Hypoperfusion Volume Research Articles

Systematic CT perfusion acquisition in acute stroke increases vascular occlusion detection and thrombectomy rates

BackgroundIn patients with stroke, current guidelines recommend non-invasive vascular imaging to identify intracranial vessel occlusions (VO) that may benefit from endovascular treatment (EVT). However, VO can be missed in CT...

Relevance of Brain Regions' Eloquence Assessment in Patients With a Large Ischemic Core Treated With Mechanical Thrombectomy.

Individualized patient selection for mechanical thrombectomy (MT) in patients with acute ischemic stroke (AIS) and large ischemic core (LIC) at baseline is an unmet need. We tested the hypothesis that assessing the functional relevance of both infarcted and hypoperfused brain tissue would improve the selection framework of patients with LIC for MT. We performed a multicenter, retrospective study of adults with LIC (ischemic core volume >70 mL on MRI diffusion-weighted imaging) with MRI perfusion treated with MT or best medical management (BMM). Primary outcome was 3-month modified Rankin Scale (mRS), favorable if 0-3. Global and regional eloquence-based core perfusion mismatch ratios were derived. The predictive accuracy for clinical outcome of eloquent regions involvement was compared in multivariable and bootstrap random forest models. A total of 138 patients with baseline LIC were included (MT n = 96 or BMM n = 42; mean age ± SD, 72.4 ± 14.4 years; 34.1% female; mRS 0-3: 45.1%). Mean core and critically hypoperfused volume were 100.4 mL ± 36.3 mL and 157.6 ± 56.2 mL, respectively, and did not differ between groups. Models considering the functional relevance of the infarct location showed a better accuracy for the prediction of mRS 0-3 with a c statistic of 0.76 and 0.83 for logistic regression model and bootstrap random forest testing sets, respectively. In these models, the interaction between treatment effect of MT and the mismatch was significant (p = 0.04). In comparison, in the logistic regression model disregarding functional eloquence, the c statistic was 0.67 and the interaction between MT and the mismatch was insignificant. Considering functional eloquence of hypoperfused tissue in patients with a large infarct core at baseline allows for a more precise estimation of treatment expected benefit. This study provides Class II evidence that, in patients with AIS and LIC, considering the functional eloquence of the infarct location improves prediction of disability status at 3 months.

Perfusion profile evaluated by severity-weighted multiple Tmax strata predicts early neurological deterioration in minor stroke with large vessel occlusion

Minor stroke due to large vessel occlusion (LVO) is associated with poor outcomes. Hypoperfused tissue fate may be more accurately predicted by severity-weighted multiple perfusion strata than by a single perfusion threshold. We investigated whether poor perfusion profile evaluated by multiple Tmax strata is associated with early neurological deterioration (END) in patients with minor stroke with LVO. Ninety-four patients with a baseline National Institute of Health Stroke Scale score ≤5 and anterior circulation LVO admitted within 24 hours of onset were included. Tmax strata proportions (Tmax 2–4 s, 4–6 s, 6–8 s, 8–10 s, and >10 s) against the entire hypoperfusion volume (Tmax >2 s) were measured. The perfusion profile was defined as the shift of the distribution of the Tmax strata proportions towards worse hypoperfusion severity compared with that of the entire cohort using the Wilcoxon-Mann-Whitney generalised odds ratio (OR); its performance to predict END was tested. The area under the curve of perfusion profile was 0.785 (95% confidence interval [CI]: 0.691–0.878, p < 0.001). Poor perfusion profile (generalised OR >1.052) was independently associated with END (adjusted OR 13.42 [95% CI: 4.38–41.15], p < 0.001). Thus, perfusion profile with severity-weighted multiple Tmax strata may predict END in minor stroke and LVO.

Contrast Bolus Interference in a Multimodal CT Stroke Protocol.

Whether CTP is performed before or after CTA varies within multimodal CT stroke protocols. CTA after CTP might show venous filling, and CTP metrics might be disturbed by prior CTA. Therefore, we compared CTP metrics conducted before and after CTA in a large cohort of patients with stroke and analyzed interferences of the CTA bolus with the CTP measurement. We analyzed 1980 patients (368 patients with CTP performed before CTA [group A] versus 1612 patients with CTP performed after [group B]) in a retrospective study. Mean curves, histograms of CTP baseline Hounsfield units, CBF, CBV, time-to-maximum, hypoperfusion, and core volumes were calculated using the software VEOcore. CTA and CTP interferences were analyzed, and a detection and correction method was proposed. Mean CTP baseline values were significantly different in both groups (41 versus 45 HU within the groups A and B, respectively). However, perfusion metrics, hypoperfusion, and core volumes yielded no significant differences. In 49 patients, the descending flank of the CTA bolus interfered with the baseline of the CTP measurement, leading to erroneously low CBV values. These errors vanished when a correction method was applied. CTP can be reliably performed after CTA without a relevant net effect on perfusion metrics. However, when measuring CTP after CTA, either a short pause on the order of 30 seconds should be observed or an appropriate correction method should be applied. It may help to avoid excluding patients from mechanical thrombectomy by overestimating infarct cores.

MRI software for diffusion-perfusion mismatch analysis may impact on patients\u2019 selection and clinical outcome

ObjectiveImpact of different MR perfusion software on selection and outcome of patients with acute ischemic stroke (AIS) and large vessel occlusion (LVO) treated by endovascular thrombectomy (EVT) is unclear. We aimed at comparing two commercial MRI software, semi-automated with unadjusted (method A) and adjusted mask (method B), and fully automated (method C) in this setting.MethodsMRI from 144 consecutive AIS patients with anterior circulation LVO was retrospectively analysed. All diffusion- and perfusion-weighted images (DWI-PWI) were post-processed with the three methods using standard thresholds. Concordance for core and hypoperfusion volumes was assessed with Lin’s test. Clinical outcome was compared between groups in patients who underwent successful EVT in the early and late time window.ResultsMean core volume was higher and mean hypoperfusion volume was lower in method C than in methods A and B. In the early time window, methods A and B found fewer patients with a mismatch ratio ≤ 1.2 than method C (1/67 [1.5%] vs. 12/67 [17.9%], p = 0.0013). In the late time window, methods A and B found fewer patients with a mismatch ratio < 1.8 than method C (3/46 [6.5%] and 2/46 [4.3%] vs. 18/46 [39.1%], p ≤ 0.0002). More patients with functional independence at 3 months would not have been treated using method C versus methods A and B in the early (p = 0.0063) and late (p ≤ 0.011) time window.ConclusionsMRI software for DWI-PWI analysis may influence patients’ selection before EVT and clinical outcome.Key Points• Method C detects fewer patients with favourable mismatch profile.• Method C might underselect more patients with functional independence at 3 months.• Software used before thrombectomy may influence patients’ outcome.

Early Neurological Deterioration and Hypoperfusion Volume Ratio on Arterial Spin Labeling in Patients with Acute Ischemic Stroke

BackgroundArterial spin labeling (ASL) is a magnetic resonance imaging (MRI) technique used to quantify cerebral blood perfusion by labeling blood water as it flows throughout the brain. Hypoperfusion volume ratio (HVR) can be calculated using proportional hypoperfusion volume on ASL-based cerebral blood flow (CBF). This study aimed to explore the relation between HVR and early neurological deterioration (END) in AIS patients. Subjects and MethodsPatients with AIS were recruited consecutively, and ASL and regular MRI scans were performed. HVR was calculated from 1.5 and 2.5s post labeling delay (PLD) ASL-CBF maps. END was defined as ≥2 points increment of NIHSS within 72 hours of stroke onset. Univariate and multivariate analysis were used to evaluate the relation between HVR and END. Receiver operating characteristic (ROC) curves were used to determine the ability of HVR in predicting END. ResultsOf the 52 enrolled patients, 18 (34.5%) were determined with END. In patients with END, the median hypoperfusion volume was 20 mL [Inter Quartile Range)IQR, 6-72.5 mL] at 1.5s PLD, and 11.2 mL (IQR, 5.3-26 mL) at 2.5s PLD; Sixteen (88.9%) patients had HVR ≥50%, and 13 (72.2%) patients hypoperfusion volume at 2.5s PLD ASL were greater than diffusion-weighted imaging (DWI) infarct volume. In patients without END, median hypoperfusion volume was 7 mL (IQR, 4-30 mL) at 1.5s PLD, and 4 mL (IQR, 1.5-8.5 mL) at 2.5s; Eleven (32.4%) patients had HVR ≥50%, and 10 (29.4%) patients hypoperfusion volume at 2.5s PLD ASL were greater than DWI infarct volume. The proportion of HVR ≥50% and hypoperfusion volume >DWI infarct volume were more frequent in patients with END than patients without (all P<0.001). After adjusted for age, admission NIHSS, proportion of hypoperfusion volume > DWI infarct and arterial transit artifact (ATA) by logistic regression analysis, HVR ≥50% (OR=13.1, P=0.003) was an independent risk factor for END. ROC analysis demonstrated that the HVR could predict END with an area under the curve of 0.794 (P=0.001). ConclusionsHVR obtained from the 1.5 and 2.5s PLD ASL may be a useful predictor of END in AIS. The value of HVR may be a marker for hemodynamic impairments.

Risk Factors of Hypoperfusion on MRI of Ischemic Stroke Patients Within 7 Days of Onset.

Objective: Hypoperfusion is an important factor determining the prognosis of ischemic stroke patients. The present study aimed to investigate possible predictors of hypoperfusion on MRI of ischemic stroke patients within 7 days of stroke onset.Methods: Ischemic stroke patients, admitted to the comprehensive Stroke Center of Shanghai Fourth People's Hospital affiliated to Tongji University within 7 days of onset between January 2016 and June 2017, were recruited to the present study. Magnetic resonance imaging (MRI), including both diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI), was performed within 7 days of the symptom onset. Time to maximum of the residue function (Tmax) maps were automatically evaluated using the RAPID software. The volume of hypoperfusion was measured outside the infarct area based on ADC < 620 × 10−6 mm2/s. The 90 d mRS score was assessed through either clinic visits or telephone calls. Multivariate step-wise analysis was used to assess the correlation between MR findings and clinical variables, including the demographic information, cardio-metabolic characteristics, and functional outcomes.Results: Among 635 patients admitted due to acute ischemic stroke within 7 days of onset, 241 met the inclusion criteria. Hypoperfusion volume of 38 ml was the best cut-off value for predicting poor prognosis of patients with cerebral infarction (90 d-mRS score ≥ 2). The incidences of MR perfusion Tmax > 4–6 s maps with a volume of 0–38 mL or >38 mL were 51.9% (125/241) and 48.1% (116/241), respectively. Prior stroke and vascular stenosis (≥70%) were associated with MR hypoperfusion. Multivariate step-wise analysis showed that prior stroke and vascular stenosis (≥70%) were risk factors of Tmax > 4–6 s maps, and the odds ratios (OR) were 3.418 (adjusted OR 95% CI: 1.537–7.600), and 2.265 (adjusted OR, 95% CI: 1.199–4.278), respectively.Conclusion: Our results suggest that prior stroke and vascular stenosis (≥70%) are strong predictors of hypoperfusion in patients with acute ischemic stroke within 7 days of stroke onset.

Intracranial atherosclerotic disease mechanistic subtypes drive hypoperfusion patterns.

In symptomatic intracranial atherosclerotic stenosis (ICAS), borderzone infarct pattern and perfusion mismatch are associated with increased risk of recurrent strokes, which may reflect the shared underlying mechanism of hypoperfusion distal to the intracranial atherosclerosis. Accordingly, we hypothesized a correlation between hypoperfusion volumes and ICAS infarct patterns based on the respective underlying mechanistic subtypes. We conducted a retrospective analysis of consecutive symptomatic ICAS cases, acute strokes due to subocclusive (50%-99%) intracranial stenosis. The following mechanistic subtypes were assigned based on the infarct pattern on the diffusion-weighted imaging: Branch occlusive disease (BOD), internal borderzone (IBZ), and thromboembolic (TE). Perfusion parameters, obtained concurrently with the MRI, were studied in each group. A total of 42 patients (57% women, mean age 71±13 years old) with symptomatic ICAS received MRI within 24 h of acute presentation. Fourteen IBZ, 11 BOD, and 17 TE patterns were identified. IBZ pattern yielded higher total Tmax >4s and Tmax >6s perfusion delay volumes, as well as corresponding Tmax >4s and Tmax >6s mismatch volume, compared to BOD. TE pattern exhibited greater median Tmax >6s hypoperfusion delay in volume compared to BOD. In IBZ versus TE, the volume difference between Tmax >4s and Tmax >6s (Δ Tmax >4s - Tmax >6s) was substantially greater. ICAS infarct patterns, in keeping with their respective underlying mechanisms, may correlate with distinct perfusion profiles.

Epidemiological Surveillance of the Impact of the COVID-19 Pandemic on Stroke Care Using Artificial Intelligence

The degree to which the coronavirus disease 2019 (COVID-19) pandemic has affected systems of care, in particular, those for time-sensitive conditions such as stroke, remains poorly quantified. We sought to evaluate the impact of COVID-19 in the overall screening for acute stroke utilizing a commercial clinical artificial intelligence platform. Data were derived from the Viz Platform, an artificial intelligence application designed to optimize the workflow of patients with acute stroke. Neuroimaging data on suspected patients with stroke across 97 hospitals in 20 US states were collected in real time and retrospectively analyzed with the number of patients undergoing imaging screening serving as a surrogate for the amount of stroke care. The main outcome measures were the number of computed tomography (CT) angiography, CT perfusion, large vessel occlusions (defined according to the automated software detection), and severe strokes on CT perfusion (defined as those with hypoperfusion volumes >70 mL) normalized as number of patients per day per hospital. Data from the prepandemic (November 4, 2019 to February 29, 2020) and pandemic (March 1 to May 10, 2020) periods were compared at national and state levels. Correlations were made between the inter-period changes in imaging screening, stroke hospitalizations, and thrombectomy procedures using state-specific sampling. A total of 23 223 patients were included. The incidence of large vessel occlusion on CT angiography and severe strokes on CT perfusion were 11.2% (n=2602) and 14.7% (n=1229/8328), respectively. There were significant declines in the overall number of CT angiographies (-22.8%; 1.39-1.07 patients/day per hospital, P<0.001) and CT perfusion (-26.1%; 0.50-0.37 patients/day per hospital, P<0.001) as well as in the incidence of large vessel occlusion (-17.1%; 0.15-0.13 patients/day per hospital, P<0.001) and severe strokes on CT perfusion (-16.7%; 0.12-0.10 patients/day per hospital, P<0.005). The sampled cohort showed similar declines in the rates of large vessel occlusions versus thrombectomy (18.8% versus 19.5%, P=0.9) and comprehensive stroke center hospitalizations (18.8% versus 11.0%, P=0.4). A significant decline in stroke imaging screening has occurred during the COVID-19 pandemic. This analysis underscores the broader application of artificial intelligence neuroimaging platforms for the real-time monitoring of stroke systems of care.

Abstract 42: Epidemiological Surveillance of the Impact of the Covid-19 Pandemic on Stroke Care Using Artificial Intelligence

Background: The degree to which the COVID-19 pandemic has affected systems of care, in particular those for time-sensitive conditions such as stroke, remains poorly quantified. We sought to evaluate the impact of COVID-19 in the overall screening for acute stroke utilizing a commercial clinical artificial intelligence (AI) platform. Methods: Data were derived from the Viz Platform, an AI application designed to optimize the workflow of acute stroke patients. Neuroimaging data on suspected stroke patients across 97 hospitals in 20 US states were collected in real-time and retrospectively analyzed with the number of patients undergoing imaging screening serving as a surrogate for the amount of stroke care. The main outcome measures were the number of CTA, CTP, Large vessel occlusions (LVOs) (defined according to the automated software detection), and severe strokes on CTP (defined as those with hypoperfusion volumes&gt;70mL) normalized as number of patients per day per hospital. Data from the pre-pandemic (November 4, 2019 to February 29, 2020) and pandemic (March 1 to May 10, 2020) periods were compared at national and state levels. Correlations were made between the inter-period changes in imaging screening, stroke hospitalizations, and thrombectomy procedures using state-specific sampling. Results: A total of 23,223 patients were included. The incidence of LVO on CTA and severe strokes on CTP were 11.2%(n=2,602) and 14.7%(n=1,229/8,328), respectively. There were significant declines in the overall number of CTAs (-22.8%;1.39 to 1.07 patients/day/hospital,p&lt;0.001) and CTPs (-26.1%;0.50 to 0.37 patients/day/hospital,p&lt;0.001) as well as in the incidence of LVO (-17.1%;0.15 to 0.13 patients/day/hospital,p&lt;0.001) and severe strokes on CTP (-16.7%;0.12 to 0.10 patients/day/hospital, p&lt;0.005). The sampled cohort showed similar declines in the rates of LVOs versus thrombectomy (18.8%vs.19.5%, p=0.9) and CSC hospitalizations (18.8%vs.11.0%, p=0.4). Conclusions: A significant decline in stroke imaging screening has occurred during the COVID-19 pandemic. This underscores the broader application of AI neuroimaging platforms for the real-time monitoring of stroke systems of care.

Effects of cerebral hypoperfusion on the cerebral white matter: a meta‑analysis.

Decreased cerebral blood flow (CBF) in aging is known to induce aging‑related cerebral deteriorations, such as neuronal degeneration, white matter (WM) alterations, and vascular deformations. However, the effects of cerebral hypoperfusion on WM alterations remain unclear. This study investigates the relationship between cerebral hypoperfusion and WM total volume changes by assessing the trends in CBF and WM changes by meta‑analysis. In this meta‑analysis, the differences in CBF were compared according to cerebral hypoperfusion type and the effect of cerebral hypoperfusion on the total volume of WM changes in rodents. Using subgroup analysis, 13 studies were evaluated for comparing CBF according to the type of cerebral hypoperfusion; 12 studies were evaluated for comparing the effects of cerebral hypoperfusion on the total volume of WM changes. Our meta‑analysis shows that the total volume of WM decreases with a decrease in CBF. However, the reduction in\r\nthe total volume of WM was greater in normal aging mice than in the cerebral hypoperfusion model mice. These results suggest that the reduction of cerebral WM volume during the aging process is affected by other factors in addition to a decrease in CBF.

Association of Collateral Status and Ischemic Core Growth in Patients With Acute Ischemic Stroke.

To test the hypothesis that patients with acute ischemic stroke with poorer collaterals would have faster ischemic core growth, we included 2 cohorts in the study: cohort 1 of 342 patients for derivation and cohort 2 of 414 patients for validation. Patients with acute ischemic stroke with large vessel occlusion were included. Core growth rate was calculated by the following equation: core growth rate = acute core volume on CT perfusion (CTP)/time from stroke onset to CTP. Collateral status was assessed by the ratio of severe hypoperfusion volume within the hypoperfusion region of CTP. The CTP collateral index was categorized in tertiles; for each tertile, core growth rate was summarized as median and interquartile range. Simple linear regressions were then performed to measure the predictive power of CTP collateral index in core growth rate. For patients allocated to good collateral on CTP (tertile 1 of collateral index), moderate collateral (tertile 2), and poor collateral (tertile 3), the median core growth rate was 2.93 mL/h (1.10-7.94), 8.65 mL/h (4.53-18.13), and 25.41 mL/h (12.83-45.07), respectively. Increments in the collateral index by 1% resulted in an increase of core growth by 0.57 mL/h (coefficient 0.57, 95% confidence interval [0.46, 0.68], p < 0.001). The relationship of core growth and CTP collateral index was validated in cohort 2. An increment in collateral index by 1% resulted in an increase of core growth by 0.59 mL/h (coefficient 0.59 [0.48-0.71], p < 0.001) in cohort 2. Collateral status is a major determinant of ischemic core growth.

Collateral Status at Single-Phase and Multiphase CT Angiography versus CT Perfusion for Outcome Prediction in Anterior Circulation Acute Ischemic Stroke.

Background Collateral status assessed with single- or multiphase CT angiography can be used to predict outcome in patients with acute ischemic stroke (AIS); however, little is known about whether these measures could be comparable with CT perfusion parameters. Purpose To compare the predictive ability of collateral score systems assessed with single- or multiphase CT angiography and CT perfusion parameters in determining clinical outcomes in patients with AIS. Materials and Methods In this retrospective study, data obtained from October 2017 to August 2018 in consecutive patients with AIS caused by isolated anterior circulation large artery occlusion and that were obtained within 24 hours after onset were reviewed. The collateral score was assessed by using established scoring systems described by Menon et al. The correlations between single- and multiphase collateral scores, hypoperfusion, and ischemic core volume and final infarct volume (FIV) determined by follow-up diffusion-weighted imaging or unenhanced CT were studied. Receiver operating characteristic curves and multivariable logistic regression analysis were performed to assess the predictive ability of scoring systems and CT perfusion parameters for a favorable clinical outcome. Results A total of 119 patients (median age, 75 years; interquartile range, 66-82 years; 74 men) were included. Both single- and multiphase Menon scores had a moderate negative correlation with FIV (r = -0.43, P < .001; r = -0.44, P < .001). Receiver operating characteristic curve analysis revealed the multiphase Menon score performed better than the single-phase Menon score (area under the curve [AUC], 0.72 vs 0.64; P = .045) in the prediction of a favorable 90-day modified Rankin scale score. There was no difference between multiphase Menon score and hypoperfusion volume (AUC, 0.72 vs 0.72; P = .97) or ischemic core volume (AUC, 0.72 vs 0.71; P = .94). Multivariable analysis showed multiphase Menon score was an independent predictor of good clinical outcomes (odds ratio = 3.04, P = .001). Conclusion Multiphase Menon score performed better than single-phase Menon score and was comparable with CT perfusion parameters in determining clinical outcomes in patients with acute ischemic stroke. © RSNA, 2020.

Optimal intracranial pressure in patients with aneurysmal subarachnoid hemorrhage treated with coiling and requiring external ventricular drainage.

Optimal management of intracranial pressure (ICP) among aneurysmal subarachnoid hemorrhage (aSAH) patients requiring external ventricular drainage (EVD) is controversial. To analyze predictors of delayed cerebral ischemia (DCI)-related cerebral infarction after aSAH and the influence of ICP values on DCI, we prospectively collected consecutive patients with aSAH receiving coiling and requiring EVD. Predictors of DCI-related cerebral infarction (new CT hypodensities developed within the first 3weeks not related to other causes) were studied. Vasospasm and brain hypoperfusion were studied with CT angiography and CT perfusion (RAPID-software). Among 50 aSAH patients requiring EVD, 21 (42%) developed DCI-related cerebral infarction, while 27 (54%) presented vasospasm. Mean ICP ranged between 2 and 19mmHg. On the multivariate analysis, the mean ICP (OR = 2, 95%CI = 1.01-3.9, p = 0.042) and the mean hypoperfusion volume on Tmax delay > 6 (OR = 1.2, 95%CI = 1.01-1.3, p = 0.025) were independent predictors of DCI. To predict DCI-related cerebral infarction, Tmax delay > 6s presented the highest AUC (0.956, SE = 0.025), with a cutoff value of 18ml showing sensitivity, specificity, PPV, NPV, and accuracy of 90.5% (95%CI = 69-98.8%), 86.2% (95%CI = 68.4-96%), 82.6% (95%CI = 65.4-92%), 92.5% (95%CI = 77-98%), and 88% (95%CI = 75-95%), respectively. The AUC of the mean ICP was 0.825 (SE = 0.057), and the best cutoff value was 6.7mmHg providing sensitivity, specificity, PPV, NPV, and accuracy of 71.4% (95%CI = 48-89%), 62% (95%CI = 42-79%), 58% (95%CI = 44-70%), 75% (95%CI = 59-86%), and 66% (95%CI = 51-79%) for the prediction of DCI-related cerebral infarction, respectively. Among aSAH patients receiving coiling and EVD, lower ICP (< 6.7mmHg in our study) could potentially be beneficial in decreasing DCI-related cerebral infarction. Brain hypoperfusion with a volume > 18ml at Tmax delay > 6s presents a high sensibility and specificity in prediction of DCI-related cerebral infarction.

Comparing the outcomes of two independent computed tomography perfusion softwares and their impact on therapeutic decisions in acute ischemic stroke

BackgroundTo compare the computed tomography perfusion (CTP) outcomes derived from two commercial CTP processing software and evaluate their concordance in terms of eligibility for mechanical thrombectomy (MT) in acute ischemic...

Computed Tomography Perfusion After Thrombectomy: An Immediate Surrogate Marker of Outcome After Recanalization in Acute Stroke.

Background and Purpose- Despite recanalization, almost 50% of patients undergoing endovascular treatment (EVT) experience poor outcome. We aim to evaluate the value of computed tomography perfusion as immediate outcome predictor postendovascular treatment. Methods- Consecutive patients receiving endovascular treatment who achieved recanalization (modified Thrombolysis in Cerebral Ischemia [mTICI] 2a-3) underwent computed tomography perfusion within 30 minutes from recanalization (CTPpost). Hypoperfusion was defined as the Tmax>6 second volume; hyperperfusion as visually increased cerebral blood flow/cerebral blood volume with reduced Tmax compared with unaffected hemisphere. Dramatic clinical recovery (DCR) was defined as 24-hour National Institutes of Health Stroke Scale score ≤2 or ≥8 points drop. Delayed recovery was defined as no-DCR with favorable outcome (modified Rankin Scale score 0-2) at 3 months. Results- We included 151 patients: median National Institutes of Health Stroke Scale score 16 (interquartile range, 10-21), median admission ASPECTS 9 (interquartile range, 8-10). Final recanalization was the following: mTICI2a 11 (7.3%), mTICI2b 46 (30.5%), and mTICI3 94 (62.3%). On CTPpost, 80 (52.9%) patients showed hypoperfusion (median Tmax>6 seconds: 4 cc [0-25]) and 32 (21.2%) hyperperfusion. There was an association between final TICI and CTPpost hypoperfusion(median Tmax>6: 91 [56-117], 15 [0-37.5], and 0 [0-7] cc, for mTICI 2a, 2b, and 3, respectively, P<0.01). Smaller hypoperfusion volumes on CTPpost were observed in patients with DCR (0 cc [0-13] versus non-DCR 8 cc [0-56]; P<0.01) or favorable outcome (modified Rankin Scale score 0-2: 0 cc [0-13] versus 7 [0-56] cc; P<0.01). No associations were detected with hyperperfusion pattern. An hypoperfusion volume <3.5 cc emerged as independent predictor of DCR (OR, 4.1 [95% CI, 2.0-8.3]; P<0.01) and 3 months favorable outcome (OR, 3.5 [95% CI, 1.6-7.8]; P<0.01). Conclusions- Hypoperfusion on CTPpost constitutes an immediate accurate surrogate marker of success after endovascular treatment and identifies those patients with delayed recovery and favorable outcome.

Hypoperfusion intensity ratio correlates with angiographic collaterals in acute ischaemic stroke with M1 occlusion

Among patients with an acute ischaemic stroke secondary to large-vessel occlusion, the hypoperfusion intensity ratio (HIR) [time to maximum (TMax)>10volume/TMax>6volume] is a strong predictor of infarct growth. We studied the correlation between HIR and collaterals assessed with digital subtraction angiography (DSA) before thrombectomy. Between January 2014 and March 2018, consecutive patients with an acute ischaemic stroke and an M1 middle cerebral artery (MCA) occlusion who underwent perfusion imaging and endovascular treatment at our center were screened. Ischaemic core (mL), HIR and perfusion mismatch (TMax>6s minus core volume) were assessed through magnetic resonance imaging or computed tomography perfusion. Collaterals were assessed on pre-intervention DSA using the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) scale. Baseline clinical and perfusion characteristics were compared between patients with good (ASITN/SIR score 3-4) and those with poor (ASITN/SIR score 0-2) DSA collaterals. Correlation between HIR and ASITN/SIR scores was evaluated using Pearson's correlation. Receiver operating characteristic analysis was performed to determine the optimal HIR threshold for the prediction of good DSA collaterals. A total of 98 patients were included; 49% (48/98) had good DSA collaterals and these patients had significantly smaller hypoperfusion volumes (TMax>6s, 89 vs. 125mL; P=0.007) and perfusion mismatch volumes (72 vs. 89mL; P=0.016). HIR was significantly correlated with DSA collaterals (-0.327; 95% confidence interval, -0.494 to -0.138; P=0.01). An HIR cut-off of <0.4 best predicted good DSA collaterals with an odds ratio of 4.3 (95% confidence interval, 1.8-10.1) (sensitivity, 0.792; specificity, 0.560; area under curve, 0.708). The HIR is a robust indicator of angiographic collaterals and might be used as a surrogate of collateral assessment in patients undergoing magnetic resonance imaging. HIR <0.4 best predicted good DSA collaterals.

Retrograde blood flow in the internal jugular veins of humans with hypertension may have implications for cerebral arterial blood flow.

To use multi-parametric magnetic resonance imaging (MRI) to test the hypothesis that hypertensives would have higher retrograde venous blood flow (RVBF) in the internal jugular veins (IJV) vs. normotensives, and that this would inversely correlate with arterial inflow and gray matter, white matter, and cerebrospinal fluid volumes. Following local institutional review board approval and written consent, a prospective observational 3-T MRI study of 42 hypertensive patients (53 ± 2years, BMI 28.2 ± 0.6kg/m2, ambulatory daytime systolic BP 148 ± 2mmHg, ambulatory daytime diastolic BP 101 ± 2mmHg) and 35 normotensive patients (48 ± 2years, BMI 25.2 ± 0.8kg/m2, ambulatory daytime systolic BP 119 ± 3mmHg, ambulatory daytime diastolic BP 90 ± 2mmHg) was performed. Phase contrast imaging calculated percentage retrograde venous blood flow (%RVBF), brain segmentation estimated regional brain volumes from 3D T1-weighted images, and pseudo-continuous arterial spin labeling measured regional cerebral blood perfusion. Statistical analysis included two-sample equal variance Student's T tests, two-way analysis of variance with Tukey's post hoc correction, and permutation-based two-group general linear modeling (p < 0.05). In the left IJV, %RVBF was higher in hypertensives (6.1 ± 1.5%) vs. normotensives (1.1 ± 0.3%, p = 0.003). In hypertensives, there was an inverse relationship of %RVBF (permutation-based general linear modeling) to cerebral blood flow in several brain regions, including the left occipital pole and the cerebellar vermis (p < 0.01). Percentage retrograde flow in the left IJV correlated inversely with the total matter volume (gray plus white matter volume) in hypertensives (r = - 0.49, p = 0.004). RVBF in the left IJV is greater in hypertensives vs. normotensives and is linked to regional hypoperfusion and brain total matter volume. • Hypertensive humans have higher retrograde cerebral venous blood flow, associated with regional brain hypoperfusion and lower tissue volume, compared with controls. • Cerebral retrograde venous blood flow may add further stress to already hypoperfused tissue in hypertensive patients. • The amount of retrograde venous blood flow in hypertensive patients may predict which patients might be at higher risk of developing cerebral pathologies.

Abstract WMP17: Computerized Tomography Perfusion to Characterize Lack of Clinical Improvement After Recanalization in Acute Ischemic Stroke

A significant proportion of patients with acute ischemic stroke (AIS) treated with endovascular thrombectomy (EVT) present poor functional outcome despite recanalization. We aim to investigate computed tomography perfusion (CTP) patterns after EVT and their association with outcome Methods: Prospective study of anterior large vessel occlusion AIS patients who achieved complete recanalization (defined as modified Thrombolysis in Cerebral Ischemia (TICI) 2b - 3) after EVT. CTP was performed within 30 minutes post-EVT recanalization (POST-CTP): hypoperfusion was defined as volume of time to maximal arrival of contrast (Tmax) delay ≥6 seconds in the affected territory. Hyperperfusion was defined as visual increase in cerebral blood flow (CBF) and volume (CBV) with advanced Tmax compared with the unaffected hemisphere. Dramatic clinical recovery (DCR) was defined as a decrease of ≥8 points in NIHSS score at 24h or NIHSS≤2 and good functional outcome by mRS ≤2 at 3 months. Results: One-hundred and forty-one patients were included. 49 (34.7%) patients did not have any perfusion abnormality on POST-CTP, 60 (42.5%) showed hypoperfusion (median volume Tmax≥6s 17.5cc, IQR 6-45cc) and 32 (22.8%) hyperperfusion. DCR appeared in 56% of patients and good functional outcome in 55.3%. Post-EVT hypoperfusion was related with worse final TICI, and associated worse early clinical evolution, larger final infarct volume (p&lt;0.01 for all) and was an independent predictor of functional outcome (OR 0.98, CI 0.97-0.99, p=0.01). Furthermore, POST-CTP identified patients with delayed improvement: in patients without DCR (n=62, 44%), there was a significant difference in post-EVT hypoperfusion volume according to functional outcome (hypoperfusion volume of 2cc in good outcome vs 11cc in poor outcome, OR 0.97 CI 0.93-0.99, p=0.04), adjusted by confounding factors. Hyperperfusion was not associated with worse outcome (p=0.45) nor symptomatic hemorrhagic transformation (p=0.55). Conclusion: Hypoperfusion volume after EVT is an accurate predictor of functional outcome. In patients without dramatic clinical recovery, hypoperfusion predicts good functional outcome and defines a “stunned-brain” pattern. POST-CTP may help to select EVT patients for additional therapies.

Eligibility for intravenous thrombolysis in acute ischemic stroke patients presenting in the 4.5-9h window.

Recent randomized-controlled clinical trials have provided preliminary evidence for expanding the time window of intravenous thrombolysis (IVT) in acute ischemic stroke (AIS) patients by applying certain neuroimaging criteria. We prospectively assessed the potential eligibility for IVT in the extended time window (4.5-9h) among consecutive AIS patients treated in a comprehensive stroke center during a nine-month period. Potential eligibility for IVT in the extended time window was evaluated by using inclusion criteria from the EXTEND trial. All patients were underwent baseline emergent neurovascular imaging using either computed tomography angiography/computed tomography perfusion (CTA/CTP) or magnetic resonance angiography/magnetic resonance perfusion (MRA/MRP). Images were post processed by the automated software RAPID. Our study population consisted of 317 AIS patients, and, among them, 31 (9.8%) patients were presented in the time window of 4.5-9h. Seven patients (2.2%) fulfilled the EXTEND neuroimaging criteria. Four patients (1.3%) were treated with IVT because they fulfilled both clinical and neuroimaging EXTEND criteria. Patients eligible for EXTEND neuroimaging criteria had no ischemic core lesion, whereas the mean volume of critical hypoperfusion was relatively small (17.0 ± 11.8ml). There was no hemorrhagic complication in any of the patients treated with IVT. The median mRS score at three months was 0 (range: 0-3) among patients who were eligible for EXTEND neuroimaging criteria. Our everyday clinical practice experience suggests 9.8% of consecutive AIS patients present in the 4.5-9h window and 2.2% adhere to EXTEND neuroimaging eligibility criteria for IVT. Only 1.3% of AIS is eligible for IVT according to EXTEND neuroimaging and clinical eligibility criteria.