Late-window Patients Research Articles

Impact of time from symptom onset to puncture, and puncture to reperfusion, in endovascular therapy in the late time window (>6 hours).

Background- Increased times from symptom onset to puncture (TSOP) and from puncture to reperfusion (TPTR) are associated with worse outcome in ischemic stroke patients treated with endovascular therapy (EVT) in the early time window (<6 hours). However, these associations are less described in the late window (>6 hours), where patients may benefit from EVT because of a more favorable imaging profile (late window paradox). We sought to compare the effect of these timeframes between these two periods on efficacy and safety outcomes.Methods- The ETIS Registry (Endovascular Treatment in Ischemic Stroke) is an ongoing, prospective, observational study in 21 centers that perform EVT in France. We included adult patients with an anterior occlusion, successfully treated by EVT (mTICI 2b-3) between January 2015 and June 2023, with a known time of stroke onset. The cohort was divided into 2 groups according to the TSOP (≤6h vs >6h). Primary outcome was favorable outcome (modified Rankin Scale 0-2 at 90 days).Results- 7,516 patients were included, with 5,936 patients being treated ≤6h and 1,580 >6h. In the early window, TSOP and TPTR were associated with worse outcomes at 90 days (adjusted OR=0.68 per hour; 95%CI, 0.64-0.73; p<0.001 and aOR=0.92 per 10 minutes increment; 95%CI, 0.90-0.94, p<0.001, respectively). TSOP was not associated with worse outcomes at 90 days in the late window (p=0.955), but TPTR was associated with worse outcomes (aOR=0.91 per 10 minutes increment; 95%CI, 0.86-0.96, p=0.001), every 10 additional minutes in TPTR being associated with a 1.7% (95%CI, 0.6%-2.7%) decreased probability of favorable outcome.Conclusions- Only EVT procedural time is associated to unfavorable outcomes at 90 days in late window patients. These results highlight how the late window paradox may end at the start of EVT and underscore the need for timely management, particularly for the EVT, even for late window patients with a presumed more favorable imaging profile.

Deep venous outflow as a surrogate for collaterals in late-window patients with successful revascularization from the DEFUSE 3 cohort.

Deep venous outflow (VO) may be an important surrogate marker of collateral blood flow in acute ischemic stroke patients with a large vessel occlusion (AIS-LVO). Researchers have yet to determine the relationship between deep VO status in late-window patients and imaging measures of collaterals, which are key in preserving tissue. We performed a multicenter retrospective cohort study on a subset of DEFUSE 3 patients recruited across 38 centers between May 2016 and May 2017 who underwent successful thrombectomy revascularization. Internal cerebral vein opacification was scored on a scale of 0-2. This metric was added to the cortical vein opacification score to derive the comprehensive VO (CVO) score from 0 to 8. Patients were stratified by favorable (ICV+) and unfavorable (ICV-) ICV scores, and similarly CVO+ and CVO-. Analyses comparing outcomes were primarily conducted by Mann-Whitney U and χ2 tests. Forty-five patients from DEFUSE 3 were scored and dichotomized into CVO+, CVO-, ICV+, and ICV- categories, with comparable demographics. Hypoperfusion intensity ratio, a marker of tissue level collaterals, was significantly worse in the ICV- and CVO- groups (p = 0.005). ICV- alone was also associated with a larger perfusion lesion (138 ml vs 87 ml; p = 0.023). No significant differences were noted in functional and safety outcomes. Impaired deep venous drainage alone may be a marker of poor tissue level collaterals and a greater degree of affected tissue in AIS-LVO patients presenting in the late-window who subsequently undergo successful revascularization.

Abstract WMP62: Infarct Core Volume Estimation on Non-Contrast Computed Tomography in Late Window Patients Using a Machine Learning Algorithm Software

Introduction: A simplified patient selection paradigm can reduce time to reperfusion and widen the eligibility of large vessel occlusions (LVO) for endovascular therapy (EVT). We developed and externally validated a machine learning (ML) algorithm to estimate infarct core volume (ICV) on non-contrast computed tomography (NCCT) in anterior circulation LVOs presenting in the late window (≥ 6-24 hours). Methods: LVOs from prospective databases in US and Spain were included. For development, 2858 stroke activations with NCCT/CT angiography[s1] were included. For validation, consecutive LVOs with admission NCCT/CT perfusion (CTP), post-EVT diffusion-weighted imaging (DWI) within 24 hours, and mTICI ≥2b were included. Neuroimaging experts adjudicated ASPECTS on NCCT and final infarct volume (FIV) on DWI (ground truth). ML algorithm was trained using UNet architecture with ResNet 34 encoder to identify ICV on NCCT. Estimated ICVs (algorithm, CTP [&lt;30% cerebral blood flow], and ASPECTS) were compared to ground truth using correlations (intraclass correlation coefficient [ICC] and Spearman’s [r s ]) and Bland Altman plots. Superiority tests between correlations (to compare modalities) and subgroup analyses were performed. Results: 98 patients (median age, 70 years; IQR:59-80; 51% females) were included for validation. Median time to first imaging was 11.4 hours (IQR:9.0-14.7). Correlations (Table) were moderate with the ML algorithm (ICC:0.59) and poor with ASPECTS (r s :-0.31) and CTP ICV (ICC:0.42;). Bland Altman plots showed that ML algorithm had a mean difference closest to zero (-34.2 mL) while the CTP ICV had a larger mean difference (-45.8 mL). Superiority tests (Table), [s2] ML algorithm correlation showed superiority to both the CTP ( p sup =.018) and ASPECTS ( p sup =.003) correlations. Conclusion: On late window patients, estimation of ICV on NCCT with the ML algorithm seems to be superior to CTP and ASPECTS. Further prospective studies are needed.

March 2023 Stroke Highlights.

March 2023 Stroke Highlights.

Abstract WP115: DWI/FLAIR Mismatch Is Common In Late Window Patients With Target Perfusion Mismatch

Introduction: The presence of a DWI/FLAIR mismatch has been suggested as a method to identify patients within 4.5 hours from stroke symptom onset. We studied patients from DEFUSE 2 and 3 with the target perfusion mismatch profile to evaluate the rates of DWI/FLAIR mismatch in patients with who have favorable collaterals in early and late time windows. We hypothesize that the persistence of DWI/FLAIR mismatch in late window patients may reflect good collateral circulation. Methods: We identified 58 eligible patients in D2 and 30 patients from D3. Imaging was reviewed by two neuroradiologists and one neurologist who rated the presence of DWI-FLAIR mismatch. Results: The inter-rater agreement for the presence of DWI/FLAIR mismatch was 88.3%. There were 32 patients who were &lt; 6 hours from last known well (LKW) or symptom onset, 17 patients who were ≥ 6 hours from symptom onset, and 26 patients who were ≥ 6 hours from LKW with an unknown time of symptom onset. These are categorized as early, late, and suspected late window, respectively. The rate of DWI/FLAIR mismatch was 56% in the early window group, 41% in the late window group, and 35% in the suspected late window group. The overall rate of DWI/FLAIR mismatch did not differ significantly between these three groups (56% vs. 41% vs. 35%, p=0.239). Of the early window patients, the rate of DWI-FLAIR mismatch was higher in those with the target perfusion mismatch profile (67%) compared to those without (36%). All but one the known onset late window patients had the target perfusion mismatch profile, and the rate of DWI-FLAIR mismatch in this group was 35%. Forthcoming analyses will include predictors of DWI-FLAIR mismatch such as hypoperfusion intensity ratio, time from symptom onset, and NIHSS score. Conclusions: More than one-third of patients presenting &gt;6 hours from symptom onset with a target perfusion mismatch profile have DWI/FLAIR mismatch. This could reflect the presence of good collateral circulation that may delay the appearance of a FLAIR lesion. The rate of DWI/FLAIR mismatch did not differ among early, late, and expected late window patients. This suggests that, among patients with favorable collaterals, DWI/FLAIR mismatch does not reliably identify early window patients.

Review of Current Large Core Volume Stroke Thrombectomy Clinical Trials: Controversies and Progress

Large clinical trials have helped establish the benefit of endovascular treatment (EVT) in patients with acute ischemic stroke with large vessel occlusion and small infarct core volume as determined by scores ≥6 on the Alberta Stroke Program Early CT Scores. Several small studies have suggested that patients with large infarct core volume (LICV) may also benefit from EVT. Currently, at least 6 randomized clinical trials are examining the benefit of extending EVT to this population of patients with acute ischemic stroke. These trials were independently conceived and have significant differences in their inclusion criteria. Understanding these inclusion criteria and other differences in trial design is pivotal for the field to interpret the upcoming results of these trials. In this review, the designs of the 6 trials are summarized and compared. Specific differences are described, including (1) the rationale for EVT treatment in patients with LICV, (2) how to define LICV and the imaging modality used to identify LICV, (3) inclusion of an Alberta Stroke Program Early CT Score 0 to 5 versus 3 to 5, (4) use of the mismatch between blood flow and the size of infarct as an inclusion criterion, and (5) inclusion of early window and/or late window patients. The potential impact of these trial results on current guidelines for acute ischemic stroke is discussed. Differences in trial design as well as inclusion and exclusion criteria may influence trial outcomes. The implications of these trial results will likely be enhanced by a pooled analysis.

Characterizing reasons for stroke thrombectomy ineligibility among potential candidates transferred in a hub-and-spoke network.

Access to endovascular thrombectomy (EVT) is relatively limited. Hub-and-spoke networks seek to transfer appropriate large vessel occlusion (LVO) candidates to EVT-capable hubs. However, some patients are ineligible upon hub arrival, and factors that drive transfer inefficiencies are not well described. We sought to quantify EVT transfer efficiency and identify reasons for EVT ineligibility. Consecutive EVT candidates presenting to 25 spokes from 2018-2020 with pre-transfer CTA-defined LVO and ASPECTS ≥6 were identified from a prospectively maintained database. Outcomes of interest included hub EVT, reasons for EVT ineligibility, and 90-day modified Rankin Scale (mRS) ≤2. Among 258 patients, the median age was 70 years (IQR 60-81); 50% were female. 56% were ineligible for EVT after hub arrival. Cited reasons were large established infarct (49%), mild symptoms (33%), recanalization (6%), distal occlusion (5%), sub-occlusive lesion (3%), and goals of care (3%). Late window patients [last known well (LKW) >6 hours] were more likely to be ineligible (67% vs 43%, P<0.0001). EVT ineligible patients were older (73 vs 68 years, p=0.04), had lower NIHSS (10 vs 16, p<0.0001), longer LKW-hub arrival time (8.4 vs 4.6 hours, p<0.0001), longer spoke Telestroke consult-hub arrival time (2.8 vs 2.2 hours, p<0.0001), and received less intravenous thrombolysis (32% vs 45%, p=0.04) compared to eligible patients. EVT ineligibility independently reduced the odds of 90-day mRS≤2 (aOR=0.26, 95%CI=0.12,0.56; p=0.001) when controlling for age, NIHSS, and LKW-hub arrival time. Among patients transferred for EVT, there are multiple reasons for ineligibility upon hub arrival, with most excluded for infarct growth and mild symptoms. Understanding factors that drive transfer inefficiencies is important to improve EVT access and outcomes.

Endovascular thrombectomy for anterior circulation stroke beyond 6 hours of onset in Sweden 2015 to 2020: rates and outcomes in a nationwide register-based study

BackgroundEndovascular thrombectomy (EVT) for ischemic stroke (IS) beyond 6 hours has been proven effective in randomized controlled trials. We present data on implementation and outcomes for EVT beyond 6 hours...

Abstract 88: Workflow Delays And Outcome Of Endovascular Thrombectomy In The Late Stroke Window:results From A Pooled Multicenter Analysis

Background: Efficient healthcare workflow leads to faster reperfusion and better functional outcomes of stroke in the early-time window. We investigated the impact of care delays on the outcomes of stroke patients treated with endovascular thrombectomy (EVT) in the late window. Methods: Pooled data from seven randomized clinical trials and registries that only included patients who underwent EVT in the late time window (onset/last known well (LKW) time to imaging time of 6 hours or more) were combined for this analysis. The time intervals from stroke onset to successful reperfusion were analyzed. Logistic regression was used to estimate the likelihood of a functionally independent outcome at 90 days (modified Rankin scale 0-2) for each time interval while adjusting for relevant patients’ characteristics. Negative binomial regression was used to evaluate the relationship between each time interval and the predictors. Results: 584 patients were included in this analysis. The median age was 70 years (IQR: 21), 293 [50.17%] were females, 298 (53.31%) had wake-up strokes, and the median ASPECTS was 8 (IQR: 2). All patients had CT, and CTA imaging, and 360 (61.64%) underwent perfusion imaging. Successful reperfusion was achieved in 469 (80.45%) patients, and 249 (44.54%) had independent outcomes at 90 days. For every 30 minutes delay, the estimated probability of functional independence decreased by 19% for the emergency department (ED) arrival to imaging time interval, by 25% from groin puncture to end of EVT, and by 12% from ED arrival to end of EVT. Older age and higher NIHSS were associated with longer time from imaging to groin puncture. However, only age was associated with a longer estimated times from stroke onset/LKW to arrival in ED and from stroke onset/LKW to the end of EVT. Conclusion: Faster in-hospital care is associated with improved functional independence among late-window patients. Page 1

Abstract WMP51: Outcome Prediction In Late-Window Endovascular Treatment - Application Of MR PREDICTS To Patients Treated Beyond 6 Hours

Introduction: Outcome prediction tools for large vessel occlusion (LVO) stroke patients receiving endovascular treatment (EVT) focus on patients treated within 6h from onset. We aimed to apply a validated tool to EVT-treated patients in the late window (beyond 6h from onset) and to investigate any outcome differences according to the imaging paradigm used for selection. Methods: MR PREDICTS is a prediction tool of the effect and benefit of EVT on functional outcome based on MR CLEAN and HERMES data sets. We applied the algorithm to patients treated with late-window EVT from three multicenter international trials (ESCAPE, ESCAPE-NA1, and ProVe-IT). We assessed the model performance by calculating its discrimination and calibration for the overall patient sample and for the subset of patients who underwent CTP. Results: We included 152 patients: 93 (61.2%) from the control arm of ESCAPE-NA1, 35 (23.0%) from ProVe-IT, and 24 (15.8%) from ESCAPE. Median age was 68.0 years (IQR: 58.0 - 77.2), median baseline NIHSS was 16 (IQR: 12 - 20) and 72.4% had M1-occlusions. Median time from onset to groin puncture was 592min (IQR: 496 - 666). Good functional outcome (mRS 0-2) at 3 months was achieved in 72/152 patients (47.4%). The averaged predicted probability of mRS 0-2 was 47.6%. In the CTP-subgroup 44/94 patients (46.8%) achieved mRS 0-2, the averaged predicted probability of mRS 0-2 was 46.5%. Evaluation of model performance resulted in a reasonable discriminative ability (Harrel’s c-statistic: overall 0.75, 95%CI 0.67 - 0.82, CTP-subgroup: 0.73, 95%CI 0.62 - 0.82, figure 1). Conclusions: The outcome-prediction model performed reasonably well when applied to EVT patients in the late time window. Our data supports the use of available prediction tools in patients treated beyond 6h of symptom onset until specific models are developed for late-window patients.

Advances in Stroke: Treatments-Interventional.

Advances in Stroke: Treatments-Interventional.

Endovascular treatment in anterior circulation stroke beyond 6.5 hours after onset or time last seen well: results from the MR CLEAN Registry

BackgroundRandomised controlled trials with perfusion selection have shown benefit of endovascular treatment (EVT) for ischaemic stroke between 6 and 24 hours after symptom onset or time last seen well. However,...

Imaging criteria across pivotal randomized controlled trials for late window thrombectomy patient selection

BackgroundThe DAWN and DEFUSE-3 trials showed the benefit of endovascular treatment (EVT) in acute ischemic stroke patients presenting beyond 6 hours from last known well (LKW) and selected by perfusion...

Optimal Imaging at the Primary Stroke Center.

Optimal Imaging at the Primary Stroke Center.

Mechanical Thrombectomy for Acute Stroke: Early versus Late Time Window Outcomes.

Recent trials have shown benefit of thrombectomy in patients selected by penumbral imaging in the late (>6 hours) window. However, the role penumbral imaging is not clear in the early (0-6 hours) window. We sought to evaluate if time to treatment modifies the effect of endovascular reperfusion in stroke patients with evidence of salvageable tissue on CT perfusion (CTP). We retrospectively analyzed consecutive patients who underwent thrombectomy in a single center. Demographics, comorbidities, National Institute of Health Stroke Scale (NIHSS), rtPA administration, ASPECTS, core infarct volume, onset to skin puncture time, recanalization (mTICI IIb/III), final infarct volume were compared between patients with good and poor 90-day outcomes (mRS 0-2 vs. 3-6). Multivariable logistic regression analyses were used to identify independent predictors of a good (mRS 0-2) 90-day outcome. A total of 235 patients were studied, out of which 52.3% were female. Univariate analysis showed that the groups (early vs. late) were balanced for age (P = .23), NIHSS (P = .63), vessel occlusion location (P = .78), initial core infarct volume (P = .15), and recanalization (mTICI IIb/III) rates (P = .22). Favorable outcome (mRS 0-2) at 90 days (P = .30) were similar. There was a significant difference in final infarct volume (P = .04). Shift analysis did not reveal any significant difference in 90-day outcome (P = .14). After adjustment; age (P< .001), NIHSS (P = .01), recanalization (P = .008), and final infarct volume (P<.001) were predictive of favorable outcome. Penumbral imaging-based selection of patients for thrombectomy is effective regardless of onset time and yields similar functional outcomes in early and late window patients.

Abstract WP44: Less Infarct Volume Growth in Early Window Mechanical Thrombectomy Compared to Late Window in Emergent Large Vessel Occlusion

Background: While clearly beneficial based on outcome analysis, there has been limited data regarding prevention of further infarct growth in late (6-24 hour) compared to the early window (&lt;6 hour) mechanical thrombectomy (MT). More expedient revascularization in the early group prevents further growth, but the presence of good collaterals in late window patients may prevent infarct progression over time. The aim of this study is to compare infarct growth between early and late window intervention. Methods: We reviewed consecutive patients presenting to a comprehensive stroke center from January 2016 to December 2018 with emergent large vessel occlusion (ELVO) undergoing MT. Standard protocol included pre-procedural MRI imaging and only those with post-procedural MRI were included. Patients were divided into early (&lt;6 hour from onset to arterial puncture) and late (6-24 hour from onset to arterial puncture) groups. Infarct volume on MRI was measured using region of interest analysis by investigators blinded to group. MRI growth between pre- and post- MT MRI was compared using both absolute difference (post minus pre volume) and ratio (pre:post volume). Results: Among 117 patients meeting inclusion criteria, 40 (34.2%) patients had early and 77 (65.8%) late interventions. Those in the early group showed a trend toward lower infarct volume growth compared to those in the late group (16.0 +/- 42.9 vs 31.4 +/- 60.9 mL growth, p = 0.16). Ratios of pre to post MT infarct volume was significantly different in early and late intervention group (1.07 +/- 1.6 vs 0.63 +/- 0.33, p = 0.02), signifying less infarct growth in the early group. Conclusion: In patients with ELVO for whom MT was performed, there was less infarct growth in the early time window compared to the late window.

One-Stop Management with Perfusion for Transfer Patients with Stroke due to a Large-Vessel Occlusion: Feasibility and Effects on In-Hospital Times.

In-hospital time delays lead to a relevant deterioration of neurologic outcomes in patients with stroke with large-vessel occlusions. At the moment, CT perfusion is relevant in the triage of late-window patients with stroke. We conducted this study to determine whether one-stop management with perfusion is feasible and leads to a reduction of in-hospital times. In this observational study, we report the first 15 consecutive transfer patients with stroke with externally confirmed large-vessel occlusions who underwent flat panel detector CT perfusion and thrombectomy in the same room. Preinterventional imaging consisted of noncontrast flat panel detector CT and flat panel detector CT perfusion, acquired with a biplane angiography system. The flat panel detector CT perfusion was used to reconstruct a flat panel detector CT angiography to confirm the large-vessel occlusions. After confirmation of the large-vessel occlusion, the patient underwent mechanical thrombectomy. We recorded time metrics and safety parameters prospectively and compared them with those of transfer patients whom we treated before the introduction of one-stop management with perfusion. Fifteen transfer patients underwent flat panel detector CT perfusion and were treated with mechanical thrombectomy from June 2017 to January 2019. The median time from symptom onset to admission was 241 minutes. Median door-to-groin time was 24 minutes. Compared with 23 transfer patients imaged with multidetector CT, it was reduced significantly (24 minutes; 95% CI, 19-37 minutes, versus 53 minutes; 95% CI, 44-66 minutes; P < .001). Safety parameters were comparable between groups. In this small series, one-stop management with perfusion led to a significant reduction of in-hospital times compared with our previous workflow.

Outcomes of Thrombectomy in Transferred Patients With Ischemic Stroke in the Late Window

Although thrombectomy benefit was maintained in transfer patients with ischemic stroke in early-window trials, overall functional independence rates were lower in thrombectomy and medical management-only groups. To evaluate whether the imaging-based selection criteria used in the Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3 (DEFUSE 3) trial would lead to comparable outcome rates and treatment benefits in transfer vs direct-admission patients. Subgroup analysis of DEFUSE 3, a prospective, randomized, multicenter, blinded-end point trial. Patients were enrolled between May 2016 and May 2017 and were followed up for 90 days. The trial comprised 38 stroke centers in the United States and 182 patients with stroke with a large-vessel anterior circulation occlusion and initial infarct volume of less than 70 mL, mismatch ratio of at least 1.8, and mismatch volume of at least 15 mL, treated within 6 to 16 hours from last known well. Patients were stratified based on whether they presented directly to the study site or were transferred from a primary center. Data were analyzed between July 2018 and October 2018. Endovascular thrombectomy plus standard medical therapy vs standard medical therapy alone. The primary outcome was the distribution of 90-day modified Rankin Scale scores. Of the 296 patients who consented, 182 patients were randomized (66% were transfer patients and 34% directly presented to a study site). Median age was 71 years (interquartile range [IQR], 60-79 years) vs 70 years (IQR, 59-80 years); 69 transfer patients were women (57%) and 23 of the direct group were women (37%). Transfer patients had longer median times from last known well to study site arrival (9.43 vs 9 hours) and more favorable collateral profiles (based on hypoperfusion intensity ratio): median for transfer, 0.35 (IQR, 0.18-0.47) vs 0.42 (IQR, 0.25-0.56) for direct (P = .05). The primary outcome (90-day modified Rankin Scale score shift) did not differ in the direct vs transfer groups (direct OR, 2.9; 95% CI, 1.2-7.2; P = .01; transfer OR, 2.6; 95% CI, 1.3-4.8; P = .009). The overall functional independence rate (90-day modified Rankin Scale score 0-2) in the thrombectomy group did not differ (direct 44% vs transfer 45%) nor did the treatment effect (direct OR, 2.0; 95% CI, 0.9-4.4 vs transfer OR, 3.1; 95% CI, 1.6-6.1). Thrombectomy reperfusion rates, mortality, and symptomatic intracranial hemorrhage rates did not differ. In late-window patients selected by penumbral mismatch criteria, both the favorable outcome rate and treatment effect did not decline in transfer patients. These results have health care implications indicating transferring potential candidates for late-window thrombectomy is associated with substantial clinical benefits and should be encouraged. ClinicalTrials.gov identifier: NCT02586415.

Abstract 113: Late Window Transfer Patients had Favorable Outcomes Following Thrombectomy in DEFUSE 3

Background: Although the treatment benefit of endovascular thrombectomy (EVT) was maintained in transfer patients in the early window trials, overall rates of functional independence were lower in both the EVT and control groups among transfer patients. We hypothesized that the imaging-based selection criteria employed in DEFUSE 3 would lead to comparable outcome rates and treatment efficacy in transfer vs. direct admission patients. Methods: DEFUSE 3 patients were stratified based on if they presented directly to the study site or were transferred from a primary center. The primary and secondary efficacy and safety outcomes of DEFUSE 3 were compared. Results: Of 182 patients randomized, 121 (66%) were transfers and 61 (34%) direct. The 2 groups had similar baseline characteristics, other than transfers had 30 min longer median times from last known well time to arrival at the study site. The primary efficacy outcome (mRS shift at day 90) did not differ in the direct vs. transfer groups, OR 2.9, 95% CI 1.2-7.2, P=0.014 for direct and OR=2.6, 95% CI 1.3-4.8, P=0.009 for transfer (Fig 1). The overall rate of functional independence (mRS 0-2 at day 90) in the EVT group did not differ (44% direct, 45% transfer) nor did the treatment effect: RR 2.0 (0.9-4.4) direct vs. 3.1 (1.6-6.1) for transfer. EVT reperfusion rates were identical (mTICI≥2b 76%) in both groups. The rates of death and SICH did not differ. Transfer patients had more favorable collateral profiles (based on the hypoperfusion intensity ratio) median (IQR) for transfer 0.35 (0.18-0.47) vs. 0.42 (0.25-0.56) for direct, p=0.050. Conclusions: In late window patients selected by penumbral mismatch criteria, both the favorable outcome rates and treatment effects did not decline in transfer patients. These results have healthcare implications indicating transferring potential candidates for late window thrombectomy to EVT centers is associated with substantial clinical benefits and should be strongly encouraged.

Abstract 112: Identifying Patients Who May Benefit From Thrombectomy in the Late Time Window: Predictors of Good Outcome Beyond Advanced Imaging

Background: The DAWN trial showed EVT effectiveness in the late time window (6-24 hrs), however, DAWN patients were carefully selected based on advanced perfusion imaging, CTP and MRI. Similar to the early window (0-6 hrs), simple imaging (CT) and other clinical variables may select patients for thrombectomy beyond 6 hours. We evaluated a largescale, real world practice for predictors that could identify patients who may benefit from EVT in the late time window. Methods: Patients with LVO in the anterior circulation (M1, M2, ICA) from a prospective, single arm, multicenter, international registry (Trevo Retriever Registry) treated in the late window LSN to groin puncture (GP) (6-24 hrs) were included. Univariate and multivariate analyses assessed factors independently correlating with good outcome (90 day mRS 0-2). Furthermore, patients outcomes were compared based on their baseline imaging selection CT vs CTP and MRI. Results: 549 patients were treated beyond 6 hours. The average age was 67, median/IQR ASPECTS 8(6-9), median/IQR NIHSS was 15 (9-20), median/IQR time LSN to GP (hr) was 9.7 (7.3-13.6) and IV-tPA rate were 22.8%. CT was the only imaging selection method in 15.9%, while additional advanced imaging was utilized in the remaining patients; CTP (70%), and MRI(14.1%). Good outcomes were observed in 51.4% of late window patients. Age (aOR 0.96, 95% CI 0.94-0.98, p&lt;0.001), stroke severity by NIHSS (aOR 0.9, 95% CI 0.86-0.95, p&lt;0.001) and ASPECTS (for each point increment in ASPECTS aOR 1.24, 95% CI 1.05-1.47, p=0.012) were independent pre-intervention predictors of good outcome in the late window. The addition of advanced imaging beyond CT, including CTP or MRI, did not confer higher correlation with good outcome (aOR 1.45, 95% CI 0.77-2.73, p=0.25). Good outcome was achieved in 56% of CT selected patients as compared to 53% patients selected by CTP or MRI. Conclusion: Simple imaging and clinical variables can identify patients that could benefit from thrombectomy in the late window. Importantly, ASPECTS reliably predicted good outcome beyond 6 hours without adjunctive benefit from adding advanced perfusion imaging, a finding that may simplify patients selection to facilitate and generalize the intervention in the late window to wide, real world practice.