6Department of Neurosurgery Columbia University Medical Center, New York, New York, United States of America Introduction: Flow diverters (FD) have demonstrated to be highly effective in the treatment of intracranial aneurysms (IA). Multiple international studies have reported long-term occlusion rates between 85% and 95%. When treating IA, FD frequently does cover side branches or perforators. The fate of these covered vessels has not systematically been evaluated. We did a post-hoc data analysis of the SCENT trial and studied the long-term patency of these vessels and correlated it with clinical outcome. Methods: Subjects enrolled in the SCENT Trial with at least a 1-year angiographic follow-up were included. Patency of covered ophthalmic (OphA), anterior choroidal (AChA) and lenticulostriate arteries (LSA) were retrospectively analyzed on angiograms by two independent experienced neurointerventionalists. Images were available at the time of the procedure, at 6 months and at 1, 3, and 5 years. Flow within the side branches and perforators were scored as brisk, slow or absent. The artery was considered occluded if not discerned on follow-up imaging. Occlusions were classified as symptomatic or asymptomatic and changes in vessel patency over multiple follow-up angiographic studies were recorded. Results: A total of 171 subjects out of 180 enrolled in the Surpass SCENT trial with ICA aneurysms treated were available for assessment. Six-hundred fifteen angiograms were reviewed and scored. Follow-up angiography was available for: 153/171 (89.4%) of the patients at 1 year; 109/171 (63.7%) patients at 3 years; 29/171 (17.0%) patients at 5 years. In total 225 side branches or perforators were covered. OphA, AChA, and LSA were covered in 143 (84%), 63 (37%), and 19 (11%) of the subjects respectively. Ophthalmic arteries were patent at one year in 119/127 (93%) patients and the number of the compromised vessels remained the same at 3 years. One 1/51 (2%) AchA progressed to an occlusion at 3 years; one AchA with a slow flow - did not change over time. There were no LSA (0/19) occlusions at 1 and 3 years. From a total of 225 covered vessels, 7 (3.1%) were symptomatic, and were associated with the OphA [7/127 (5.5%)]; there