M1 Occlusion Research Articles

Late Lesion Growth following Endovascular Therapy: Is 24 h Too Early to Assess Acute Infarct Size Including the Effects of Secondary Injury?

Introduction: Stroke lesion volume on MRI or CT provides objective evidence of tissue injury as a consequence of ischemic stroke. Measurement of “final” lesion volume at 24-h following endovascular therapy (post-EVT) has been used in multiple studies as a surrogate for clinical outcome. However, despite successful recanalization, a significant proportion of patients do not experience favorable clinical outcome. The goals of this study were to quantify lesion growth during the first week after treatment, identify early predictors, and explore the association with clinical outcome. Methods: This is a prospective study of stroke patients at two centers who met the following criteria: (i) anterior large vessel occlusion acute ischemic stroke, (ii) attempted EVT, and (iii) had 3T MRI post-EVT at 24-h and 5-day. We defined “early” and “late” lesion growth as ≥10 mL lesion growth between baseline and 24-h diffusion-weighted imaging (DWI) and between 24-h DWI and 5-day fluid attenuated inversion recovery imaging, respectively. Complete reperfusion was defined as >90% reduction of the volume of tissue with perfusion delay (Tmax>6 s) between pre-EVT and 24-h post-EVT. Favorable clinical outcome was defined as modified Rankin scale (mRS) of 0–2 at 30 or 90 days. Results: One hundred twelve patients met study criteria with median age 67 years, 56% female, median admit NIHSS 19, 54% received IV or IA thrombolysis, 66% with M1 occlusion, and median baseline DWI volume 21.2 mL. Successful recanalization was achieved in 87%, and 68% had complete reperfusion, with an overall favorable clinical outcome rate of 53%. Nearly two-thirds (65%) of the patients did not have late lesion growth with a median volume change of −0.3 mL between 24-h and 5-day and an associated high rate of favorable clinical outcome (64%). However, ∼1/3 of patients (35%) did have significant late lesion growth despite successful recanalization (87%: 46% mTICI 2b/41% mTICI 3). Late lesion growth patients had a 27.4 mL change in late lesion volume and 30.1 mL change in early lesion volume. These patients had an increased hemorrhagic transformation (HT) rate of 68% with only 1 in 3 patients having favorable clinical outcome. Late lesion growth was independently associated with incomplete reperfusion, HT, and unfavorable outcome. Conclusion: Approximately 1 out of 3 patients had late lesion growth following EVT, with a favorable clinical outcome occurring in only 1 out of 3 of these patients. Most patients with no early lesion growth had no late lesion growth. Identification of patients with late lesion growth could be critical to guide clinical management and inform prognosis post-EVT. Additionally, it can serve as an imaging biomarker for the development of adjunctive therapies to mitigate reperfusion injury.

Comparison between transradial and transfemoral mechanical thrombectomy for ICA and M1 occlusions: insights from the Stroke Thrombectomy and Aneurysm Registry (STAR)

BackgroundThe role for the transradial approach for mechanical thrombectomy is controversial. We sought to compare transradial and transfemoral mechanical thrombectomy in a large multicenter database of acute ischemic stroke.MethodsThe prospectively...

Standardized approach to direct first pass aspiration technique for endovascular thrombectomy: Description and initial experience with CANADAPT

Background Endovascular thrombectomy (EVT) is standard of care for acute ischemic stroke. Stent assisted EVT with aspiration (SOLUMBRA) technique has remained a mainstay approach. There is growing evidence that A Direct Aspiration First Pass Technique (ADAPT) is a safe, efficient and effective approach for EVT, offering several advantages. This study describes and reports initial institutional experience in the use of a standardized scientific based aspiration only technique: CANADAPT. Methods Single center prospective cohort study was performed on consecutive patients treated for large/medium vessel ischemic stroke with CANADAPT. Intravenous thrombolytics were administered according to routine practice, independent of the decision to proceed with EVT. A sequential stepwise aspiration only technique was then applied, CANADAPT, consisting of three maneuvers, A, B and C. The reperfusion success rate, number of passes, use of rescue technique, complication rate and procedural cost were determined. Results Twenty-two patients were included in this case series representing M1 (17, 77%), M1/2 (2, 9%), carotid-T (2, 9%) and basilar (1, 5%) occlusions. First pass recanalization was achieved in 11 (50%) of patients. A further four patients had successful reperfusion with a second pass of CANADAPT (total 68% success rate). Only one patient had successful reperfusion with the aspiration catheter at the clot interface (CANADAPT A). All others required some withdrawal of the aspiration catheter for reperfusion (CANADAPT B and C). Seven patients had SOLUMBRA rescue. Of these, five patients (22% of total patients) had further successful reperfusion. Overall median procedural time was 23 min for first recanalization and 30 min for final recanalization. The cost per procedure was $6630 ± 1069 for CANADAPT, and $13,530 ± 2706 for SOLUMBRA techniques. Conclusions CANADAPT represents a standardized scientific-based approach to aspiration only thrombectomy intervention. This initial study demonstrates the safety, efficiency and efficacy of this technique for use in EVT.

Neurological Improvement by One-Thirds Is Associated With Early Recanalization in Stroke With Large Vessel Occlusion.

A proportion of large vessel occlusion strokes demonstrate early recanalization, obviating the initial intention to proceed to endovascular thrombectomy. Neurological improvement is a possible surrogate marker for reperfusion. We aimed to determine the optimal threshold of neurological improvement, as defined by the National Institutes of Health Stroke Scale (NIHSS), which best associates with early recanalization. We retrospectively analyzed consecutive patients with large vessel occlusion transferred from primary stroke centers to a tertiary comprehensive stroke center in Melbourne, Australia, for possible endovascular thrombectomy from January 2018 to December 2022. Absolute and percentage changes in NIHSS between transfer, as well as other definitions of neurological improvement, were compared using receiver operating characteristic curve analysis for association with recanalization as defined by the absence of occlusion in the internal carotid artery, middle cerebral artery (M1 or M2 segments), or basilar artery on repeat vascular imaging. Six hundred and fifty-four transferred patients with large vessel occlusion were included in the analysis: mean age was 68.8±14.0 years, 301 (46.0%) were women, and 338 (52%) received intravenous thrombolytics. The proportion of extracranial internal carotid artery, intracranial internal carotid artery, M1, proximal M2, and basilar artery occlusion was 18.8%, 13.6%, 48.3%, 15.0%, and 4.3%, respectively, on initial computed tomography angiogram. Median NIHSSprimary stroke center and NIHSScomprehensive stroke center scores were 15 (interquartile range, 9-18) and 13 (interquartile range, 8-19), respectively. Early recanalization occurred in 82 (13%) patients. NIHSS reduction of ≥33% was the best tradeoff between sensitivity (64%) and specificity (83%) for identifying recanalization. NIHSS reduction of ≥33% had the highest discriminative ability to predict recanalization (area under the curve, 0.735) in comparison with other definitions of neurological improvement. One-third neurological improvement between the primary hospital and tertiary center was the best predictor of early recanalization.

Variation in Vessel Size and Angiographic Outcomes Following Stent‐Retriever Thrombectomy in Acute Ischemic Stroke: STRATIS Registry

Background Mechanical thrombectomy is established for large‐vessel occlusions in acute ischemic stroke, but the potential role in distal vessel occlusions of medium arteries is less well established. Such medium or distal arterial segments have not been assessed with respect to thrombectomy devices used during endovascular therapy. We conducted an analysis of arterial size, segmental anatomy, and stent‐retriever device performance with respect to vessel size during thrombectomy. Methods The STRATIS registry angiography core laboratory adjudicated the exact location of the occlusion, proximal, and distal device deployment, relationship to arterial bifurcations, and anatomic nomenclature. Arterial diameters were measured at all these sites. Statistical analyses examined the relationship between vessel and stent size, and arterial recanalization using expanded Thrombolysis in Cerebral Infarction reperfusion score. Results Overall, 665 patients with stroke were included following thrombectomy using various Solitaire device sizes, including Solitaire 4×40, Solitaire 6×30, Solitaire 4×20, Solitaire 6×20, and Solitaire 4×15. Arterial diameter at the occlusion site was a median of 2.17 mm (interquartile range [IQR], 1.88–2.60 mm) in the distal M1, 1.67 mm (IQR, 1.47–2.06 mm) in the proximal M2 middle cerebral artery, 1.50 mm (IQR, 1.15–1.61 mm) in the distal M2 middle cerebral artery, 1.24 mm (IQR, 1.11–1.24 mm) in the M3 middle cerebral artery, and 1.88 mm (IQR, 1.49–1.94 mm) in the P1 posterior cerebral artery. Expanded Thrombolysis in Cerebral Infarction 2b to 3 reperfusion was achieved in all M3 or P1 segment occlusions. The rate of first‐pass recanalization was significantly higher in patients with medium (0.75–2 mm) versus large (>2 mm) vessel occlusion (69.5% versus 57.1%; P = 0.003). Conclusion Considerable overlap was noted between arterial sizes at occlusion sites carrying different segmental arterial nomenclature or vessel names. Substantial reperfusion may be achieved with currently available mechanical thrombectomy devices in medium arteries.

Abstract TP129: Automated Vessel Density Maps on CT Angiography Identify M2 Occlusions

Introduction: Patients with occlusions of the M2 branch of the middle cerebral artery are frequently considered for endovascular thrombectomy. Most AI software programs focus on identification of large vessel occlusions and frequently miss M2 inclusions. An automated software program with good sensitivity for detecting more distal occlusions could help rapidly identify patients for reperfusion therapies. Methods: Consecutive patients with a final diagnosis of occlusion of an M2 branch of the middle cerebral artery were identified from the Johns Hopkins Stroke database. All occlusions were verified by a neuroradiologist (VY). The baseline CTA from these patients was evaluated with the Rapid CTA vessel density software. This software identifies a reduction in vessel density within the middle cerebral artery territory and classifies the vessel density reduction as as: 20-25%, 26-40%,41-55% or >55%. A reduction of greater than 20% or greater was consider positive as a potential indicator of M2 occlusion. Adding a sample of about 50 pts with no evidence of vessel occlusion would be desirable to be able to report specificity. Results: Forty-four of 62 patients (71%) with M2 occlusions had a reduction in vessel density of at least 20% on automated CTA. Among the positive cases, 20 percent had a 20-25% reduction, 20% had 26-40%, 30% had 41-55% and 30% had a >55% reduction. Conclusion: The Rapid CTA hyperdensity program identified 71% of M2 occlusions with most patients having more than a 25% reduction in vessel density. Automated software has the potential to quickly identify patients with M2 branch inclusions.

Abstract WP138: Collateral Status Measured by Hypoperfusion Intensity Ratio Correlates With Infarct Core Size and Growth Rate in MCA Medium Vessel Occlusions <6 Hours and 6-24 Hours Post Onset

Purpose: Hypoperfusion intensity ratio (HIR) derived from CT perfusion (CTP) has shown to be a useful surrogate marker of collateral status, but prior studies focused on ICA/M1 large vessel occlusions (LVO). We aimed to determine: associations between HIR and clinical/imaging metrics of stroke severity for M2 and M3 medium vessel occlusions (MVO), any differences between <6h and 6-24h from onset as MVO often present later than LVO, and what optimal HIR threshold describes infarct growth rate (IGR) >10mL/h (fast progressor). Methods: We retrospectively analyzed consecutive patients arriving within 24h from onset, with M2 or M3 occlusion on CTA, and had concurrent CTP. RAPID generated maps of infarct core defined as rCBF<30% and HIR defined as Tmax>10s/Tmax>6s. IGR was defined as core size/onset-to-CTP time. ASPECTS and NIHSS data were also collected. Correlations were tested using Spearman's rank analysis, for the cohort and separately for <6h and 6-24h subgroups. Difference in HIR between subgroups was tested using Mann-Whitney U. Optimal threshold for IGR>10mL/h was determined by ROC analysis. Results: 78 patients included with median (IQR) age of 79 (64-84), onset of 7.5h (2.5-14.5), NIHSS of 12 (7-18), ASPECTS of 7 (9-10), core size of 4 mL (0-22), and IGR of 0.57 mL/h (0-2.8). 63 M2 and 15 M3 occlusions identified with median HIR of 0.35 (0.06-0.52). For the cohort, HIR was highly correlated to core size r=0.740 and IGR r=0.710, moderately correlated to NIHSS r=0.474 and ASPECTS r=-0.331 (all p<0.003). 28 and 50 patients presented <6h and 6-24h, respectively, without significant difference in HIR, median 0.31 vs 0.36 (p=0.543). For <6h, HIR was moderately correlated to core size r=0.672, IGR r=0.639, NIHSS r=0.435, and ASPECTS r=-0.496 (all p<0.021). For 6-24h, HIR was highly correlated to core size r=0.791 and IGR r=0.777, moderately correlated to NIHSS r=0.502 and ASPECTS r=-0.376 (all p<0.007). ROC analysis showed AUC of 0.860 (p<0.001) for IGR>10mL/h, with optimal HIR threshold at 0.43 for sensitivity of 100% [95% CI: 59.0-100], specificity of 64.8% [95% CI: 52.5-75.5]. Conclusion: In acute MCA MVO strokes <6h and 6-24h, HIR as marker of collateral status is moderate to highly correlated to stroke severity, especially size and growth rate of the infarct core.

Abstract WMP66: Detecting Medium Vessel Occlusions and Collateral Assessment With Multimodality AI Approach

Introduction: Recent advances and the use of Artificial intelligence (AI) is changing the standards of care in stroke patients. AI software has a high sensitivity and specificity for identifying Large Vessel Occlusions (LVOs), but the accuracy for detecting Medium Vessel Occlusions (MeVOs) is limited. We investigated the performance of the combination of two different AI modules for the identification of MeVOs. Methods: 150 patients with MeVOs were identified on CTA, using CTP to help localize the lesions, from retrospective databases at the MUSC, Stanford, and Royal Melbourne. Additionally, 55 patients with LVOs on CTA were included. A neuroradiologist confirmed the occluded vessel on CTA for each patient. LVOs were defined as occlusions of the intracranial ICA or horizontal segment of the M1. MeVOs were defined at M2, M3, ACA (A2/A3), or PCA (P2/P3) occlusions. All cases were processed through Rapid LVO, the Rapid Vessel Density module (which assesses hemispheric differences in blood vessel density), and Rapid CTP (Ischemaview Inc., Menlo Park, CA), [AZ1] using automated hypoperfusion intensity ratio (HIR) on CT perfusion (CTP), which estimates collateral flow, differed in LVOs vs. MeVOs. Results: Rapid LVO alone identified occlusions in 41/150 (27.3%) of MeVO patients. Rapid Vessel Density maps identified an additional 38/150 (25.3%) patients with either a 20-25% vessel density reduction or 26-40% reduction. Together, these two modules identified 79/150 (52.6%) of MeVO patients. 54/55 (98.1%) of the LVOs were detected by the Rapid LVO module. The mean HIR was lower in MeVO vs. LVO patients (0.25 vs. 0.45, P-value < 0.001). Patients with M1 or ICA occlusions (LVOs) had average HIRs of 0.46 and 0.47 respectively. Patients with M2, M3, ACA, or PCA occlusions (MeVOs) had average HIRs of 0.30, 0.14, 0.22, and 0.20 respectively. Conclusion: MeVos detection was almost doubled with the use of the RapidAI Vessel Density in conjunction with the LVO module.

Abstract TP195: Impact of Intracranial Atherosclerotic Disease on Thrombectomy Outcomes in Acute Cerebral Infarction With Large Vessel Occlusion

Introduction: In acute cerebral infarction with Large Vessel Occlusion (LVO), Intracranial Atherosclerotic Disease (ICAD) often causes vascular occlusion. Previous studies have noted that ICAD-related LVOs, compared to embolic occlusions, have longer procedural times and lower successful reperfusion rates. However, clinical outcomes remain similar. This study compares post-thrombectomy outcomes in both groups, matched by initial NIHSS scores. Method: From October 2017 to March 2023, we studied LVO cases undergoing thrombectomy for acute ischemic stroke. Our primary focus was on evaluating thrombectomy outcomes within two distinct groups— ICAD-related LVO group (ICAD group) and Embolic LVO group (Embolic group)—matched based on preoperative NIHSS scores. ICAD group was defined as persistent occlusion or residual stenosis at the initial occlusion site. Patient outcomes at 3 months were assessed using modified Rankin Scale (mRS) scores, defining devastating outcomes as mRS 5-6. Successful recanalization was defined as Thrombolysis in Cerebral Ischemia score ≥2b. Logistic regression identified factors independently associated with devastating outcomes. Result: Analyzing 2407 cases, we extracted matched pairs (33 each) adjusted by NIHSS. ICAD group had lower atrial fibrillation frequency, lower BNP levels, more M1 occlusions, and fewer M2 occlusions compared to the Embolic group. In treatment outcomes, ICAD group had lower successful recanalization (82% vs 43%, P =0.001), higher reocclusion rates (0% vs 21%, P =0.005), and longer puncture-to-reperfusion time (median 51 vs 88 minutes, P <0.001). Devastating outcomes were higher in ICAD group (15% vs 39%, P =0.027). Multivariate analysis showed ICAD's independent association with devastating outcomes (Odds ratio, 6.54; 95% CI, 1.56-27.4; P =0.010) along with age, NIHSS, and tPA absence. Conclusion: In thrombectomy-treated LVO patients, matching based on admission NIHSS scores revealed significantly higher devastating outcomes in the ICAD group when compared to the Embolic group.

Abstract WP133: Phase MRI Clot Characteristic and Radiologic Thrombectomy Outcomes in Acute Ischemic Stroke

Background: Magnetic Resonance (MR) susceptibility weighted imaging (SWI) sequences produce filtered Phase images where blood products demonstrate signal intensities opposite to calcifications. Though susceptibility Vessel Sign (SVS) on pre-interventional MRI has been reported as an indicator of outcome following thrombectomy, the association of Phase MR imaging with thrombectomy outcomes is not previously studied. Methods: In this retrospective cohort study of consecutive acute large vessel occlusion strokes with Phase MR imaging prior to thrombectomy, we evaluated the correlation between clot features on pre-interventional MR imaging with radiographic outcomes following thrombectomy. The clot characteristics included the presence of SVS and its geometrical features on both Phase and GRE sequenced MRIs and thrombus extension. Results: A total of 57 patients were included in this analysis (mean age: 65.04 ± 15.8, 33% Female, mean NIHSS: 13.0 (7.5, 19.5), 33% M1 occlusion), among which 52 (91%) patients had positive SVS on phase-sequence MRI. Successful recanalization was achieved in 91% and successful first pass recanalization was observed in 46%. In univariate analysis, baseline demographics and clinical characteristics including age, sex, and comorbidities were not associated with successful recanalization. Homogeneity of Phase-SVS was significantly associated with the first pass successful recanalization (Odds ratio (OR) 1.81; Confidence interval (CI) [1.14-2.88], p: 0.006). Conclusion: Our study suggests MRI Phase-SVS clot homogeneity as a novel predictor of first pass successful recanalization following mechanical thrombectomy in acute stroke.

Abstract WP190: Comparison of Collateral Score to ASPECTS to Exclude "Very Large" Infarct Core Volumes in Anterior Circulation Large Vessel Occlusion Strokes at 0-24 Hours

Purpose: ASPECTS<3 was an explicit exclusion criterion in the SELECT2 trial to exclude "very large" infarcts (>100mL) for reperfusion using endovascular thrombectomy (EVT). While specific, ASPECTS<3 may be too insensitive of a threshold on noncontrast CT at 0-24 hours (especially 0-6 hours). We aim to determine if CTA based Collateral Score (CS) can be a more sensitive surrogate marker for infarct core volume (ICV)>100mL while maintaining similar specificity to ASPECTS. Methods: Retrospective analysis included consecutive stroke patients arriving within 24 hours of onset, with intracranial ICA and/or M1 occlusion on CTA, and had concurrent CT perfusion. RAPID AI software estimated ICV using the rCBF<30% threshold. CS was scored on CTA using the method of Tan et al on a 4-point scale for % collaterals compared to contralateral side: 0 none, 1 >0 but <50%, 2 >=50 but <100%, and 3 100%. ROC curve analysis was used to find the optimal CS cutpoint with high specificity for ICV>100mL. Sensitivity and specificity of that CS threshold vs ASPECTS<3 were compared using the N-1 chi square test. Results: 164 patients were included with median (IQR) age of 74 (66-84), NIHSS of 20 (12-25), and time of onset-to-CT of 4 hours (2-7.5). The LVOs were 17 ICA (10.4%), 108 M1 (65.9%), and 39 both (23.8%), with median ICV of 12mL (0-45). 16 patients had ICV>100mL (9.8%) with median of 136mL (105-172). Using ASPECTS<3 identified only 1 of these (ICV of 118mL at 18.5 hours), sensitivity of 6.3% (95% CI: 0.16-30.2%), with no false positives, specificity of 100% (95% CI: 97.6-100%). ROC analysis for CS showed AUC=0.818 (p<0.001), with maximal specificity at CS=0 (no visible collaterals). Using CS=0 identified 6 of these infarcts, sensitivity of 37.5% [95% CI: 15.2-64.6%], with 2 false positives, specificity of 98.7% [95% CI: 95.2-99.8%]. The 2 false positives were ICV of 97mL at 2 hours and 96mL at 3 hours. The improved sensitivity of CS=0 over ASPECTS<3 was significant (p=0.036) while the difference in specificity was not (p=0.144). Conclusion: In our cohort of LVOs, CS=0 was a more sensitive surrogate marker for ICV>100mL compared to ASPECTS<3 while maintaining near 100% specificity. If confirmed in future prospective studies, CS=0 has the potential to further streamline patient selection for EVT.

Competitive leptomeningeal flow impact on thrombectomy reperfusion grade rating

BackgroundCompetitive leptomeningeal flow (CLF) can be observed immediately after mechanical thrombectomy (MT) reperfusion with retrograde contrast clearing of the distal leptomeningeal branches from non-contrast opacified flow through different vascular territories....

Abstract WMP64: Late Lesion Growth Following Endovascular Therapy: Is 24 Hours Too Early to Assess Acute Infarct Size Including the Effects of Secondary Injury?

Background: Measurement of “final” lesion volume at 24hr following endovascular therapy (post-EVT) has been used in multiple studies as a surrogate for clinical outcome. However, despite successful recanalization, a significant proportion of patients do not experience favorable clinical outcome. Methods: This is a prospective study of acute ischemic stroke patients at two stroke centers who met the following criteria: i) anterior large vessel occlusion (LVO) acute ischemic stroke, ii) attempted EVT, iii) written informed consent obtained, and iv) had MRI post-EVT at 24hr and 5-day. We defined “Early” and “Late” lesion growth as ≥10mL lesion growth between baseline and 24hr DWI, and between 24hr DWI and 5-day FLAIR, respectively. Results: One hundred fourteen patients met study criteria with median age 67 years, 56% female, median admit NIHSS 19, 54% received IV or IA thrombolysis, 67% with M1 occlusion, and median baseline DWI volume 28.2mL. Successful recanalization was achieved in 86% and 67% had complete reperfusion, with an overall favorable clinical outcome rate of 54%. Nearly two thirds (65%) of the patients did not have Late lesion growth with a median volume change of -0.2mL between 24hr and 5-days and an associated high rate of favorable clinical outcome (65%). However, ~1/3 of patients (35%) did have significant Late lesion growth despite successful recanalization (85% TICI 2b/3). Late lesion growth patients had a 26.2mL change in Late lesion volume and 19.9mL change in Early lesion volume. These patients had an increased hemorrhagic transformation rate of 68% with only 1 in 3 patients having favorable clinical outcome. Late lesion growth was independently associated with incomplete reperfusion, hemorrhagic transformation, and unfavorable outcome even after adjusting for admit NIHSS and Early lesion growth. Conclusions: Approximately 1 out of 3 patients had Late lesion growth following EVT, with a favorable clinical outcome occurring in only 1 out of 3 of these patients. Identification of patients with Late lesion growth could be critical to guide clinical management and inform prognosis post-EVT. Additionally it can serve as an imaging biomarker for the development of adjunctive therapies to mitigate reperfusion injury.

Abstract WP141: Leptomeningeal Competitive Flow Impact on Thrombectomy Reperfusion Grade Rating

Background: The extent of reperfusion following thrombectomy (MT) for large vessel occlusion strokes is predictive of outcomes. There is still inter-rater variability in the reperfusion scoring. We noticed that some patients present with retrograde contrast clearing of the distal branches from non-contrast-opacified flow originated from different territories. We aim to evaluate the frequency of this phenomenon (“competitive flow” (CF)), to evaluate if it has an association with the degree of leptomeningeal collaterals, and its impact on eTICI score. Methods: This is a retrospective-analysis of our MT database spanning 11/2020-12/2021. We included consecutive cases of intracranial internal carotid (i-ICA) and middle cerebral artery (MCA) M1 occlusions. CF was defined by the observation of retrograde clearing of distal MCA branches that were previously opacified by antegrade reperfusion. The clearance of the distal branches is presumed to occur due to CF via non-contrast-opacified PCA or ACA flow. The washout was considered CF if it cleared abruptly with or without forward reconstitution of antegrade opacification. Results: We included a 125 patients. Median age was 64years, 51%were males. Baseline median NIHSS was 17 and ASPECTS 9. Median last-known-well-time to puncture was 7 hours, 30.4% received tPA. Final eTICI2c-3 was achieved in 81.6%. CF was present in 32(25.6%)patients. Baseline characteristics were similar between both groups. The CF arm had better leptomeningeal single-phase-CTA-collaterals(p=0.01) and smaller CTP malignant hypoperfusion volume(p=0.06) VS non-CF. The inter-rater-agreement for eTICI score was moderate when CF was present and excellent in its absence (Krippendorf’s alpha=0.65 and 0.81,respectively). There was poor agreement (K-value=0.3) for the presence versus absence of CF between both operators. Reviewer 1 (2-year-post-training) had correctly identified 46% of patients with consensus CF vs 90% to Reviewer 2 (9-year-post-training) after the consensus read. Conclusion: CF was observed in 32% of patients. CF was found to be associated with better collateral flow, and to impact the reported procedural eTICI rating.

Abstract TP130: Prevalence of Fast Progressors of Infarct Growth in Anterior Circulation Large Vessel Occlusions <6 Hours From Onset

Background/Purpose: Fast progressors (FP) of infarct growth in anterior circulation large vessel occlusions (LVO) may be prevalent in the <6h period depending on how it is defined. The 3 recently completed randomized trials of endovascular thrombectomy (EVT) on large infarct core volumes (ICV) all used ASPECTS criterion of 3-5 which approximates 70-100mL in absolute volume. We aimed to investigate the prevalence of FP in LVO <6h and how many of these were at or on pace to reach the 70mL or 100mL ICV threshold for EVT selection. Methods: We retrospectively included consecutive stroke patients arriving <6h from symptom onset with ICA and/or M1 occlusion on CTA and had concurrent CT perfusion (CTP). RAPID AI software generated maps of ICV depicted as rCBF<30% and critical hypoperfusion depicted as Tmax>6s. Infarct growth rate (IGR) was calculated as ICV/onset-to-imaging time. FP was defined at 2 levels: as "FP70" with IGR >11.7mL/h (which would result in an ICV >70mL by 6h) and had >=70mL of overall hypoperfusion present; and as "FP100" with IGR >16.7mL/h (which would result in an ICV >100mL by 6h) and had >=100mL of overall hypoperfusion present. Results: 108 patients were included with median (IQR) age of 75.5 (67-85), NIHSS of 20 (12-24), onset time of 2h (1.5-4), median ICV of 11mL (0-40), hypoperfusion volume of 122mL (70-164), and mismatch volume of 86.5mL (58-130). The sites of LVO were ICA 12 (11.1%), M1 73 (67.6%), and both 23 (21.3%). Median IGR for the cohort was 3.8mL/h (0-16.4). 31 FP70 were found (28.7%, 95% CI: 19.5-40.7%) with median IGR of 31.3mL/h (16.8-42). 14 of these (45.2%, 95% CI: 24.7-75.8%) already had ICV>70mL upon arrival, with median of 100mL (86-156) and 8 of 14 also showed mismatch ratio <1.8. 25 FP100 were found (23.1%, 95% CI: 16.2-36.9%) with median IGR of 38.7mL/h (24.6-51.4). 8 of these (32.0%, 95% CI: 13.8-63.1%) already had ICV>100mL upon arrival, with median of 138mL (101-172) and 5 of 8 also showed mismatch ratio <1.8. Conclusion: In a cohort of acute anterior circulation LVO strokes <6h from onset, the vast majority were good candidates for EVT with small to medium size core volumes. However, ~25% were fast progressors that may require more caution in selection, with ICV at or on pace to reach 70-100mL thresholds by 6h.

Abstract WP184: Intravenous Thrombolysis Improves Outcomes in Stroke Patients With Unsuccessful Mechanical Thrombectomy

Introduction: The benefits of intravenous thrombolysis (IVT) in acute ischemic stroke (AIS) patients with unsuccessful mechanical thrombectomy (MT) are not well established. Methods: This study included patients from the Stroke Thrombectomy and Aneurysm Registry (STAR) who underwent MT for ICA, M1, or M2 occlusions with unsuccessful MT (mTICI score ≤ 2a). Patients who received IVT prior to MT were compared to those who received MT alone. Propensity score (PS) matching was performed using age, sex, premorbid modified Rankin Scale (mRS), admission National Institute of Health Stroke Scale (NIHSS), occluded vessel, ASPECTS score, mTICI score, and symptom onset to groin puncture time. The primary outcome was favorable 90-day outcomes (mRS 0-2). Results: Of 610 patients with unsuccessful MT, 219 were matched in each group. Median ages were 70 [IQR: 61 - 80] and 73 [IQR: 62 - 81] in the IVT + MT and MT alone groups, respectively. In the IVT + MT group. Final TICI scores of 0, 1, and 2a were achieved in 92 (42.0%), 33 (15.1%), and 94 (42.9%) patients, respectively, compared to 76 (34.7%), 29 (13.2%), and 114 (52.1%) in the MT alone group. The IVT + MT group showed a significantly. higher 90-day mRS of 0-2 (aOR: 2.54, 95% CI: 1.53-4.32) and mRS of 0-3 (aOR: 2.05, 95% CI: 1.36-3.12). There were no significant differences between the groups in intracranial hemorrhage (ICH), symptomatic ICH, or 90-day mortality rates. Conclusions: IVT is associated with improved functional outcomes in patients with unsuccessful MT. Ensuring that IVT is provided to all eligible stroke patients should remain a priority.

Abstract WP208: Infarction Size Affects Clinical Outcomes in Emergent Carotid Artery Stenting With Mechanical Thrombectomy

Background: Management of large vessel occlusion with extensive ipsilateral internal carotid artery (ICA) occlusion is unknown. We evaluated patients who underwent emergent carotid artery stenting (CAS) of the ICA with mechanical thrombectomy (MT). Methods: We retrospectively collected baseline demographic, clinical, and radiographic data on 27 patients who presented as a stroke alert within 24 hours of symptoms and had extensive (from bifurcation to distal ICA) occlusion by computerized tomography angiography from 2019-2023 at our institution. All patients underwent CAS with MT and received dual antiplatelet therapy. We measured outcomes by: (1) development of symptomatic ICH at 24 hours, (2) mortality, (3) Modified Rankin Scale (mRS) at 90 days, and (4) change in NIHSS at 24 hours. Baseline characteristics were reported by descriptive statistics. Statistical analyses were completed using Fisher’s exact test, Wilcoxon rank sum test, and logistic regression. Differences were statistically significant at p < 0.05. Results: The mean age for our cohort was 64.5 ± 10.62 and nine patients were females (33.3%). Sixteen had M1 (59.3%) while 10 had M2 occlusion (37%), 14 patients received IV tPA (51.9%), and mean NIHSS at presentation was 15.6 ± 5.99. All patients achieved TICI 2b or TICI 3 recanalization. In our cohort, patients with lower ASPECT score 7.4 ± 1.8 compared to those with higher ASPECT score 9.0 ± 1.0 were more likely to have symptomatic ICH ( p = 0.032), and higher odds of mortality OR = 0.496, 95% CI (0.261-0.945). The development of symptomatic ICH at 24 hours following procedure was associated with severe disability (mRS 4-6) at 90 days ( p = 0.032). Administration of intravenous tPA was significantly associated with improvement of 4 or more points on NIHSS at 24 hours ( p = 0.032), but not with symptomatic ICH ( p = 0.419). Age, NIHSS at presentation, systolic blood pressure, and diabetes mellitus were not associated with mortality or symptomatic ICH. Conclusion: The area of infarction at the time of presentation (ASPECT score) is an essential factor in stratifying patient selection for emergent CAS during MT in extensive internal carotid artery occlusion. Further studies are needed to evaluate infarction size for safe interventions.

Abstract TP198: Factors Associated With Need for Decompressive Hemicraniectomy After Mechanical Thrombectomy in Stroke Patients

Background: Mechanical thrombectomy (MT) has significantly reduced morbidity and mortality in acute ischemic stroke (AIS). This study aims to analyze the outcomes and factors associated with decompressive hemicraniectomy (DHC) in AIS patients who underwent MT. Methods: We retrospectively analyzed data from an ongoing, multicenter database to investigate AIS patients who underwent MT for ICA, M1, or M2 occlusion. We compared clinical and procedural variables between patients who underwent DHC and those who did not. Propensity score (PS) matching between the two groups was conducted using age, sex, admission NIHSS, occluded vessel, ASPECTS, time from symptoms onset to arterial puncture, intracranial hemorrhage (ICH), and symptomatic ICH (sICH). Results: Among the 3,135 MT patients who met our inclusion criteria, 113 underwent DHC. A 1:3 propensity matching yielded a well-matched cohort of 113 in the DHC group versus 339 in the non-DHC group. The DHC group had a significantly higher rate of successful recanalization (mTICI ≥ 2C) (175 [51.6%] versus 36 [31.9%], P < 0.001) and a longer procedure duration, with a median of 30 minutes (IQR: 17-54) compared to 44 minutes (IQR: 25-78) in the non-DHC group (P = <0.001). Further comparison of patients with low ASPECTS (≤ 5) who underwent DHC (n = 36) with those who did not (n = 99) showed no significant difference in successful recanalization rates (15 [41.7%] versus 43 [43.4%], P > 0.90). However, procedure duration was significantly longer in the DHC group with a median of 29 minutes (IQR: 13-52), compared to 39 minutes (IQR: 27-86) in the non-DHC group (P = 0.02). Conclusions: Successful recanalization can help in preventing DHC in AIS patients with high ASPECTS, but not those with low ASPECTS. Procedure duration is independently related to DHC following MT, especially in low ASPECTS patients.

Abstract WP180: Novel Machine Learning Model for Prediction of Futile Recanalization in Acute Ischemic Stroke Patients With Anterior Circulation Large Vessel Occlusion

Introduction: Up to 50% of acute ischemic stroke (AIS) patients who undergo successful mechanical thrombectomy (MT) fail to achieve favorable outcomes (futile recanalization). In this study we aim to develop a machine learning (ML) model to predict futile recanalization (FR) in AIS patients who undergo MT. Methods: We used data from an ongoing large, multicenter database from 2013 to 2023. We included AIS patients treated with MT for ICA, M1, or M2 occlusion with successful recanalization (modified Thrombolysis in Cerebral Infarction [mTICI] score ≥ 2C) and procedure durations under 60 minutes. FR was defined as successful recanalization with 90-day modified Rankin Scale (mRS) 3-6. The dataset was divided into 75% for training and 25% for external validation. Using the Caret Package in R, multiple models were tested, and their performances were evaluated by the area under the curve (AUC) of receiver operating. Both baseline and pre-interventional characteristics were incorporated into the model. The selected model was then externally validated on a 25% validation dataset. Results: Among 2,546 qualified patients, FR occurred in 1,342 (52.7%). In univariate analysis, baseline characteristics were significantly different between FR and non-FR groups. The M5P model demonstrated the highest performance (AUC: 0.833; 95% CI: 0.7989-0.852; PPV: 0.8101) in comparison to other tested models such as logistic regression (AUC: 0.74), RF (AUC: 0.78), J48 (AUC: 0.78), SVM (AUC: 0.79), and GB (AUC: 0.79). The external validation of the model showed satisfactory results (AUC: 75.25; 95% CI: 70-80; PPV: 76.87). Conclusion: Utilizing clinical, pre-procedural, and imaging parameters, the M5P model can efficiently predict F) in AIS patients before attempting MT. This tool can assist neurointerventionalists in adequately choosing their MT candidates.

Abstract 41: Conventional vs Advanced Imaging for the Selection of Stroke Therapy in the Extended Window (VESTA Study)

Background: The optimal imaging modality for treatment selection in the extended stroke window is uncertain. VESTA study (NCT05299034) compared conventional imaging (noncontrast CT + CT angiography) with advanced imaging (adding perfusion) in extended window stroke patients, focusing on EVT selection rate, safety and functional outcome. Methods: From the prospective Catalan Stroke Registry (CICAT, 29 centers) ischemic stroke patients within 6-24h of symptom onset and NIHSS ≥6 (Jan 2019 -Dec 2021) were selected. Imaging modality was decided according to the local site protocol. Images were re-evaluated by a central core lab with full access to each patient’s images. LVO was defined as intracranial ICA, M1 or proximal M2 occlusion. Blinded investigators centrally assessed 90-day functional independence, defined as mRS≤2. We employed a propensity score matching algorithm to adjust for age, sex, NIHSS, established infarct, and time from onset to arrival. Results: We included 1405 patients in the analysis (median age 76y, median NIHSS 11; 48% women). Conventional imaging was performed in 48% of patients, while 52% received advanced imaging. Patients receiving conventional vs. advanced imaging showed lower NIHSS (11 vs. 12, p=0.006), and lower rates of LVO (45% vs. 58%, p<0.001) and EVT indication (33% vs. 41%, p=0.01). Demographics and time metrics were comparable between techniques. The matched adjusted analysis showed no differences between modalities in 90-day functional independence (OR=0.9 [0.7;1.2]), mortality (1.18 [0.9;1.6]), or symptomatic hemorrhage (OR=1.35 [0.47;3.8]). The figure displays subgroup analysis for patients arriving at a comprehensive stroke center and for patients with anterior LVO. Conclusions: Advanced imaging allowed the identification of more occlusions and the selection of more patients for EVT; however, patients undergoing either conventional or advanced imaging had similar clinical outcomes at 90 days.