Imaging Triage of Patients with Late-Window (6-24 Hours) Acute Ischemic Stroke: A Comparative Study Using Multiphase CT Angiography versus CT Perfusion

Effect of time delay in inter-hospital transfer on outcomes of endovascular treatment of acute ischemic stroke

Background

Endovascular treatment (EVT) with mechanical thrombectomy is the standard of care for large vessel occlusion (LVO) in acute ischemic stroke (AIS). The most common approach today is to perform EVT in a comprehensive stroke center (CSC) and transfer relevant patients for EVT from a primary stroke center (PSC). Rapid and efficient treatment of LVO is a key factor in achieving a good clinical outcome.

Methods

We present our retrospective cohort of patients who underwent EVT between 2018 and 2021, including direct admissions and patients transferred from PSC. Primary endpoints were time intervals (door-to-puncture, onset-to-puncture, door-to-door) and favorable outcome (mRS ≤ 2) at 90 days. Secondary outcomes were successful recanalization, mortality rate, and symptomatic intracranial hemorrhage (sICH). Additional analysis was performed for transferred patients not treated with EVT; endpoints were time intervals, favorable outcomes, and reason for exclusion of EVT.

Results

Among a total of 405 patients, 272 were admitted directly to our EVT center and 133 were transferred; there was no significant difference between groups in the occluded vascular territory, baseline NIHSS, wake-up strokes, or thrombolysis rate. Directly admitted patients had a shorter door-to-puncture time than transferred patients (190 min vs. 293 min, p < 0.001). The median door-to-door shift time was 204 min. We found no significant difference in functional independence, successful recanalization rates, or sICH rates. The most common reason to exclude transferred patients from EVT was clinical or angiographic improvement (55.6% of patients).

Conclusion

Our results show that transferring patients to the EVT center does not affect clinical outcomes, despite the expected delay in EVT. Reassessment of patients upon arrival at the CSC is crucial, and patient selection should be done based on both time and tissue window.

Automated advanced imaging in acute ischemic stroke. Certainties and uncertainties

The purpose of this is study was to review pearls and pitfalls of advanced imaging, such as computed tomography perfusion and diffusion-weighed imaging and perfusion-weighted imaging in the selection of acute ischemic stroke (AIS) patients suitable for endovascular treatment (EVT) in the late time window (6-24 h from symptom onset). Advanced imaging can quantify infarct core and ischemic penumbra using specific threshold values and provides optimal selection parameters, collectively called target mismatch. More precisely, target mismatch criteria consist of core volume and/or penumbra volume and mismatch ratio (the ratio between total hypoperfusion and core volumes) with precise cut-off values. The parameters of target mismatch are automatically calculated with dedicated software packages that allow a quick and standardized interpretation of advanced imaging. However, this approach has several limitations leading to a misclassification of core and penumbra volumes. In fact, automatic software platforms are affected by technical artifacts and are not interchangeable due to a remarkable vendor-dependent variability, resulting in different estimate of target mismatch parameters. In addition, advanced imaging is not completely accurate in detecting infarct core, that can be under- or overestimated. Finally, the selection of candidates for EVT remains currently suboptimal due to the high rates of futile reperfusion and overselection caused by the use of very stringent inclusion criteria. For these reasons, some investigators recently proposed to replace advanced with conventional imaging in the selection for EVT, after the demonstration that non-contrast CT ASPECTS and computed tomography angiography collateral evaluation are not inferior to advanced images in predicting outcome in AIS patients treated with EVT. However, other authors confirmed that CTP and PWI/DWI postprocessed images are superior to conventional imaging in establishing the eligibility of patients for EVT. Therefore, the routine application of automatic assessment of advanced imaging remains a matter of debate. Recent findings suggest that the combination of conventional and advanced imaging might improving our selection criteria.

ASPECTS-based net water uptake outperforms target mismatch for outcome prediction in patients with acute ischemic stroke and late therapeutic window

OBJECTIVE

To compare the prognostic value of net water uptake (NWU) and target mismatch (TM) on CT perfusion (CTP) in acute ischemic stroke (AIS) patients with late time window.

METHODS

One hundred and nine consecutive AIS patients with anterior-circulation large vessel occlusion presenting within 6-24 h from onset/last seen well were enrolled. Automated Alberta Stroke Program Early CT Score-based NWU (ASPECTS-NWU) was calculated from admission CT. The correlation between ASPECTS-NWU and CTP parameters was assessed. Predictors for favorable outcome (modified Rankin Scale score ≤ 2) at 90 days were assessed using logistic regression analysis. The ability of outcome prediction between ASPECTS-NWU and TM (an ischemic core < 70 mL, a mismatch ratio ≥ 1.8, and an absolute difference ≥ 15 mL) was compared using receiver operating characteristic (ROC) curve.

RESULTS

A higher level of ASPECTS-NWU was associated with a larger ischemic core (r = 0.66, p < 0.001) and a larger hypoperfusion volume (r = 0.38, p < 0.001). ASPECTS-NWU performed better than TM for outcome stratification (area under the curve [AUC], 0.738 vs 0.583, p = 0.004) and was the only independent neuroimaging marker associated with favorable outcomes compared with CTP parameters (odds ratio, 0.73; 95% confidence interval [CI] 0.62-0.87, p < 0.001). An outcome prediction model including ASPECTS-NWU and clinical variables (National Institutes of Health Stroke Scale scores and age) yielded an AUC of 0.828 (95% CI 0.744-0.893; sensitivity 65.4%; specificity 87.7%).

CONCLUSION

ASPECTS-NWU performed better than TM for outcome prediction in AIS patients with late time window and might be an alternative imaging biomarker to CTP for patient selection.

CLINICAL RELEVANCE STATEMENT

Automated Alberta Stroke Program Early CT Score-based net water uptake outperforms target mismatch on CT perfusion for the outcome prediction in patients with acute ischemic stroke and can be an alternative imaging biomarker for patient selection in late therapeutic window.

KEY POINTS

• A higher ASPECTS-based net water uptake was associated with larger ischemic cores and hypoperfusion volumes on CT perfusion. • ASPECTS-based net water uptake outperformed target mismatch for outcome prediction in acute ischemic stroke with extended therapeutic window. • ASPECTS-based net water uptake can be an alternative biomarker to target mismatch for selecting acute ischemic stroke patients with late therapeutic window.

Nomogram Based on Dual-Layer Spectral Detector CTA Parameter for the Prediction of Infarct Core in Patients with Acute Ischemic Stroke

(1) Background: Acute ischemic stroke (AIS) is time-sensitive. The accurate identification of the infarct core and penumbra areas in AIS patients is an important basis for formulating treatment plans, and is the key to dual-layer spectral detector computed tomography angiography (DLCTA), a safer and more accurate diagnostic method for AIS that will replace computed tomography perfusion (CTP) in the future. Thus, this study aimed to investigate the value of DLCTA in differentiating infarct core from penumbra in patients with AIS to establish a nomogram combined with spectral computed tomography (CT) parameters for predicting the infarct core and performing multi-angle evaluation. (2) Methods: Data for 102 patients with AIS were retrospectively collected. All patients underwent DLCTA and CTP. The patients were divided into the non-infarct core group and the infarct core group, using CTP as the reference. Multivariate logistic regression analysis was used to screen predictors related to the infarct core and establish a nomogram model. The receiver operating characteristic (ROC) curve, the calibration curve, and decision curve analysis (DCA) were used to evaluate the predictive efficacy, accuracy, and clinical practicability of the model, respectively. (3) Results: Multivariate logistic analysis identified three independent predictors: iodine density (OR: 0.022, 95% CI: 0.003-0.170, p < 0.001), hypertension (OR: 7.179, 95% CI: 1.766-29.186, p = 0.006), and triglycerides (OR: 0.255, 95% CI: 0.109-0.594, p = 0.002). The AUC-ROC of the nomogram was 0.913. Calibration was good. Decision curve analysis was clinically useful. (4) Conclusions: The spectral CT parameters, specifically iodine density values, effectively differentiate between the infarct core and penumbra areas in patients with AIS. The nomogram, based on iodine density values, showed strong predictive power, discrimination, and clinical utility to accurately predict infarct core in AIS patients.

Prognostic value of multiphase CT angiography: estimated infarct core volume in the patients with acute ischaemic stroke after mechanical thrombectomy

BACKGROUND AND PURPOSE

Recent studies reported the feasibility of quantifying a reliable infarct core (IC) volume using multiphase computed tomography (mCTA) based on deep learning, however its prognostic value was not fully clarified. Therefore, we aimed to evaluate the prognostic value of mCTA-estimated IC volume in patients with acute ischemic stroke (AIS) after mechanical thrombectomy (MT).

MATERIALS AND METHODS

We retrospectively reviewed patients who underwent mCTA and MT for large vessel occlusion in middle cerebral artery and (or) internal carotid artery within 6 hours after symptom onset between January 2018 and November 2019. Patients were dichotomized into good (modified Rankin Scale [mRS] score, 0-2) and poor (mRS, 3-6) outcome groups. mCTA-estimated IC volume were generated based on a multi-scale three-dimensional convolutional neural network. Univariate, multivariate logistic regression and receiver operating characteristic (ROC) curve analyses were used to identify the independent variables, and evaluate their performances in predicting the clinical outcome.

RESULTS

Of 44 included patients, 27 (61.4%) patients achieved good outcome. National Institutes of Health Stroke Scale scores at admission [NIHSSpre] (odds ratio [OR], 1.191; 95%confidence interval [CI], 1.028-1.379; P=0.020) and mCTA-estimated IC volume (OR, 1.076; 95%CI, 1.016-1.140; P=0.013) were found to be independently associated with functional outcome in patients with AIS after MT. After integrating NIHSSpre and mCTA-estimated IC volume, optimal performance (area under the ROC curve, 0.874; 95%CI, 0.739-0.954) could be obtained in predicting the clinical outcome.

CONCLUSIONS

mCTA-estimated IC volume might be promising for predicting the prognosis, and assisting in making individualized treatment decision in patients with AIS.

Aspiration thrombectomy with the Penumbra System for patients with stroke and late onset to treatment: a subset analysis of the COMPLETE registry

Background

The purpose of this study was to report the safety and performance of aspiration thrombectomy with the Penumbra System for patients with acute ischemic stroke (AIS) due to anterior circulation large vessel occlusion (LVO) and late onset to treatment.

Methods

This is a retrospective subset analysis of a global prospective multicenter registry (COMPLETE) that enrolled adults with AIS due to LVO and a pre-stroke modified Rankin Scale score (mRS) of 0 or 1 who were treated first-line with aspiration thrombectomy either alone (A Direct Aspiration First Pass Technique [ADAPT]) or in combination with the 3D Revascularization Device (ADAPT + 3D). This subset analysis included all patients in the registry who had anterior circulation LVO, an Alberta Stroke Program Early CT Score of at least 6, and late onset to treatment (>6 h from stroke onset to puncture).

Results

Of the 650 patients in the COMPLETE registry, 167 were included in this subset analysis. The rate of successful revascularization (modified thrombolysis in cerebral infarction score 2b-3 achieved) at the end of the procedure was 83.2%, the rate of good functional outcome (mRS 0-2) at 90 days was 55.4%, and the all-cause mortality rate at 90 days was 14.4%. No device-related serious adverse events (SAEs) occurred. Procedure-related SAEs occurred in 9 patients (5.4%) within 24 h and in 12 patients (7.2%) overall. The rate of successful revascularization was higher for patients treated first-line with ADAPT (88.0%) than for patients treated first-line with ADAPT + 3D (75.0%; p = 0.035); no significant difference was observed between the ADAPT and ADAPT + 3D groups for any other primary or secondary outcome.

Conclusion

For patients with AIS due to anterior circulation LVO and with late onset to treatment, aspiration thrombectomy with the Penumbra System appears to be safe and effective. The rates of good functional outcome and all-cause mortality from this study compared favorably with those rates from the medical management arms of the DAWN and DEFUSE-3 studies.

Clinical trial registration

https://www.clinicaltrials.gov, NCT03464565.

Stroke imaging modality for endovascular therapy in the extended window: systematic review and meta-analysis

BACKGROUND

In anterior circulation large vessel occlusion (LVO) in the extended time window, the guidelines recommend advanced imaging (ADVI) to select patients for endovascular therapy (EVT). However, questions remain regarding its availability and applicability in the real world. It is unclear whether an approach to the extended window EVT that does not use ADVI would be equivalent.

METHODS

In April 2022, a literature search was performed to identified randomized controlled trials (RCT) and observational studies describing 90-day outcomes. We performed a meta-analysis of the proportion of aggregate using a random effect to estimate rates of functional independence, defined as modified Rankin Scale (mRS) score ≤2 at 90 days, mean mRS, mortality and symptomatic intracranial hemorrhage (sICH) stratified by imaging modality.

RESULTS

Four RCTs and 28 observational studies were included. The pooled proportion of functional independence among patients selected by ADVI was 44% (95% CI 39% to 48%; I2=80%) and 48% (95% CI 41% to 55%; I2=75%) with non-contrast CT/CT angiography (NCCT/CTA) (p=0.36). Mean mRS with ADVI was 2.88 (95% CI 2.36 to 3.41; I2=0.0%) and 2.79 (95% CI 2.31 to 3.27; I2=0.0%) with NCCT (p=0.79). Mortality in patients selected by ADVI was 13% (95% CI 10% to 17%; I2=81%) and 16% (95% CI 12% to 22%; I2=69%) with NCCT (p=0.29). sICH with ADVI was 4% (95% CI 3% to 7%; I2=73%) and 6% with NCCT/CTA (95% CI 4% to 8%; I2=6%, p=0.27).

CONCLUSIONS

Our study suggests that, in anterior circulation LVO, the rates of functional independence may be similar when patients are selected using ADVI or NCCT for EVT in the extended time window. A simplified triage protocol does not seem to increase mortality or sICH. PROTOCOL REGISTRATION NUMBER: (PROSPERO ID: CRD42021236092).

Pivotal role of multiphase computed tomography angiography for collateral assessment in patients with acute ischemic stroke

The cerebral collateral circulation is the main compensatory mechanism that maintains the ischemic penumbra viable, the tissue at risk for infarction that can be saved if blood flow is restored by reperfusion therapies. In clinical practice, the extent of collateral vessels recruited after vessel occlusion can be easily assessed with computed tomography angiography (CTA) using two different techniques: single-phase CTA (sCTA) and multi-phase CTA (mCTA). Both these methodologies have demonstrated a high prognostic predictive value for prognosis due to the strong association between the presence of good collaterals and favorable radiological and clinical outcomes in patients with acute ischemic stroke (AIS). However, mCTA seems to be superior to sCTA in the evaluation of collaterals and a promising tool for identifying AIS patients who can benefit from reperfusion therapies. In particular, it has recently been proposed the use of mCTA eligibility criteria has been recently proposed for the selection of AIS patients suitable for endovascular treatment instead of the current accepted criteria based on CT perfusion. In this review, we analyzed the characteristics, advantages and disadvantages of sCTA and mCTA to better understand their fields of application and the potential of mCTA in becoming the method of choice to assess collateral extent in AIS patients.

Outcomes with Endovascular Treatment of Patients with M2 Segment MCA Occlusion in the Late Time Window

BACKGROUND AND PURPOSE

Randomized trials in the late window have demonstrated the efficacy and safety of endovascular thrombectomy in large-vessel occlusions. Patients with M2-segment MCA occlusions were excluded from these trials. We compared outcomes with endovascular thrombectomy in patients with M2-versus-M1 occlusions presenting 6-24 hours after symptom onset.

MATERIALS AND METHODS

Analyses were on pooled data from studies enrolling patients with stroke treated with endovascular thrombectomy 6-24 hours after symptom onset. We compared 90-day functional independence (mRS ≤ 2), mortality, symptomatic intracranial hemorrhage, and successful reperfusion (expanded TICI = 2b-3) between patients with M2 and M1 occlusions. The benefit of successful reperfusion was then assessed among patients with M2 occlusion.

RESULTS

Of 461 patients, 367 (79.6%) had M1 occlusions and 94 (20.4%) had M2 occlusions. Patients with M2 occlusions were older and had lower median baseline NIHSS scores. Patients with M2 occlusion were more likely to achieve 90-day functional independence than those with M1 occlusion (adjusted OR = 2.13; 95% CI, 1.25-3.65). There were no significant differences in the proportion of successful reperfusion (82.9% versus 81.1%) or mortality (11.2% versus 17.2%). Symptomatic intracranial hemorrhage risk was lower in patients with M2-versus-M1 occlusions (4.3% versus 12.2%, P = .03). Successful reperfusion was independently associated with functional independence among patients with M2 occlusions (adjusted OR = 2.84; 95% CI, 1.11-7.29).

CONCLUSIONS

In the late time window, patients with M2 occlusions treated with endovascular thrombectomy achieved better clinical outcomes, similar reperfusion, and lower symptomatic intracranial hemorrhage rates compared with patients with M1 occlusion. These results support the safety and benefit of endovascular thrombectomy in patients with M2 occlusions in the late window.

Recommendations on the use of computed tomography in the stroke code: Consensus document SENR, SERAU, GEECV-SEN, SERAM

The Spanish Society of Emergency Radiology (SERAU), the Spanish Society of Neuroradiology (SENR), the Spanish Society of Neurology through its Cerebrovascular Diseases Study Group (GEECV-SEN) and the Spanish Society of Medical Radiology (SERAM) have met to draft this consensus document that will review the use of computed tomography in the stroke code patients, focusing on its indications, the technique for its correct acquisition and the possible interpretation mistakes.

Neuroimaging of Acute Ischemic Stroke: Multimodal Imaging Approach for Acute Endovascular Therapy

Advances in acute ischemic stroke (AIS) treatment have been contingent on innovations in neuroimaging. Neuroimaging plays a pivotal role in the diagnosis and prognosis of ischemic stroke and large vessel occlusion, enabling triage decisions in the emergent care of the stroke patient. Current imaging protocols for acute stroke are dependent on the available resources and clinicians' preferences and experiences. In addition, differential application of neuroimaging in medical decision-making, and the rapidly growing evidence to support varying paradigms have outpaced guideline-based recommendations for selecting patients to receive intravenous or endovascular treatment. In this review, we aimed to discuss the various imaging modalities and approaches used in the diagnosis and treatment of AIS.

The diagnostic value of quantitative parameters on dual-layer detector-based spectral CT in identifying ischaemic stroke

Objective

To investigate the diagnostic value of quantitative parameters of spectral computed tomography (CT) in ischaemic stroke areas.

Methods

The medical records of 57 patients with acute ischaemic stroke (AIS) who underwent plain computed tomography (CT) head scans, CT angiography (CTA), and CT perfusion (CTP) were retrospectively reviewed. The ischaemic areas (including the core infarct area and penumbra) and non-ischaemic areas in each patient were quantitatively analyzed using F-STROKE software. Two independent readers measured the corresponding values of the spectroscopic quantitative parameters (effective atomic number [Zeff value], iodine density value, and iodine-no-water value) in the ischaemic area and contralateral normal area alone. The differences in spectroscopic quantitative parameters between the two groups were compared, and their diagnostic efficacy was obtained.

Results

The Zeff, iodine-no-water value, and iodine density value of the ischaemic area all showed significant lower than those of non-ischaemic tissue (P < 0.001). For differentiating the ischaemic area from non-ischaemic tissue, the area under the curve (AUC) of the Zeff value reached 0.869 (cut-off value: 7.385; sensitivity: 93.0%; specificity: 70.2%), the AUC of the iodine density value reached 0.932 (cut-off value: 0.235; sensitivity: 91.2%; specificity: 82.5%), and the AUC of the iodine-no-water value reached 0.922 (cut-off value: 0.205; sensitivity: 96.5%; specificity: 78.9%).

Conclusion

The study showed the spectral CT would be a potential novel rapid method for identifying AIS. The spectral CT quantitative parameters (Zeff, iodine density values, and iodine-no-water values) can effectively differentiate the ischaemic area from non-ischaemic tissue in stroke patients.

A multivariate prediction model and its application in forecasting acute ischemic stroke: Protocol for a retrospective clinical study

BACKGROUND

Acute ischemic stroke (AIS) occurs due to brain ischemia as a result of thrombosis of a cerebral blood vessel. It is a common cerebral blood circulation disorder worldwide and an important cause of death and disability.

OBJECTIVE

This study aims to establish a prediction model of multiple single category indicators and a joint model, through which to plot multiple receiver operating characteristic curves and compare area under curve of the models so as to predict the occurrence of AIS, explore the pathogenesis of AIS, and provide reference for clinical diagnosis and treatment of AIS.

METHODS

A retrospective clinical study was conducted in a Level A tertiary hospital in Sichuan Province, China. The patients participated in this study were over 18 years of age and suffered from acute ischemic stroke. They were hospitalized in department of neurology from October 1, 2019 to September 30, 2022, and underwent coronary artery computed tomographic arteriography (CTA) and blood biomarker detection. We collected demographic information, CTA data and blood biomarker detection values of all these patients.

CONCLUSION

Through analyzing the clinical data of high-risk groups, this study provides guidance for the prevention and treatment of AIS, and promote further research.

Comparison between collateral status and DEFUSE 3 or DAWN criteria in patient selection for endovascular thrombectomy within 6-24 hours after stroke: a protocol for meta-analysis

INTRODUCTION

Perfusion imaging according to the DEFUSE 3 or DAWN criteria has been applied to select patients with large vascular occlusive stroke undergo endovascular therapy (EVT) in the extended time window. Emerging studies have shown that collateral blood flow-based criteria may be as effective as DEFUSE 3 and DAWN criteria for the evaluation of EVT eligibility beyond 6 hours. We will conduct a meta-analysis to compare collateral status-based criteria with DEFUSE 3 or DAWN criteria.

METHODS AND ANALYSIS

We will conduct a search for the studies comparing collateral blood flow-based imaging with CT perfusion using the DEFUSE 3 or DAWN criteria in selecting patients with acute ischaemic stroke undergo EVT in the Web of Science, PubMed, EMBASE and the Cochrane Library databases between November 2017 and November 2021. We will also search the sources of grey literature, the reference lists of included studies and the newly published studies during the review period. Two investigators will independently screen the eligible studies and extract data. The study quality will be assessed by using the Newcastle-Ottawa Scale or the Cochrane risk bias tool. Stata V.17 will be used to conduct data analysis.

ETHICS AND DISSEMINATION

Patient informed consent and ethics approval are not necessary as this study uses only published studies. The finding of this meta-analysis will be propagated through committee conferences or peer-reviewed journals.

PROSPERO REGISTRATION NUMBER

CRD42021281928.

Early Diagnosis of Acute Ischemic Stroke by Brain Computed Tomography Perfusion Imaging Combined with Head and Neck Computed Tomography Angiography on Deep Learning Algorithm

The purpose of the research was to discuss the application values of deep learning algorithm-based computed tomography perfusion (CTP) imaging combined with head and neck computed tomography angiography (CTA) in the diagnosis of ultra-early acute ischemic stroke. Firstly, 88 patients with acute ischemic stroke were selected as the research objects and performed with cerebral CTP and CTA examinations. In order to improve the effect of image diagnosis, a new deconvolution network model AD-CNNnet based on deep learning was proposed and used in patient CTP image evaluation. The results showed that the peak signal-to-noise ratio (PSNR) and feature similarity (FSIM) of the AD-CNNnet method were significantly higher than those of traditional methods, while the normalized mean square error (NMSE) was significantly lower than that of traditional algorithms (P < 0.05). 80 cases were positive by CTP-CTA, including 16 cases of hyperacute ischemic stroke and 64 cases of acute ischemic stroke. The diagnostic sensitivity was 93.66%, and the specificity was 96.18%. The cerebral blood flow (CBF), cerebral blood volume (CBV), and the mean transit time (MTT) in the infarcted area were significantly greater than those in the corresponding healthy side area, and the time to peak (TTP) was significantly less than that in the corresponding healthy side area (P < 0.05). The cerebral perfusion parameters CBF, TTP, and MTT in the penumbra were significantly different from those in the infarct central area and the corresponding contralateral area, and TTP was the most sensitive (P < 0.05). To sum up, deep learning algorithm-based CTP combined with CTA could find the location of cerebral infarction lesions as early as possible to provide a reliable diagnostic result for the diagnosis of ultra-early acute ischemic stroke.

Stroke imaging prior to thrombectomy in the late window: results from a pooled multicentre analysis

BACKGROUND AND PURPOSE

Collateral assessment using CT angiography is a promising modality for selecting patients for endovascular thrombectomy (EVT) in the late window (6-24 hours). The outcome of these patients compared with those selected using perfusion imaging is not clear.

METHODS

We pooled data from seven trials and registries of EVT-treated patients in the late-time window. Patients were classified according to the baseline imaging into collateral imaging alone (collateral cohort) and perfusion plus collateral imaging (perfusion cohort). The primary outcome was the proportion of patients achieving independent 90-day functional outcome (modified Rankin Scale 'mRS' 0-2). We used the propensity score-weighting method to balance important predictors between the cohorts.

RESULTS

In 608 patients, the median onset/last-known-well to emergency arrival time was 8.8 hours and 53.2% had wake-up strokes. Both cohorts had collateral imaging and 379 (62.3%) had perfusion imaging. Independent functional outcome was achieved in 43.1% overall: 168/379 patients (45.5%) in the perfusion cohort versus 94/214 (43.9%) in the collateral cohort (p=0.71). A logistic regression model adjusting for inverse-probability-weighting showed no difference in 90-day mRS score of 0-2 among the perfusion versus collateral cohorts (adjusted OR 1.05, 95% CI 0.69 to 1.59, p=0.83) or in a favourable shift in 90-day mRS (common adjusted OR 1.01, 95% CI 0.69 to 1.47, p=0.97).

CONCLUSION

This pooled analysis of late window EVT showed comparable functional outcomes in patients selected for EVT using collateral imaging alone compared with patients selected using perfusion and collateral imaging.

PROSPERO REGISTRATION NUMBER

CRD42020222003.

Acute stroke imaging selection for mechanical thrombectomy in the extended time window: is it time to go back to basics? A review of current evidence

Treatment with endovascular therapy in the extended time window for acute ischaemic stroke with large vessel occlusion involves stringent selection criteria based on the two landmark studies DAWN and DEFUSE3. Current protocols typically include the requirement of advanced perfusion imaging which may exclude a substantial proportion of patients from receiving a potentially effective therapy. Efforts to offer endovascular reperfusion therapies to all appropriate candidates may be facilitated by the use of simplified imaging selection paradigms with widely available basic imaging techniques, such as non-contrast CT and CT angiography. Currently available evidence from our literature review suggests that patients meeting simplified imaging selection criteria may benefit as much as those patients selected using advanced imaging techniques (CT perfusion or MRI) from endovascular therapy in the extended time window. A comprehensive understanding of the role of imaging in patient selection is critical to optimising access to endovascular therapy in the extended time window and improving outcomes in acute stroke. This article provides an overview on current developments and future directions in this emerging area.

Sex-Related Differences in Outcomes After Endovascular Treatment of Patients With Late-Window Stroke

BACKGROUND AND PURPOSE

Sex-related differences exist in many aspects of acute stroke and were mainly investigated in the early time window with conflicting results. However, data regarding sex disparities in late presenters are scarce. Therefore, we sought to investigate differences in outcomes between women and men treated with endovascular treatment in the late time window.

METHODS

Analyses were based on the SOLSTICE Consortium (Selection of Late-Window Stroke for Thrombectomy by Imaging Collateral Extent), which was an individual-patient level analysis of seven trials and registries. Baseline characteristics, 90-day functional independence (modified Rankin Scale score ≤2), mortality, and symptomatic intracranial hemorrhage were compared between women and men. Effect of sex on the association of age and successful reperfusion (final Thrombolysis in Cerebral Infarction 2b-3) with outcomes was assessed using multivariable logistic regression adjusted for age, National Institutes of Health Stroke Scale score, Alberta Stroke Program Early CT Score, time from onset to puncture, occlusion location, intravenous thrombolysis, and successful reperfusion, with interaction terms.

RESULTS

Among 608 patients treated with endovascular treatment, 50.5% were women. Women were older than men (median age of 72 versus 68 years, P=0.02) and had a lower prevalence of tandem occlusions (14.0% versus 22.9%, P=0.005). Workflow times were similar between sexes. Adjusted outcomes did not differ between women and men. Functional independence at 90 days was achieved by 127 out of 292 women (43.5%) and 135 out of 291 men (46.4%). Mortality at 90 days (54 [18.5%] versus 48 [16.5%]) and symptomatic intracranial hemorrhage (37 [13.3%] versus 33 [11.6%]) were similar between women and men. There was no sex-by-age interaction on functional outcomes. However, men had higher likelihood of mortality (P_interaction=0.003) and symptomatic intracranial hemorrhage (P_interaction=0.017) with advancing age. Sex did not influence the relation between successful reperfusion and outcomes.

CONCLUSIONS

In this multicenter analysis of late patients treated with endovascular treatment, sex was not associated with functional outcome. However, sex influenced the association between age and safety outcomes, with men experiencing worse outcomes with advancing age.

Impact of Multiphase Computed Tomography Angiography for Endovascular Treatment Decision-Making on Outcomes in Patients with Acute Ischemic Stroke

BACKGROUND AND PURPOSE

Various imaging paradigms are used for endovascular treatment (EVT) decision-making and outcome estimation in acute ischemic stroke (AIS). We aim to compare how these imaging paradigms perform for EVT patient selection and outcome estimation.

METHODS

Prospective multi-center cohort study of patients with AIS symptoms with multi-phase computed tomography angiography (mCTA) and computed tomography perfusion (CTP) baseline imaging. mCTA-based EVT-eligibility was defined as presence of large vessel occlusion (LVO) and moderate-to-good collaterals on mCTA. CTP-based eligibility was defined as presence of LVO, ischemic core (defined on relative cerebral blood flow, absolute cerebral blood flow, and cerebral blood volume maps) <70 mL, mismatch-ratio >1.8, absolute mismatch >15 mL. EVT-eligibility and adjusted rates of good outcome (modified Rankin Scale 0-2) based on these imaging paradigms were compared.

RESULTS

Of 289/464 patients with LVO, 263 (91%) were EVT-eligible by mCTA-criteria versus 63 (22%), 19 (7%) and 103 (36%) by rCBF, aCBF, and CBV-CTP-criteria. CTP and mCTA-criteria were discordant in 40% to 53%. Estimated outcomes were best in patients who met both mCTA and CTP eligibility-criteria and were treated with EVT (62% to 87% good outcome). Patients eligible for EVT by mCTA-criteria and not by CTP-criteria receiving EVT achieved good outcome rates of 53% to 57%. Few patients met CTP-criteria and not mCTA-criteria for EVT.

CONCLUSIONS

Simpler imaging selection criteria that rely on little else than detection of the occluded blood vessel may be more sensitive and less specific, thus resulting in more patients being offered EVT and arguably benefiting from it.

[Border areas of thrombectomy]

Die mechanische Thrombektomie (MT) hat sich als Standardverfahren für die Behandlung akuter ischämischer Schlaganfälle aufgrund eines Verschlusses einer großen, proximalen Hirnarterie der vorderen Zirkulation etabliert. Dennoch sind nach aktuellen Guidelines noch große Patientenkollektive von dieser hocheffektiven Behandlungsmethode ausgeschlossen. Diese Arbeit gibt daher einen Überblick über mögliche Erweiterungen der Behandlungsindikationen für die MT, wie z. B. Patienten im erweiterten Zeitfenster, mit distalen Verschlüssen, mit großem Infarktkern oder auch für sehr alte (> 90 Jahre) und junge (0–17 Jahre) Patienten. Zusätzlich besprechen wir neue Entwicklungen in der interventionellen Behandlung von Schlaganfällen, wie z. B. neue Triage-Konzepte oder die Fragestellung, ob die zusätzliche intravenöse Thrombolyse bei MT-Patienten notwendig ist. Abschließend geben wir für die besprochenen Behandlungsindikationen unsere Einschätzungen basierend auf der aktuellen Literatur und unserer klinischen Erfahrung.

Acute reperfusion therapies for acute ischemic stroke patients with unknown time of symptom onset or in extended time windows: an individualized approach

Recent randomized controlled clinical trials (RCTs) have revolutionized acute ischemic stroke care by extending the use of intravenous thrombolysis and endovascular reperfusion therapies in time windows that have been originally considered futile or even unsafe. Both systemic and endovascular reperfusion therapies have been shown to improve outcome in patients with wake-up strokes or symptom onset beyond 4.5 h for intravenous thrombolysis and beyond 6 h for endovascular treatment; however, they require advanced neuroimaging to select stroke patients safely. Experts have proposed simpler imaging algorithms but high-quality data on safety and efficacy are currently missing. RCTs used diverse imaging and clinical inclusion criteria for patient selection during the dawn of this novel stroke treatment paradigm. After taking into consideration the dismal prognosis of nonrecanalized ischemic stroke patients and the substantial clinical benefit of reperfusion therapies in selected late presenters, we propose rescue reperfusion therapies for acute ischemic stroke patients not fulfilling all clinical and imaging inclusion criteria as an option in a subgroup of patients with clinical and radiological profiles suggesting low risk for complications, notably hemorrhagic transformation as well as local or remote parenchymal hemorrhage. Incorporating new data to treatment algorithms may seem perplexing to stroke physicians, since treatment and imaging capabilities of each stroke center may dictate diverse treatment pathways. This narrative review will summarize current data that will assist clinicians in the selection of those late presenters that will most likely benefit from acute reperfusion therapies. Different treatment algorithms are provided according to available neuroimaging and endovascular treatment capabilities.

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

Background

Randomised 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, outcomes after EVT in these late window patients without perfusion imaging are largely unknown. We assessed their characteristics and outcomes in routine clinical practice.

Methods

The Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands Registry, a prospective, multicentre study in the Netherlands, included patients with an anterior circulation occlusion who underwent EVT between 2014 and 2017. CT perfusion was no standard imaging modality. We used adjusted ordinal logistic regression analysis to compare patients treated within versus beyond 6.5 hours after propensity score matching on age, prestroke modified Rankin Scale (mRS), National Institutes of Health Stroke Scale, Alberta Stroke Programme Early CT Score (ASPECTS), collateral status, location of occlusion and treatment with intravenous thrombolysis. Outcomes included 3-month mRS score, functional independence (defined as mRS 0–2), and death.

Results

Of 3264 patients who underwent EVT, 106 (3.2%) were treated beyond 6.5 hours (median 8.5, IQR 6.9–10.6), of whom 93 (87.7%) had unknown time of stroke onset. CT perfusion was not performed in 87/106 (80.2%) late window patients. Late window patients were younger (mean 67 vs 70 years, p<0.04) and had slightly lower ASPECTS (median 8 vs 9, p<0.01), but better collateral status (collateral score 2–3: 68.3% vs 57.7%, p=0.03). No differences were observed in proportions of functional independence (43.3% vs 40.5%, p=0.57) or death (24.0% vs 28.9%, p=0.28). After matching, outcomes remained similar (adjusted common OR for 1 point improvement in mRS 1.04, 95% CI 0.56 to 1.93).

Conclusions

Without the use of CT perfusion selection criteria, EVT in the 6.5–24-hour time window was not associated with poorer outcome in selected patients with favourable clinical and CT/CT angiography characteristics. randomised controlled trials with lenient inclusion criteria are needed to identify more patients who can benefit from EVT in the late window.

Role of neuroimaging before reperfusion therapy. Part 1 - IV thrombolysis - Review

This review paper summarises the yield of the different imaging modalities in the evaluation of patients for IV thrombolysis. Non-contrast CT and CTA or brain MRI combined with MRA are the recommended sequences for the evaluation of patients within the 4.5 hours time window. Multimodal MRI (DWI/PWI), and more recently, CT perfusion, offer reliable surrogate of salvageable penumbra, the target mismatch, which is now currently used as selection criteria for revascularisation treatment in an extended time window. Those sequences may also help the physician for the management of other limited cases when the diagnosis of acute ischemic stroke is difficult. Another approach the DWI/FLAIR mismatch has been proposed to identify among wake-up stroke patients those who have been experiencing an acute ischemic stroke evolving from less than 4.5hrs. Other biomarkers, such as the clot imaging on MRI and CT, help to predict the recanalisation rate after IVT, while the impact of the presence microbleeds on MRI remains to be determined.

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

BACKGROUND

The 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 imaging criteria. The ESCAPE NA1-trial selected patients based on non-contrast CT (NCCT) Alberta Stroke Program Early CT Score (ASPECTS) and multiphase CT angiography (CTA) collateral status. This study compares baseline characteristics, workflow, and outcomes in the EVT arms of DAWN and DEFUSE-3 with late-window patients from the EVT-only arm of ESCAPE-NA1.

METHODS

Aggregate data on baseline characteristics, workflow, reperfusion quality, final infarct volume, and clinical outcomes (modified Rankin Score [mRS] at 90 days) in subjects enrolled in the DAWN and DEFUSE-3 EVT arms were compared with similar data from the ESCAPE-NA1 control arm (EVT-only arm) presenting beyond 6 hours from LKW using descriptive statistics.

RESULTS

Baseline characteristics among late-window patients in the ESCAPE NA1 trial were similar to those in the DAWN and DEFUSE-3 EVT arms. Median time from LKW-to-puncture in subjects enrolled in the ESCAPE NA1 trial was 9 hrs (IQR: 7.5-11 hours) when compared with DAWN (n=107; 12.8 hours, IQR: 10.6-16.7 hours) and DEFUSE-3 (n=92; 11.5 hours, IQR: 9.2-12.8 hours). Median post-treatment infarct-volume was largest in the ESCAPE NA1-patients (47 mL [IQR: 19-146] vs median 8 mL [IQR: 0-48] in the DAWN group and 35 mL [IQR: 18-82] in DEFUSE-3), while % mRS 0-2 at 90 days were similar across the three trials (ESCAPE NA1: 50/111 [45%], DAWN: 52/107 [49%], DEFUSE-3: 41/92 [45%]).

CONCLUSION

Patients enrolled beyond 6 hours from LKW in the ESCAPE-NA1 trial based on NCCT-ASPECTS and mCTA had similar clinical outcomes when compared with patients selected by perfusion imaging in the DAWN and DEFUSE-3 trials.

Automated Perfusion Calculations vs. Visual Scoring of Collaterals and CBV-ASPECTS : Has the Machine Surpassed the Eye?

Purpose

Use of automated perfusion software has gained importance for imaging of stroke patients for mechanical thrombectomy (MT). We aim to compare four perfusion software packages: 1) with respect to their association with 3‑month functional outcome after successful reperfusion with MT in comparison to visual Cerebral Blood Volume - Alberta Stroke Program Early CT Score (CBV-ASPECTS) and collateral scoring and 2) with respect to their agreement in estimation of core and penumbra volume.

Methods

This retrospective, multicenter cohort study (2015–2019) analyzed data from 8 centers. We included patients who were functionally independent before and underwent successful MT of the middle cerebral artery. Primary outcome measurements were the relationship of core and penumbra volume calculated by each software, qualitative assessment of collaterals and CBV-APECTS with 3‑month functional outcome and disability (modified Rankin scale >2). Quantitative differences between perfusion software measurements were also assessed.

Results

A total of 215 patients (57% women, median age 77 years) from 8 centers fulfilled the inclusion criteria. Multivariable analyses showed a significant association of RAPID core (common odds ratio, cOR 1.02; p = 0.015), CBV-ASPECTS (cOR 0.78; p = 0.007) and collaterals (cOR 0.78; p = 0.001) with 3‑month functional outcome (shift analysis), while RAPID core (OR 1.02; p = 0.018), CBV-ASPECTS (OR 0.77; p = 0.024), collaterals (OR 0.78; p = 0.007) and OLEA core (OR 1.02; p = 0.029) were significantly associated with 3‑month functional disability. Mean differences on core estimates between VEOcore and RAPID were 13.4 ml, between syngo.via and RAPID 30.0 ml and between OLEA and RAPID −3.2 ml.

Conclusion

Collateral scoring, CBV-ASPECTS and RAPID were independently associated with functional outcome at 90 days. Core and Penumbra estimates using automated software packages varied significantly and should therefore be used with caution.

Electronic supplementary material

The online version of this article (10.1007/s00062-020-00974-3) contains supplementary material, which is available to authorized users.

Detecting Large Vessel Occlusion at Multiphase CT Angiography by Using a Deep Convolutional Neural Network

Background Large vessel occlusion (LVO) stroke is one of the most time-sensitive diagnoses in medicine and requires emergent endovascular therapy to reduce morbidity and mortality. Leveraging recent advances in deep learning may facilitate rapid detection and reduce time to treatment. Purpose To develop a convolutional neural network to detect LVOs at multiphase CT angiography. Materials and Methods This multicenter retrospective study evaluated 540 adults with CT angiography examinations for suspected acute ischemic stroke from February 2017 to June 2018. Examinations positive for LVO (n = 270) were confirmed by catheter angiography and LVO-negative examinations (n = 270) were confirmed through review of clinical and radiology reports. Preprocessing of the CT angiography examinations included vasculature segmentation and the creation of maximum intensity projection images to emphasize the contrast agent-enhanced vasculature. Seven experiments were performed by using combinations of the three phases (arterial, phase 1; peak venous, phase 2; and late venous, phase 3) of the CT angiography. Model performance was evaluated on the held-out test set. Metrics included area under the receiver operating characteristic curve (AUC), sensitivity, and specificity. Results The test set included 62 patients (mean age, 69.5 years; 48% women). Single-phase CT angiography achieved an AUC of 0.74 (95% confidence interval [CI]: 0.63, 0.85) with sensitivity of 77% (24 of 31; 95% CI: 59%, 89%) and specificity of 71% (22 of 31; 95% CI: 53%, 84%). Phases 1, 2, and 3 together achieved an AUC of 0.89 (95% CI: 0.81, 0.96), sensitivity of 100% (31 of 31; 95% CI: 99%, 100%), and specificity of 77% (24 of 31; 95% CI: 59%, 89%), a statistically significant improvement relative to single-phase CT angiography (P = .01). Likewise, phases 1 and 3 and phases 2 and 3 also demonstrated improved fit relative to single phase (P = .03). Conclusion This deep learning model was able to detect the presence of large vessel occlusion and its diagnostic performance was enhanced by using delayed phases at multiphase CT angiography examinations. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Ospel and Goyal in this issue.

Expansion of the dimensions in the current management of acute ischemic stroke

Stroke is the fifth leading cause of death in the United States with a huge burden on health care. Acute ischemic stroke (AIS) accounts for 87% of all stroke. The use of thrombolytic agents in AIS treatment is well known since 1950 but no FDA approval until 1996, due to lack of strong evidence showing benefits outweigh the risk of intracranial hemorrhage. The NINDS trial led to the approval of intravenous tissue plasminogen activator treatment (IV recombinant tPA) within 3 h of stroke. Due to this limitation of 3-4.5 h. window, evolution began in the development of effective endovascular therapy (EVT). Multiple trials were unsuccessful in establishing the strong evidence for effectiveness of EVT. In 2015, MR CLEAN trial made progress and showed improved outcomes with EVT in AIS patients with large vessel occlusion (LVO), with 6-h window period. In 2018, two major trials-DAWN and DEFUSE 3-along with few other trials had shown improved outcomes with EVT and stretched window period from 6 to 24 h. AHA Stroke Council is constantly working to provide focused guidelines and recommendations in AIS management since 2013. SVIN had started the initiative "Mission Thrombectomy-2020" to increase global EVT utilization rate 202,000 procedures by 2020. Physicians are using safer and easier approach like brachial and radial approach for EVT. TeleNeurology and artificial intelligence also played a significant role in increasing the availability of IV recombinant tPA in AIS treatment in remote hospitals and also in screening, triaging and identifying LVO patients for EVT. In this review article, we aim to describe the history of stroke management along with the new technological advancements in AIS treatment.