Effect of thrombus size on recanalization by bridging intravenous thrombolysis

Effect of Intravenous Thrombolysis Prior to Mechanical Thrombectomy According to the Location of M1 Occlusion

BACKGROUND AND PURPOSE

The additive effects of intravenous thrombolysis (IVT) before mechanical thrombectomy (MT) remain unclear. We aimed to investigate the efficacy and safety of IVT prior to MT depending on the location of M1 occlusion.

METHODS

We reviewed the cases of patients who underwent MT for emergent large-vessel occlusion of the M1 segment. Baseline characteristics as well as clinical and periprocedural variables were compared according to the location of M1 occlusion (i.e., proximal and distal M1 occlusion). The main outcome was the achievement of functional independence (modified Rankin Scale score, 0-2) at 3 months after stroke. The main outcomes were compared between the proximal and distal groups based on the use of IVT before MT.

RESULTS

Among 271 patients (proximal occlusion, 44.6%; distal occlusion, 55.4%), 33.9% (41/121) with proximal occlusion and 24.7% (37/150) with distal occlusion underwent IVT prior to MT. Largeartery atherosclerosis was more common in patients with proximal M1 occlusion; cardioembolism was more common in those with distal M1 occlusion. In patients with proximal M1 occlusion, there was no association between IVT before MT and functional independence. In contrast, there was a significant association between the use of IVT prior to MT (odds ratio=5.30, 95% confidence interval=1.56-18.05, P=0.007) and functional independence in patients with distal M1 occlusion.

CONCLUSION

IVT before MT was associated with improved functional outcomes in patients with M1 occlusion, especially in those with distal M1 occlusion but not in those with proximal M1 occlusion.

Direct Mechanical Thrombectomy Versus Prior Bridging Intravenous Thrombolysis in Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

BACKGROUND

The current guideline recommends using an intravenous tissue-type plasminogen activator (IV tPA) prior to mechanical thrombectomy (MT) in eligible acute ischemic stroke (AIS) with emergent large vessel occlusion (ELVO). Some recent studies found no significant differences in the long-term functional outcomes between bridging therapy (BT, i.e., IV tPA prior to MT) and direct MT (dMT).

METHODS

We conducted a systematic review and meta-analysis to compare the safety and functional outcomes between BT and dMT in AIS patients with ELVO who were eligible for IV tPA administration. Based on the ELVO location, patients were categorized as the anterior group (occlusion of the anterior circulation), or the combined group (occlusion of the anterior and/or posterior circulation). A subgroup analysis was performed based on the study type, i.e., RCT and non-RCT.

RESULTS

Thirteen studies (3985 patients) matched the eligibility criteria. Comparing the BT and dMT groups, no significant differences in terms of mortality and good functional outcome were observed at 90 days. Symptomatic intracranial hemorrhagic (sICH) events were more frequent in BT patients in the combined group (OR = 0.73, p = 0.02); this result remained significant only in the non-RCT subgroup (OR = 0.67, p = 0.03). The RCT subgroup had a significantly higher rate of successful revascularization in BT patients (OR = 0.73, p = 0.02).

CONCLUSIONS

Our meta-analysis uncovered no significant differences in functional outcome and mortality rate at 90 days between dMT and BT in patients with AIS who had ELVO. Although BT performed better in terms of successful recanalization rate, there is a risk of increased sICH rate in this group.

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.

Early recanalization in large-vessel occlusion stroke patients transferred for endovascular treatment

Background

We performed an exploratory analysis to identify patient and thrombus characteristics associated with early recanalization in large-vessel occlusion (LVO) stroke patients transferred for endovascular treatment (EVT) from a primary (PSC) to a comprehensive stroke center (CSC).

Methods

We included patients with an LVO stroke of the anterior circulation who were transferred to our hospital for EVT and underwent repeated imaging between January 2016 and June 2019. We compared patient characteristics, workflow time metrics, functional outcome (modified Rankin Scale at 90 days), and baseline thrombus imaging characteristics, which included: occlusion location, thrombus length, attenuation, perviousness, distance from terminus of intracranial carotid artery to the thrombus (DT), and clot burden score (CBS), between early-recanalized LVO (ER-LVO), and non-early-recanalized LVO (NER-LVO) patients.

Results

One hundred and forty-nine patients were included in the analysis. Early recanalization occurred in 32% of patients. ER-LVO patients less often had a medical history of hypertension (31% vs 49%, P=0.04), and more often had clinical improvement between PSC and CSC (ΔNIHSS −5 vs 3, P<0.01), compared with NER-LVO patients. Thrombolysis administration was similar in both groups (88% vs 78%, P=0.18). ER-LVO patients had no ICA occlusions (0% vs 27%, P<0.01), more often an M2 occlusion (35% vs 17%, P=0.01), longer DT (27 mm vs 12 mm, P<0.01), shorter thrombi (17 mm vs 27 mm, P<0.01), and higher CBS (8 vs 6, P<0.01) at baseline imaging. ER-LVO patients had lower mRS scores (1 vs 3, P=0.02).

Conclusions

Early recanalization is associated with clinical improvement between PSC and CSC admission, more distal occlusions and shorter thrombi at baseline imaging, and better functional outcome.

Large Vessel Occlusion Secondary to COVID-19 Hypercoagulability in a Young Patient: A Case Report and Literature Review

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) initially most appreciated for its pulmonary symptoms, is now increasingly recognized for causing multi-organ disease and stroke in the setting of a hypercoagulable state. We report a case of 33-year-old African American woman with COVID-19 who developed acute malignant middle cerebral artery infarction due to thromboembolic occlusion of the left terminal internal carotid artery and middle cerebral artery stem. Mechanical thrombectomy was challenging and ultimately unsuccessful resulting in limited reperfusion of <67% of the affected vascular territory, and thrombectomized clot was over 50 mm in length, at least three times the average clot length. The final stroke size was estimated at 224 cubic centimeters. On admission her D-dimer level was 94,589 ng/mL (normal 0-500 ng/ml). Throughout the hospitalization D-dimer decreased but never reached normal values while fibrinogen trended upward. Hypercoagulability panel was remarkable for mildly elevated anticardiolipin IgM of 16.3 MPL/mL (normal: 0-11.0 MPL/mL). With respect to remaining stroke workup, there was no evidence of clinically significant stenosis or dissection in the proximal internal carotid artery or significant cardioembolic source including cardiomyopathy, atrial fibrillation, cardiac thrombus, cardiac tumor, valvular abnormality, aortic arch atheroma, or patent foramen ovale. She developed malignant cytotoxic cerebral edema and succumbed to complications. This case underscores the importance of recognizing hypercoagulability as a cause of severe stroke and poor outcome in young patients with COVID-19 and highlights the need for further studies to define correlation between markers of coagulopathy in patients with COVID-19 infection and outcome post stroke.

Differences in Pathological Composition Among Large Artery Occlusion Cerebral Thrombi, Valvular Heart Disease Atrial Thrombi and Carotid Endarterectomy Plaques

Background and Purpose: Acute ischemic stroke (AIS) with large artery occlusion (LAO) may lead to severe disability or death if not promptly treated. To determine the source of cerebral artery occlusion thrombosis, we studied the pathological components of cerebral artery thrombosis with different etiological classifications to guide clinical formulation of preventive treatment.

Materials and Methods: Eighty-eight thrombi from AIS patients with LAO, 12 atrial thrombi from patients with valvular heart disease (VHD), and 11 plaques obtained by carotid endarterectomy (CEA) from patients with carotid artery stenosis were included in this retrospective study. The hematoxylin and eosin–stained specimens were quantitatively analyzed for erythrocytes, white blood cells (WBCs) and fibrin; platelets were shown by immunohistochemistry for CD31.

Results: The thrombi of VHD showed the highest percentage of fibrin, followed by those of cardioembolism (CE) and stroke of undetermined etiology (SUE), and these values were higher than those of the other groups. Plaques obtained by CEA showed the highest erythrocyte number, followed by the large artery atherosclerosis (LAA) thrombi, and showed significantly noticeable differences between other stroke subtypes. The proportions of fibrin and erythrocytes in the thrombi of CE and SUE were most similar to those in the thrombi of VHD, and the LAA thrombi were the closest to those obtained by CEA. CE thrombi and CEA plaques had a higher percentage of WBCs than thrombi of other stroke thrombus subtypes and VHD.

Conclusions: CE and most cryptogenic thrombi may originate from the heart, and the formation of carotid atherosclerotic plaques may be related to atherosclerotic cerebral embolism. Inflammation may be involved in their formation.

Intravenous r-tPA Dose Influence on Outcome after Middle Cerebral Artery Ischemic Stroke Treatment by Mechanical Thrombectomy

Background and Objectives: Pretreatment with intravenous thrombolysis (IVT) is still recommended in all eligible acute ischemic stroke patients with large-vessel occlusion before mechanical thrombectomy (MTE). However, the added value and safety of bridging therapy versus direct MTE remains controversial. We aimed at evaluating the influence of r-tPA dose level in patients with middle cerebral artery (MCA) occlusion treated with MTE. Materials and Methods: We prospectively compared clinical and radiological outcomes in 38 bridging patients, with 65 receiving direct MTE for MCA stroke admitted to Vilnius University Hospital Santaros Clinics. Following our protocol, r-tPA infusion was stopped just before MTE in the operating room. Therefore, we divided all bridging patients into three groups according to the amount of r-tPA they received: bolus, partial dose or full dose. Functional independence at 90 days was assessed by a modified Rankin Scale score, i.e., from 0–2. The safety outcomes included 90-day mortality and any intracerebral hemorrhage (ICH). Results: Baseline characteristics and functional outcome at 90 days did not differ between the bridging and direct MTE groups. Shorter MTE procedure and hospitalization time (p = 0.025 and p = 0.036, respectively) were observed in the direct MTE group. An IVT treatment subgroup analysis showed higher rates of symptomatic ICH (p < 0.001) and longer intervals between imaging to MTE (p = 0.005) in the full r-tPA dose group. Conclusions: In patients with an MCA stroke, direct MTE seems to be a safe and equally effective as bridging therapy. The optimal r-tPA dose remains unclear. Randomized trials are needed to accurately evaluate the added value of r-tPA in patients treated with MTE.

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.

Value of thrombus imaging in predicting the outcomes of patients with large-vessel occlusive strokes after endovascular therapy

BACKGROUND

Acute ischemic stroke leads to serious long-term disability and high mortality, especially in patients with large-vessel occlusive strokes. Nowadays, endovascular therapy is considered as an alternative treatment for these patients. Several studies have used thrombus characteristics based on non-contrast computed tomography (NCCT) and computed tomography angiography (CTA) to predict prognosis in ischemic stroke. We conducted a systematic review to identify potential imaging predictive factors for successful recanalization and improved clinical outcome after endovascular therapy in patients with large-vessel occlusion (LVO) in anterior arterial circulation.

METHODS

The PubMed databases were searched for related studies reported between September 18, 2009, and September 18, 2019.

RESULTS

We selected 11 studies on revascularization and 12 studies on clinical outcome. Patients with thrombus of higher Hounsfield unit (HU), shorter length, higher clot burden score, and increased thrombus permeability may achieve higher recanalization and improved clinical outcome, but the matter is still under debate.

CONCLUSION

Imaging of thrombus can be used as an aseessment tool to predict the outcomes and it needs further studies in the future.

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.

Characterization of clot composition in acute cerebral infarct using machine learning techniques

Objective

Clot characteristics can provide information on the cause of cerebral artery occlusion and may guide acute revascularization and secondary prevention strategies. We developed a rapid automated clot analysis system using machine learning (ML) and validated its accuracy in patients undergoing endovascular treatment.

Methods

Pre‐endovascular treatment gradient echo (GRE) images from consecutive patients with middle cerebral artery occlusion were utilized to develop and validate an ML system to predict whether atrial fibrillation (AF) was the underlying cause of ischemic stroke. The accuracy of the ML algorithm was compared with that of visual inspection by neuroimaging specialists for the presence of blooming artifact. Endovascular procedures and outcomes were compared in patients with and without AF.

Results

Of 67 patients, 29 (43.3%) had AF. Of these, 13 had known AF and 16 were newly diagnosed with cardiac monitoring. By visual inspection, interrater correlation for blooming artifact was 0.73 and sensitivity and specificity for AF were 0.79 and 0.63, respectively. For AF classification, the ML algorithms yielded an average accuracy of > 75.4% in fivefold cross‐validation with clot signal profiles obtained from 52 patients and an area under the curve >0.87 for the average AF probability from five signal profiles in external validation (n = 15). Analysis with an in‐house interface took approximately 3 min per patient. Absence of AF was associated with increased number of passes by stentriever, high reocclusion frequency, and additional use of rescue stenting and/or glycogen IIb/IIIa blocker for recanalization.

Interpretation

ML‐based rapid clot analysis is feasible and can identify AF with high accuracy, enabling selection of endovascular treatment strategy.

Thrombectomy or intravenous thrombolysis in patients with NIHSS of 5 or less?

BACKGROUND AND PURPOSE

To compare outcomes of minor stroke patients with intracranial vessel occlusions (IVO) underwent mechanical thrombectomy (MT) versus those treated with intravenous thrombolysis alone (IVT).

METHODS

We retrospectively reviewed two large prospective stroke databases from two European centers searching for patients admitted with minor stroke (i.e. NIHSS Score░≤░5), baseline mRS░=░0 and occlusion of the M1-M2 segment of the middle cerebral artery (MCA). Groups receiving (A) IVT alone and (B) MT+/-IVT were compared. Primary outcome measures were MT safety, successful recanalization rate (mTICI 2b-3) and NIHSS shift (discharge NIHSS minus admission NIHSS); secondary outcomes included discharge rates and excellent outcome (mRS 0-1) at 3 months. Univariate and multivariate analyses were performed.

RESULTS

Thirty-two patients were enrolled in Group B (19░MT alone; 13 MT░+░IVT) and 24 in Group A. Successful recanalization (mTICI 2b-3) was obtained in 100% of cases in Group B vs 38% in Group A. Symptomatic hemorrhagic transformation rate did not differ between the two groups. Multivariate analysis reported MT as the only predictor of early (<░12░h) favorable NIHSS shift and lower NIHSS at discharge. Moreover, discharge at home and excellent outcome at 3-month follow-up were statistically associated with MT.

CONCLUSIONS

MT in patients with minor strokes and intracranial vessel occlusion (IVO) is safe and can determine a rapid improvement of NIHSS Score. MT seems also associated with a higher rate of patients discharged at home after hospitalization and better clinical outcome at 3-month follow-up. Larger randomized trials are warranted to confirm these results.

Post-Thrombolysis Recanalization in Stroke Referrals for Thrombectomy

Background and Purpose—

Whether all acute stroke patients with large vessel occlusion need to undergo intravenous thrombolysis before mechanical thrombectomy (MT) is debated as (1) the incidence of post-thrombolysis early recanalization (ER) is still unclear; (2) thrombolysis may be harmful in patients unlikely to recanalize; and, conversely, (3) transfer for MT may be unnecessary in patients highly likely to recanalize. Here, we determined the incidence and predictors of post-thrombolysis ER in patients referred for MT and derive ER prediction scores for trial design.

Methods—

Registries from 4 MT-capable centers gathering patients referred for MT and thrombolyzed either on site (mothership) or in a non MT-capable center (drip-and-ship) after magnetic resonance– or computed tomography–based imaging between 2015 and 2017. ER was identified on either first angiographic run or noninvasive imaging. In the magnetic resonance imaging subsample, thrombus length was determined on T2*-based susceptibility vessel sign. Independent predictors of no-ER were identified using multivariable logistic regression models, and scores were developed according to the magnitude of regression coefficients. Similar registries from 4 additional MT-capable centers were used as validation cohort.

Results—

In the derivation cohort (N=633), ER incidence was ≈20%. In patients with susceptibility vessel sign (n=498), no-ER was independently predicted by long thrombus, proximal occlusion, and mothership paradigm. A 6-point score derived from these variables showed strong discriminative power for no-ER (C statistic, 0.854) and was replicated in the validation cohort (n=353; C statistic, 0.888). A second score derived from the whole sample (including negative T2* or computed tomography–based imaging) also showed good discriminative power and was similarly validated. Highest grades on both scores predicted no-ER with >90% specificity, whereas low grades did not reliably predict ER.

Conclusions—

The substantial ER rate underlines the benefits derived from thrombolysis in bridging populations. Both prediction scores afforded high specificity for no-ER, but not for ER, which has implications for trial design.

Direct mechanical thrombectomy in tPA-ineligible and -eligible patients versus the bridging approach: a meta-analysis

Background

Whether pretreatment with intravenous thrombolysis prior to mechanical thrombectomy (IVT+MTE) adds additional benefit over direct mechanical thrombectomy (dMTE) in patients with large vessel occlusions (LVO) is a matter of debate.

Methods

This study-level meta-analysis was presented in accord with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Pooled effect sizes were calculated using the inverse variance heterogeneity model and displayed as summary Odds Ratio (sOR) and corresponding 95% confidence interval (95% CI). Sensitivity analysis was performed by distinguishing between studies including dMTE patients eligible for IVT (IVT-E) or ineligible for IVT (IVT-IN). Primary outcome measures were functional independence (modified Rankin Scale≤2) and mortality at day 90, successful reperfusion, and symptomatic intracerebral hemorrhage.

Results

Twenty studies, incorporating 5279 patients, were included. There was no evidence that rates of successful reperfusion differed in dMTE and IVT+MTE patients (sOR 0.93, 95% CI 0.68 to 1.28). In studies including IVT-IN dMTE patients, patients undergoing dMTE tended to have lower rates of functional independence and had higher odds for a fatal outcome as compared with IVT+MTE patients (sOR 0.78, 95% CI 0.61 to 1.01 and sOR 1.45, 95% CI 1.22 to 1.73). However, no such treatment group effect was found when analyses were confined to cohorts with a lower risk of selection bias (including IVT-E dMTE patients).

Conclusion

The quality of evidence regarding the relative merits of IVT+MTE versus dMTE is low. When considering studies with lower selection bias, the data suggest that dMTE may offer comparable safety and efficacy as compared with IVT+MTE. The conduct of randomized-controlled clinical trials seems justified.

Mechanical thrombectomy in MCA-mainstem occlusion in patients with low NIHSS scores

Introduction While effectiveness of mechanical thrombectomy (MTE) in M1 segment occlusion is approved for patients with severe impairment, there is a lack of evidence for a potential benefit of MTE in patients with minor to moderate symptoms. The purpose of this study was to evaluate neurological outcome and occurrence of periprocedural complications after MTE in patients with low National Institutes of Health Stroke Scale (NIHSS) scores. Materials and methods A retrospective analysis of 1081 consecutive patients with anterior circulation ischemic stroke due to M1 occlusion detected by computed tomography angiography and treated with MTE at our hospital between February 2012 and November 2017 was performed. NIHSS, Barthel Index (BI) and modified Rankin Scale (mRS) scores between admission and discharge were compared with paired Mann-Whitney test, and recanalization rate and complications were assessed in patients with NIHSS ≤ 5 at admission. Results Thirty patients were included with a median NIHSS score of 4. NIHSS score (median: 4 vs. 1; p < 0.001), BI (median: 43 vs. 80; p < 0.001) and mRS (2 vs. 1; p < 0.001) showed significant improvement from admission to discharge after MTE. Recanalization rate was Thrombolysis in Cerebral Infarction (TICI) 2b to 3 in 29 of 30 patients (96.7%). One case of an intracerebral reperfusion hematoma (ECASS: PH2) required surgical treatment. Conclusion MTE might lead to a significantly improved clinical outcome also for patients with low NIHSS score due to M1 segment occlusion. Periprocedural complications appeared infrequently. These results encourage further evaluation of the benefit-risk profile of MTE compared to standard treatment in patients with low NIHSS scores in future randomized trials.

Computed Tomography-Based Thrombus Imaging for the Prediction of Recanalization after Reperfusion Therapy in Stroke

The prediction of successful recanalization following thrombolytic or endovascular treatment may be helpful to determine the strategy of recanalization treatment in acute stroke. Thrombus can be detected using noncontrast computed tomography (CT) as a hyperdense artery sign or blooming artifact on a T2^*-weighted gradient-recalled image. The detection of thrombus using CT depends on slice thickness. Thrombus burden can be determined in terms of the length, volume, and clot burden score. The thrombus size can be quantitatively measured on thin-section CT or CT angiography/magnetic resonance angiography. The determination of thrombus size may be predictive of successful recanalization/non-recanalization after intravenous thrombolysis and endovascular treatment. However, cut-offs of thrombus size for predicting recanalization/non-recanalization are different among studies, due to different methods of measurements. Thus, a standardized method to measure the thrombus is necessary for thrombus imaging to be useful and reliable in clinical practice. Software-based measurements may provide a reliable and accurate assessment. The measurement should be easy and rapid to be more widely used in practice, which could be achieved by improvement of the user interface. In addition to prediction of recanalization, sequential measurements of thrombus volume before and after the treatment may also be useful to determine the efficacy of new thrombolytic drugs. This manuscript reviews the diagnosis of thrombus, prediction of recanalization using thrombus imaging, and practical considerations for the measurement of thrombus burden and density on CT.

Mechanical thrombectomy in patients with M1 occlusion and NIHSS score ≤5: a single-centre experience

Background

The recent success of several mechanical thrombectomy trials has resulted in a significant change in management for patients presenting with stroke. However, it is still unclear how to manage patients that present with stroke and low National Institutes of Health Stroke Scale (NIHSS) ≤5. We sought to review our experience of mechanical thrombectomy in patients with low NIHSS and confirmed M1 occlusion.

Methods

We retrospectively analysed our prospectively maintained database of all patients undergoing mechanical thrombectomy between January 2008 and August 2016. We identified 41 patients with confirmed M1 occlusion and low NIHSS (≤5) on admission to our hospital. We collected demographic, radiological, procedural and outcome data.

Results

The mean age of patients was 72±14, with 20 male patients. Associated medical conditions were common with hypertension seen in ∼80%. Just over 50% presented with NIHSS 4 or 5. The average ASPECTS score on admission was 8.8 (range 6–10), and the average clot length 10 mm. Angiographically Thrombolysis in Cerebral Infarction (TICI) ≥2b was obtained in 87.8% of patients. 7 patients had haemorrhage on follow-up, 2 of which were symptomatic. Of 40 patients with 90-day follow-up, 75% had modified Rankin Scale (mRS) score 0–2. There were 3 deaths at 90 days.

Conclusions

Mechanical thrombectomy in patients with low NIHSS and proximal large vessel occlusion is technically possible and carries a high degree of success with good safety profile. Patients with low NIHSS and confirmed occlusion should be considered for mechanical thrombectomy.

Impact of thrombus length on recanalization and clinical outcome following mechanical thrombectomy in acute ischemic stroke

PURPOSE

The impact of thrombus length on recanalization in IV thrombolysis for acute intracranial artery occlusion has been well studied. Here we analyzed the influence of thrombus length on the number of thrombectomy maneuvers needed for recanalization, intraprocedural complications, recanalization success, and clinical outcome after mechanical thrombectomy.

METHODS

We retrospectively analyzed angiographic and clinical data from 72 consecutive patients with acute occlusion of the M1 segment of the middle cerebral artery who were treated with mechanical thrombectomy using stent retrievers. Successful recanalization was defined as a Thrombolysis in Cerebral Infarction score of 2b or 3. Good neurological outcome was defined as a modified Rankin Scale score of ≤2 at 90 days after stroke onset.

RESULTS

Mean thrombus length was 13.4±5.2 mm. Univariate binary logistic regression did not show an association of thrombus length with the probability of a good clinical outcome (OR 0.95, 95% CI 0.84 to 1.03, p=0.176) or successful recanalization (OR 0.92, 95% CI 0.81 to 1.05, p=0.225). There was no significant correlation between thrombus length and the number of thrombectomy maneuvers needed for recanalization (p=0.112). Furthermore, thrombus length was not correlated with the probability of intraprocedural complications (p=0.813), including embolization in a new territory (n=3).

CONCLUSIONS

In this study, thrombus length had no relevant impact on recanalization, neurological outcome, or intraprocedural complications following mechanical thrombectomy of middle cerebral artery occlusions. Therefore, mechanical thrombectomy with stent retrievers can be attempted with large clots.

Incidence and Predictors of Early Recanalization After Intravenous Thrombolysis

Background and Purpose—

After the demonstration of efficacy of bridging therapy, reliably predicting early recanalization (ER; ≤3 hours after start of intravenous thrombolysis) would be essential to limit futile, resource-consuming, interhospital transfers. We present the first systematic review on the incidence and predictors of ER after intravenous thrombolysis alone.

Methods—

We systematically searched for studies including patients solely treated by intravenous thrombolysis that reported incidence of ER and its association with baseline variables. Using meta-analyses, we estimated pooled incidence of ER, including according to occlusion site, and summarized the available evidence regarding predictors of no-ER.

Results—

We identified 26 studies that together included 2063 patients. The overall incidence of partial or complete ER was 33% (95% confidence interval, 27–40). It varied according to occlusion site: 52% (39–64) for distal middle cerebral artery, 35% (28–42) for proximal middle cerebral artery, 13% (6–22) for intracranial carotid artery, and 13% (0–35) for basilar occlusion. Corresponding rates for complete ER were 38% (22–54), 21% (15–29), 4% (1–8), and 4% (0–22), respectively. Proximal occlusion and higher National Institute of Health Stroke Scale were the most consistent no-ER predictors. Other factors, such as long or totally occlusive thrombus and poor collateral circulation, emerged as potential predictors but will need confirmation.

Conclusion—

The overall incidence of ER after intravenous thrombolysis is substantial, highlighting the importance of reliably predicting ER to limit futile, interhospital transfers. Incidence of no-ER is particularly high for proximal occlusion and severe strokes. Given the scarcity of published data, further studies are needed to improve no-ER prediction accuracy.

Mechanical Thrombectomy in Patients with Acute Ischemic Stroke and Lower NIHSS Scores: Recanalization Rates, Periprocedural Complications, and Clinical Outcome

BACKGROUND AND PURPOSE

Mechanical thrombectomy, in addition to intravenous thrombolysis, has become standard in acute ischemic stroke treatment in patients with large-vessel occlusion in the anterior circulation. However, previous randomized controlled stroke trials were not focused on patients with mild-to-moderate symptoms. Thus, there are limited data for patient selection, prediction of clinical outcome, and occurrence of complications in this patient population. The purpose of this analysis was to assess clinical and interventional data in patients treated with mechanical thrombectomy in case of ischemic stroke with mild-to-moderate symptoms.

MATERIALS AND METHODS

We performed a retrospective analysis of a prospectively collected stroke data base. Inclusion criteria were anterior circulation ischemic stroke treated with mechanical thrombectomy at our institution between September 2010 and October 2015 with an NIHSS score of ≤8.

RESULTS

Of 484 patients, we identified 33 (6.8%) with the following characteristics: median NIHSS = 5 (interquartile range, 4-7), median onset-to-groin puncture time = 320 minutes (interquartile range, 237-528 minutes). Recanalization (TICI = 2b-3) was achieved in 26 (78.7%) patients. Two cases of symptomatic intracranial hemorrhage were observed. Favorable (mRS 0-2) and moderate (mRS 0-3) clinical outcome at 90 days was achieved in 21 (63.6%) and 30 (90.9%) patients, respectively.

CONCLUSIONS

The clinical outcome of patients undergoing mechanical thrombectomy for acute ischemic stroke with mild stroke due to large-vessel occlusion appears to be predominately favorable, even in a prolonged time window. However, although infrequent, angiographic complications could impair clinical outcome. Future randomized controlled trials should assess the benefit compared with the best medical treatment.