Patients with the malignant profile within 3 hours of symptom onset have very poor outcomes after intravenous tissue-type plasminogen activator therapy

Neurological prognosis in surgically treated acute aortic dissection with brain computed tomography perfusion

OBJECTIVES

The aim of this study was to explore the prognostic value of brain computed tomography perfusion (CTP) for postoperative new stroke in acute type A aortic dissection (ATAAD) patients.

METHODS

Patients with ATAAD and suspected cerebral malperfusion who underwent brain CTP and surgical repair were retrospectively analysed. Brain perfusion was quantified mainly with the averaged cerebral blood flow. Significant clinical and imaging findings were identified through univariable and multivariable regression analysis. Furthermore, the added prognostic benefit of perfusion parameters was confirmed with the receiver operating characteristic curves in the entire cohort and subgroup analysis.

RESULTS

The incidence of postoperative new stroke was 30.8% (44/143). The independent adjusted predictors of postoperative new stroke included an impaired averaged cerebral blood flow (ml/100 ml/min) (odds ratio: 0.889; P < 0.001), severe stenosis (odds ratio: 5.218; P = 0.011) or occlusion (odds ratio: 14.697; P = 0.048) of the true lumen in common carotid artery (CCA), hypotension on admission (odds ratio: 9.644; P = 0.016) and a longer surgery time (odds ratio: 1.593; P = 0.021). The area under the receiver operating characteristic curves significantly improved after adding perfusion parameters to clinical and computed tomography angiography characteristics (P = 0.048). This benefit was more pronounced in patients with severe stenosis or occlusion in CCA true lumen (P = 0.004).

CONCLUSIONS

Brain CTP could be a useful prognostic tool for surgically treated ATAAD patients and especially beneficial in patients with severe stenosis or occlusion of the CCA true lumen.

Novel brain computed tomography perfusion for cerebral malperfusion secondary to acute type A aortic dissection

OBJECTIVES

The management of acute type A aortic dissection with malperfusion syndrome remains challenging. To evaluate preoperative condition, symptoms might be subjective and objective evaluation of cerebral artery has not yet been established. For quantitative evaluation, this study focused on brain computed tomography perfusion (CTP), which has been recommended by several guidelines of acute ischaemic stroke.

METHODS

In the last 2 years, 147 patients hospitalized due to acute type A aortic dissection were retrospectively reviewed. Among the 23 (16%) patients with cerebral malperfusion, 14 who underwent brain CTP (6 preoperative and 8 postoperative) were enrolled. CTP parameters, including regional blood flow and time to maximum, were automatically computed using RApid processing of Perfusion and Diffusion software. The median duration from the onset to hospital arrival was 129 (31-659) min.

RESULTS

Among the 6 patients who underwent preoperative CTP, 4 with salvageable ischaemic lesion (penumbra: 8-735 ml) without massive irreversible ischaemic lesion (ischaemic core: 0-31 ml) achieved acceptable neurological outcomes after emergency aortic replacement regardless of preoperative neurological severity. In contrast, 2 patients with an ischaemic core of >50 ml (73, 51 ml) fell into a vegetative state or neurological death due to intracranial haemorrhage. CTP parameters guided postoperative blood pressure augmentation without additional supra-aortic vessel intervention in the 8 patients who underwent postoperative CTP, among whom 6 achieved normal neurological function regardless of common carotid true lumen stenosis severity.

CONCLUSIONS

CTP was able to detect irreversible ischaemic core, guide critical decisions in preoperative patients and aid in determining the blood pressure augmentation for postoperative management focusing on residual brain ischaemia.

Automated CT Perfusion Imaging to Aid in the Selection of Patients With Acute Ischemic Stroke for Mechanical Thrombectomy: A Health Technology Assessment

BACKGROUND

Stroke is a sudden interruption in the blood supply to a part of the brain, causing loss of neurological function. It is the third leading cause of death in Canada and affects mainly older people. In the acute setting, neuroimaging is integral to stroke evaluation and decision-making. The neuroimaging results guide patient selection for mechanical thrombectomy. Using automated image processing techniques facilitates efficient review of this information and communication between centres. We conducted a health technology assessment of automated CT perfusion imaging as a tool for selecting stroke patients with anterior circulation occlusion for mechanical thrombectomy. This assessment included an evaluation of clinical effectiveness, cost-effectiveness, and the budget impact of publicly funding automated CT perfusion imaging.

METHODS

We performed a systematic literature search of the clinical evidence. We assessed the risk of bias of each study using QUADAS-2 or the Cochrane risk-of-bias tool, and the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. We performed a systematic economic literature search and approximated cost-effectiveness based on previous analyses. We also analyzed the budget impact of publicly funding automated CT perfusion imaging to evaluate people with acute ischemic stroke in Ontario.

RESULTS

Automated CT perfusion imaging had a sensitivity of 84% for identifying the infarct core (dead tissue that does not recover despite restoring blood flow with mechanical thrombectomy), compared with diffusion-weighted MRI imaging at 24 hours. One study reported that 7% of patients were misclassified with respect to eligibility for mechanical thrombectomy (either erroneously classified as eligible or erroneously classified non-eligible). Two randomized controlled trials (DEFUSE 3 and DAWN) demonstrated the efficacy of mechanical thrombectomy up to 24 hours after stroke onset, with patient selection guided by automated CT perfusion imaging. These data showed that a significantly higher proportion of patients in the mechanical thrombectomy group achieved functional independence compared with the standard care group (DEFUSE 3: risk ratio: 2.67 [95% confidence interval 1.60-4.48]; DAWN: adjusted rate difference: 33% [95% credible interval 21%-44%]; GRADE: Moderate).A previous health technology assessment in stroke patients presenting at 0 to 6 hours after stroke symptom onset and the results from recent randomized controlled trials for patients presenting at 6 to 24 hours informed the evaluation of cost-effectiveness. Mechanical thrombectomy informed by automated CT perfusion imaging to assess eligibility is likely to be cost-effective for patients presenting at 6 to 24 hours after stroke symptom onset. The annual budget impact of publicly funding automated CT perfusion imaging in Ontario over the next 5 years would be $1.3 million in year 1 and $0.9 million each year thereafter. Some of the costs of automated CT perfusion imaging could be offset by avoiding unnecessary patient transfers between hospitals.

CONCLUSIONS

Automated CT perfusion imaging has an acceptable sensitivity and specificity for detecting brain areas that have been affected by stroke. In patients selected for mechanical thrombectomy using automated CT perfusion imaging, there was significant improvement in functional independence. Mechanical thrombectomy informed by automated CT perfusion imaging is likely to be cost-effective. We estimate that publicly funding automated CT perfusion imaging in Ontario would result in additional costs of $1.3 million in year 1 and $0.9 million per year thereafter.

Predicting Poor Outcome Before Endovascular Treatment in Patients With Acute Ischemic Stroke

Background: Although endovascular treatment (EVT) has greatly improved outcomes in acute ischemic stroke, still one third of patients die or remain severely disabled after stroke. If we could select patients with poor clinical outcome despite EVT, we could prevent futile treatment, avoid treatment complications, and further improve stroke care. We aimed to determine the accuracy of poor functional outcome prediction, defined as 90-day modified Rankin Scale (mRS) score ≥5, despite EVT treatment.

Methods: We included 1,526 patients from the MR CLEAN Registry, a prospective, observational, multicenter registry of ischemic stroke patients treated with EVT. We developed machine learning prediction models using all variables available at baseline before treatment. We optimized the models for both maximizing the area under the curve (AUC), reducing the number of false positives.

Results: From 1,526 patients included, 480 (31%) of patients showed poor outcome. The highest AUC was 0.81 for random forest. The highest area under the precision recall curve was 0.69 for the support vector machine. The highest achieved specificity was 95% with a sensitivity of 34% for neural networks, indicating that all models contained false positives in their predictions. From 921 mRS 0–4 patients, 27–61 (3–6%) were incorrectly classified as poor outcome. From 480 poor outcome patients in the registry, 99–163 (21–34%) were correctly identified by the models.

Conclusions: All prediction models showed a high AUC. The best-performing models correctly identified 34% of the poor outcome patients at a cost of misclassifying 4% of non-poor outcome patients. Further studies are necessary to determine whether these accuracies are reproducible before implementation in clinical practice.

Detection of ischemic changes on baseline multimodal computed tomography: expert reading vs. Brainomix and RAPID software

PURPOSE

The aim of the study was to compare the assessment of ischemic changes by expert reading and available automated software for non-contrast CT (NCCT) and CT perfusion on baseline multimodal imaging and demonstrate the accuracy for the final infarct prediction.

METHODS

Early ischemic changes were measured by ASPECTS on the baseline neuroimaging of consecutive patients with anterior circulation ischemic stroke. The presence of early ischemic changes was assessed a) on NCCT by two experienced raters, b) on NCCT by e-ASPECTS, and c) visually on derived CT perfusion maps (CBF<30%, Tmax>10s). Accuracy was calculated by comparing presence of final ischemic changes on 24-hour follow-up for each ASPECTS region and expressed as sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The subanalysis for patients with successful recanalization was conducted.

RESULTS

Of 263 patients, 81 fulfilled inclusion criteria. Median baseline ASPECTS was 9 for all tested modalities. Accuracy was 0.76 for e-ASPECTS, 0.79 for consensus, 0.82 for CBF<30%, 0.80 for Tmax>10s. e-ASPECTS, consensus, CBF<30%, and Tmax>10s had sensitivity 0.41, 0.46, 0.49, 0.57, respectively; specificity 0.91, 0.93, 0.95, 0.91, respectively; PPV 0.66, 0.75, 0.82, 0.73, respectively; NPV 0.78, 0.80, 0.82, 0.83, respectively. Results did not differ in patients with and without successful recanalization.

CONCLUSION

This study demonstrated high accuracy for the assessment of ischemic changes by different CT modalities with the best accuracy for CBF<30% and Tmax>10s. The use of automated software has a potential to improve the detection of ischemic changes.

Optimizing Patient Selection for Endovascular Treatment in Acute Ischemic Stroke (SELECT): A Prospective, Multicenter Cohort Study of Imaging Selection

OBJECTIVE

The primary imaging modalities used to select patients for endovascular thrombectomy (EVT) are noncontrast computed tomography (CT) and CT perfusion (CTP). However, their relative utility is uncertain. We prospectively assessed CT and CTP concordance/discordance and correlated the imaging profiles on both with EVT treatment decisions and clinical outcomes.

METHODS

A phase 2, multicenter, prospective cohort study of large-vessel occlusions presented up to 24 hours from last known well was conducted. Patients received a unified prespecified imaging evaluation (CT, CT angiography, and CTP with Rapid Processing of Perfusion and Diffusion software mismatch determination). The treatment decision, EVT versus medical management, was nonrandomized and at the treating physicians' discretion. An independent, blinded, neuroimaging core laboratory adjudicated favorable profiles based on predefined criteria (CT:Alberta Stroke Program Early CT Score ≥ 6, CTP:regional cerebral blood flow (<30%) < 70ml with mismatch ratio ≥ 1.2 and mismatch volume ≥ 10ml).

RESULTS

Of 4,722 patients screened from January 2016 to February 2018, 361 patients were included. Two hundred eighty-five (79%) received EVT, of whom 87.0% had favorable CTs, 91% favorable CTPs, 81% both favorable profiles, 16% discordant, and 3% both unfavorable. Favorable profiles on the 2 modalities correlated similarly with 90-day functional independence rates (favorable CT = 56% vs favorable CTP = 57%, adjusted odds ratio [aOR] = 1.91, 95% confidence interval [CI] = 0.40-9.01, p = 0.41). Having a favorable profile on both modalities significantly increased the odds of receiving thrombectomy as compared to discordant profiles (aOR = 3.97, 95% CI = 1.97-8.01, p < 0.001). Fifty-eight percent of the patients with favorable profiles on both modalities achieved functional independence as compared to 38% in discordant profiles and 0% when both were unfavorable (p < 0.001 for trend). In favorable CT/unfavorable CTP profiles, EVT was associated with high symptomatic intracranial hemorrhage (sICH) (24%) and mortality (53%) rates.

INTERPRETATION

Patients with favorable imaging profiles on both modalities had higher odds of receiving EVT and high functional independence rates. Patients with discordant profiles achieved reasonable functional independence rates, but those with an unfavorable CTP had higher adverse outcomes. Ann Neurol 2020;87:419-433.

Exploring the relationship between ischemic core volume and clinical outcomes after thrombectomy or thrombolysis

OBJECTIVE

To assess whether complete reperfusion after IV thrombolysis (IVT-R) would result in similar clinical outcomes compared to complete reperfusion after endovascular thrombectomy (EVT-R) in patients with a large vessel occlusion (LVO).

METHODS

EVT-R patients were matched by age, clinical severity, occlusion location, and baseline perfusion lesion volume to IVT-R patients from the International Stroke Perfusion Imaging Registry (INSPIRE). Only patients with complete reperfusion on follow-up imaging were included. The excellent clinical outcome rates at day 90 on the modified Rankin Scale (mRS) were compared between EVT-R vs IVT-R patients within quintiles of increasing baseline ischemic core and penumbral volumes.

RESULTS

From INSPIRE, there were 141 EVT-R patients and 141 matched controls (IVT-R) who met the eligibility criteria. In patients with a baseline core <30 mL, EVT-R resulted in a lower odds of achieving an excellent outcome at day 90 compared to IVT-R (day 90 mRS 0-1 odds ratio 0.01, p < 0.001). The group with a baseline core <30 mL contained mostly patients with distal M1 or M2 occlusions, and good collaterals (p = 0.01). In patients with a baseline ischemic core volume >30 mL (internal carotid artery and mostly proximal M1 occlusions), EVT-R increased the odds of patients achieving an excellent clinical outcome (day 90 mRS 0-1 odds ratio 1.61, p < 0.001) and there was increased symptomatic intracranial hemorrhage in the IVT-R group with core >30 mL (20% vs 3% in EVT-R, p = 0.008).

CONCLUSION

From this observational cohort, LVO patients with larger baseline ischemic cores and proximal LVO, with poorer collaterals, clearly benefited from EVT-R compared to IVT-R alone. However, for distal LVO patients, with smaller ischemic cores and better collaterals, EVT-R was associated with a lower odds of favorable outcome compared to IVT-R alone.

Validation and iteration of CT perfusion defined malignant profile thresholds for acute ischemic stroke

BACKGROUND

Malignant profile computed tomography perfusion (CTP) lesions are associated with poor outcomes after administration of intravenous tissue-plasminogen activator (IV-tPA) for ischemic stroke.

AIMS

To determine whether published CTP-based lesion thresholds predictive of poor outcomes in a predominantly 8 cm of CTP anatomic coverage cohort would predict poor outcomes in an independent 4 cm of CTP anatomic coverage cohort and to generate optimized 4 cm CTP thresholds.

METHODS

Ischemic stroke patients with baseline CTP imaging with 4 cm of anatomic coverage before receiving IV-tPA at a single institution were retrospectively studied. Perfusion lesion time to maximum of tissue residue function (Tmax) and cerebral blood flow (CBF) volumes were determined using RAPID automated software. Fisher's exact tests assessed associations between lesion thresholds and outcomes. Receiver operating characteristic (ROC) curves generated optimized thresholds for 4 cm of CTP coverage.

RESULTS

Sixty-three patients were included. Poor outcomes were associated with published thresholds of Tmax >6 s > 103 mL, Tmax > 8 s > 86 mL, and Tmax > 10 s > 78 mL but not CBF core >53 mL. Thresholds optimized for 4 cm of CTP coverage and associated with poor outcomes were Tmax > 6 s > 100 mL, Tmax > 8 s > 65 mL, Tmax >10 s > 46 mL, and CBF core >39 mL.

CONCLUSIONS

We validated the ability of published CTP Tmax lesion volume thresholds to predict poor outcomes despite IV-tPA in an independent cohort using only 4 cm of CTP anatomical coverage. A CBF > 39 mL threshold, rather than the predominantly 8 cm CTP coverage derived CBF threshold of >53 mL, was associated with poor outcomes in this 4 cm CTP coverage cohort.

Significance of hyperintense arteries on Gd-enhanced 3D T1W black-blood imaging in acute stroke

OBJECTIVES

To elucidate the pathogenesis of hyperintense arteries on Gd-enhanced 3D T1W BB FSE and their clinical significance in acute middle cerebral artery (MCA) stroke.

METHODS

We retrospectively reviewed 20 patients with MCA infarction. We measured the contrast-to-noise ratio between hyperintense artery and adjacent grey matter on T2-FLAIR and Gd-enhanced 3D T1W BB FSE and compared them by using Student's t test. The agreement of positive hyperintense artery between T2 FLAIR and Gd-enhanced 3D T1WI BB FSE was estimated with intraclass correlation coefficient. Our cohort was dichotomised into two groups depending on hyperintense artery scores, and clinical data were compared between two groups by using Student's t test and chi-square test.

RESULTS

The contrast between hyperintense artery and grey matter on Gd-enhanced 3D T1W BB FSE was significantly higher than that on T2-FLAIR (2.27 ± 1.65 versus 0.94 ± 0.86, p = 0.01). Overall, agreement of hyperintense arteries on T2-FLAIR and Gd-enhanced 3D T1W BB FSE was excellent (ρ = 0.76, p < 0.01). Patients with higher hyperintense artery scores had higher perfusion deficits that those with lower hyperintense artery scores (196.7 ± 41.4 vs 100.1 ± 130.1, p = 0.03).

CONCLUSION

Hyperintense arteries on Gd-enhanced 3D T1W BB FSE in acute MCA stroke may be associated with slow collateral flows. Their territories corresponded to those of FLAIR, but had a better contrast. The patients with hyperintense arteries in a wider territory showed larger perfusion deficit than those with hyperintense arteries in a narrower territory.

KEY POINTS

• Hyperintense arteries on Gd-enhanced 3D T1W BB FSE are slow collateral flows. • Hyperintense arteries on Gd-enhanced 3D T1W BB FSE are well matched with FLAIR hyperintense vessels. • Hyperintense arteries are associated with perfusion deficit in stroke patients.

Computed Tomography Perfusion Alberta Stroke Program Early Computed Tomography Score Is Associated with Hemorrhagic Transformation after Acute Cardioembolic Stroke

Alberta Stroke Program Early Computed Tomography (CT) score (ASPECTS) has been applied to CT perfusion (CTP) with good interrater agreement to predict early ischemic stroke, and it can be useful in decision making in acute ischemic stroke. The aim of the present study was to assess the predictive value of CTP ASPECTS of hemorrhagic transformation (HT) in acute cardioembolic stroke. This is a single-enter, retrospective study. All patients hospitalized with acute cardioembolic stroke from January 2008 to September 2013 were included. ASPECTS of baseline non-contrast CT, CTP maps of cerebral blood volume (CBV), cerebral blood flow, and mean transit time were collected from 52 consecutive patients with less than 12-h anterior circulation ischemic stroke. MRI scan was performed within 72 h of symptom onset after index stroke including T2*-weighted gradient echo to identify HT. For bleeding risk assessment, CTP and diffusion-weighted imaging ASPECTS were categorized into 0–7 or 8–10. Baseline characteristics, ASPCETS scores and HT were compared. Eighteen (34.6%) patients had HT and four (7.7%) developed symptomatic HT. On univariate analysis, the proportion of patients with CBV-ASPECTS 0–7 was significantly higher in HT patients as compared to patients without HT (44 versus 9%, P = 0.005). CBV ASPECTS 0–7 remained independent prognostic factors for HT after adjustment for clinical baseline variables. CBV ASPECTS could be of value to predict HT risk after acute cardioembolic stroke and may be a quick risk assessment approach before reperfusion therapy.

Comparison of multimodal intra-arterial treatment versus intravenous thrombolysis for hypertensive patients with severe large vessel cerebral infarction

Since intravenous thrombolysis (IVT) is often associated with poor outcomes in hypertensive patients with severe acute cerebral infarction (ACI) due to occlusions of the internal carotid, basilar, or proximal middle cerebral artery, we evaluated whether multimodal intra-arterial treatment (IAT) might improve functional outcomes in this patient population. We retrospectively reviewed the charts of eligible patients who underwent multimodal IAT including intra-arterial thrombolysis, mechanical thrombectomy, balloon and/or stent angioplasty (IAT group) or IVT alone (IVT group). Outcomes included the revascularization rate 24 hours postprocedure, the frequency of survival at 7, 90, and 180 days postonset, and a measure of functional outcomes using the modified Rankin Scale (mRS). The IAT group included 62 patients and the IVT group included 31 patients. Multimodal IAT increased the revascularization rate at 24 hours (p<0.001) and the frequency of survival and functional independence (mRS ≤2) at 7 days (p<0.001 and p=0.018, respectively), 90 days (both p<0.001), and 180 days (both p<0.001). Independent predictors of longer survival were treatment with multimodal IAT (HR 0.1; 95% CI 0.0 to 0.4; p<0.001) and revascularization (HR 0.1; 95% CI 0.0 to 0.4; p<0.001), whereas a longer duration from onset to treatment was a risk factor for death (HR 1.4; 95% CI 1.2 to 1.8; p<0.001). There was no significant between-group difference for symptomatic hemorrhagic transformation. This study found that for patients with severe hypertensive ACI with large vessel occlusions, multimodal IAT improved the outcomes, including early revascularization, survival, and functional outcome.

Diffusion and Perfusion MR Imaging in Acute Stroke: Clinical Utility and Potential Limitations for Treatment Selection

Magnetic resonance (MR) diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) offer unique insight into acute ischemic stroke pathophysiology. These techniques may offer the ability to apply pathophysiology to accurately individualize acute stroke reperfusion treatment, including extending the opportunity of reperfusion treatment to well beyond the current time-based treatment windows.This review examines the use of DWI and PWI in the major stroke trials, their current clinical utility, and potential limitations for reperfusion treatment selection. DWI and PWI continue to be investigated in ongoing randomized controlled trials, and continued research into these techniques will help achieve the goal of tissue-based decision making and individualized acute stroke treatment.

Optimal Computed Tomographic Perfusion Scan Duration for Assessment of Acute Stroke Lesion Volumes

BACKGROUND AND PURPOSE

The minimal scan duration needed to obtain reliable lesion volumes with computed tomographic perfusion (CTP) has not been well established in the literature.

METHODS

We retrospectively assessed the impact of gradual truncation of the scan duration on acute ischemic lesion volume measurements. For each scan, we identified its optimal scan time, defined as the shortest scan duration that yields measurements of the ischemic lesion volumes similar to those obtained with longer scanning, and the relative height of the fitted venous output function at its optimal scan time.

RESULTS

We analyzed 70 computed tomographic perfusion scans of acute stroke patients. An optimal scan time could not be determined in 11 scans (16%). For the other 59 scans, the median optimal scan time was 32.7 seconds (90th percentile 52.6 seconds; 100th percentile 68.9 seconds), and the median relative height of the fitted venous output function at the optimal scan times was 0.39 (90th percentile 0.02; 100th percentile 0.00). On the basis of a linear model, the optimal scan time was T₀ plus 1.6 times the width of the venous output function (P<0.001; R²=0.49).

CONCLUSIONS

This study shows how the optimal duration of a computed tomographic perfusion scan relates to the arrival time and width of the contrast bolus. This knowledge can be used to optimize computed tomographic perfusion scan protocols and to determine whether a scan is of sufficient duration. Provided a baseline (T₀) of 10 seconds, a total scan duration of 60 to 70 seconds, which includes the entire downslope of the venous output function in most patients, is recommended.

Imaging in Endovascular Stroke Trials

Ischemic stroke remains a leading cause of death and disability worldwide. Various endovascular trials have addressed clinical outcomes without elucidating the impact of imaging studies in patient selection. The success of recent endovascular trials was bolstered by the use of advanced imaging techniques for optimal selection of reperfusion candidates. This seminal juncture in the history of stroke trials warrants further consideration on the use of imaging to guide future refinements in the treatment of acute stroke. In this article, we systematically review the imaging methodology and key facets used in all published endovascular stroke trials to date, discuss the success of recent trials using latest advanced imaging techniques and focus on the importance of imaging studies for future patient selection.

A benchmarking tool to evaluate computer tomography perfusion infarct core predictions against a DWI standard

Differences in research methodology have hampered the optimization of Computer Tomography Perfusion (CTP) for identification of the ischemic core. We aim to optimize CTP core identification using a novel benchmarking tool. The benchmarking tool consists of an imaging library and a statistical analysis algorithm to evaluate the performance of CTP. The tool was used to optimize and evaluate an in-house developed CTP-software algorithm. Imaging data of 103 acute stroke patients were included in the benchmarking tool. Median time from stroke onset to CT was 185 min (IQR 180-238), and the median time between completion of CT and start of MRI was 36 min (IQR 25-79). Volumetric accuracy of the CTP-ROIs was optimal at an rCBF threshold of <38%; at this threshold, the mean difference was 0.3 ml (SD 19.8 ml), the mean absolute difference was 14.3 (SD 13.7) ml, and CTP was 67% sensitive and 87% specific for identification of DWI positive tissue voxels. The benchmarking tool can play an important role in optimizing CTP software as it provides investigators with a novel method to directly compare the performance of alternative CTP software packages.

Impact of Initial Diffusion-Weighted Imaging Lesion Growth Rate on the Success of Endovascular Reperfusion Therapy

Background and Purpose—

Initial diffusion-weighted imaging lesion growth rate (IGR) assessed by diffusion-weighted imaging lesion volume divided by the delay from onset to magnetic resonance imaging offers an estimate of early brain infarction progression. We investigated the impact of IGR on the rate of favorable outcome according to the occurrence of a successful endovascular revascularization within 6 hours after onset in patients experiencing an acute brain infarction complicating internal carotid artery terminus/middle cerebral artery M1 occlusion.

Methods—

The primary study end point was a favorable outcome defined by a modified Rankin Scale score of ≤2, 90 days after onset. A Thrombolysis in Cerebral Infarction score 2b/3 defined a successful recanalization.

Results—

A total of 166 patients were included. Median IGR was 7 mL/h (interquartile range, 2–26). Sixty-eight patients (41%) experienced a favorable outcome. After adjustment on age, systolic blood pressure, vessel site occlusion, National Institutes of Health Stroke Scale, and antithrombotic medication, increase in IGR was associated with a decreased occurrence of favorable outcome with an odds ratio per SD increase of 0.60 (95% confidence interval, 0.38–0.94; P =0.03). A successful recanalization was achieved among 56% of the patients after a median delay of 251 minutes (interquartile range, 211–291 minutes). Increasing IGR was associated with a decreased favorable outcome only when a successful recanalization was not achieved (adjusted odds ratio, 0.32; 95% confidence interval, 0.12–0.85; P =0.02).

Conclusions—

Proximal internal carotid artery/M1 occlusion did result into a wide range of IGR within 6 hours after onset. Increasing IGR was associated with a lower rate of favorable outcome after endovascular treatment overall and when a successful recanalization was not achieved.

Ischemic core and hypoperfusion volumes predict infarct size in SWIFT PRIME

OBJECTIVE

Within the context of a prospective randomized trial (SWIFT PRIME), we assessed whether early imaging of stroke patients, primarily with computed tomography (CT) perfusion, can estimate the size of the irreversibly injured ischemic core and the volume of critically hypoperfused tissue. We also evaluated the accuracy of ischemic core and hypoperfusion volumes for predicting infarct volume in patients with the target mismatch profile.

METHODS

Baseline ischemic core and hypoperfusion volumes were assessed prior to randomized treatment with intravenous (IV) tissue plasminogen activator (tPA) alone versus IV tPA + endovascular therapy (Solitaire stent-retriever) using RAPID automated postprocessing software. Reperfusion was assessed with angiographic Thrombolysis in Cerebral Infarction scores at the end of the procedure (endovascular group) and Tmax > 6-second volumes at 27 hours (both groups). Infarct volume was assessed at 27 hours on noncontrast CT or magnetic resonance imaging (MRI).

RESULTS

A total of 151 patients with baseline imaging with CT perfusion (79%) or multimodal MRI (21%) were included. The median baseline ischemic core volume was 6 ml (interquartile range= 0-16). Ischemic core volumes correlated with 27-hour infarct volumes in patients who achieved reperfusion (r = 0.58, p < 0.0001). In patients who did not reperfuse (<10% reperfusion), baseline Tmax > 6-second lesion volumes correlated with 27-hour infarct volume (r = 0.78, p = 0.005). In target mismatch patients, the union of baseline core and early follow-up Tmax > 6-second volume (ie, predicted infarct volume) correlated with the 27-hour infarct volume (r = 0.73, p < 0.0001); the median absolute difference between the observed and predicted volume was 13 ml.

INTERPRETATION

Ischemic core and hypoperfusion volumes, obtained primarily from CT perfusion scans, predict 27-hour infarct volume in acute stroke patients who were treated with reperfusion therapies.

Endovascular stent thrombectomy: the new standard of care for large vessel ischaemic stroke

BACKGROUND

Results of initial randomised trials of endovascular treatment for ischaemic stroke, published in 2013, were neutral but limited by the selection criteria used, early-generation devices with modest efficacy, non-consecutive enrollment, and treatment delays.

RECENT DEVELOPMENTS

In the past year, six positive trials of endovascular thrombectomy for ischaemic stroke have provided level 1 evidence for improved patient outcome compared with standard care. In most patients, thrombectomy was performed in addition to thrombolysis with intravenous alteplase, but benefits were also reported in patients ineligible for alteplase treatment. Despite differences in the details of eligibility requirements, all these trials required proof of major vessel occlusion on non-invasive imaging and most used some imaging technique to exclude patients with a large area of irreversibly injured brain tissue. The results indicate that modern thrombectomy devices achieve faster and more complete reperfusion than do older devices, leading to improved clinical outcomes compared with intravenous alteplase alone. The number needed to treat to achieve one additional patient with independent functional outcome was in the range of 3·2-7·1 and, in most patients, was in addition to the substantial efficacy of intravenous alteplase. No major safety concerns were noted, with low rates of procedural complications and no increase in symptomatic intracerebral haemorrhage. WHERE NEXT?: Thrombectomy benefits patients across a range of ages and levels of clinical severity. A planned meta-analysis of individual patient data might clarify effects in under-represented subgroups, such as those with mild initial stroke severity or elderly patients. Imaging-based selection, used in some of the recent trials to exclude patients with large areas of irreversible brain injury, probably contributed to the proportion of patients with favourable outcomes. The challenge is how best to implement imaging in clinical practice to maximise benefit for the entire population and to avoid exclusion of patients with smaller yet clinically important potential to benefit. Although favourable imaging identifies patients who might benefit despite long delays from symptom onset to treatment, the proportion of patients with favourable imaging decreases with time. Health systems therefore need to be reorganised to deliver treatment as quickly as possible to maximise benefits. On the basis of available trial data, intravenous alteplase remains the initial treatment for all eligible patients within 4·5 h of stroke symptom onset. Those patients with major vessel occlusion should, in parallel, proceed to endovascular thrombectomy immediately rather than waiting for an assessment of response to alteplase, because minimising time to reperfusion is the ultimate aim of treatment.

Endovascular therapy for ischemic stroke with perfusion-imaging selection

BACKGROUND

Trials of endovascular therapy for ischemic stroke have produced variable results. We conducted this study to test whether more advanced imaging selection, recently developed devices, and earlier intervention improve outcomes.

METHODS

We randomly assigned patients with ischemic stroke who were receiving 0.9 mg of alteplase per kilogram of body weight less than 4.5 hours after the onset of ischemic stroke either to undergo endovascular thrombectomy with the Solitaire FR (Flow Restoration) stent retriever or to continue receiving alteplase alone. All the patients had occlusion of the internal carotid or middle cerebral artery and evidence of salvageable brain tissue and ischemic core of less than 70 ml on computed tomographic (CT) perfusion imaging. The coprimary outcomes were reperfusion at 24 hours and early neurologic improvement (≥8-point reduction on the National Institutes of Health Stroke Scale or a score of 0 or 1 at day 3). Secondary outcomes included the functional score on the modified Rankin scale at 90 days.

RESULTS

The trial was stopped early because of efficacy after 70 patients had undergone randomization (35 patients in each group). The percentage of ischemic territory that had undergone reperfusion at 24 hours was greater in the endovascular-therapy group than in the alteplase-only group (median, 100% vs. 37%; P<0.001). Endovascular therapy, initiated at a median of 210 minutes after the onset of stroke, increased early neurologic improvement at 3 days (80% vs. 37%, P=0.002) and improved the functional outcome at 90 days, with more patients achieving functional independence (score of 0 to 2 on the modified Rankin scale, 71% vs. 40%; P=0.01). There were no significant differences in rates of death or symptomatic intracerebral hemorrhage.

CONCLUSIONS

In patients with ischemic stroke with a proximal cerebral arterial occlusion and salvageable tissue on CT perfusion imaging, early thrombectomy with the Solitaire FR stent retriever, as compared with alteplase alone, improved reperfusion, early neurologic recovery, and functional outcome. (Funded by the Australian National Health and Medical Research Council and others; EXTEND-IA ClinicalTrials.gov number, NCT01492725, and Australian New Zealand Clinical Trials Registry number, ACTRN12611000969965.).

Collaterals: an important determinant of prolonged ischemic penumbra versus rapid cerebral infarction?

Intravenous tissue plasminogen activator is the mainstay for the treatment of acute ischemic stroke in patients presenting within 4.5 h of symptom onset. Studies have demonstrated that treating patients early leads to improved long-term outcomes. MR imaging currently allows quantification of the ischemic penumbra in order to better identify individuals most likely to benefit from intervention, irrespective of “time last seen normal.” Its increasing use in clinical practice has demonstrated individual differences in rate of infarction. One explanation for this variability is a difference in collateral blood flow. We report two cases that highlight the individual variability of infarction rate, and discuss potential underlying mechanisms that may influence treatment decisions and outcomes.

Imaging predictors of outcome following intravenous thrombolysis in acute stroke

Intravenous tissue plasminogen activator is the only approved medical treatment for patients with acute ischemic stroke. While it is associated with excellent clinical outcome in about 30 %, even with timely thrombolysis administration, certain strokes continue to evolve and lead to poor outcomes. Several studies have attempted to identify predictors of outcome despite timely thrombolysis. Persistence of a proximal clot burden and large vessel occlusion following thrombolysis are markers for patients who may potentially benefit from advanced treatment modalities like intra-arterial thrombolysis and thrombectomy. Timely brain imaging and interpretation play a crucial role in providing these treatment decisions. In this review, various imaging predictors of poor outcome among patients with acute ischemic stroke treated with intravenous thrombolysis are outlined. Despite identification of these imaging predictors, thrombolysis should not be withheld, as it may still be beneficial in a subset of patients. Knowledge of these predictors may set benchmarks for selecting candidates who may potentially benefit from advanced management strategies in future trials.

The role of advanced neuroimaging in intracerebral hemorrhage

In this report, the authors sought to summarize existing literature to provide an overview of the currently available techniques and to critically assess the evidence for or against their application in intracerebral hemorrhage (ICH) for management, prognostication, and research. Functional imaging in ICH represents a potential major step forward in the ability of physicians to assess patients suffering from this devastating illness due to the advantages over standing imaging modalities focused on general tissue structure alone, but its use is highly controversial due to the relative paucity of literature and the lack of consolidation of the predominantly small data sets that are currently in existence. Current data support that diffusion tensor imaging and tractography, diffusion-perfusion weighted MRI techniques, and functional MRI all possess major potential in the areas of highlighting motor deficits, motor recovery, and network reorganization. Novel clinical studies designed to objectively assess the value of each of these modalities on a wider scale in conjunction with other methods of investigation and management will allow for their rapid incorporation into standard practice.

Stroke treatment academic industry roundtable: research priorities in the assessment of neurothrombectomy devices

BACKGROUND AND PURPOSE

The goal of the Stroke Treatment Academic Industry Roundtable (STAIR) meetings is to advance the development of stroke therapies. At STAIR VIII, consensus recommendations were developed for clinical trial strategies to demonstrate the benefit of endovascular reperfusion therapies for acute ischemic stroke.

SUMMARY OF REVIEW

Prospects for success with forthcoming endovascular trials are robust, because new neurothrombectomy devices have superior reperfusion efficacy compared with earlier-generation interventions. Specific recommendations are provided for trial designs in 3 populations: (1) patients undergoing intravenous fibrinolysis, (2) early patients ineligible for or having failed intravenous fibrinolysis, and (3) wake-up and other late-presenting patients. Among intravenous fibrinolysis-eligible patients, key principles are that CT or MRI confirmation of target arterial occlusions should precede randomization; endovascular intervention should be pursued with the greatest rapidity possible; and combined intravenous and neurothrombectomy therapy is more promising than neurothrombectomy alone. Among patients ineligible for or having failed intravenous fibrinolysis, scientific equipoise was affirmed and the need to randomize all eligible patients emphasized. Vessel imaging to confirm occlusion is mandatory, and infarct core and penumbral imaging is desirable in later time windows. Additional STAIR VIII recommendations include approaches to test multiple devices in a single trial, utility weighting of disability end points, and adaptive designs to delineate time and tissue injury thresholds at which benefits from intervention no longer accrue.

CONCLUSIONS

Endovascular research priorities in acute ischemic stroke are to perform trials testing new, highly effective neuro thrombectomy devices rapidly deployed in patients confirmed to have target vessel occlusions.

Perfusion patterns of ischemic stroke on computed tomography perfusion

CT perfusion (CTP) has been applied increasingly in research of ischemic stroke. However, in clinical practice, it is still a relatively new technology. For neurologists and radiologists, the challenge is to interpret CTP results properly in the context of the clinical presentation. In this article, we will illustrate common CTP patterns in acute ischemic stroke using a case-based approach. The aim is to get clinicians more familiar with the information provided by CTP with a view towards inspiring them to incorporate CTP in their routine imaging workup of acute stroke patients.

Advanced imaging to extend the therapeutic time window of acute ischemic stroke

Reperfusion therapy for acute stroke has evolved from the initial use of intravenous tissue plasminogen activator (tPA) within 3 hours of symptom onset to more recent guideline-recommended use up to 4.5 hours. In addition, endovascular therapy is increasingly utilized for stroke treatment and is typically initiated up to 8 hours after onset. Recent studies demonstrate that imaging of the ischemic penumbra with diffusion/perfusion magnetic resonance imaging (MRI) can identify subgroups of patients who are likely to improve following successful reperfusion (Target Mismatch profile) and others who are at increased risk for hemorrhage and poor clinical outcomes (Malignant profile). New data indicate that stent retriever devices provide better recanalization efficacy and clinical outcomes than the previously available mechanical thrombectomy devices. Going forward, we believe that the use of penumbral imaging with validated MRI techniques, as well as the currently less well-validated computed tomography (CT) perfusion approach, will maximize benefit and reduce the risk of adverse events and poor outcomes when used both early after stroke onset and at later time points. New trials that feature diffusion/perfusion MRI or CT perfusion-based patient selection for treatment with intravenous tPA and or endovascular therapies versus nonreperfused control groups are planned or in progress. We predict that these trials will confirm the hypothesis that penumbral imaging can enhance patient selection and extend the therapeutic time window for acute ischemic stroke.