Distinct intra-arterial clot localization affects tissue-level collaterals and venous outflow profiles

Poor venous outflow is associated with hyperintense acute reperfusion marker on follow-up MRI in patients with acute ischemic stroke with a large vessel occlusion

BACKGROUND

Hyperintense acute reperfusion marker (HARM) refers to delayed enhancement in the subarachnoid or subpial space on post-contrast fluid attenuated inversion recovery (FLAIR) images. HARM is a measure of blood-brain barrier breakdown, which has been correlated with poor outcomes in patients with acute ischemic stroke with large vessel occlusion (AIS-LVO). We hypothesized that unfavorable venous outflow (VO) would be correlated with HARM after thrombectomy treatment of AIS-LVO.

OBJECTIVE

To determine whether poor VO is associated with HARM on follow-up MRI after stroke in patients with AIS-LVO.

METHODS

Patients with AIS-LVO from the prospective CRISP2 and DEFUSE2 studies with a baseline CT angiography (CTA) scan and a follow-up MRI with FLAIR sequence were screened for enrollment. VO was measured on the baseline CTA scan using the cortical venous opacification score (COVES). HARM was determined on FLAIR sequences at the follow-up MRI. The primary outcome was the occurrence of HARM between those with good VO (VO+; COVES 3-6) and bad VO (VO-; COVES 0-2).

RESULTS

121 patients were included; 60.3% (n=73) had VO+ and 39.7% (n=48) had VO-. Patients with VO- had higher presentation National Institutes of Health Stroke Scale scores (18 (IQR 12-20) vs 12 (IQR 8-16) in VO+; P<0.001). Middle cerebral artery M1 segment occlusions were more common in VO- patients (65% vs 43% VO+; P=0.028). VO- patients also had a larger pre-treatment ischemic core (23 (4-44) mL vs 12 (3-22) mL in VO+; P=0.049) and Tmax >6 s volumes (105 (72-142) mL vs 66 (35-95) mL in VO+; P<0.001). VO- patients were more likely to develop HARM after thrombectomy (31% vs 10% in VO+; P=0.003). On multivariable regression analysis, VO- (OR=3.6 (95% CI 1.2 to 10.6); P=0.02) and the presence of any ICH (OR=3.6 (95% CI 1.2 to 10.5); P=0.02) were independently associated with the occurrence of HARM.

CONCLUSIONS

In patients with AIS-LVO, VO- correlated with HARM on post-thrombectomy MRI.

CT perfusion to measure venous outflow in acute ischemic stroke in patients with a large vessel occlusion

BACKGROUND

Robust venous outflow (VO) profiles, measured by degree of venous opacification on pre-thrombectomy CT angiography (CTA) studies, are strongly correlated with favorable outcomes in patients with large vessel occlusion acute ischemic stroke treated by thrombectomy. However, VO measurements are laborious and require neuroimaging expertise.

OBJECTIVE

To develop a semi-automated method to measure VO using CTA and CT perfusion imaging studies.

METHODS

We developed a graphical interface using The Visualization Toolkit, allowing for voxel selection at the confluence and bilateral internal cerebral veins on CTA along with arterial input functions (AIFs) from both internal carotid arteries. We extracted concentration-time curves from the CT perfusion study at the corresponding locations associated with AIF and venous output function (VOF). Outcome analyses were primarily conducted by the Mann-Whitney U and Jonckheere-Terpstra tests.

RESULTS

Segmentation at the pre-selected AIF and VOF locations was performed on a sample of 97 patients. 65 patients had favorable VO (VO+) and 32 patients had unfavorable VO (VO-). VO+ patients were found to have a significantly shorter VOF time to peak (8.26; 95% CI 7.07 to 10.34) than VO- patients (9.44; 95% CI 8.61 to 10.91), P=0.007. No significant difference was found in VOF curve width and the difference in time between AIF and VOF peaks.

CONCLUSIONS

Time to peak of VOF at the confluence of sinuses was significantly associated with manually scored venous outflow. Further studies should aim to understand better the association between arterial inflow and venous outflow, and capture quantitative metrics of venous outflow at other locations.

Flow restoration during mechanical thrombectomy for large vessel occlusion is associated with an immediate reduction of systemic blood pressure

INTRODUCTION

Managing blood pressure in patients with large vessel occlusion affects infarct size and clinical outcomes. We examined how restoring blood flow impacts systemic blood pressure during mechanical thrombectomy.

PATIENTS AND METHODS

Patients with large vessel occlusion in the anterior circulation undergoing mechanical thrombectomy between June 2016 and January 2018 were screened. We included those treated under local anesthesia or conscious sedation and analyzed standardized anesthesia protocols to assess systolic and diastolic blood pressure levels throughout the procedure. The primary outcome was the change of blood pressure, compared 5 min before versus 5 min after the last recanalization attempt. Successful reperfusion was defined as Thrombolysis in Cerebral Infarction score ⩾ 2b.

RESULTS

Of 134 patients, 117 (87%) achieved successful angiographic reperfusion, showing a notable systolic blood pressure drop 5 min after flow restoration (10.2 ± 14.6 vs 3.24 ± 8.65 mm Hg, p = 0.009). Successful angiographic reperfusion was a significant predictor for this decrease in multivariable logistic regression: OR = 1.34 (95% CI: 1.03-1.73, p = 0.0299). Among 66 patients not given circulation-affecting meds, a significant systolic pressure reduction was also observed (155 ± 17 mm Hg to 148 ± 17 mm Hg ; p < 0.001). No diastolic pressure changes were significant.

DISCUSSION AND CONCLUSIONS

Flow restoration was associated with an immediate reduction of systolic blood pressure values in patients undergoing mechanical recanalization under local anesthesia or conscious sedation. This suggests a complex interplay between endovascular stroke therapy and cardiovascular hemodynamics.

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

BACKGROUND

Deep venous outflow (VO) may be an important surrogate marker of collateral blood flow in acute ischemic stroke patients with a large vessel occlusion (AIS-LVO). Researchers have yet to determine the relationship between deep VO status in late-window patients and imaging measures of collaterals, which are key in preserving tissue.

MATERIALS AND METHODS

We performed a multicenter retrospective cohort study on a subset of DEFUSE 3 patients recruited across 38 centers between May 2016 and May 2017 who underwent successful thrombectomy revascularization. Internal cerebral vein opacification was scored on a scale of 0-2. This metric was added to the cortical vein opacification score to derive the comprehensive VO (CVO) score from 0 to 8. Patients were stratified by favorable (ICV+) and unfavorable (ICV-) ICV scores, and similarly CVO+ and CVO-. Analyses comparing outcomes were primarily conducted by Mann-Whitney U and χ2 tests.

RESULTS

Forty-five patients from DEFUSE 3 were scored and dichotomized into CVO+, CVO-, ICV+, and ICV- categories, with comparable demographics. Hypoperfusion intensity ratio, a marker of tissue level collaterals, was significantly worse in the ICV- and CVO- groups (p = 0.005). ICV- alone was also associated with a larger perfusion lesion (138 ml vs 87 ml; p = 0.023). No significant differences were noted in functional and safety outcomes.

CONCLUSIONS

Impaired deep venous drainage alone may be a marker of poor tissue level collaterals and a greater degree of affected tissue in AIS-LVO patients presenting in the late-window who subsequently undergo successful revascularization.

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

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

Hypoperfusion Intensity Ratio Is Associated with Early Neurologic Deficit Severity and Deterioration after Mechanical Thrombectomy in Large-Vessel Occlusion Ischemic Stroke

BACKGROUND AND PURPOSE

The hypoperfusion intensity ratio is a surrogate marker for collateral status and a predictor of infarct growth, malignant cerebral edema, and hemorrhagic transformation. Its utility to predict a poor NIHSS score and early neurologic deterioration after mechanical thrombectomy for large vessel (LVO) versus distal and medium vessel occlusions (DMVO) has not been investigated. The objective of this study was to determine whether the higher hypoperfusion intensity ratio is associated with a worse NIHSS score at 24 hours post-mechanical thrombectomy and early neurologic deterioration in LVO versus DMVO acute ischemic stroke.

MATERIALS AND METHODS

This was a retrospective study of 231 patients with acute ischemic stroke with LVO or DMVO amenable for mechanical thrombectomy and available CTP for hypoperfusion intensity ratio assessment pre-mechanical thrombectomy. Clinical and imaging characteristics were abstracted from the medical records. The primary outcome was the NIHSS score at 24 hours post-mechanical thrombectomy. The secondary outcome was early neurologic deterioration, defined as a >4-point increase in the NIHSS score between the initial assessment and 24 hours post-mechanical thrombectomy. All analyses were first conducted in the entire cohort and then separately for the LVO versus DMVO groups.

RESULTS

The optimal hypoperfusion intensity ratio threshold to detect early neurologic deterioration was 0.54. A hypoperfusion intensity ratio ≥ 0.54 was more frequently present in LVO versus DMVO (n = 37 [77.1%] versus n = 11 [22.9%]; P < .001). On multivariable linear regression, the hypoperfusion intensity ratio ≥ 0.54 was independently associated with a worse NIHSS score at 24 hours post-mechanical thrombectomy in the entire cohort (β = 0.163; P = .002) and the LVO group (β = 0.210; P = .005), but not in the DMVO group. The early neurologic deterioration occurred in 26 (11.3%) subjects. On multivariable logistic regression, there was no association of the hypoperfusion intensity ratio ≥ 0.54 with early neurologic deterioration in the entire cohort. However, when analyzed separately, a hypoperfusion intensity ratio ≥ 0.54 significantly increased the odds of early neurologic deterioration in subjects with LVO (OR = 5.263; 95% CI, 1.170-23.674; P = .030) but not in the DMVO group.

CONCLUSIONS

The hypoperfusion intensity ratio ≥ 0.54 was independently associated with a worse 24-hour post-mechanical thrombectomy NIHSS score and early neurologic deterioration in LVO, but not in DMVO acute ischemic stroke. Pending confirmation in future, prospective studies assessing the hypoperfusion intensity ratio may help identify patients at risk of secondary decline to improve peri-thrombectomy care and clinical decision-making.

Pretreatment CTP Collateral Parameters Predict Good Outcomes in Successfully Recanalized Middle Cerebral Artery Distal Medium Vessel Occlusions

BACKGROUND/PURPOSE

Distal medium vessel occlusions (DMVOs) account for a large percentage of vessel occlusions resulting in acute ischemic stroke (AIS) with disabling symptoms. We aim to assess whether pretreatment quantitative CTP collateral status (CS) parameters can serve as imaging biomarkers for good clinical outcomes prediction in successfully recanalized middle cerebral artery (MCA) DMVOs.

METHODS

We performed a retrospective analysis of consecutive patients with AIS secondary to primary MCA-DMVOs who were successfully recanalized by mechanical thrombectomy (MT) defined as modified thrombolysis in cerebral infarction (mTICI) 2b, 2c, or 3. We evaluated the association between the CBV index and HIR independently with good clinical outcomes (modified Rankin score 0-2) using Spearman rank correlation, logistic regression, and ROC analyses.

RESULTS

From 22 August 2018 to 18 October 2022 8/22/2018 to 10/18/2022, 60 consecutive patients met our inclusion criteria (mean age 71.2 ± 13.9 years old [mean ± SD], 35 female). The CBV index (r = -0.693, p < 0.001) and HIR (0.687, p < 0.001) strongly correlated with 90-day mRS. A CBV index ≥ 0.7 (odds ratio, OR, 2.27, range 6.94-21.23 [OR] 2.27 [6.94-21.23], p = 0.001)) and lower likelihood of prior stroke (0.13 [0.33-0.86]), p = 0.024)) were independently associated with good outcomes. The ROC analysis demonstrated good performance of the CBV index in predicting good 90-day mRS (AUC 0.73, p = 0.003) with a threshold of 0.7 for optimal sensitivity (71% [52.0-85.8%]) and specificity (76% [54.9-90.6%]). The HIR also demonstrated adequate performance in predicting good 90-day mRS (AUC 0.77, p = 0.001) with a threshold of 0.3 for optimal sensitivity (64.5% [45.4-80.8%]) and specificity (76.0% [54.9-90.6%]).

CONCLUSION

A CBV index ≥ 0.7 may be independently associated with good clinical outcomes in our cohort of AIS caused by MCA-DMVOs that were successfully treated with MT. Furthermore, a HIR < 0.3 is also associated with good clinical outcomes. This is the first study of which we are aware to identify a CBV index threshold for MCA-DMVOs.

Pretreatment parameters associated with hemorrhagic transformation among successfully recanalized medium vessel occlusions

Although pretreatment radiographic biomarkers are well established for hemorrhagic transformation (HT) following successful mechanical thrombectomy (MT) in large vessel occlusion (LVO) strokes, they are yet to be explored for medium vessel occlusion (MeVO) acute ischemic strokes. We aim to investigate pretreatment imaging biomarkers representative of collateral status, namely the hypoperfusion intensity ratio (HIR) and cerebral blood volume (CBV) index, and their association with HT in successfully recanalized MeVOs. A prospectively collected registry of acute ischemic stroke patients with MeVOs successfully recanalized with MT between 2019 and 2023 was retrospectively reviewed. A multivariate logistic regression for HT of any subtype was derived by combining significant univariate predictors into a forward stepwise regression with minimization of Akaike information criterion. Of 60 MeVO patients successfully recanalized with MT, HT occurred in 28.3% of patients. Independent factors for HT included: diabetes mellitus history (p = 0.0005), CBV index (p = 0.0071), and proximal versus distal occlusion location (p = 0.0062). A multivariate model with these factors had strong diagnostic performance for predicting HT (area under curve [AUC] 0.93, p < 0.001). Lower CBV indexes, distal occlusion location, and diabetes history are significantly associated with HT in MeVOs successfully recanalized with MT. Of note, HIR was not found to be significantly associated with HT.

Early neurological deterioration in patients with acute ischemic stroke is linked to unfavorable cerebral venous outflow

INTRODUCTION

Early neurological deterioration (END) is associated with poor outcomes in patients with acute ischemic stroke due to large vessel occlusion (AIS-LVO). Causes of END after mechanical thrombectomy (MT) include unsuccessful recanalization and reperfusion hemorrhages. However, little is known about END excluding the aforementioned causes. We aimed to investigate factors associated with unexplained END (ENDunexplained) with regard to the cerebral collateral status.

PATIENTS AND METHODS

Multicenter retrospective study of AIS-LVO patients with successful MT (mTICI 2b-3). On admission CT angiography (CTA), pial arterial collaterals and venous outflow (VO) were assessed using the modified Tan-Scale and the Cortical Vein Opacification Score (COVES), respectively. ENDunexplained was defined as an increase in NIHSS score of ⩾ 4 within the first 24 hours after MT without parenchymal hemorrhage on follow-up imaging. Multivariable regression analyses were performed to examine factors of ENDunexplained and unfavorable functional outcome (modified Rankin Scale score 3-6).

RESULTS

A total of 620 patients met the inclusion criteria. ENDunexplained occurred in 10% of patients. While there was no significant difference in pial arterial collaterals, patients with ENDunexplained exhibited more often unfavorable VO (81% vs. 53%; P < 0.001). Unfavorable VO (aOR [95% CI]; 2.56 [1.02-6.40]; P = 0.045) was an independent predictor of ENDunexplained. ENDunexplained was independently associated with unfavorable functional outcomes at 90 days (aOR [95% CI]; 6.25 [2.06-18.94]; P = 0.001).

DISCUSSION AND CONCLUSION

Unfavorable VO on admission CTA was associated with ENDunexplained. ENDunexplained was independently linked to unfavorable functional outcomes at 90 days. Identifying AIS-LVO patients at risk of ENDunexplained may help to select patients for intensified monitoring and guide to optimal treatment regimes.

Microvascular dysfunction associated with unfavorable venous outflow in acute ischemic stroke patients

Unfavorable venous outflow (VO) is associated with cerebral edema, which represents microvascular dysfunction. This study estimated the relationship between VO and microvascular function in acute ischemic stroke patients. We retrospectively included 102 MCA/ICA occluded patients with anterior circulation infarction who underwent reperfusion therapy between July 2017 and April 2022. Unfavorable VO was defined as a cortical vein opacification score of 0-3 and favorable VO as that of 4-6. The clinical characteristics, collateral status, microvascular integrity, and outcomes were compared between patients with favorable and unfavorable VO. Multivariate analysis and receiver operator characteristic (ROC) analysis were used. The patients with unfavorable VO had higher extravascular-extracellular volume fraction (Ve) in the infarct core and a lower percentage of robust arterial collateral circulation. ROC analysis revealed that Ve in the infarct core predicts unfavorable VO (AUC = 0.67, sensitivity = 65.08%, specificity = 69.23%). The higher Ve in the infarct core (odds ratio = 1.011, 95% CI = 1.000-1.021, P = 0.046) and poor arterial collateral flow (odds ratio = 0.102, 95% CI = 0.032-0.327, P < 0.001) were independent predictors of unfavorable VO. This suggests that microvascular dysfunction may be one of the mechanisms underlying impaired VO.

Hypoperfusion intensity ratio as a predictor of outcomes after thrombectomy triage: A call for data homogeneity

Background

Collateral blood flow markers have been associated with outcomes after thrombectomy in patients presenting with acute ischemic stroke due to large vessel occlusion (AIS-LVO). Hypoperfusion intensity ratio (HIR), a metric reflecting tissue level collaterals, is one such marker with the potential to delineate patients who do and do not do well after thrombectomy. We determined if HIR correlated with successful reperfusion after thrombectomy.

Methods

Using Nested Knowledge, we screened literature for studies comparing patients with favorable versus unfavorable HIR, distinguished by a cutoff of 0.4, who underwent thrombectomy triage. The primary outcome was reperfusion success, as measured by thrombolysis in cerebral infarction ≥2b and secondary outcomes included rate of symptomatic intracranial hemorrhage, mortality at 90 days, and modified Rankin scale scores 0–2 at 90 days. A random effects model was used to compute pooled prevalence rates and their corresponding 95% confidence intervals (CI).

Results

Three studies with 973 patients, 496 with favorable HIR, and 477 with unfavorable HIR were included in this meta-analysis. The odds of reperfusion success were not significantly different between patients who had favorable versus unfavorable HIR (OR 0.96, 95% CI: 0.31–3.04) across two of the studies. Analysis of the remaining outcome variables was precluded by significant heterogeneity in data element reporting.

Conclusions

This meta-analysis was considerably limited by heterogeneity. Future meta-analyses on this topic, and other topics in the field of neurointervention would benefit from improved harmonization of study design and data element reporting.

Stroke recurrence is associated with unfavorable intracranial venous outflow in patients with symptomatic intracranial atherosclerotic large vessel severe stenosis or occlusion

Objective

The purpose of this study was to investigate the predictive value of intracranial venous outflow for recurrent cerebral ischemic events (RCIE) in patients with symptomatic intracranial atherosclerotic large-vessel severe stenosis or occlusion (sICAS-S/O).

Methods

This retrospective study included sICAS-S/O patients with anterior circulation who underwent dynamic computed tomography angiography (dCTA) and computed tomography perfusion (CTP). Arterial collaterals were evaluated using the pial arterial filling score for dCTA data, tissue-level collaterals (TLC) were assessed using the high-perfusion intensity ratio (HIR, Tmax >10 s/Tmax >6 s), and cortical veins were evaluated using the multi-phase venous score (MVS) for the vein of Labbé (VOL), sphenoparietal sinus (SPS), and superficial cerebral middle vein (SCMV). The relationships between multi-phase venous outflow (mVO), TLC, and 1-year RCIE were analyzed.

Results

Ninety-nine patients were included, 37 of whom had unfavorable mVO (mVO-) and 62 of whom had favorable mVO (mVO+). Compared with the mVO+ patients, mVO- patients had a higher admission National Institutes of Health Stroke Scale (NIHSS) score (median, 4 [interquartile range (IQR), 0-9] vs. 1 [IQR, 0-4]; p = 0.048), larger ischemic volume (median, 74.3 [IQR, 10.1-177.9] vs. 20.9 [IQR, 5-86.4] mL; p = 0.042), and worse tissue perfusion (median, 0.04 [IQR, 0-0.17] vs. 0 [IQR, 0-0.03]; p = 0.007). Multivariate regression analysis showed that mVO- was an independent predictor of 1-year RCIE.

Conclusion

For patients with sICAS-S/O of the anterior circulation, unfavorable intracranial venous outflow is a potential imaging indicator for predicting higher 1-year RCIE risk.

Delayed low cerebellar perfusion status is associated with poor outcomes in top-of-basilar occlusion treated with thrombectomy

Background and purpose

Top-of-basilar artery occlusion (TOB) is one of the most devastating strokes despite successful mechanical thrombectomy (MT). We aimed to investigate the impact of initial low cerebellum perfusion delay on the outcomes of TOB treated with MT.

Methods

We included patients who underwent MT for TOB. Clinical and peri-procedural variables were obtained. Perfusion delay in the low cerebellum was defined as (1) time-to-maximum (Tmax) >10 s lesions or (2) relative time-to-peak (rTTP) map >9.5 s with a diameter of ≥6 mm in the low cerebellum. The good functional outcome was defined as the achievement of a modified Rankin Scale score of 0-3 at 3 months after stroke.

Results

Among the 42 included patients, 24 (57.1%) patients showed perfusion delay in the low cerebellum. The admission National Institutes of Health Stroke Scale (NIHSS) score was significantly higher in those with perfusion delay [17 (12-24) vs. 8 (6-15), P = 0.002]. Accordingly, the proportion of good functional outcomes was lower in those with perfusion delay than in those without [5 (20.8%) vs. 13 (72.2%), P = 0.003]. From the multivariable analysis, the admission NIHSS score [odds ratio (OR) = 0.86, 95% confidence intervals (CIs) = 0.75-0.98, P = 0.021] and low cerebellum perfusion delay (OR = 0.18, 95% Cis = 0.04-0.86, P = 0.031) were independently associated with the 3-month functional outcomes.

Conclusion

We found that initial perfusion delay proximal to TOB in the low cerebellum might be a predictor for poor functional outcomes in TOB treated with MT.

Collateral Blood Flow and Ischemic Core Growth

Treatment of a large vessel occlusion in the acute ischemic stroke setting focuses on vessel recanalization, and endovascular thrombectomy results in favorable outcomes in appropriate candidates. Expeditious treatment is imperative, but patients often present to institutions that do not have neurointerventional surgeons and need to be transferred to a comprehensive stroke center. These treatment delays are common, and it is important to identify factors that mitigate the progression of the ischemic core in order to maximize the preservation of salvageable brain tissue. Collateral blood flow is the strongest factor known to influence ischemic core growth, which includes the input arterial vessels, tissue-level vessels, and venous outflow. Collateral blood flow at these different levels may be imaged by specific imaging techniques that may also predict ischemic core growth during treatment delays and help identify patients who would benefit from transfer and endovascular therapy, as well as identify those patients in whom transfer may be futile. Here we review collateral blood flow and its relationship to ischemic core growth in stroke patients.

Poor venous outflow profiles increase the risk of reperfusion hemorrhage after endovascular treatment

To investigate whether unfavorable cerebral venous outflow (VO) predicts reperfusion hemorrhage after endovascular treatment (EVT), we conducted a retrospective multicenter cohort study of patients with acute ischemic stroke and large vessel occlusion (AIS-LVO). 629 AIS-LVO patients met inclusion criteria. VO profiles were assessed on admission CT angiography using the Cortical Vein Opacification Score (COVES). Unfavorable VO was defined as COVES ≤ 2. Reperfusion hemorrhages on follow-up imaging were subdivided into no hemorrhage (noRH), hemorrhagic infarction (HI) and parenchymal hematoma (PH). Patients with PH and HI less frequently achieved good clinical outcomes defined as 90-day modified Rankin Scale scores of ≤ 2 (PH: 13.6% vs. HI: 24.6% vs. noRH: 44.1%; p < 0.001). The occurrence of HI and PH on follow-up imaging was more likely in patients with unfavorable compared to patients with favorable VO (HI: 25.1% vs. 17.4%, p = 0.023; PH: 18.3% vs. 8.5%; p = <0.001). In multivariable regression analyses, unfavorable VO increased the likelihood of PH (aOR: 1.84; 95% CI: 1.03-3.37, p = 0.044) and HI (aOR: 2.05; 95% CI: 1.25-3.43, p = 0.005), independent of age, sex, admission National Institutes Health Stroke Scale scores and arterial collateral status. We conclude that unfavorable VO was associated with the occurrence of HI and PH, both related to worse clinical outcomes.

Delayed CTP-Derived Deep Venous Outflow: A Novel Predictor of Striatocapsular Infarction after M1 Thrombectomy

BACKGROUND AND PURPOSE

Isolated striatocapsular infarction occurs commonly in patients with ischemic stroke following M1 thrombectomy. We aimed to explore the correlation between CTP-derived parameters of deep venous outflow at presentation and subsequent striatocapsular infarction in a retrospective cohort of such patients.

MATERIALS AND METHODS

TTP and peak enhancement were measured on CTP-derived time-attenuation curves of the internal cerebral and thalamostriate veins bilaterally. The difference in TTP (ΔTTP) and the relative decrease in venous enhancement between the ischemic and normal sides were calculated. NCCT performed 24 (SD, 12) hours postthrombectomy was used to determine tissue fate in the caudate head, caudate body, lentiform nucleus, and internal capsule. Striatocapsular ischemia (striatocapsular infarction-positive) was defined as infarction and striatocapsular injury as either infarction, contrast enhancement, or hemorrhagic transformation in ≥1 of these regions. A striatocapsular ischemia score was calculated (0 = no ischemic region, 1 = 1 ischemic region, 2 = ≥2 ischemic regions).

RESULTS

One hundred sixteen patients were included in the analysis. Sixty-one patients had striatocapsular infarction (striatocapsular infarction-positive). The mean thalamostriate ΔTTP was 1.95 (SD, 1.9) seconds for patients positive for striatocapsular infarction and 0.79 (SD, 2.1) for patients negative for it (P = .010). Results were similar for striatocapsular injury. The mean thalamostriate ΔTTP was 0.79 (SD, 2.1), 1.68 (SD, 1.4), and 2.05 (SD, 2) for striatocapsular infarction scores of 0, 1, and 2, respectively (P = .030).

CONCLUSIONS

CTP-derived thalamostriate ΔTTP is an excellent surrogate marker for striatocapsular infarction in patients post-M1 thrombectomy. The novel approach of extracting venous outflow parameters from CTP has numerous potential applications and should be further explored.

Cerebral venous outflow profiles are associated with the first pass effect in endovascular thrombectomy

BACKGROUND

Recent studies found that favorable venous outflow (VO) profiles are associated with higher reperfusion rates after mechanical thrombectomy (MT) in patients with acute ischemic stroke due to large vessel occlusion (AIS-LVO). Fewer retrieval attempts and first-pass revascularization during MT lead to better functional outcomes.

OBJECTIVE

To examine the hypothesis that favorable VO profiles assessed on baseline CT angiography (CTA) images correlate with successful vessel reperfusion after the first retrieval attempt and fewer retrieval attempts.

METHODS

A multicenter retrospective cohort study of patients with AIS-LVO treated by MT. Baseline CTA was used to determine the cortical vein opacification score (COVES). Favorable VO was defined as COVES ≥3. Primary outcomes were successful with excellent vessel reperfusion status, defined as Thrombolysis in Cerebral Infarction (TICI) 2b/3 and 2c/3 after first retrieval attempt.

RESULTS

617 patients were included in this study, of whom 205 (33.2%) had first pass reperfusion. In univariate analysis, ordinal COVES (p=0.011) values were significantly higher in patients with first pass than in those with non-first pass reperfusion, while the number of patients exhibiting favorable pial arterial collaterals using the Maas scale on CTA did not differ (p=0.243). In multivariable logistic regression analysis, higher COVES were independently associated with TICI 2b/3 (OR=1.25, 95% CI 1.1 to 1.42; p=0.001) and TICI 2c/3 (OR=1.2, 95% CI 1.04 to 1.36; p=0.011) reperfusion after one retrieval attempt, controlling for penumbra volume and time from symptom onset to vessel reperfusion.

CONCLUSIONS

Favorable VO, classified as higher COVES, is independently associated with successful and excellent first pass reperfusion in patients with AIS-LVO treated by endovascular thrombectomy.

Hypoperfusion Intensity Ratio Predicts Infarct Growth After Successful Thrombectomy for Distal Medium Vessel Occlusion

BACKGROUND AND PURPOSE

This study evaluated whether quantitative measurement of collaterals by the hypoperfusion intensity ratio (HIR) on baseline computed tomography perfusion (CTP) correlated with infarct growth and clinical outcome after successful endovascular recanalization of acute ischemic stroke (AIS) caused by primary distal medium vessel occlusions (DMVO).

METHODS

We performed a retrospective analysis of consecutive AIS patients who underwent an initial CTP and were successfully recanalized by thrombectomy (modified thrombolysis In cerebral infarction 2b or 3) for DMVO. We evaluated the association of baseline HIR with infarct growth and clinical outcome.

RESULTS

Between January 2018 and January 2021, 40 patients with an AIS caused by a DMVO were successfully recanalized by MT (65%, 26/40 female, median age 72 years, range 65-83 years). Baseline HIR was strongly correlated with infarct growth after successful recanalization (r = 0.501, p = 0.001). An HIR<0.3 was the optimal threshold for good collaterals using ROC analysis. Patients with HIR ≥ 0.3 had higher infarct growth compared to HIR < 0.3 (23.8 mL, IQR: 9.1-45.1 vs. 7.2 mL, interquartile range (IQR): 4.2-11.7, relative risk 7.9, p = 0.024 in multivariate analysis); their clinical outcome was poorer in univariate analysis (75%, 21/28 patients with a 3 months modified Rankin scale of 0-2 vs. 33%,4/12, p < 0.017, odds ratio (OR) 6.0, 1.37-26.20) but it did not remain significant in multivariate analysis (p = 0.107).

CONCLUSION

Good collaterals on initial CTP assessed by an HIR < 0.3 are associated with less infarct growth after successful recanalization of AIS caused by a DMVO.

Intravenous tPA (Tissue-Type Plasminogen Activator) Correlates With Favorable Venous Outflow Profiles in Acute Ischemic Stroke

BACKGROUND

Intravenous tPA (tissue-type plasminogen activator) is often administered before endovascular thrombectomy (EVT). Recent studies have questioned whether tPA is necessary given the high rates of arterial recanalization achieved by EVT, but whether tPA impacts venous outflow (VO) is unknown. We investigated whether tPA improves VO profiles on baseline computed tomography (CT) angiography (CTA) images before EVT.

METHODS

Retrospective multicenter cohort study of patients with acute ischemic stroke due to large vessel occlusion undergoing EVT triage. Included patients underwent CT, CTA, and CT perfusion before EVT. VO profiles were determined by opacification of the vein of Labbé, sphenoparietal sinus, and superficial middle cerebral vein on CTA as 0, not visible; 1, moderate opacification; and 2, full. Pial arterial collaterals were graded on CTA, and tissue-level collaterals were assessed on CT perfusion using the hypoperfusion intensity ratio. Clinical and demographic data were determined from the electronic medical record. Using multivariable regression analysis, we determined the correlation between tPA administration and favorable VO profiles.

RESULTS

Seven hundred seventeen patients met inclusion criteria. Three hundred sixty-five patients received tPA (tPA+), while 352 patients were not treated with tPA (tPA-). Fewer tPA+ patients had atrial fibrillation (n=128 [35%] versus n=156 [44%]; P=0.012) and anticoagulants/antiplatelet treatment before acute ischemic stroke due to large vessel occlusion onset (n=130 [36%] versus n=178 [52%]; P<0.001) compared with tPA- patients. One hundred eighty-five patients (51%) in the tPA+ and 100 patients (28%) in the tPA- group exhibited favorable VO (P<0.001). Multivariable regression analysis showed that tPA administration was a strong independent predictor of favorable VO profiles (OR, 2.6 [95% CI, 1.7-4.0]; P<0.001) after control for favorable pial arterial CTA collaterals, favorable tissue-level collaterals on CT perfusion, age, presentation National Institutes of Health Stroke Scale, antiplatelet/anticoagulant treatment, history of atrial fibrillation and time from symptom onset to imaging.

CONCLUSIONS

In patients with acute ischemic stroke due to large vessel occlusion undergoing thrombectomy triage, tPA administration was strongly associated with the presence of favorable VO profiles.

Favourable arterial, tissue-level and venous collaterals correlate with early neurological improvement after successful thrombectomy treatment of acute ischaemic stroke

BACKGROUND AND PURPOSE

Early neurological improvement (ENI) after thrombectomy is associated with better long-term outcomes in patients with acute ischaemic stroke due to large vessel occlusion (AIS-LVO). Whether cerebral collaterals influence the likelihood of ENI is poorly described. We hypothesised that favourable collateral perfusion at the arterial, tissue-level and venous outflow (VO) levels is associated with ENI after thrombectomy.

MATERIALS AND METHODS

Multicentre retrospective study of patients with AIS-LVO treated by thrombectomy. Tissue-level collaterals (TLC) were measured on cerebral perfusion studies by the hypoperfusion intensity ratio. VO and pial arterial collaterals (PAC) were determined by the Cortical Vein Opacification Score and the modified Tan scale on CT angiography, respectively. ENI was defined as improvement of ≥8 points or a National Institutes of Health Stroke Scale score of 0 hour or 1 24 hours after treatment. Multivariable regression analyses were used to determine the association of collateral biomarkers with ENI and good functional outcomes (modified Rankin Scale 0-2).

RESULTS

646 patients met inclusion criteria. Favourable PAC (OR: 1.9, CI 1.2 to 3.1; p=0.01), favourable VO (OR: 3.3, CI 2.1 to 5.1; p<0.001) and successful reperfusion (OR: 3.1, CI 1.7 to 5.8; p<0.001) were associated with ENI, but favourable TLC were not (p=0.431). Good functional outcomes at 90-days were associated with favourable TLC (OR: 2.2, CI 1.4 to 3.6; p=0.001), VO (OR: 5.7, CI 3.5 to 9.3; p<0.001) and ENI (OR: 5.7, CI 3.3 to 9.8; p<0.001), but not PAC status (p=0.647).

CONCLUSION

Favourable PAC and VO were associated with ENI after thrombectomy. Favourable TLC predicted longer term functional recovery after thrombectomy, but the impact of TLC on ENI is strongly dependent on vessel reperfusion.

Venous outflow profiles are associated with early edema progression in ischemic stroke

BACKGROUND

In patients with acute ischemic stroke due to large vessel occlusion (AIS-LVO), development of extensive early ischemic brain edema is associated with poor functional outcomes, despite timely treatment. Robust cortical venous outflow (VO) profiles correlate with favorable tissue perfusion. We hypothesized that favorable VO profiles (VO+) correlate with a reduced early edema progression rate (EPR) and good functional outcomes.

METHODS

Multicenter, retrospective analysis to investigate AIS-LVO patients treated by mechanical thrombectomy between May 2013 and December 2020. Baseline computed tomography angiography (CTA) was used to determine VO using the cortical vein opacification score (COVES); VO+ was defined as COVES ⩾ 3 and unfavorable as COVES ⩽ 2. EPR was determined as the ratio of net water uptake (NWU) on baseline non-contrast CT and time from symptom onset to admission imaging. Multivariable regression analysis was performed to assess primary (EPR) and secondary outcome (good functional outcomes defined as 0-2 points on the modified Rankin scale).

RESULTS

A total of 728 patients were included. Primary outcome analysis showed VO+ (β: -0.03, SE: 0.009, p = 0.002), lower presentation National Institutes of Health Stroke Scale (NIHSS; β: 0.002, SE: 0.001, p = 0.002), and decreased time from onset to admission imaging (β: -0.00002, SE: 0.00004, p < 0.001) were independently associated with reduced EPR. VO+ also predicted good functional outcomes (odds ratio (OR): 5.07, 95% CI: 2.839-9.039, p < 0.001), while controlling for presentation NIHSS, time from onset to imaging, general vessel reperfusion, baseline Alberta Stroke Program Early CT Score, infarct core volume, EPR, and favorable arterial collaterals.

CONCLUSIONS

Favorable VO profiles were associated with slower infarct edema progression and good long-term functional outcomes as well as better neurological status and ischemic brain alterations at admission.