The velocity of collateral filling predicts recanalization in acute ischemic stroke after intravenous thrombolysis

Visualization of both proximal M2-MCA segments in patients (the Tilted-V Sign) with acute M1-MCA occlusion stroke is associated with better procedural and prognostic outcomes

Introduction

We aimed to assess the clinical significance of M1-MCA occlusion with visualization of both MCA-M2 segments ["Tilted-V sign" (TVS)] on initial CT angiography (CTA) in patients with acute ischemic stroke (AIS) undergoing endovascular thrombectomy (EVT).

Methods

Data for patients with consecutive AIS undergoing EVT for large vessel occlusion (LVO) in two academic centers are recorded in ongoing databases. Patients who underwent EVT for M1-MCA occlusions ≤ 6 h from symptom onset were included in this retrospective analysis.

Results

A total of 346 patients met the inclusion criteria; 189 (55%) had positive TVS. Patients with positive TVS were younger (68 ± 14 vs. 71 ± 14 years, P = 0.028), with similar rates of vascular risk factors and baseline modified Rankin scores (mRS) 0-2. The rates of achieving thrombolysis in cerebral ischemia (TICI) 2b-3 were similar to the two groups (79%), although successful first-pass recanalization was more common with TVS (64 vs. 36%, p = 0.01). On multivariate analysis, higher collateral score [odds ratio (OR) 1.38 per unit increase, p = 0.008] and lower age (OR 0.98 per year increase, p = 0.046) were significant predictors of TVS. Patients with positive TVS had higher post-procedural Alberta Stroke Program Early CT Score (ASPECTS; 6.9 ± 2.2 vs. 5.2 ± 2.3, p = 0.001), were discharged with lower National Institutes of Health Stroke Score (NIHSS; 6±6 vs. 9±7, p = 0.003) and higher rates of mRS 0-2 (29.5 vs. 12%, p = 0.001), and had lower rates of 90-day mortality (13.2 vs. 21.6%, p = 0.038). However, TVS was not an independent predictor of functional independence (OR 2.51; 95% CI 0.7-8.3).

Conclusion

Tilted-V Sign, an easily identifiable radiological marker, is associated with fewer recanalization attempts, better functional outcomes, and reduced mortality.

Prediction of Early Recanalization after Intravenous Thrombolysis in Patients with Large-Vessel Occlusion

Background and Purpose

We aimed to develop a model predicting early recanalization after intravenous tissue plasminogen activator (t-PA) treatment in large-vessel occlusion.

Methods

Using data from two different multicenter prospective cohorts, we determined the factors associated with early recanalization immediately after t-PA in stroke patients with large-vessel occlusion, and developed and validated a prediction model for early recanalization. Clot volume was semiautomatically measured on thin-section computed tomography using software, and the degree of collaterals was determined using the Tan score. Follow-up angiographic studies were performed immediately after t-PA treatment to assess early recanalization.

Results

Early recanalization, assessed 61.0±44.7 minutes after t-PA bolus, was achieved in 15.5% (15/97) in the derivation cohort and in 10.5% (8/76) in the validation cohort. Clot volume (odds ratio [OR], 0.979; 95% confidence interval [CI], 0.961 to 0.997; P=0.020) and good collaterals (OR, 6.129; 95% CI, 1.592 to 23.594; P=0.008) were significant factors associated with early recanalization. The area under the curve (AUC) of the model including clot volume was 0.819 (95% CI, 0.720 to 0.917) and 0.842 (95% CI, 0.746 to 0.938) in the derivation and validation cohorts, respectively. The AUC improved when good collaterals were added (derivation cohort: AUC, 0.876; 95% CI, 0.802 to 0.950; P=0.164; validation cohort: AUC, 0.949; 95% CI, 0.886 to 1.000; P=0.036). The integrated discrimination improvement also showed significantly improved prediction (0.097; 95% CI, 0.009 to 0.185; P=0.032).

Conclusions

The model using clot volume and collaterals predicted early recanalization after intravenous t-PA and had a high performance. This model may aid in determining the recanalization treatment strategy in stroke patients with large-vessel occlusion.

Cerebral collaterals in acute ischaemia: Implications for acute ischaemic stroke patients receiving reperfusion therapy

The cerebral collaterals play an important role in penumbral tissue sustenance after an acute ischaemic stroke. Recent studies have demonstrated the potential role of collaterals in the selection of acute ischaemic stroke patients eligible for reperfusion therapy. However, the understanding of the significance and evidence around the role of collateral status in predicting outcomes in acute ischaemic stroke patients treated with reperfusion therapy is still unclear. Moreover, the use of pre-treatment collaterals in patient selection and prognosis is relatively underappreciated in clinical settings. A focused review of the literature was performed on the various methods of collateral evaluation and the role of collateral status in acute ischaemic stroke patients receiving reperfusion therapy. We discuss the methods of evaluating pre-treatment collaterals in clinical settings. The patient selection based on collateral status as well as the prognostic and therapeutic value of collaterals in acute ischaemic stroke, in settings of intravenous thrombolysis or endovascular therapy alone, and bridge therapy, are summarized. Recommendations for future research and possible pharmacological intervention strategies aimed at collateral enhancement are also discussed. Collaterals may play an important role in identifying acute ischaemic stroke patients who are likely to benefit from endovascular treatment in an extended time window. Future neuroscientific efforts to better improve our understanding of the role of collaterals in acute ischaemia as well as clinical studies to delineate its role in patient selection and acute stroke prognosis are warranted.

Relationships between brain perfusion and early recanalization after intravenous thrombolysis for acute stroke with large vessel occlusion

In large vessel occlusion (LVO) stroke, it is unclear whether severity of ischemia is involved in early post-thrombolysis recanalization over and above thrombus site and length. Here we assessed the relationships between perfusion parameters and early recanalization following intravenous thrombolysis administration in LVO patients. From a multicenter registry, we identified 218 thrombolysed LVO patients referred for thrombectomy with both (i) pre-thrombolysis MRI, including diffusion-weighted imaging (DWI), T2*-imaging, MR-angiography and dynamic susceptibility-contrast perfusion-weighted imaging (PWI); and (ii) evaluation of recanalization on first angiographic run or non-invasive imaging ≤ 3 h from thrombolysis start. Infarct core volume on DWI, PWI-DWI mismatch volume and hypoperfusion intensity ratio (HIR; defined as Tmax ≥ 10 s volume/ Tmax ≥ 6 s volume, low HIR indicating milder hypoperfusion) were determined using a commercially available software. Early recanalization occurred in 34 (16%) patients, and multivariable analysis was associated with lower HIR (P = 0.006), shorter thrombus on T2*-imaging (P < 0.001) and more distal occlusion (P = 0.006). However, the relationship between HIR and early recanalization was robust only for thrombus length <14 mm. In summary, the present study disclosed an association between lower HIR and early post-thrombolysis recanalization. Early post-thrombolysis recanalization is therefore determined not only by thrombus site and length but also by severity of ischemia.

Better Collaterals Are Independently Associated With Post-Thrombolysis Recanalization Before Thrombectomy

Background and Purpose—

In acute stroke patients with large vessel occlusion, the goal of intravenous thrombolysis (IVT) is to achieve early recanalization (ER). Apart from occlusion site and thrombus length, predictors of early post-IVT recanalization are poorly known. Better collaterals might also facilitate ER, for instance, by improving delivery of the thrombolytic agent to both ends of the thrombus. In this proof-of-concept study, we tested the hypothesis that good collaterals independently predict post-IVT recanalization before thrombectomy.

Methods—

Patients from the registries of 6 French stroke centers with the following criteria were included: (1) acute stroke with large vessel occlusion treated with IVT and referred for thrombectomy between May 2015 and March 2017; (2) pre-IVT brain magnetic resonance imaging, including diffusion-weighted imaging, T2*, MR angiography, and dynamic susceptibility contrast perfusion-weighted imaging; and (3) ER evaluated ≤3 hours from IVT start on either first angiographic run or noninvasive imaging. A collateral flow map derived from perfusion-weighted imaging source data was automatically generated, replicating a previously validated method. Thrombus length was measured on T2*-based susceptibility vessel sign.

Results—

Of 224 eligible patients, 37 (16%) experienced ER. ER occurred in 10 of 83 (12%), 17 of 116 (15%), and 10 of 25 (40%) patients with poor/moderate, good, and excellent collaterals, respectively. In multivariable analysis, better collaterals were independently associated with ER ( P =0.029), together with shorter thrombus ( P <0.001) and more distal occlusion site ( P =0.010).

Conclusions—

In our sample of patients with stroke imaged with perfusion-weighted imaging before IVT and intended for thrombectomy, better collaterals were independently associated with post-IVT recanalization, supporting our hypothesis. These findings strengthen the idea that advanced imaging may play a key role for personalized medicine in identifying patients with large vessel occlusion most likely to benefit from IVT in the thrombectomy era.

Acute reperfusion without recanalization: Serial assessment of collaterals within 6 h of using perfusion-weighted magnetic resonance imaging

Acute reperfusion despite persistent arterial occlusion may occur in up to 30% of ischemic stroke patients. Recruitment of leptomeningeal collaterals may explain this phenomenon. Using dynamic susceptibility-contrast perfusion imaging (DSC-PI), we assessed acute changes in collateral flow among patients without recanalization. From a multicenter prospective database (I-KNOW), 46 patients with magnetic resonance angiography visible occlusion in whom both reperfusion and recanalization were assessed within 6 h of onset were identified. Maps of collateral flow at arterial, capillary and late venous phases were generated from DSC-PI through inter-frame registration, baseline signal subtraction and temporal summation, and graded blind to all other relevant clinical and radiological data using the Higashida scale. Flow direction and the acute evolution of collaterals were evaluated against the reperfusion status. Among patients without recanalization ( n = 33), flow direction remained retrograde. Collateral grades significantly improved between admission and acute follow-up in patients who reperfused (OR: 4.57; 95% CI: 1.1-22.7; p = 0.048), but not in those without reperfusion (OR: 1.34; 95% CI: 0.4-4.5; p = 0.623). Our study confirmed that acute reperfusion without recanalization is associated with a significant improvement of retrograde collateral flow. DSC-PI can detect acute changes in collateral flow, and may help evaluate novel treatments targeting leptomeningeal collaterals.

Slow Collateral Flow Is Associated with Thrombus Extension in Patients with Acute Large-Artery Occlusion

BACKGROUND AND PURPOSE

It is still poorly understood about the dynamic changes of the thrombus after intravenous thrombolysis and how the remaining thrombus affects clinical outcome in human stroke. Collateral flow was assumed to help to deliver endo/exogenous tissue-type plasminogen activator to the clot. We aimed to analyze the impact of collateral flow on the dynamic changes of the thrombus in patients with acute large-artery occlusion who received intravenous thrombolysis.

MATERIALS AND METHODS

We reviewed consecutive patients with acute ischemic stroke with M1 segment or distal internal carotid artery occlusion who underwent multimodal MR imaging or CT perfusion before and 24 hours after intravenous thrombolysis without recanalization. Patients were divided into 3 groups (thrombus extension, shortening, and no change) according to thrombus-length change between baseline and 24 hours. Collateral flow was measured with arrival time delay and the collateral scoring system. Poor outcome was defined as a 3-month modified Rankin Scale score of ≥3.

RESULTS

Among 51 patients, 18 (35.3%) had thrombus extension, 14 (27%) had thrombus shortening, and 19 (37.3%) had thrombus without change. Arrival time delay was independently associated with thrombus extension (OR = 1.499; 95% CI, 1.053-2.135; P = .025). Similarly, the collateral score on the peak artery phase was independently associated with thrombus extension (OR = 0.456; 95% CI, 0.211-0.984; P = .045), whereas baseline National Institutes of Health Stroke Scale score (OR = 0.768; 95% CI, 0.614-0.961; P = .021) and baseline thrombus length (OR = 1.193; 95% CI, 1.021-1.394; P = .026) were associated with thrombus shortening. All patients with thrombus extension had poor outcomes.

CONCLUSIONS

Slow collateral flow was related to thrombus extension in patients with large-artery occlusion without recanalization after intravenous thrombolysis.

Temporal remodeling of pial collaterals and functional deficits in a murine model of ischemic stroke

BACKGROUND

Leptomeningeal anastomoses play a critical role in regulating reperfusion following cerebrovascular obstruction; however, methods to evaluate their temporospatial remodeling remains under investigation.

NEW METHOD

We combined arteriole-specific vessel painting with histological evaluation to assess the density and diameter of inter-collateral vessels between the middle cerebral artery and anterior cerebral artery (MCA-ACA) or posterior cerebral artery (MCA-PCA) in a murine model of permanent middle cerebral artery occlusion (pMCAO).

RESULTS

While the overall density was not influenced by pMCAO, the size of MCA-ACA and MCA-PCA vessels had significantly increased 2days post-pMCAO and peaked by 4days compared to the un-injured hemisphere. Using a combination of vessel painting and immunofluorescence, we uniquely observed an induction of cellular division and a remodeling of the smooth muscle cells within the collateral niche following post-pMCAO on whole mount tissue sections. Vessel painting was also applied to pMCAO-injured Cx3cr1GFP mice, in order to identify the spatial relationship between Cx3cr1-positive peripheral-derived monocyte/macrophages and the vessel painted collaterals. Our histological findings were supplemented with analysis of cerebral blood flow using laser Doppler imaging and behavioral changes following pMCAO.

COMPARISON WITH EXISTING METHODS

Compared to polyurethane and latex methods for collateral labeling, this new method provides detailed cell-type specific analysis within the collateral niche at the microscopic level, which has previously been unavailable.

CONCLUSIONS

This simple and reproducible combination of techniques is the first to dissect the temporospatial remodeling of pial collateral arterioles. The method will advance investigations into the underlying mechanisms governing the intricate processes of arteriogenesis.

Improving Cerebral Blood Flow after Arterial Recanalization: A Novel Therapeutic Strategy in Stroke

Ischemic stroke is caused by a disruption in blood supply to a region of the brain. It induces dysfunction of brain cells and networks, resulting in sudden neurological deficits. The cause of stroke is vascular, but the consequences are neurological. Decades of research have focused on finding new strategies to reduce the neural damage after cerebral ischemia. However, despite the incredibly huge investment, all strategies targeting neuroprotection have failed to demonstrate clinical efficacy. Today, treatment for stroke consists of dealing with the cause, attempting to remove the occluding blood clot and recanalize the vessel. However, clinical evidence suggests that the beneficial effect of post-stroke recanalization may be hampered by the occurrence of microvascular reperfusion failure. In short: recanalization is not synonymous with reperfusion. Today, clinicians are confronted with several challenges in acute stroke therapy, even after successful recanalization: (1) induce reperfusion, (2) avoid hemorrhagic transformation (HT), and (3) avoid early or late vascular reocclusion. All these parameters impact the restoration of cerebral blood flow after stroke. Recent advances in understanding the molecular consequences of recanalization and reperfusion may lead to innovative therapeutic strategies for improving reperfusion after stroke. In this review, we will highlight the importance of restoring normal cerebral blood flow after stroke and outline molecular mechanisms involved in blood flow regulation.

Impact of collateral circulation status on favorable outcomes in thrombolysis treatment: A systematic review and meta-analysis

Collateral circulation affects the prognosis of patients with acute ischemic stroke (AIS) treated by thrombolysis. The present study performed a systematic assessment of the impact of the collateral circulation status on the outcomes of patients receiving thrombolysis treatment. Relevant full-text articles from the Cochrane Library, Ovid, Medline, Embase and PubMed databases published from January 1, 2000 to November 1, 2016 were retrieved. The quality of the studies was assessed and data were extracted by 2 independent investigators. The random-effects model was used to estimate the impact of good vs. poor collateral circulation, as well as baseline characteristics, on the outcome within the series presented as risk ratios. Subgroup analyses explored the potential factors that may interfere with the effects of the collateral circulation status on the outcome. A total of 29 studies comprising 4,053 patients were included in the present meta-analysis. A good collateral circulation status was revealed to have a beneficial effect on favorable functional outcome (modified Rankin scale, 0–3 at 3–6 months; P<0.001) and a higher rate of recanalization (P<0.001) compared with poor collateral circulation. Good collateral circulation was also associated with a lower rate of symptomatic intracranial hemorrhage (P<0.01), a lower rate of mortality (P<0.01) and a smaller infarct size (P<0.01). In conclusion, good collateral circulation was demonstrated to have a favorable prognostic value regarding the outcome for patients with AIS receiving thrombolysis treatment. Assessment of collateral circulation and penumbra area during pre-treatment imaging within an appropriate time-window prior to thrombolytic therapy will therefore improve the identification of AIS patients who may benefit from thrombolysis treatment.

Desmoteplase for Acute Ischemic Stroke within 3 to 9 Hours after Symptom Onset: Evidence from Randomized Controlled Trials

Recent studies have shown inconsistent results regarding the value of desmoteplase for treating acute ischemic stroke (AIS) when administered within an extended time window. We performed a meta-analysis to explore the value of desmoteplase in AIS treatment. The MEDLINE, EMBASE, and Cochrane Library databases were searched for randomized controlled trials (RCTs) that had evaluated desmoteplase versus placebo for AIS. The primary outcomes were intracranial hemorrhage (ICH) within 72 hours and favorable outcome at Day 90. We pooled 819 patients from 5 RCTs. Desmoteplase treatment showed a neutral effect on favorable outcome (P = 0.42) but a favorable safety profile in terms of ICH (P = 0.64) compared with the placebo group. In the subgroup analysis, 90 μg/kg desmoteplase, a late time to treatment (6–9 hours), and serious stroke symptoms at baseline (NIHSS > 12) subgroups showed high risks of ICH (P ≤ 0.02). A high dose of desmoteplase (125 μg/kg) showed a tendency to improve recanalization (P = 0.05), but was also associated with an increased risk of death (P = 0.04). In conclusion, desmoteplase administered over an extended time window had no significant effect on functional recovery but exhibited a favorable safety profile in patients with AIS.