Anterior Circulation Stroke Research Articles

Diagnostic Performance of Carotid Ring Sign on CT-Angiography in Internal Carotid True Occlusion.

To differentiate between pseudo occlusion (PO) and true occlusion (TO) of internal carotid artery (ICA) is important in thrombectomy treatment planning for patients with acute ischemic stroke. Although delayed contrast filling has been differentiated carotid PO from TO, its application has been limited by the implementations of multiphasic computed tomography angiography. In this study, we hypothesized that carotid ring sign, which is readily acquired from single-phasic CTA, can sufficiently differentiate carotid TO from PO. One thousand four hundred and twenty patients with anterior circulation stroke receiving endovascular therapy were consecutively recruited through a hospital- and web-based registry. Two hundred patients with nonvisualization of the proximal ICA were included in the analysis after a retrospective screening. Diagnosis of PO or TO of the cervical segment of ICA was made based on digital subtraction angiography. Diagnostic performances of carotid ring sign on arterial-phasic CTA and delayed contrast filling on multiphasic computed tomography angiography were evaluated and compared. One-hundred twelve patients had ICA PO and 88 had TO. Carotid ring sign was more common in patients with TO (70.5% versus 6.3%; P<0.001), whereas delayed contrast filling was more common in PO (94.9% versus 7.7%; P<0.001). The sensitivity and specificity of carotid ring sign in diagnosing carotid TO were 0.70 and 0.94, respectively, whereas sensitivity and specificity of delayed contrast filling was 0.95 and 0.92 in judging carotid PO. Carotid ring sign is a potent imaging marker in diagnosing ICA TO. Carotid ring sign could be complementary to delayed contrast filling sign in differentiating TO from PO, in particular in centers with only single-phasic CTA.

Frequency, Severity, Risk Factors, and Outcome of Hemorrhagic Transformation in Anterior and Posterior Stroke.

Background: There are few data on hemorrhagic transformation in posterior circulation strokes (PCS) compared to anterior circulation strokes (ACS). The aim of this study was to retrospectively analyze the incidence of hemorrhagic transformation, its different subtypes, the associations with different risk factors, and the outcome of ACS and PCS patients. Methods: A retrospective analysis of consecutive ischemic stroke patients with hemorrhagic transformation was performed. Clinical and demographic data were collected from electronic patient records. Results: Included were 186 ACS patients and 67 PCS patients. The median age was 77 years, with PCS patients being slightly younger than ACS patients. ACS patients were more likely to be treated with acetylsalicylic acid before stroke. ACS and PCS patients had comparable frequencies and severity of hemorrhagic transformation. After excluding ACS patients who received thrombectomy, PCS patients developed hemorrhagic transformation more frequently compared to ACS patients. Risk factors for hemorrhagic transformation did not differ between ACS and PCS patients and included vitamin K antagonist use before stroke and thrombectomy in ACS patients. There was no correlation between hemorrhagic transformation and stroke outcome. Conclusions: Hemorrhagic transformation occurs with similar frequency in PCS and ACS patients but is more common in PCS patients after the exclusion of ACS patients undergoing thrombectomy.

Clinically Asymptomatic Hemorrhagic Conversion Is Associated with Need for Inpatient Rehabilitation After Mechanical Thrombectomy for Anterior Circulation Ischemic Stroke

Hemorrhagic conversion (HC) is a known complication following acute ischemic stroke(AIS) in patients undergoing mechanical thrombectomy(MT). While symptomatic HC(sHC) has been shown to lead to poor neurologic outcomes, the effect of asymptomatic HC(aHC) is unclear. This study aims to identify predictors of aHC and to determine the short-term outcomes. This is a single-institution retrospective study of patients with anterior circulation stroke(AIS) who underwent MT between January 2016 and September 2022. Radiographic HC was identified on post-operative imaging. Asymptomatic hemorrhage was defined as no acute neurologic decline attributable to imaging findings. Baseline characteristics, technical aspects, and outcomes were compared between aHC and no HC groups. Logistic regression and multivariate analysis were performed. 615 patients underwent MT for AIS, of which 496 met inclusion criteria. 235 (47.4%) patients had evidence of aHC. Diabetes mellitus (OR 1.59; 95% CI 1.06 - 2.41; p=0.03), hyperglycemia (OR 1.01; 95% CI 1.00 - 1.01; p=0.002), greater number of passes (OR 1.14; 95% CI 1.00 - 1.31; p=0.05), and longer time to reperfusion (OR 1.02; 95% CI 1.00 - 1.05; p=0.05) were associated with aHC. Patients with aHC were significantly more likely to require rehabilitation, whereas those without HC were more likely to discharge home (p<0.001). There were no significant differences in long-term outcomes. HC occurred in up to half of patients who underwent MT for AIS, of which the majority were clinically asymptomatic. Despite clinical stability, aHC was significantly associated greater need for inpatient rehabilitation. Predictors of aHC included hyperglycemia and longer time to reperfusion.

External validation and comparison of MBE, EDEMA, and modified EDEMA scores for predicting malignant cerebral EDEMA in Chinese patients with large hemispheric infarction patients without revascularization

BackgroundMalignant cerebral edema (MCE) is a severe condition characterized by rapid neurological deterioration and a potentially poor prognosis. Scoring systems including the malignant brain edema (MBE) score, Enhanced Detection of Edema in Malignant Anterior Circulation Stroke score (EDEMA), and modified EDEMA score, have been developed to predict MCE in patients with large hemispheric infarction (LHI). We aimed to externally validate and comparethe predictive efficacy of these scores in LHI patients within 48 h of onset and not undergoing reperfusion therapy. MethodsDemographic, clinical and radiological data were retrospectively collected from LHI patients within 48 h of onset and not receiving reperfusion therapy. Patients were divided into MCE and non-MCE group. The calibration, discrimination, and clinical practicability of the three scores were verified using Hosmer-Lemeshow goodness-of-fit test, receiver operating characteristic (ROC) curve analysis and decision curve analysis (DCA), respectively. Finally, continuous net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were applied to determine the discrimination performance of the three scores. ResultsA total of 314 patients were included in the study, with 122 cases being MCE patients. The Hosmer–Lemeshow goodness-of-fit test showed excellent fitting ability across the MBE (p = 0.36), EDEMA (p = 0.61), and modified EDEMA scores (p = 0.62) in our patients. The MBE, EDEMA, and modified EDEMA scores had the AUCs of 0.855 (95 % CI 0.818–0.898), 0.782 (95 % CI 0.727–0.837) and 0.878 (95 % CI 0.844–0.919) respectively. The MBE (NRI, 0.33; 95 % CI, 0.11–0.56, p = 0.003 and IDI, 0.11; 95 % CI, 0.03–0.18; p = 0.004) and modified EDEMA scores (NRI, 1.10; 95 % CI, 0.94–1.26; p < 0.001 and IDI, 0.17; 95 % CI, 0.13–0.20, p < 0.001) showed better performance than the EDEMA score. DCA demonstrated that the modified EDEMA score outperformed the other two scores, possessing heightened clinical usefulness. ConclusionsThe MBE, EDEMA, and modified EDEMA scores for predicting MCE are also applicable in non-revascularization LHI patients within 48 h of onset. Both the MBE and modified EDEMA scores demonstrated higher predictive validity as predictive tools for MCE in LHI patients than the EDEMA score. Furthermore, the modified EDEMA score could be a suitable prediction tool in Chinese patients for its excellent clinical utility.

Exploring the use of ChatGPT in predicting anterior circulation stroke functional outcomes after mechanical thrombectomy: a pilot study

BackgroundAccurate prediction of functional outcomes is crucial in stroke management, but this remains challenging.ObjectiveTo evaluate the performance of the generative language model ChatGPT in predicting the functional outcome of patients...

Evaluation of the relationship between computed tomography angiography collateral scores and clinical outcome.

The relationship between collateral circulation and prognosis after endovascular treatment in anterior circulation strokes has been reported in many studies. In this study, we aimed to compare the predictive power of clinical outcome by comparing five different collateral scores that are frequently used. Among the patients who underwent endovascular treatment in our clinic between November 2019 and December 2021, patients with premorbid mRS < 3, intracranial ICA and/or MCA M1 occlusion, and a pre-procedural multiphase CTA examination were included in the study. Demographic, technical, and duration information about the procedure, major events after the procedure, and clinical outcomes at 3 months were recorded. The mCTA, Tan, Maas, Miteff, and rLMC collateral scores of the patients were evaluated. Clinical outcome at 3 months were good in 37 of the 68 patients included in the study (mRS ≤ 2). Only the mCTA and rLMC collateral scores were statistically significantly higher in those with a good clinical outcome. Significant correlation with 3-month mRS was detected only in mCTA and rLMC scores. Although rLMC and mCTA collateral scores showed a statistically significant association with prognosis, they were not sufficient to be an independent predictor of prognosis. mCTA and rLMC were found to have the highest predictive power of clinical outcome and the highest correlation with the 3-month clinical outcome. Our study suggests that it would be beneficial to develop a new scoring system over multiphase CTA, which combines regional and temporal evaluation, which are the strengths of both collateral scoring.

Brush Sign on pre-treatment imaging is associated with good functional outcome in stroke patients treated with mechanical thrombectomy: A prospective monocentric study

BackgroundThe Brush Sign (BrS) is a radiological biomarker (MRI) showing signal decrease of subependymal and deep medullary veins on paramagnetic-sensitive magnetic resonance sequences. Previous studies have shown controversial results regarding the prognostic value of BrS. We aimed to assess whether BrS on T2*-weighted sequences could predict functional prognosis in patients treated with mechanical thrombectomy (MT). MethodsWe included all consecutive patients with large artery occlusion related stroke in anterior circulation treated with MT between February 2020 and August 2022 at Reims University Hospital. Multivariable logistic regression models were used to investigate factors associated with BrS and its impact on outcomes. ResultsOf the 327 included patients, 124 (37,9%) had a BrS on baseline MRI. Mean age was 72 ± 16 years and 184 (56,2 %) were female. In univariate analysis, BrS was associated with a younger age (67 vs 74; p<0.001), a higher NIHSS score (16(10–20) vs 13(8–19); p = 0.047) history of diabetes (15.3% vs 26.1 %; p = 0.022) and a shorter onset to MRI time (145.5 (111.3–188.5) vs 162 (126–220) p = 0.008). In multivariate analyses, patients with a BrS were younger (OR:0.970 (0.951 – 0.989)), tend to have a higher NIHSS score at baseline (OR:1.046 (1.000 – 1.094) and were less likely to have diabetes (OR: 0.433; 0.214–0.879). The presence of BrS was independently associated with functional independence (OR: 2.234(1.158–4,505) at 3 months but not with mortality nor with symptomatic intracerebral hemorrhage. ConclusionBrS on pre-treatment imaging could be considered as a biomarker of physiological adaptation to cerebral ischemia, allowing prolonged viability of brain tissue and might participate in the therapeutic decision.

Intravenous Thrombolysis in Posterior versus Anterior Circulation Stroke: Clinical Outcome Differs Only in Patients with Large Vessel Occlusion.

The safety and efficacy of intravenous thrombolysis (IVT) are well established in anterior circulation stroke (ACS) but are much less clear for posterior circulation stroke (PCS). The aim of this study was to evaluate the occurrence of parenchymal hematoma (PH) and 3-month clinical outcomes after IVT in PCS and ACS. In an observational, cohort multicenter study, we analyzed data from ischemic stroke patients treated with IVT prospectively collected in the SITS (Safe Implementation of Treatments in Stroke) registry in the Czech Republic between 2004 and 2018. Out of 10,211 patients, 1166 (11.4%) had PCS, and 9045 (88.6%) ACS. PH was less frequent in PCS versus ACS patients: 3.6 vs. 5.9%, odds ratio (OR) = 0.594 in the whole set, 4.4 vs. 7.8%, OR = 0.543 in those with large vessel occlusion (LVO), and 2.2 vs. 4.7%, OR = 0.463 in those without LVO. At 3 months, PCS patients compared with ACS patients achieved more frequently excellent clinical outcomes (modified Rankin scale [mRS] 0-1: 55.5 vs. 47.6%, OR = 1.371 in the whole set and 49.2 vs. 37.6%, OR = 1.307 in those with LVO), good clinical outcomes (mRS 0-2: 69.9 vs. 62.8%, OR = 1.377 in the whole set and 64.5 vs. 50.5%, OR = 1.279 in those with LVO), and had lower mortality (12.4 vs. 16.6%, OR = 0.716 in the whole set and 18.4 vs. 25.5%, OR = 0.723 in those with LVO) (p < 0.05 in all cases). In PCS versus ACS patients, an extensive analysis showed a lower risk of PH both in patients with and without LVO, more frequent excellent and good clinical outcomes, and lower mortality 3 months after IVT in patients with LVO.

Association between occlusion location, net water uptake and ischemic lesion growth in large vessel anterior circulation strokes

Ischemic lesion net water uptake (NWU) represents a quantitative imaging biomarker for cerebral edema in acute ischemic stroke. Data on NWU for distinct occlusion locations remain scarce, but might help to improve the prognostic value of NWU. In this retrospective multicenter cohort study, we compared NWU between patients with proximal large vessel occlusion (pLVO; ICA or proximal M1) and distal large vessel occlusion (dLVO; distal M1 or M2). NWU was quantified by densitometric measurements of the early ischemic region. Arterial collateral status was assessed using the Maas scale. Regression analysis was used to investigate the relationship between occlusion location, NWU and ischemic lesion growth. A total of 685 patients met inclusion criteria. Early ischemic lesion NWU was higher in patients with pLVO compared with dLVO (7.7% vs 3.9%, P < .001). The relationship between occlusion location and NWU was partially mediated by arterial collateral status. NWU was associated with absolute ischemic lesion growth between admission and follow-up imaging (β estimate, 5.50, 95% CI, 3.81–7.19, P < .001). This study establishes a framework for the relationship between occlusion location, arterial collateral status, early ischemic lesion NWU and ischemic lesion growth. Future prognostic thresholds for NWU might be optimized by adjusting for the occlusion location.

Abstract 75: Validation of Vascular Location Subcodes for Acute Ischemic Stroke by the International Classification of Diseases-10

Background: The affected vascular region is included in the International Classification of Diseases-10 (ICD-10) coding scheme for stroke. These data have the potential to enable studies of vascular and regional location. For example, differentiating anterior versus posterior circulation stroke. However, the coding in real world practice has not been validated. The purpose of this study was to evaluate the validity of these subcodes. Methods: We identified all hospitalizations for ischemic stroke at a single center from 2018-2022. We selected a random sample of 100 hospitalizations with vascular region subcoding specifying 50 with anterior circulation subcodes (carotid, anterior cerebral artery [CA], middle CA) and 50 with posterior circulation subcodes (vertebral, basilar, cerebellar, posterior CA). The gold standard classification for the primary infarct vascular distribution was made by the study team, blinded to the subcode, after review of the available imaging studies and the medical record. We calculated the sensitivity, specificity, positive predictive value, and negative predictive value of the administrative data posterior circulation subcodes versus anterior circulation subcodes with the gold standard classification. We also calculated the kappa statistic for overall agreement of the 7 vascular regions. Results: The final study population was 50 ICD-10 anterior circulation ischemic stroke hospitalizations and 50 ICD-10 posterior circulation ischemic stroke hospitalizations. Mean age was 68 (SD, 15) and 44% (44/100) were female. Mean NIHSS was 8 (SD, 8). Neuroimaging was performed in 100% (100/100): Head CT, 95% (95/100); MRI brain, 77% (77/100). The accuracy of the ICD-10 classification for primary posterior circulation stroke was as follows: sensitivity 89% (49/55); specificity 98% (44/45); PPV 98% (49/50); NPV 88% (44/50), respectively. The reliability of the 7-region classification was excellent (kappa statistic, 0.85). Conclusions: We found that the ICD-10 subcode classification for vascular location used in clinical practice had excellent agreement with our gold standard based on medical review. These data validate the use of these subcodes for anterior versus posterior circulation stroke studies.

Abstract TP188: Diving MCA and First-Pass Reperfusion: A Subgroup Analysis of the Arise II Study

Introduction: Tortuosity of Internal carotid artery impact on achieving first pass in mechanical thrombectomy has been previously described. Here, we investigate the association of middle cerebral artery(MCA) tortuosity on radiographic and functional outcome. Methods: The Analysis of Revascularization in Ischemic Stroke with EmboTrap II was utilized to identify patients with anterior circulation stroke. MCA tortuosity was calculated using Inflection Count Metric(ICM) by two blinded readers to angiographical/clinical outcomes. The total cohort was trichotomized into 3 groups (A, B, C) based on M1 tortuosity tertiles. The primary efficacy end point was achievement of modified Thrombolysis in Cerebral Ischemia (mTICI) reperfusion scores of ≥2b on first pass. Good functional outcomes was defined as mRS0-2 on 90-day followup. Baseline and procedural data were compared between groups. Results: A total of 200 with known MCA tortuosity were identified. Patients within group A were significantly older (P&lt;0.05) . Group C patient were more likely to have renal disease and atrial fibrillation (P&lt;0.05). There was no differences in terms of NIHSS score at presentation nor ASPECT score between groups. Achieving first-pass success was more likely in group A (60.6%) vs 47% and 38.2%, P=0.033 for groups B and C, respectively. Likewise, the rate of mTICI≥2c was higher in group A (54.5%) vs 36.4% and 26.5%, p=0.003. Achieving mRS0-2 was more likely in group A (76.6%) vs 73.4% and 49.3%, p=0.001. There were no differences in distal emboli, or symptomatic intracranial hemorrhage. Findings of first-pass and angiographic outcomes were consistent with standard tortuosity scoring system. Conclusion: Patients with higher MCA tortuosity are less likely to have successful reperfusion and good functional outcome post mechanical thrombectomy for acute ischemic stroke.

WITHDRAWN: Malignant transformation of ischemic stroke in the era of mechanical thrombectomy: When is decompressive craniectomy required?

ObjectiveThe treatment of choice for ischemic stroke due to intracranial arterial occlusion of the anterior circulation has been mechanical thrombectomy (MT). The success rate of MT is described as 71%, but malignant infarction can nonetheless ensue. In these cases, decompressive craniectomy (DHC) is often necessary. To date, only few factors are known to correlate significantly with the need for DHC after MT. MethodsWe conducted a retrospective analysis of patients admitted with anterior circulation stroke at our department who underwent MT with and without subsequent DHC. Patients were matched according to ASPECT score on pre-MT CT scan. Established predictors for neurological outcome, TICI grade of recanalization, as well as imaging were then compared between the groups to elucidate which of them were predictive of DHC. ResultsA total of 86 patients were included in the analysis. DHC was performed in 43 patients (50%). In a univariate analysis, male sex (p = 0.037), lower TICI grade of recanalization (p < 0.001) and hemorrhagic transformation (p = 0.014) were predictive of DHC. Patients who received later intravenous thrombolysis were also at higher risk for needing DHC (p = 0.050). Patients suffering from hypercholesterolemia (p < .001) and who were on antiplatlet agents (p = .039) were at lower risk for needing DHC. ConclusionsPatients with higher rates of recanalization were protected against DHC. Later administration of IV tPA was correlated with DHC, thus suggesting a synergistic effect of IV tPA and MT in protecting against malignant transformation. Prior use of antiplatelet agents appears to be a protective factor against DHC in stroke, which warrants further investigation.

Abstract TP142: Perfusion Profiles to Identify Acute Extracranial Internal Carotid Artery Atherosclerosis-Related Stroke Prior to Endovascular Therapy

Introduction: Perfusion imaging has been used to assess collateral status in patients with acute ischemic stroke secondary to anterior large-vessel occlusion. We aimed to evaluate the hypoperfusion intensity ratio (HIR), a surrogate of collateral status, in acute stroke secondary to extracranial atherosclerosis disease (AD) compared with extracranial non-AD etiologies prior to EVT. Methods: We retrospectively reviewed the data of consecutive EVT stroke patients in our prospectively collected registry from January 2019 to December 2022. Inclusion criteria: patients with anterior circulation stroke with concomitant extracranial internal carotid artery (ICA) disease with 70-100% stenosis per NASCET criteria and patients who underwent computed tomography perfusion (CTP) before EVT. Patients were divided into those with extracranial AD and non-AD based on clinical and radiological characteristics. HIR was calculated as the volume of ischemic brain tissue with a Tmax&gt;10s divided by a Tmax&gt;6s. A relative CBF&lt;30% was also obtained. Multivariable regression was used to identify the HIR independently associated with extracranial ICA AD-related stroke; adjusted odds ratio with 95%CIs were calculated using the non-AD group as a reference. Results: Among all 624 EVT patients, 79 met inclusion criteria. Of these patients (21 women [36.2%]; median age 67 [60-75] years), 58 (72.5%) had extracranial ICA AD. Patients in the AD group had significantly lower CBF&lt;30% (median 8ml [0-17] vs 19ml [9-36]), lower Tmax&gt;10s (median 29ml [11-69] vs 68ml [38-117]), and lower HIR (median 0.27 [0.13-0.45] vs 0.49 [0.42-0.59]). There was no significant difference in time from last know well to CTP between groups. Lower HIR was independently associated with AD after adjusting for variables related to AD (Figure1). Conclusions: Low HIR values was a predictor of stroke secondary to extracranial ICA AD and could be helpful to differentiate from other non-AD etiologies prior to EVT.

Abstract TP217: Thrombus Migration in Acute Ischemic Stroke Patients Receiving Mechanical Thrombectomy

Background: Thrombus migration is occasionally observed during mechanical thrombectomy in acute ischemic stroke patients. However, the factors influencing migration and its impact on imaging and clinical prognosis remain unclear. We investigated the clinical and imaging predictors of thrombus migration and to evaluate the corresponding outcomes. Methods: We retrospectively analyzed data from patients with acute anterior circulation (internal carotid artery, M1, M2) stroke who underwent mechanical thrombectomy at two comprehensive stroke centers. Thrombus migration was defined as any distal movement of the proximal end of the thrombus on digital subtraction angiography (DSA) compared to pre-interventional computed tomography (CT) angiography. A comprehensive imaging review was performed, including Alberta Stroke Program Early CT Score, hyperdense vessel sign on non-contrast CT, collateral flow grading on CT angiography and DSA. Univariate and multivariable logistic regression analyses were performed to determine the association between clinical and imaging parameters and thrombus migration. In addition, we compared clinical outcomes according to the presence of thrombus migration. Results: Of the 365 patients enrolled, thrombus migration was observed in 81 patients (22.2%). In 40 of these, the thrombus migrated beyond the vessel segment. In multivariable analysis, hyperdense vessel sign (adjusted odds ratio [aOR], 5.41; 95% CI 2.9-10.07), older age (aOR, 1.04; 95% CI, 1.01-1.08), and onset-to-image time (aOR 1.00; 95% CI 0.99-1.00) were associated with thrombus migration. In particular, thrombus migration is an independent predictor of first-pass effect (aOR 2.17; 95% CI, 1.15-4.1). However, there was no significant effect on functional outcome as measured by modified Rankin Scale at 3 months. Conclusions: In large-vessel occlusion stroke, the location of the thrombus may change before mechanical thrombectomy compared to pre-interventional angiographic imaging. The composition of the thrombus, as indicated by the hyperdense vessel sign, may influence its tendency to migrate. While thrombus migration is associated with a first-pass effect, it does not influence functional outcomes.

Abstract TP141: Understanding Potential Limitations of CTP Imaging in Early Window Large Vessel Anterior Circulation Strokes

Background: Computerized tomography perfusion (CTP) imaging serves as a valuable modality for the assessment of individuals with a large vessel anterior circulation stroke. Current literature proposes that employing CTP imaging in patients within the initial time frame of less than 8 hours, may lead to an overestimation of the projected infarct core, specifically when utilizing cerebral blood flow (CBF) less than 30%. The hypoperfusion intensity ratio (HIR) may result in overestimation. We sought to further investigate the interplay of CTP parameters in patients presenting within 8 hours of symptom onset of stroke, to assess the accuracy of core infarct estimation. Methods: A retrospective cohort study analyzing patients with large vessel anterior occlusion (LVAO) who underwent CTP and mechanical thrombectomy within 24 hours of symptom onset between January 2017 to December 2022. RAPID software estimates the infarct core using CBF &lt;30%. DWI-MRI determined final infarct volume. A multivariate logistic regression model was employed to assess the impact of HIR and reperfusion success on outcomes. Results: Ninety-seven patients were identified within an 8-hour time window. CBF&lt;30% overestimated core infarct volume (mL) in 22 patients (22.6%) with a mean of 15.72 (range 4.4-37.7) and a median of 22.85. Of these, 2 patients experienced poor reperfusion (9%) while 20 had successful reperfusion (91%). Of the patients who did have successful reperfusion, an average of 13.57mL core was overpredicted compared to the DWI volumes. A multivariate logistic regression model adjusting for degree of reperfusion, administration of thrombolytic, and time from symptom onset showed that HIR strongly predicted the probability of core estimation with an odds ratio of 148.6, 95% CI [21.0-1048.8], (p&lt;0.001). Conclusion: HIR exceeding 0.4 demonstrates a predictive capacity for core overestimation in early-window LVAO patients. Our study affirms this observation with statistical significance. The integration of HIR as a parameter for early-window LVAO core computation shows promise, and has potential ramifications for patient selection for thrombectomy. In this context, utilization of further databases is imperative for validation and broader application of HIR.

Abstract TP133: Clot Burden Score Correlates Best With Hypoperfusion Volume and Predicts Final Infarct ASPECTS&lt;=3 in Anterior Circulation Ischemic Strokes

Purpose: Clot Burden Score (CBS) is a semiquantitative measure of thrombus extent on CTA for proximal anterior circulation strokes whose relationship with perfusion metrics has not been fully explored. CBS has potential added value during stroke triage if perfusion imaging is not available or suboptimal. We aimed to investigate if CBS is (1) correlated to perfusion estimates of infarct core volume, hypoperfusion volume, or collateral status, and (2) a predictor of final infarct extent without reperfusion therapy. Methods: Retrospective analysis included consecutive patients (1) arriving &lt;24 hours from onset, (2) with occlusion in the intracranial ICA, M1, M2, or A1 or combination, (3) with concurrent CTP, and (4) had followup CT or DWI during hospitalization. CBS is a 10-point negative ordinal scale: 2-points subtracted for occlusion of supraclinoid ICA, proximal M1, or distal M1, and 1-point subtracted for occlusion of infraclinoid ICA, A1, or M2. Correlation of CBS with perfusion metrics was evaluated using Spearman's rank test. Final infarct ASPECTS were scored for those without thrombolysis or thrombectomy. Multivariate logistic regression was used to identify predictors of final ASPECTS&lt;=3 (approximating &gt;=100mL). ROC analysis was evaluated to assess performance and optimal thresholds. Results: 222 patients included with median (IQR) age of 75 (65-84) and NIHSS of 18 (11-24). Median CBS was 7 (6-9) and best correlated to Tmax&gt;6s r=-0.579 (hypoperfusion volume), followed by HIR r=-0.401 (collateral status) and rCBF&lt;30% r=-0.306 (core volume), all p&lt;0.001. 71 (32.0%) untreated patients also had median CBS of 7 (6-9). CBS and Tmax&gt;6s had the strongest correlation to final ASPECTS in this subgroup, r=0.637 and r=-0.686 (both p&lt;0.001). 22 of these (30.1%) had final ASPECTS&lt;=3. Multivariate logistic regression including CBS, Tmax&gt;6s, HIR, baseline ASPECTS, and NIHSS showed only CBS as independent predictor of final ASPECTS&lt;=3 (p&lt;0.001). ROC AUC for CBS was 0.902 [95% CI: 0.819-0.985] with optimal threshold of &lt;=6 for sensitivity 86.4% and specificity 81.6%. Conclusion: CBS as a measure of thrombus extent correlates best with baseline hypoperfusion volume on CTP and independently predicts very large final infarcts (ASPECTS&lt;=3) without treatment.

Abstract TP246: Circadian Variability of the Clot Burden Score in Acute Anterior Circulation Ischemic Stroke

Background/Purpose: Fibrinolytic activity in blood plasma displays a circadian rhythm with a drop in the morning hours that may predispose to acute thrombotic events. The Clot Burden Score (CBS) is a semiquantitative measure on CT angiography (CTA) of thrombus extent in proximal anterior circulation strokes that has been correlated with functional outcome. Higher clot burden has also been shown to have lower recanalization rates with intravenous thrombolytics. We aimed to investigate whether CBS is a parameter that displays circadian variability. Methods: We performed a retrospective analysis on consecutive stroke patients presenting &lt;24 hours from symptom onset or last known well (LKW) with an occlusion in the anterior circulation confirmed on CTA. CBS was scored on a 10-point negative ordinal scale with 2-points subtracted for occlusion of the supraclinoid ICA, proximal M1, or distal M1, and 1-point subtracted for occlusion of the infraclinoid ICA, A1, or either M2 branches. No points were subtracted for occlusion distal to A1 or M2. Subjects were grouped into four 6-hour intervals, MORNING: 6:00-11:59, DAY: 12:00-17:59, EVENING: 18:00-23:59, and NIGHT: 0:00-5:59, based on the time of onset/LKW. CBS values were compared between groups using the Kruskal-Wallis test with pairwise comparisons. Results: 240 subjects were included with median age of 75 (IQR 65-84), NIHSS score of 17 (IQR 10-24), and time from onset/LKW to CTA of 5 hours (IQR 2-11). 73 subjects had onset during the MORNING, 56 during the DAY, 86 during the EVENING, and 25 during the NIGHT. The median CBS from MORNING time onset was 6 (IQR 5-9), compared to 7 (IQR 6-9) from the DAY, 7.5 (IQR 6-9) from the EVENING, and 7 (IQR 5-8.5) from the NIGHT. CBS was significantly lower in the MORNING compared to the EVENING, p=0.037. CBS was not significantly different between all other pairwise comparisons, p&gt;0.107. Conclusion: CBS as a measure of thrombus extent in proximal anterior circulation strokes on CTA appears to show circadian variability, with lower scores (higher clot burden) during MORNING onset (6:00-11:59) than the EVENING (18:00-23:59). This may have implications for future studies of chronotherapeutic protocols.

Abstract WP205: Development and Validation of a Prediction Model for Outcome in Mechanical Thrombectomy for Large-Vessel Occlusion Anterior Circulation Stroke With Low ASPECTS

Introduction: Recent randomized control trials suggested that mechanical thrombectomy (MT) was associated with good functional outcomes after acute ischemic stroke (AIS) due to large vessel occlusion (LVO) in patients presenting with low Alberta Stroke Program Early CT Score (ASPECTS) (defined as ASPECTS 2-5). The aim of this study is to develop and validate a stroke prediction tool for outcome in MT for AIS patients with low ASPECTS using data from an ongoing international multicenter registry, the Stroke Thrombectomy and Aneurysm Registry (STAR). Methods: 236 AIS patients with low ASPECTS caused by LVO who undertook MT between January 2010 and December 2022 were retrospectively investigated. Univariate and multivariate logistic regression results were used to screen model predictors and construct nomograms of 90-day modified Rankin Scale scores (mRS) 0-3. The performance of the model was detected by using receiver operating characteristic analysis. The bootstrap resampling method was considered internal validation of the model. Results: Age (&lt; 70 years), premorbid status (mRS 0), National Institutes of Health Stroke Scale (NIHSS) (&lt; 20), and recanalization status after the MT (modified Thrombolysis in Cerebral Ischemia [mTICU] ≥2b) were related to 90-day mRS 0-3. Predictive score was calculated by adding 1 point for age (&lt; 70 years), premorbid status (mRS 0), and NIHSS &lt; 20 and 3 points for a mTICI ≥2b (ranging 0-6). 90-day mRS 0-3 was observed in 0% of patients with a score of 0 or 1, 6.3% with a score of 2, 17.7% with a score of 3, 22.2% with a score of 4, 45.7% with a score of 5, and 73.7% with a score of 6. The score showed relatively high performance in predicting 90-day mRS0-3 (area under the curve: 0.79 [95% CI 0.73-0.79] and 0.78 [95% CI 0.78-0.78] for derivation and validation cohorts, respectively). Conclusions: This study indicates the STAR score can be calculated with baseline and periprocedural characteristics to predict the 90-day outcome after MT in AIS patients with low ASPECTS.

Abstract WP192: Impact of Second Line Thrombectomy Technique Following Failed First Pass Thrombectomy for Anterior Circulation Stroke: To Switch or Not to Switch?

Introduction: Despite comparable outcomes for different frontline techniques in mechanical thrombectomy (MT) for acute ischemic stroke (AIS), there are sparse data regarding if and when to switch techniques if the first pass is unsuccessful. We aimed to investigate the impact of converting from one MT technique to another on the second MT attempt for AIS among patients with large vessel occlusion (LVO). Methods: This was a retrospective observational study using data from the large multicenter international Stroke Thrombectomy and Aneurysm Registry (STAR). Data from 29 stroke centers for 10,229 AIS patients treated with MT for LVO between January 2010 and December 2022 was investigated. The primary outcome measure was successful recanalization defined as modified Thrombolysis in Cerebral Ischemia (mTICI) score of 2b or higher. 90-day modified Rankin score (mRS) 0-2, mortality and symptomatic hemorrhage were used as secondary outcomes. Clinical and technical outcomes after the second MT attempt were compared between those with or without technique conversion. Results: Among 10,229 AIS patients, 1,797 AIS patients with LVO failed first pass recanalization and were included in this retrospective analysis. 927 patients were female (52%) and median (interquartile range) age was 72 (61-81) years. Converting to alternative techniques following a first failed attempt was more likely to be associated with successful recanalization at the second attempt (adjusted odds ratio 2.30, 95% CI: 1.37-3.86, P = 0.002) and 90-day good clinical outcome (adjusted odds ratio 2.10, 95% CI: 1.15-3.85, P = 0.02) after multivariate adjustment. Conclusions: This study demonstrates better clinical and technical outcomes with conversion of MT technique for the second attempt in AIS patients with LVO who failed first pass recanalization.

Abstract TP132: Optimal CT Perfusion Post-Processing Method in Posterior Circulation Stroke

Objective: CT-perfusion (CTP) has revolutionised stroke care by improving diagnostic accuracy and expanding eligibility to acute therapies. Software packages utilise various mathematical techniques to transform raw perfusion data into measures of infarct core and ischaemic penumbra. These techniques have been derived from studies of anterior-circulation stroke and not yet validated in posterior circulation stroke (PCS). We examined the optimal CTP thresholds for acute PCS. Methods: Data were analysed from 331-patients diagnosed with a PCS enrolled in the International-stroke-perfusion-registry (INSPIRE). Twenty-seven-patients with baseline multimodal-CT with occlusion of a large posterior-circulation (PC) artery and follow up diffusion-weighted-MRI at 24-48 hours were included. CTP parametric maps were generated using five different post-processing methods. Receiver-operating-curve analysis was used to determine the optimal perfusion parameter and thresholds. Results: Partial deconvolution was the optimal post-processing method for characterisation of ischaemic penumbra and infarct core. Mean transit time (MTT) at a threshold of &gt;165% and &gt;195% most accurately defined ischaemic core (AUC=0.73) and penumbra (AUC=0.78) respectively. Post-processing technique influenced accuracy of core (AUC range=0.54-0.73) and penumbra (AUC range=0.72-0.79) estimates. MTT was consistently the most accurate parameter at distinguishing core and penumbra across all post-processing methods. Conclusion: CTP has significant diagnostic utility in PCS. Accuracy of CTP varies considerably by post-processing method. The underlying post-processing technique employed by individual software packages should be considered when interpreting the accuracy of ischemic core and penumbra estimates.