Redefining 'success': a systematic review and meta-analysis comparing outcomes between incomplete and complete revascularization

The benefit of optimizing recanalization during mechanical thrombectomy in patients with acute ischemic stroke depends on preprocedural tissue-level collateralization

PURPOSE

Thrombolysis in Cerebral Infarction (TICI) 3 represents the optimal angiographic outcome following mechanical thrombectomy (MT) for acute ischemic stroke (AIS). Although it is known to yield better outcomes than TICI 2b, the influence of preprocedural cerebral hemodynamics on the clinical advantage of TICI 3 over TICI 2b remains unexplored.

METHODS

This single-center retrospective analysis involved patients with anterior circulation AIS who underwent successful recanalization during MT at the Comprehensive Stroke Center, University Hospital, Krakow between January 2019 and July 2023. We assessed the benefit of achieving TICI 2c/3 over TICI 2b on the basis of preprocedural computed perfusion imaging results, primarily focusing on early infarct volume (EIV) and tissue-level collaterals indicated by hypoperfusion intensity ratio (HIR). Good functional outcome (GFO) was defined as a modified Rankin Score < 3 on day 90.

RESULTS

The study comprised 612 patients, of whom 467 (76.3%) achieved TICI 2c/3. GFO was more frequent in the TICI 2c/3 group (54.5% vs 69.4%, p < 0.001). There was interaction between the recanalization status and both HIR (Pi = 0.042) and EIV (Pi = 0.012) in predicting GFO, with disproportionately higher impact of HIR and EIV in TICI 2b group. The benefit from TICI 2c/3 over TICI 2b was insignificant among patients with good collaterals, defined by HIR < 0.3 (odds ratio:1.36 [0.58-3.18], p = 0.483).

CONCLUSION

TICI 2c/3 improves patient functional outcomes compared to TICI 2b regardless of EIV. However, such angiographic improvement may be clinically futile in patients with good tissue-level collateralization. Our findings suggest that preprocedural HIR should be considered when optimization of recanalization is considered during MT.

Effect of MR-guided perfusion imaging mismatch profiles within 6 h on endovascular thrombectomy outcomes

BACKGROUND

The treatment of acute ischemic stroke (AIS) aims to achieve early vascular recanalization and reperfusion of the penumbra. However, the effect of early penumbral imaging within 6 h on clinical outcomes remains unclear. The objective of this study was to determine the effect of magnetic resonance-guided (MR-guided) perfusion imaging within 6 h after symptom onset on endovascular thrombectomy outcomes in AIS patients.

METHODS

We prospectively collected the clinical information of consecutive AIS patients undergoing endovascular thrombectomy based on MR-guided perfusion imaging within 6 h after symptom onset from AISRNA and EVTRNA studies. The primary outcome was defined as the poor outcome (mRS > 2 within 90 days). The perfusion-weighted imaging/diffusion-weighted imaging (PWI/DWI) mismatch was assessed by an automated software.

RESULTS

We enrolled 84 patients (25 in the mismatch ≤ 1.8 group and 59 in the mismatch > 1.8 group). Significant difference was found between the mismatch > 1.8 group and the mismatch ≤ 1.8 group for the incidence of disabling stroke (mRS > 2) within 90 days (40.7% vs. 68.0%, OR: 3.099, 95% CI: 1.154-8.323, P = 0.025). Intracranial hemorrhage occurred in 8 patients (13.6%) in the mismatch > 1.8 group and 10 patients in the mismatch ≤ 1.8 group (40.0%) (P = 0.010). The risk of severe cerebral edema was 2/59 (3.4%) vs. 7/25 (28.0%) (P = 0.004). These findings remained stable after adjustment.

CONCLUSIONS

MR-guided perfusion imaging mismatch profiles within 6 h after symptom onset may be feasible to predictclinical outcomes and reduce clinically ineffective reperfusion after endovascular thrombectomy.

Effect of incomplete reperfusion patterns on clinical outcome: insights from the ESCAPE-NA1 trial

BACKGROUND

Incomplete reperfusion (IR) after mechanical thrombectomy (MT) can be a consequence of residual occlusion, no-reflow phenomenon, or collateral counterpressure. Data on the impact of these phenomena on clinical outcome are limited.

METHODS

Patients from the ESCAPE-NA1 trial with IR (expanded Thrombolysis In Cerebral Infarction (eTICI) 2b) were compared with those with complete or near-complete reperfusion (eTICI 2c-3) on the final angiography run. Final runs were assessed for (a) an MT-accessible occlusion, or (b) a non-MT-accessible occlusion pattern. The primary clinical outcome was modified Rankin Scale (mRS) 0-2 at 90 days. Our imaging outcome was infarction in IR territory on follow-up imaging. Unadjusted and adjusted incidence rate ratios (aIRR) with 95% confidence intervals (95% CI) were obtained.

RESULTS

Of 1105 patients, 443 (40.1%) with IR and 506 (46.1%) with complete or near-complete reperfusion were included. An MT-accessible occlusion was identified in 147/443 patients (33.2%) and a non-MT-accessible occlusion in 296/443 (66.8%). As compared with patients with near-complete/complete reperfusion, patients with IR had significantly lower chances of achieving mRS 0-2 at 90 days (aIRR 0.82, 95% CI 0.74 to 0.91). Rates of mRS 0-2 were lower in the MT-accessible occlusion group as compared with the non-MT-accessible occlusion pattern group (aIRR 0.71, 95% CI 0.60 to 0.83, and aIRR 0.89, 95% CI 0.81 to 0.98, respectively). More patients with MT-accessible occlusion patterns developed infarcts in the non-reperfused territory as compared with patients with non-MT occlusion patterns (68.7% vs 46.3%).

CONCLUSION

IR was associated with worse clinical outcomes than near-complete/complete reperfusion. Two-thirds of our patients with IR had non-MT-accessible occlusion patterns which were associated with better clinical and imaging outcomes compared with those with MT-accessible occlusion patterns.

Endovascular Thrombectomy for Acute Ischemic Stroke : Current Concept in Management

Endovascular thrombectomy (EVT) has been established as the standard of care in the treatment of acute ischemic stroke (AIS) based on landmark randomized controlled trials. Nevertheless, while the strict eligibility of EVT for AIS patients restrict the wide application of EVT, a considerable population still undergoes off-label EVT. Besides, it is important to acknowledge that recanalization is not achieved in approximately 20% of procedures, and more than 50% of patients who undergo EVT still do not experience a favorable outcome. This article reviews the brief history of EVT trials and recent progressions in the treatment of AIS, with focusing on the expanding eligibility criteria, new target for EVT, and the evolution of EVT techniques.

Extended treatment in cerebral ischemia score 2c or 3 as goal of successful endovascular treatment is associated with clinical benefit

BACKGROUND AND PURPOSE

Successful reperfusion, defined as a modified treatment in cerebral ischemia (mTICI) score 2b or 3, is an important goal for endovascular treatment (EVT) of stroke. Recently, an extension of the mTICI score with an additional grade 2c indicating near-complete reperfusion (expanded TICI, eTICI) and a revised definition of success as eTICI 2c or 3 were proposed. We evaluate whether eTICI 2c translates into improved clinical outcome compared to eTICI 2b.

MATERIAL AND METHODS

Consecutive patients with large vessel occlusion in the anterior circulation who underwent EVT between December 2013 and December 2020 were included. Clinical outcome measures were favorable functional outcome at 90 days (modified Rankin Scale [mRS] scores 0 to 2 or return to pre-stroke mRS) and early neurological improvement (National Institutes of Health Stroke Scale [NIHSS] improvement ≥4 points or a score of 0-1 at 24 h).

RESULTS

Of 1282 included patients (median age 76, median NIHSS 16), reperfusion was classified as eTICI 2b in 410 (32%), eTICI 2c in 242 (19%) and eTICI 3 in 464 (36%). eTICI 2c differed significally from 2b with respect to early neurological improvement (aOR = 1.49, 95% CI = 1.01-2.19). No statistically significant difference in favorable functional outcome at 90 days was found (eTICI 2c vs 2b, aOR = 1.31, 95% CI = 0.88-2.00).

CONCLUSION

Our study indicates early clinical benefit at 24 h of achieving eTICI 2c compared to eTICI 2b, but no significant difference was seen in favorable functional outcome at 90 days. Our results support eTICI 2c and 3 as the goal of a successful thrombectomy but do not exclude eTICI 2b as an acceptable result.

Quantification of ischemic brain edema after mechanical thrombectomy using dual-energy computed tomography in patients with ischemic stroke

Net water uptake (NWU) is a quantitative imaging biomarker used to assess cerebral edema resulting from ischemia via Computed Tomography (CT)-densitometry. It serves as a strong predictor of clinical outcome. Nevertheless, NWU measurements on follow-up CT scans after mechanical thrombectomy (MT) can be affected by contrast staining. To improve the accuracy of edema estimation, virtual non-contrast images (VNC-I) from dual-energy CT scans (DECT) were compared to conventional polychromatic CT images (CP-I) in this study. We examined NWU measurements derived from VNC-I and CP-I to assess their agreement and predictive value in clinical outcome. 88 consecutive patients who received DECT as follow-up after MT were included. NWU was quantified on CP-I (cNWU) and VNC-I (vNWU). The clinical endpoint was functional independence at discharge. cNWU and vNWU were highly correlated (r = 0.71, p < 0.0001). The median difference between cNWU and vNWU was 8.7% (IQR: 4.5-14.1%), associated with successful vessel recanalization (mTICI2b-3) (ß: 11.6%, 95% CI 2.9-23.0%, p = 0.04), and age (ß: 4.2%, 95% CI 1.3-7.0%, p = 0.005). The diagnostic accuracy to classify outcome between cNWU and vNWU was similar (AUC:0.78 versus 0.77). Although there was an 8.7% median difference, indicating potential edema underestimation on CP-I, it did not have short-term clinical implications.

Futile reperfusion of endovascular treatment for acute anterior circulation large vessel occlusion in the ANGEL-ACT registry

BACKGROUND

Some patients with large vessel occlusion (LVO) still cannot achieve functional independence despite successful reperfusion after endovascular treatment (EVT), named futile reperfusion. We aimed to explore the incidence and predictors of futile reperfusion of EVT for anterior circulation LVO in the Chinese population based on a nationwide prospective multicenter registry.

METHODS

We selected patients from the ANGEL-ACT (Endovascular Treatment Key Technique and Emergency Workflow Improvement of Acute Ischemic Stroke) registry. Successful reperfusion was defined as modified Treatment In Cerebral Ischemia (mTICI) 2b-3 after EVT, and functional independence was defined as 90-day modified Rankin Scale (mRS) 0-2. A multivariable regression model was performed to identify the independent predictors of futile reperfusion in anterior circulation LVO patients.

RESULTS

A total of 1158 anterior circulation LVO patients were included in our study. 600 of the 1158 patients (51.8%) suffered futile reperfusion. Age ≥69 (adjusted OR (aOR) 1.69, 95% CI 1.21 to 2.35, P=0.002), baseline National Institutes of Health Stroke Scale (NIHSS) ≥14 (aOR 2.36, 95% CI 1.71 to 3.27, P<0.001), baseline serum glucose ≥6.5 mmol/L (aOR 1.73, 95% CI 1.27 to 2.36, P=0.001), drip and ship (aOR 1.56, 95% CI 1.11 to 2.18, P=0.011), and general anesthesia (aOR 2.28, 95% CI 1.66 to 3.14, P<0.001) were associated with a high risk of futile reperfusion in the anterior LVO patients after EVT, whereas baseline Alberta Stroke Program Early CT Score (ASPECTS) ≥8 (aOR 0.65, 95% CI 0.47 to 0.91, P=0.011) and complete reperfusion (aOR 0.62, 95% CI 0.43 to 0.89, P=0.010) were associated with a low risk of futile reperfusion in the anterior LVO patients after EVT.

CONCLUSIONS

In the ANGEL-ACT registry, 51.8% of anterior circulation LVO patients suffered futile reperfusion after EVT. Age ≥69 years, baseline NIHSS ≥14, baseline serum glucose ≥6.5 mmol/L, drip and ship, general anesthesia, baseline ASPECTS <8, and incomplete reperfusion were the independent predictors of futile reperfusion.

Angiographic tapering sign as a surrogate marker for large vessel occlusion due to intracranial atherosclerotic stenosis and its clinical implication: a retrospective matched case-control study

BACKGROUND

The purpose of this study was to investigate whether the initial DSA appearance of the occlusion during mechanical thrombectomy (MT) can help distinguish the nature of the underlying lesion and predict radiological and clinical outcomes.

METHODS

We retrospectively reviewed cases of patients with acute ischemic stroke who underwent MT for anterior circulation occlusion between March 2017 and February 2020. Underlying intracranial atherosclerotic stenosis (ICAS) was determined based on the presence of fixed stenosis after endovascular treatment. Patients were categorized based on the appearance of the occlusion observed in the initial DSA as tapering sign (+) or (-) groups. We performed 1:2 propensity score matching to establish a proper control group among the tapering sign (-) group. We analyzed and compared baseline characteristics and clinical outcomes between the two groups.

RESULTS

A total of 293 patients (tapering sign (+), n=47; tapering sign (-), n=246) were included in the analysis. The procedure time of MT was significantly longer for the tapering sign (+) group, and the successful recanalization rate after MT was significantly lower in the tapering sign (+) group than in the tapering sign (-) group. Logistic regression showed that ICAS-related occlusion was strongly associated with a positive angiographic tapering sign, and the angiographic tapering sign was a negative factor for the first-pass effect during MT. However, a 3-month good functional outcome was not significantly associated with the angiographic tapering sign.

CONCLUSIONS

The tapering sign on the initial DSA could be a surrogate marker for ICAS-related occlusion and procedural difficulty. However, its clinical significance remains unclear.

Advances in Acute Ischemic Stroke Treatment: Current Status and Future Directions

The management of acute ischemic stroke has undergone a paradigm shift in the past decade. This has been spearheaded by the emergence of endovascular thrombectomy, along with advances in medical therapy, imaging, and other facets of stroke care. Herein, we present an updated review of the various stroke trials that have impacted and continue to transform stroke management. It is critical for the radiologist to stay abreast of the ongoing developments to provide meaningful input and remain a useful part of the stroke team.

Clinically Ineffective Reperfusion After Endovascular Therapy in Acute Ischemic Stroke

Endovascular treatment is a highly effective therapy for acute ischemic stroke due to large vessel occlusion. However, in clinical practice, nearly half of the patients do not have favorable outcomes despite successful recanalization of the occluded artery. This unfavorable outcome can be defined as having clinically ineffective reperfusion. The objective of the review is to describe clinically ineffective reperfusion after endovascular therapy and its underlying risk factors and mechanisms, including initial tissue damage, cerebral edema, the no-reflow phenomenon, reperfusion injury, procedural features, and variations in postprocedural management. Further research is needed to more accurately identify patients at a high risk of clinically ineffective reperfusion after endovascular therapy and to improve individualized periprocedural management strategies, to increase the chance of achieving favorable clinical outcomes.

Common Data Elements Reported in Mechanical Thrombectomy for Acute Ischemic Stroke: A Systematic Review of Active Clinical Trials

BACKGROUND

New trials are planned regularly to provide the highest quality of evidence and invade new occlusion territories, which requires a pre-defined reporting strategy with consistent, common data elements for more straightforward collective evidence synthesis. We sought to review all active endovascular thrombectomy trials to investigate their patient selection criteria, intervention description, and reported outcomes.

METHODS

A literature search was systematically conducted on clinicaltrials.gov for active trials and all intervention, inclusion criteria, and outcomes reported were extracted. A qualitative synthesis of the frequency of study design types and data elements are graphically and narratively presented.

RESULTS

A total of 32 studies were tagged and included in the final qualitative analysis. The inclusion criteria were highly variable, including different cut-offs for the last well-known baseline National Institutes of Health Stroke Scale, Alberta Stroke Program Early CT Score, and modified Rankin scale (mRS). Half of the studies (16/32) mentioned "thrombectomy" without defining which technique or device was used, and the final thrombolysis in cerebral infarction scale was provided in 19 (59.4%) studies. Heterogeneity was also present among the studies reporting a first-pass effect, both in how studies defined the outcome and in used ranges for mRS. Mortality and intracerebral hemorrhage (ICH) were more homogenous in their presentation and follow-up.

CONCLUSIONS

There is a great degree of heterogeneity in the active thrombectomy trials concerning inclusion criteria, interventions used, and how outcomes are being reported.

Endovascular Recanalization for Acute Internal Carotid Artery Terminus Occlusion: A Subgroup Analysis From the Direct-MT Trial

BACKGROUND

The efficacy of endovascular recanalization for internal carotid artery (ICA) terminus occlusion has not been completely evaluated.

OBJECTIVE

To investigate the efficacy of endovascular recanalization for ICA terminus occlusion.

METHODS

Data from Direct-MT, a randomized controlled trial, were applied. ICA terminus occlusions were diagnosed with preprocedure computed tomography angiography by the core laboratory. We dichotomized the ICA terminus occlusions into 2 groups (non-T and T) and analyzed the differences between them. Single-factor analysis and multiple logistic regression were applied to detect independent factors for clinical outcomes and futile recanalization.

RESULTS

The rates of first-pass effect, successful recanalization, good clinical outcome, mortality, and futile recanalization were 22.3% (50 of 224), 83.0% (181 of 224), 24.6% (55 of 224), 26.7% (60 of 224), and 69.6% (126 of 181), respectively. Baseline National Institutes of Health Stroke Scale (negative factor; odds ratio [OR] 0.89; 95% CI 0.84-0.95; P &lt; .001), hypertension (negative factor; OR 0.38; 95% CI 0.18-0.80; P = .010), Alberta Stroke Program Early CT Score ≥ 6 (OR 3.68; 95% CI 1.29-10.5; P = .014), tirofiban use (OR 2.46; 95% CI 1.16-5.19; P = .018), first-pass effect (OR 2.87; 95% CI 1.28-6.41; P = .010), and final extended thrombolysis in cerebral infarction ≥ 2b (OR, 3.50; 95% CI 1.17-10.4; P = .024) were independent factors for good clinical outcome. Baseline National Institutes of Health Stroke Scale (OR 1.12; 95% CI 1.05-1.20; P = .004), Alberta Stroke Program Early CT Score &lt; 6 (OR 4.68; 95% CI 1.51-14.5; P = .007), tirofiban use (negative factor; OR 0.39; 95% CI 0.18-0.86; P = .020), and first-pass effect (negative factor; OR 0.44; 95% CI 0.19-0.99; P = .047) were independent factors for futile recanalization.

CONCLUSION

More efforts in modifiable factors should be made to improve the efficacy of endovascular recanalization for better clinical outcomes and less futile recanalization in ICA terminus occlusions.

Continuing early mTICI 2b recanalization may improve functional outcome but is associated with a higher risk of intracranial hemorrhage

Background

Successful reperfusion (mTICI 2c/3) and low number of passes are key determinants for good clinical outcome in acute large vessel occlusion. While final mTICI 2c/3 reperfusion is superior to partial reperfusion (mTICI 2b) it remains unclear if this is also true for the subgroup of patients with early mTICI 2b (achieved in ≤2 retrieval attempts) reperfusion who are secondarily improved to mTICI 2c/3. This study was designed to examine if early mTICI2b should be continued or stopped during mechanical thrombectomy (MT).

Methods

Nine hundred and thirteen ischemic stroke patients who received MT were retrospectively analyzed. Angiography runs following each recanalization attempt were scored for mTICI. The patients with early mTICI 2b reperfusions were dichotomized in “TICI2b-stopped” (MT withdrawal after mTICI 2b was achieved with first or second retrieval) and “TICI2b-continued” (MT was continued after mTICI 2b was achieved with first or second retrieval). Functional outcome was obtained after 90 days using the modified Rankin scale (mRS90).

Results

Of 362 Patients with a M1-occlusion, 100 patients fulfilled the inclusion criteria with an early mTICI 2b. 78/100 patients were included in the “TICI2b-stopped” group and 22/100 patients were in the “TICI2b-continued” group. Of these 22 patients, none had a final mTICI score lower than 2b and 11 patients had a final mTICI score of 2c/3. Regarding good functional outcome at mRS90, “TICI2b-continued” showed by trend a slight advantage of 40.1 vs. 35.6% in “TICI2b-stopped” but in multivariate logistic regression analysis adjusted for confounders, no significant difference was found between the two groups (OR 0.75, 95% CI 0.19–2.87, p = 0.67). Symptomatic intracranial hemorrhage was significantly higher in “TICI2b-continued” compared to “TICI2b-stopped” (31.8 vs. 10.3%, p = 0.031).

Conclusion

Successfully improving an early mTICI 2b to mTICI 2c/3 reperfusion is possible in a substantial number of patients and might improve functional outcome. However, an increase in symptomatic intracranial hemorrhage (SICH) due to further retrieval attempts may diminish the potential functional benefit to continue early mTICI 2b. To support this finding, further investigation with more power is needed to account for the low number of events regarding SICH.

Characterizing reasons for stroke thrombectomy ineligibility among potential candidates transferred in a hub-and-spoke network

Background

Access to endovascular thrombectomy (EVT) is relatively limited. Hub-and-spoke networks seek to transfer appropriate large vessel occlusion (LVO) candidates to EVT-capable hubs. However, some patients are ineligible upon hub arrival, and factors that drive transfer inefficiencies are not well described. We sought to quantify EVT transfer efficiency and identify reasons for EVT ineligibility.

Methods

Consecutive EVT candidates presenting to 25 spokes from 2018-2020 with pre-transfer CTA-defined LVO and ASPECTS ≥6 were identified from a prospectively maintained database. Outcomes of interest included hub EVT, reasons for EVT ineligibility, and 90-day modified Rankin Scale (mRS) ≤2.

Results

Among 258 patients, the median age was 70 years (IQR 60-81); 50% were female. 56% were ineligible for EVT after hub arrival. Cited reasons were large established infarct (49%), mild symptoms (33%), recanalization (6%), distal occlusion (5%), sub-occlusive lesion (3%), and goals of care (3%). Late window patients [last known well (LKW) >6 hours] were more likely to be ineligible (67% vs 43%, P<0.0001). EVT ineligible patients were older (73 vs 68 years, p=0.04), had lower NIHSS (10 vs 16, p<0.0001), longer LKW-hub arrival time (8.4 vs 4.6 hours, p<0.0001), longer spoke Telestroke consult-hub arrival time (2.8 vs 2.2 hours, p<0.0001), and received less intravenous thrombolysis (32% vs 45%, p=0.04) compared to eligible patients. EVT ineligibility independently reduced the odds of 90-day mRS≤2 (aOR=0.26, 95%CI=0.12,0.56; p=0.001) when controlling for age, NIHSS, and LKW-hub arrival time.

Conclusions

Among patients transferred for EVT, there are multiple reasons for ineligibility upon hub arrival, with most excluded for infarct growth and mild symptoms. Understanding factors that drive transfer inefficiencies is important to improve EVT access and outcomes.

Association of reperfusion success and emboli in new territories with long term mortality after mechanical thrombectomy

BACKGROUND

The degree of reperfusion is the most important modifiable predictor of 3 month functional outcome and mortality in ischemic stroke patients treated with mechanical thrombectomy. Whether the beneficial effect of reperfusion also leads to a reduction in long term mortality is unknown.

METHODS

Patients undergoing mechanical thrombectomy between January 2010 and December 2018 were included. The post-thrombectomy degree of reperfusion and emboli in new territories were core laboratory adjudicated. Reperfusion was evaluated according to the expanded Thrombolysis in Cerebral Infarction (eTICI) scale. Vital status was obtained from the Swiss population register. Adjusted hazard ratios (aHRs) using time split Cox regression models were calculated. Subgroup analyses were performed in patients with borderline indications.

RESULTS

Our study included 1264 patients (median follow-up per patient 2.5 years). Patients with successful reperfusion had longer survival times, attributable to a lower hazard of death within 0-90 days and for >90 days to 2 years (aHR 0.34, 95% CI 0.26 to 0.46; aHR 0.37, 95% CI 0.22 to 0.62). This association was homogeneous across all predefined subgroups (p for interaction >0.05). Among patients with successful reperfusion, a significant difference in the hazard of death was observed between eTICI2b50 and eTICI3 (aHR 0.51, 95% CI 0.33 to 0.79). Emboli in new territories were present in 5% of patients, and were associated with increased mortality (aHR 2.3, 95% CI 1.11 to 4.86).

CONCLUSION

Successful, and ideally complete, reperfusion without emboli in new territories is associated with a reduction in long term mortality in patients treated with mechanical thrombectomy, and this was evident across several subgroups.

Successful mechanical thrombectomy in acute ischemic stroke: revascularization grade and functional independence

Most studies define the technical success of endovascular thrombectomy (EVT) as a Thrombolysis in Cerebral Infarction (TICI) revascularization grade of 2b or higher. However, growing evidence suggests that TICI 3 is the best angiographic predictor of improved functional outcomes. To assess the association between successful TICI revascularization grades and functional independence at 90 days, we performed a systematic review and network meta-analysis of thrombectomy studies that reported TICI scores and functional outcomes, measured by the modified Rankin Scale, using the semi-automated AutoLit software platform. Forty studies with 8691 patients were included in the quantitative synthesis. Across TICI, modified TICI (mTICI), and expanded TICI (eTICI), the highest rate of good functional outcomes was observed in patients with TICI 3 recanalization, followed by those with TICI 2c and TICI 2b recanalization, respectively. Rates of good functional outcomes were similar among patients with either TICI 2c or TICI 3 grades. On further sensitivity analysis of the eTICI scale, the rates of good functional outcomes were equivalent between eTICI 2b50 and eTICI 2b67 (OR 0.81, 95% CI 0.52 to 1.25). We conclude that near complete or complete revascularization (TICI 2c/3) is associated with higher rates of functional outcomes after EVT.

Heterogeneity of the Relative Benefits of TICI 2c/3 over TICI 2b50/2b67 : Are there Patients who are less Likely to Benefit?

PURPOSE

Incomplete reperfusion after mechanical thrombectomy (MT) is associated with a poor outcome. Rescue therapy would potentially benefit some patients with an expanded treatment in cerebral ischemia score (eTICI) 2b50/2b67 reperfusion but also harbors increased risks. The relative benefits of eTICI 2c/3 over eTICI 2b50/67 in clinically important subpopulations were analyzed.

METHODS

Retrospective analysis of our institutional database for all patients with occlusion of the intracranial internal carotid artery (ICA) or the M1/M2 segment undergoing MT and final reperfusion of ≥eTICI 2b50 (903 patients). The heterogeneity in subgroups of different time metrics, age, National Institutes of Health Stroke Scale (NIHSS), number of retrieval attempts, Alberta Stroke Programme Early CT Score (ASPECTS) and site of occlusion using interaction terms (p_i) was analyzed.

RESULTS

The presence of eTICI 2c/3 was associated with better outcomes in most subgroups. Time metrics showed no interaction of eTICI 2c/3 over eTICI 2b50/2b67 and clinical outcomes (onset to reperfusion p_i = 0.77, puncture to reperfusion p_i = 0.65, onset to puncture p_i = 0.63). An eTICI 2c/3 had less consistent association with mRS ≤2 in older patients (>82 years, p_i = 0.038) and patients with either lower NIHSS (≤9) or very high NIHSS (>19, p_i = 0.01). Regarding occlusion sites, the beneficial effect of eTICI 2c/3 was absent for occlusions in the M2 segments (aOR 0.73, 95% confidence interval [CI] 0.33-1.59, p_i = 0.018).

CONCLUSION

Beneficial effect of eTICI 2c/3 over eTICI 2b50/2b67 only decreased in older patients, M2-occlusions and patients with either low or very high NIHSS. Improving eTICI 2b50/2b67 to eTICI 2c/3 in those subgroups may be more often futile.

Sex-specific differences in presentations and determinants of outcomes after endovascular thrombectomy for large vessel occlusion stroke

INTRODUCTION

Sex-specific differences in ischemic stroke outcomes are prevalent. We sought to investigate sex differences in the determinants of reperfusion and functional outcomes after endovascular thrombectomy (EVT) for emergent large vessel occlusion ischemic stroke (ELVO).

METHODS

Patients presenting to a single referral center with an anterior circulation ELVO that underwent EVT from 2011 to 2019 were included in this retrospective analysis. Sex differences in history, presentation, adequate reperfusion (TICI 2b-3), and 90-day good outcome [delta modified Rankin Scale (mRS) ≤ 2 from pre-stroke] were examined. Multivariable logistic regression analyses were performed to assess sex-specific associations with outcomes.

RESULTS

Three hundred and eighty-one consecutive ELVO patients were identified. Women (N = 193) were older (75 vs 64 years, p < 0.0001), had more pre-stroke disability (17% vs 9%, p = 0.032), more atrial fibrillation (41% vs 30%, p = 0.033), but less carotid atherosclerosis (8% vs 16%, p = 0.027). Rates of TICI 2b-3 and good outcome were similar between sexes. Carotid atherosclerosis (OR 0.315, 95% CI 0.130, 0.762) and dissection (OR 0.124, 95% CI 0.027, 0.569) independently decreased the odds of TICI 2b-3 among men but not women. Older age, more severe stroke, and not achieving TICI 2b-3 independently decreased the odds of good outcome among both sexes, while prior stroke (OR 0.258, 95% CI 0.083, 0.797) and hemorrhagic transformation (OR 0.111, 0.021, 0.592) were determinants exclusive to men.

CONCLUSION

In a real-world analysis of ELVO stroke patients treated with EVT, we found that despite advanced age and more pre-stroke disability, women have comparable reperfusion rates and functional outcomes compared to men. Sex-specific determinants of reperfusion and functional outcome were identified that require further study.

Evidence-Based Updates to Thrombectomy: Targets, New Techniques, and Devices

Endovascular thrombectomy (EVT) has been validated in several randomized controlled trials in recent years for its efficacy in the treatment of acute ischemic strokes (AIS) and is now the standard of care according to international guidelines. However, in about 20% of EVT procedures, recanalization is not achieved, and over 50% of patients who undergo EVT still do not have good functional outcome. In this article, we provide an extensive review of the latest evidence and developments in the field of EVT, with particular focus on the factors that improve patient outcomes. These factors include new and adjunctive techniques such as combination of direct aspiration and stent retriever, intra-arterial urokinase or 2b/3a inhibitors, rescue stenting, as well as novel devices including balloon guide catheters and the newer generations of aspiration catheters and stent retrievers. We also examined the latest notion of using first-pass effect (FPE) as the target to achieve during EVT, which has been associated with an improved functional outcome. While the field of EVT has been rapidly evolving, further research is required in specific AIS patient populations such as those with large ischemic core, late presentation beyond 24 h, posterior circulation strokes, and with distal medium vessel occlusion or tandem lesions to better assess its efficacy and safety.

Local Intra-arterial Thrombolysis during Mechanical Thrombectomy for Refractory Large-Vessel Occlusion: Adjunctive Chemical Enhancer of Thrombectomy

BACKGROUND AND PURPOSE

Data on adjunctive intra-arterial thrombolysis during mechanical thrombectomy for refractory thrombus are sparse. The aim of this study was to evaluate the efficacy and safety of local intra-arterial urokinase as an adjunct to mechanical thrombectomy for refractory large-vessel occlusion.

MATERIALS AND METHODS

We retrospectively evaluated patients with acute ischemic stroke who underwent mechanical thrombectomy for anterior circulation large-vessel occlusion between January 2016 and December 2019. Patients were divided into 2 groups based on the use of intra-arterial urokinase as an adjunctive therapy during mechanical thrombectomy for refractory thrombus: the urokinase and nonurokinase groups. Herein, refractory thrombus was defined as the target occlusion with minimal reperfusion (TICI 0 or 1) despite >3 attempts with conventional mechanical thrombectomy. The baseline characteristics, procedural outcomes, and clinical outcome were compared between the 2 groups.

RESULTS

One hundred fourteen cases of refractory thrombus were identified. A total of 45 and 69 patients were in the urokinase and the nonurokinase groups, respectively. The urokinase group compared with the nonurokinase group showed a higher rate of successful reperfusion (82.2% versus 63.8%, P = .034), with lower procedural times (54 versus 69 minutes, P = .137). The rates of good clinical outcome, distal embolism, and symptomatic intracranial hemorrhage were similar between the 2 groups. The use of intra-arterial urokinase (OR = 3.682; 95% CI, 1.156-11.730; P = .027) was an independent predictor of successful reperfusion.

CONCLUSIONS

The use of local intra-arterial urokinase as an adjunct to mechanical thrombectomy may be an effective and safe method that provides better recanalization than the conventional mechanical thrombectomy for refractory thrombus in patients with embolic large-vessel occlusion.

Predictors of futile recanalization in patients undergoing endovascular treatment in the DIRECT-MT trial

BACKGROUND

Futile recanalization-when patients have a successful recanalization but fail to achieve a satisfactory functional outcome- is a common phenomenon of endovascular treatment of acute ischemic stroke (AIS). The present study aimed to identify the predictors of futile recanalization in AIS patients who received endovascular treatment.

METHODS

This is a post-hoc analysis of the DIRECT-MT trial. Demographics, clinical characteristics, acute stroke workflow interval times, biochemical parameters, and imaging characteristics were compared between futile and meaningful recanalization groups. Multivariate analysis was performed to identify the predictors of futile recanalization.

RESULTS

Futile recanalization was observed in 277 patients. In multivariable logistic regression analysis, older age (p<0.001), higher baseline systolic blood pressure (SBP) (p=0.032), incomplete reperfusion defined by extended Thrombolysis In Cerebral Infarction (eTICI) grades (p=0.020), and larger final infarct volume (FIV) (p<0.001) were independent predictors of futile recanalization.

CONCLUSIONS

Old age, high baseline SBP, incomplete reperfusion defined by eTICI, and large FIV were independent predictors of futile recanalization after endovascular therapy for AIS.

Adjunctive Intra-arterial Thrombolysis in Endovascular Thrombectomy: A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the safety and efficacy of intra-arterial thrombolysis (IAT) as an adjunct to endovascular thrombectomy (EVT) in ischemic stroke, we performed a systematic review and meta-analysis of the literature.

METHODS

Searches were performed using MEDLINE, Embase, and Cochrane databases for studies that compared EVT with EVT with adjunctive IAT (EVT + IAT). Safety outcomes included symptomatic intracerebral hemorrhage and mortality at 3 months. Efficacy outcomes included successful reperfusion (Thrombolysis in Cerebral Infarction score of 2b-3) and functional independence, defined as a modified Rankin Scale score of 0-2 at 3 months.

RESULTS

Five studies were identified that compared combined EVT + IAT (IA alteplase or urokinase) with EVT only and were included in the random-effects meta-analysis. There were 1693 EVT patients, including 269 patients treated with combined EVT + IAT and 1,424 patients receiving EVT only. Pooled analysis did not demonstrate any differences between EVT + IAT and EVT only in rates of symptomatic intracerebral hemorrhage (odds ratio [OR]: 0.61, 95% confidence interval [CI]: 0.20-1.85; p = 0.78), mortality (OR: 0.77, 95% CI: 0.54-1.10; p = 0.15), or successful reperfusion (OR: 1.05, 95% CI: 0.52-2.15; p = 0.89). There was a higher rate of functional independence in patients treated with EVT + IAT, although this was not statistically significant (OR: 1.34, 95% CI: 1.00-1.80; p = 0.053).

CONCLUSION

Adjunctive IAT appears to be safe. In specific situations, neurointerventionists may be justified in administering small doses of intra-arterial alteplase or urokinase as rescue therapy during EVT.

Factors associated with early reperfusion improvement after intra-arterial fibrinolytics as rescue for mechanical thrombectomy

Objective:

To identify factors associated with early angiographic reperfusion improvement (EARI) following intra-arterial fibrinolytics (IAF) after failed or incomplete mechanical thrombectomy (MT).

Methods:

A subset of patients treated with MT and IAF rescue after incomplete reperfusion included in the INFINITY (INtra-arterial FIbriNolytics In ThrombectomY) multicenter observational registry was analyzed. Multivariable logistic regression was used to identify factors associated with EARI. Heterogeneity of the clinical effect of EARI on functional independence (defined as modified Rankin Score ≤2) was tested with interaction terms.

Results:

A total of 228 patients (median age: 72 years, 44.1% female) received IAF as rescue for failed or incomplete MT and had a post-fibrinolytic angiographic control run available (50.9% EARI). A cardioembolic stroke origin (adjusted odds ratio (aOR) 3.72, 95% confidence interval (CI) 1.39–10.0) and shorter groin puncture to IAF intervals (aOR 0.82, 95% CI 0.71–0.95 per 15-min delay) were associated with EARI, while pre-interventional thrombolysis showed no association (aOR 1.15, 95% CI 0.59–2.26). The clinical benefit of EARI after IAF seemed more pronounced in patients without or only minor early ischemic changes (Alberta Stroke Program Early Computed Tomography Score (ASPECTS) ≥9, aOR 4.00, 95% CI 1.37–11.61) and was absent in patients with moderate to severe ischemic changes (ASPECTS ≤8, aOR 0.94, 95% CI 0.27–3.27, p for interaction: 0.095).

Conclusion:

Early rescue and a cardioembolic stroke origin were associated with more frequent EARI after IAF. The clinical effect of EARI seemed reduced in patients with already established infarcts. If confirmed, these findings can help to inform patient selection and inclusion criteria for randomized-controlled trials evaluating IAF as rescue after MT.

First-line contact aspiration versus first-line stent retriever for acute posterior circulation strokes: an updated meta-analysis

BACKGROUND

Both stent retriever (SR) and contact aspiration (CA) are widely used as first-line strategies for acute posterior circulation strokes (PCS). However, it is still unclear how CA and SR compare as the first-line treatment of acute PCS. Several new studies have been published recently, so we aimed to perform an updated meta-analysis.

METHODS

The meta-analysis was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) statement. Random-effects models were performed to pool the outcomes and the value of I² was calculated to assess the heterogeneity.

RESULTS

Ten observational studies with 1189 patients were included, among whom 492 received first-line CA and 697 received first-line SR. The pooled results revealed that first-line CA could achieve a significantly higher proportion of modified Thrombolysis In Cerebral Infarction (mTICI) 2b/3 (OR 1.90, 95% CI 1.33 to 2.71, I²=0%), mTICI 3 (OR 1.95, 95% CI 1.15 to 3.31, I²=59.6%), first-pass effect (OR 2.91, 95% CI 1.51 to 5.58, I²=0%), lower incidence of new-territory embolic events (OR 0.20, 95% CI 0.05 to 0.83, I²=0%), and shorter procedure time (mean difference -29.4 min, 95% CI -46.8 to -12.0 min, I²=62.8%) compared with first-line SR. At 90-day follow-up, patients subjected to first-line CA showed a higher functional independence (modified Rankin Scale score 0-2; OR 1.38, 95% CI 1.01 to 1.87, I²=23.5%) and a lower mortality (OR 0.71, 95% CI 0.50 to 1.00, p=0.050, I²=0%) than those subjected to first-line SR.

CONCLUSIONS

This meta-analysis suggests that the first-line CA strategy could achieve better recanalization and clinical outcomes for acute PCS than first-line SR. Limited by the quality of included studies, this conclusion should be drawn with caution.

Clinical impact of the first pass effect on clinical outcomes in patients with near or complete recanalization during mechanical thrombectomy for large vessel ischemic stroke

BACKGROUND AND PURPOSE

The first pass effect has been reported as a mechanical thrombectomy (MT) success metric in patients with large vessel occlusive stroke. We aimed to compare the clinical and neuroimagign outcomes of patients who had favorable recanalization (mTICI 2c or mTICI 3) achieved in one pass versus those requiring multiple passes.

METHODS

In this "real-world" multicenter study, patients with mTICI 2c or 3 recanalization were identified from three prospectively collected stroke databases from January 2016 to December 2019. Clinical outcomes were a favorable functional outcome at 90 days (modified Rankin Scale score 0-2), and the rate of symptomatic intracranial hemorrhage (ICH) any ICH, and 90-day mortality.

RESULTS

Favorable recanalization was achieved in 390/664 (59%) of consecutive patients who underwent MT (age 71.2 ± 13.2 years, 188 [48.2%] women). This was achieved after a single thrombectomy pass (n = 290) or multiple thrombectomy passes (n = 100). The rate of favorable clinical outcome was higher (41% vs. 28 %, p = .02) in the first pass group with a continued trend on multivariate analysis that did not reaching statistical significance (OR 1.68 95% confidence interval [CI] 1.0-2.95, p = .07). Similarly, the odds of any ICH were significantly lower (OR 0.56 CI 0.32-0.97, p = .03). A similar trend of favorable clinical outcomes was noticed on subgroup analysis of patients with M1 occlusion (OR 1.81 CI 1.01-3.61, p = .08).

CONCLUSION

The first-pass reperfusion was associated with a trend toward favorable clinical outcome and lower rates of ICH. These data suggest that the first-pass effect should be the mechanical thrombectomy procedure goal.

Clinical impact of EVT with failed reperfusion in patients with acute ischemic stroke: results from the ESCAPE and ESCAPE-NA1 trials

BACKGROUND AND PURPOSE

Endovascular treatment (EVT) is a powerful treatment for large vessel occlusion (LVO) stroke if reperfusion can be achieved, while in cases with failed reperfusion, EVT may cause harm, as procedure-related complications may occur. We hypothesized that EVT with failed recanalization does not result in worse outcomes compared to best medical management and compared clinical outcomes of LVO stroke patients who underwent EVT with failed reperfusion to those who were treated with best medical management.

METHODS

We included patients with failed reperfusion from the control (EVT-only) arm of the ESCAPE-NA1 trial and the EVT arm of the ESCAPE trial and patients of the ESCAPE control arm who were treated with best medical management. Failed reperfusion following EVT was defined as modified thrombolysis in cerebral infarction score 0-2a. Proportions of good outcome (modified Rankin scale 0-2) were compared between patients who did and did not undergo EVT, and adjusted effect size estimates for EVT on outcomes were obtained.

RESULTS

We included 260 patients (110 failed EVT and 150 non-EVT patients). Proportions of good outcome were 38/110 (34.6%) with failed EVT vs.43/147 (29.3%) without EVT (adjusted odds ratio[aOR]: 1.48 [95%CI: 0.81-2.68]). Mortality and proportions of sICH in the failed EVT group vs. patients treated with best medical management were 26/110 (23.6%) vs. 28/147 (19.1%), aOR: 1.12 (95%CI: 0.56-2.24), and 7/110 (6.4%) vs. 4/150 (2.7%), aOR: 2.34 (95%CI: 0.00-22.97).

CONCLUSION

Clinical outcomes of EVT patients with failed reperfusion did not differ significantly from patients treated with best medical management.

Safety and Angiographic Efficacy of Intra-Arterial Fibrinolytics as Adjunct to Mechanical Thrombectomy: Results from the INFINITY Registry

Background and Purpose

Data on safety and efficacy of intra-arterial (IA) fibrinolytics as adjunct to mechanical thrombectomy (MT) are sparse.

Methods

INtra-arterial FIbriNolytics In ThrombectomY (INFINITY) is a retrospective multi-center observational registry of consecutive patients with anterior circulation large-vessel occlusion ischemic stroke treated with MT and adjunctive administration of IA fibrinolytics (alteplase [tissue plasminogen activator, tPA] or urokinase [UK]) at 10 European centers. Primary outcome was the occurrence of symptomatic intracranial hemorrhage (sICH) according to the European Cooperative Acute Stroke Study II definition. Secondary outcomes were mortality and modified Rankin Scale (mRS) scores at 3 months.

Results

Of 5,612 patients screened, 311 (median age, 74 years; 44.1% female) received additional IA after or during MT (194 MT+IA tPA, 117 MT+IA UK). IA fibrinolytics were mostly administered for rescue of thrombolysis in cerebral infarction (TICI) 0-2b after MT (80.4%, 250/311). sICH occurred in 27 of 308 patients (8.8%), with an increased risk in patients with initial TICI0/1 (adjusted odds ratio [aOR], 2.3; 95% confidence interval [CI], 1.1 to 5.0 per TICI grade decrease) or in those with intracranial internal carotid artery occlusions (aOR, 3.7; 95% CI, 1.2 to 12.5). In patients with attempted rescue of TICI0-2b and available angiographic follow-up, 116 of 228 patients (50.9%) showed any angiographic reperfusion improvement after IA fibrinolytics, which was associated with mRS ≤2 (aOR, 3.1; 95% CI, 1.4 to 6.9).

Conclusions

Administration of IA fibrinolytics as adjunct to MT is performed rarely, but can improve reperfusion, which is associated with better outcomes. Despite a selection bias, an increased risk of sICH seems possible, which underlines the importance of careful patient selection.

Safety and efficacy of intra-arterial fibrinolytics as adjunct to mechanical thrombectomy: a systematic review and meta-analysis of observational data

Background

Achieving the best possible reperfusion is a key determinant of clinical outcome after mechanical thrombectomy (MT). However, data on the safety and efficacy of intra-arterial (IA) fibrinolytics as an adjunct to MT with the intention to improve reperfusion are sparse.

Methods

We performed a PROSPERO-registered (CRD42020149124) systematic review and meta-analysis accessing MEDLINE, PubMed, and Embase from January 1, 2000 to January 1, 2020. A random-effect estimate (Mantel-Haenszel) was computed and summary OR with 95% CI were used as a measure of added IA fibrinolytics versus control on the risk of symptomatic intracranial hemorrhage (sICH) and secondary endpoints (modified Rankin Scale ≤2, mortality at 90 days).

Results

The search identified six observational cohort studies and three observational datasets of MT randomized-controlled trial data reporting on IA fibrinolytics with MT as compared with MT alone, including 2797 patients (405 with additional IA fibrinolytics (100 urokinase (uPA), 305 tissue plasminogen activator (tPA)) and 2392 patients without IA fibrinolytics). Of 405 MT patients treated with additional IA fibrinolytics, 209 (51.6%) received prior intravenous tPA. We did not observe an increased risk of sICH after administration of IA fibrinolytics as adjunct to MT (OR 1.06, 95% CI 0.64 to 1.76), nor excess mortality (0.81, 95% CI 0.60 to 1.08). Although the mode of reporting was heterogeneous, some studies observed improved reperfusion after IA fibrinolytics.

Conclusion

The quality of evidence regarding peri-interventional administration of IA fibrinolytics in MT is low and limited to observational data. In highly selected patients, no increase in sICH was observed, but there is large uncertainty.

Impact of eloquent motor cortex-tissue reperfusion beyond the traditional thrombolysis in cerebral infarction (TICI) scoring after thrombectomy

Background

Targeted eloquence-based tissue reperfusion within the primary motor cortex may have a differential effect on disability as compared with traditional volume-based (thrombolysis in cerebral infarction, TICI) reperfusion after endovascular thrombectomy (EVT) in the setting of acute ischemic stroke (AIS).

Methods

We explored the impact of eloquent reperfusion (ER) within primary motor cortex (PMC) on clinical outcome (modified Rankin Scale, mRS) in AIS patients undergoing EVT. ER-PMC was defined as presence of flow on final digital subtraction angiography (DSA) within four main cortical branches, supplying the PMC (middle cerebral artery (MCA) – precentral, central, postcentral; anterior cerebral artery (ACA) – medial frontal branch arising from callosomarginal or pericallosal arteries) and graded as absent (0), partial (1), and complete (2). Prospectively collected data from two centers were analyzed. Multivariate analysis was conducted to assess the impact of ER-PMC on 90-day disability (mRS) among patients with anterior circulation occlusion who achieved partial reperfusion (TICI 2a and 2b).

Results

Among the 125 patients who met the study criteria, ER-PMC distribution was: absent (0) in 19/125 (15.2%); partial (1) in 52/125 (41.6%), and complete (2) in 54/125 (43.2%). TICI 2b was achieved in 102/125 (81.6%) and ER-PMC was substantially higher in those patients (P<0.001). In multivariate analysis, in addition to age and symptomatic intracranial hemorrhage, ER-PMC had a profound independent impact on 90-day disability (OR 6.10, P=0.001 for ER-PMC 1 vs 0 and OR 9.87, P<0.001 for ER-PMC 2 vs 0), while the extent of total partial reperfusion (TICI 2b vs 2a) was not related to 90-day mRS.

Conclusions

Eloquent PMC-tissue reperfusion is a key determinant of functional outcome, with a greater impact than volume-based (TICI) degree of partial reperfusion alone. PMC-targeted revascularization among patients with partial reperfusion may further diminish post-stroke disability after EVT.

Thrombolysis in Cerebral Infarction 2b Reperfusions: To Treat or to Stop?

In patients undergoing mechanical thrombectomy, achieving complete (Thrombolysis in Cerebral Infarction 3) rather than incomplete successful reperfusion (Thrombolysis in Cerebral Infarction 2b) is associated with better functional outcome. Despite technical improvements, incomplete reperfusion remains the final angiographic result in 40% of patients according to recent trials. As most incomplete reperfusions are caused by distal vessel occlusions, they are potentially amenable to rescue strategies. While observational data suggest a net benefit of up to 20% in functional independence of incomplete versus complete reperfusions, the net benefit of secondary improvement from Thrombolysis in Cerebral Infarction 2b to 3 reperfusion might differ due to lengthier procedures and delayed reperfusion. Current strategies to tackle distal vessel occlusions consist of distal (microcatheter) aspiration, small adjustable stent retrievers, and administration of intra-arterial thrombolytics. While there are promising reports evaluating those techniques, all available studies show relevant limitations in terms of selection bias, single-center design, or nonconsecutive patient inclusion. Besides an assessment of risks associated with rescue maneuvers, we advocate that the decision-making process should also include a consideration of potential outcomes if complete reperfusion would successfully be achieved. These include (1) a futile angiographic improvement (hypoperfused territory is already infarcted), (2) an unnecessary angiographic improvement (the patient would not have developed infarction if no rescue maneuver was performed), and (3) a successful rescue maneuver with clinical benefit. Currently there is paucity of data on how these scenarios can be predicted and the decision whether to treat or to stop in a patient with incomplete reperfusion involves many unknowns. To advance the status quo, we outline current knowledge gaps and avenues of potential research regarding this clinically important question.

Effect of Pre- and In-Hospital Delay on Reperfusion in Acute Ischemic Stroke Mechanical Thrombectomy

Supplemental Digital Content is available in the text.

Background and Purpose:

Post hoc analyses of randomized controlled clinical trials evaluating mechanical thrombectomy have suggested that admission-to-groin-puncture (ATG) delays are associated with reduced reperfusion rates. Purpose of this analysis was to validate this association in a real-world cohort and to find associated factors and confounders for prolonged ATG intervals.

Methods:

Patients included into the BEYOND-SWIFT cohort (Bernese-European Registry for Ischemic Stroke Patients Treated Outside Current Guidelines With Neurothrombectomy Devices Using the Solitaire FR With the Intention for Thrombectomy; https://www.clinicaltrials.gov; Unique identifier: NCT03496064) were analyzed (n=2386). Association between baseline characteristics and ATG was evaluated using mixed linear regression analysis. The effect of increasing symptom-onset-to-admission and ATG intervals on successful reperfusion (defined as Thrombolysis in Cerebral Infarction [TICI] 2b-3) was evaluated using logistic regression analysis adjusting for potential confounders.

Results:

Median ATG was 73 minutes. Prolonged ATG intervals were associated with the use of magnetic resonance imaging (+19.1 [95% CI, +9.1 to +29.1] minutes), general anesthesia (+12.1 [95% CI, +3.7 to +20.4] minutes), and borderline indication criteria, such as lower National Institutes of Health Stroke Scale, late presentations, or not meeting top-tier early time window eligibility criteria (+13.8 [95% CI, +6.1 to +21.6] minutes). There was a 13% relative odds reduction for TICI 2b-3 (adjusted odds ratio [aOR], 0.87 [95% CI, 0.79–0.96]) and TICI 2c/3 (aOR, 0.87 [95% CI, 0.79–0.95]) per hour ATG delay, while the reduction of TICI 2b-3 per hour increase symptom-onset-to-admission was minor (aOR, 0.97 [95% CI, 0.94–0.99]) and inconsistent regarding TICI 2c/3 (aOR, 0.99 [95% CI, 0.97–1.02]). After adjusting for identified factors associated with prolonged ATG intervals, the association of ATG delay and lower rates of TICI 2b-3 remained tangible (aOR, 0.87 [95% CI, 0.76–0.99]).

Conclusions:

There is a great potential to reduce ATG, and potential targets for improvement can be deduced from observational data. The association between in-hospital delay and reduced reperfusion rates is evident in real-world clinical data, underscoring the need to optimize in-hospital workflows. Given the only minor association between symptom-onset-to-admission intervals and reperfusion rates, the causal relationship of this association warrants further research.

Registration:

URL: https://www.clinicaltrials.gov. Unique identifier: NCT03496064.

Embolus Retriever with Interlinked Cages (ERIC) versus conventional stent retrievers for thrombectomy: a propensity score-based analysis

BACKGROUND

The Embolus Retriever with Interlinked Cages (ERIC) is one of the latest devices for thrombectomies. It has several architectural features that are supposed to enhance its ability to remove clots and prevent distal emboli. We aimed to compare ERIC with standard stent retrievers (SRs) using propensity score (PS) matching.

METHODS

The clinical and radiological data of all consecutive patients treated with ERIC or standard FDA-approved stent retrievers were collected from a prospective multicenter registry. We compared procedural outcomes (recanalization rates according to the modified Thrombolysis In Cerebral Infarction (mTICI) score and procedural complications) and clinical outcomes (modified Rankin Scale (mRS) and mortality at 3 months). Matching of the populations with PS was performed to account for differences in baseline characteristics.

RESULTS

A total of 1230 patients were included. In both the PS-matched cohort (195 ERIC patients, 630 SR patients) and the inverse probability of treatment weighting PS-adjusted cohort (206 ERIC patients, 1024 SR patients) there was no difference in terms of successful recanalization (modified TICI score ≥2b), good clinical outcome (mRS=0-2 or equal to pre-stroke mRS), or mortality at 3 months. Patients treated with first-line ERIC had a higher rate of complete recanalization (mTICI 3); however, they also required more passes and more frequent rescue therapy than the SR patient group.

CONCLUSION

In a large multicenter registry with PS matching, the ERIC device provided equivalent angiographic and clinical results to conventional SRs.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov Unique identifier: NCT03776877.

Direct aspiration stroke thrombectomy: a comprehensive review

Mechanical thrombectomy is now the standard of care for acute ischemic stroke patients with large vessel occlusions, and can be performed with several devices and techniques. One of these techniques, direct aspiration (DA), consists of navigating a large-bore catheter up to the face of the clot and initiating forceful suction. This comprehensive review has three objectives: (1) to describe the direct aspiration technique; (2) to present the available evidence regarding predictive factors of DA success and performance compared with other techniques; and (3) to discuss the forthcoming improvements in distal aspiration.

Implications of achieving TICI 2b vs TICI 3 reperfusion in patients with ischemic stroke: a cost-effectiveness analysis

BACKGROUND

The benefit of endovascular thrombectomy (EVT) in stroke patients with large-vessel occlusion (LVO) depends on the degree of recanalization achieved. We aimed to determine the health outcomes and cost implications of achieving TICI 2b vs TICI 3 reperfusion in acute stroke patients with LVO.

METHODS

A decision-analytic study was performed with Markov modeling to estimate the lifetime quality-adjusted life years (QALY) of EVT-treated patients, and costs based on the degree of reperfusion achieved. The study was performed with a societal perspective in the United States' setting. The base case calculations were performed in three age groups: 55-, 65-, and 75-year-old patients.

RESULTS

Within 90 days, achieving TICI 3 resulted in a cost saving of $3676 per patient and health benefit of 11 days in perfect health as compared with TICI 2b. In the long term, for the three age groups, achieving TICI 3 resulted in cost savings of $46,498, $25,832, and $15 719 respectively, and health benefits of 2.14 QALYs, 1.71 QALYs, and 1.23 QALYs. Every 1% increase in TICI 3 in 55-year-old patients nationwide resulted in a cost saving of $3.4 million and a health benefit of 156 QALYs. Among 65-year-old patients, the corresponding cost savings and health benefit were $1.9 million and 125 QALYs.

CONCLUSION

There are substantial cost and health implications in achieving complete vs incomplete reperfusion after EVT. Our study provides a framework to assess the cost-benefit analysis of emerging diagnostic and therapeutic techniques that might improve patient selection, and increase the chances of achieving complete reperfusion.

Effect of Balloon Guide Catheter Utilization on the Incidence of Sub-angiographic Peripheral Emboli on High-Resolution DWI After Thrombectomy: A Prospective Observational Study

Background: Thrombus fragmentation causing distal emboli is a feared complication during mechanical thrombectomy (MT). We aimed to investigate the impact of procedural parameters and thrombus properties on the incidence of peripheral emboli after MT for large vessel occlusions (LVO).

Methods: We performed a prospective analysis of patients with LVO stroke successfully treated with MT, defined as a score of 2b, 2c, or 3 on the thrombolysis in cerebral infarction (TICI) scale. A follow-up MRI including high-resolution diffusion-weighted imaging (DWI) was performed within 24 h following MT. The primary endpoint was the number and volume of peripheral emboli, classified as punctuate DWI lesions distant to the diffusion-restricted core lesion. Further analysis included the influence of baseline characteristics, procedural and outcome parameters, and thrombus properties on peripheral emboli.

Results: Thirty-seven patients with successful MT met the inclusion criteria. Use of a balloon guide catheter (BGC) and TICI were the only independent predictors for a reduced number of peripheral emboli. The use of a BGC led to a significant reduction in the number and volume of peripheral emboli, with a median number/volume of peripheral emboli of 4.5/287 μl (IQR 1.25–8.25/76–569 μl) vs. 12/938 μl (IQR 4–19/242–1,836 μl). In cases where BGC was not employed, the number of peripheral emboli increased with decreasing TICI scores.

Conclusions: BGC-aided MT reduces the number of peripheral emboli in successful but incomplete reperfusion (TICI 2b and 2c). The effectiveness of this strategy therefore goes above and beyond that which can be demonstrated by the TICI score alone.

Futile complete recanalization: patients characteristics and its time course

As the goal of mechanical thrombectomy is shifting toward mTICI-3 rather than mTICI-2b, we sought to clarify the limitation of the effect of mTICI-3. A post-hoc analysis of a registry of large-vessel occlusion stroke from 46 centers was conducted. Among 2,420 registered patients, 725 patients with anterior circulation occlusion who achieved successful reperfusion were analyzed. We compared outcomes between patients with mTICI-3 and mTICI-2b, and investigated how the effect of mTICI-3 changed according to baseline characteristics and time course. The proportion of patients with favorable outcomes (mRS 0–2 at day 90) was higher among patients with mTICI-3 compared to those with mTICI-2b (adjusted OR, 2.10; 95% CI, 1.49–2.97). There was no heterogeneity in the effect of mTICI-3 with respect to age, neurological deficit, alteplase use, occluded vessels, or infarct size. mTICI-3 was associated with favorable outcomes when the puncture-to-reperfusion time was <80 minutes (adjusted OR, 2.28; 95% CI, 1.52–3.41), but not when the puncture-to-reperfusion time was ≥80 minutes. A significant heterogeneity was found in the effect of mTICI-3 reperfusion across the puncture-to-reperfusion time subgroups (P for interaction = 0.025). Until when operators should continue the procedure after mTICI-2b has been achieved, needs to be studied.

Safety and Efficacy of Intra-arterial Urokinase After Failed, Unsuccessful, or Incomplete Mechanical Thrombectomy in Anterior Circulation Large-Vessel Occlusion Stroke

Importance

Achieving complete reperfusion is a key determinant of good outcome in patients treated with mechanical thrombectomy (MT). However, data on treatments geared toward improving reperfusion after incomplete MT are sparse.

Objective

To determine whether administration of intra-arterial urokinase is safe and improves reperfusion after failed or incomplete MT.

Design, Setting, and Participants

This observational cohort study included a consecutive sample of patients treated with second-generation MT from January 1, 2010, through August 4, 2017. Data were collected from the prospective registry of a tertiary care stroke center. Of 1274 patients screened, 69 refused to participate, and 993 met the observational studies inclusion criteria of a large vessel occlusion in the anterior circulation. Data were analyzed from September 1, 2017, through September 20, 2019.

Intervention

One hundred patients received intra-arterial urokinase after failed or incomplete MT using manual microcatheter injections.

Main Outcomes and Measures

Primary safety outcome was the occurrence of symptomatic intracranial hemorrhage (sICH) according to the Prolyse in Acute Cerebral Thromboembolism II criteria. Secondary end points included 90-day mortality and 90-day functional independence (defined as modified Rankin Scale score of ≤2). Efficacy was evaluated angiographically, applying the Thrombolysis in Cerebral Infarction (TICI) scale.

Results

After exclusion of patients with posterior circulation strokes and those treated with intra-arterial thrombolytics only, 993 patients were included in the final analyses (median age, 74.6 [interquartile range, 62.6-82.2] years; 505 [50.9%] women). Additional intra-arterial urokinase was administered in 100 patients (10.1%). The most common reason for administering intra-arterial urokinase was incomplete reperfusion (TICI<3) after MT (53 [53.0%]). After adjusting for baseline characteristics underlying case selection, intra-arterial urokinase was not associated with an increased risk of sICH (adjusted odds ratio [aOR], 0.81; 95% CI, 0.31-2.13) or 90-day mortality (aOR, 0.78; 95% CI, 0.43-1.40). Among 53 cases of partial or near-complete reperfusion and treated with intra-arterial urokinase, 32 (60.4%) had early reperfusion improvement, and 18 of 53 (34.0%) had an improvement in TICI grade. Correspondingly, patients treated with intra-arterial urokinase had higher rates of functional independence after adjusting for the selection bias favoring a priori poor TICI grades in the intra-arterial urokinase group (aOR, 1.93; 95% CI, 1.11-3.37).

Conclusions and Relevance

In selected patients, adjunctive treatment with intra-arterial urokinase during or after MT was safe and improved angiographic reperfusion. Systemic evaluation of this approach in a multicenter prospective registry or a randomized clinical trial seems warranted.

Risk of secondary embolism events during mechanical thrombectomy for acute ischemic stroke: A single-center study based on histological analysis

OBJECTIVE

Secondary embolism (SE) is a common adverse event during mechanical thrombectomy (MT) for acute intracranial large vessel occlusion, which could lead to incomplete revascularization and increased maneuvers. However, the mechanisms behind SE are still unclear. In this study, we aimed to investigate the risk factors of SE, with a focus on clot composition.

PATIENTS AND METHODS

Consecutive patients with retrieved clots were reviewed. Histologic examination for thrombus included Hematoxylin and eosin, Martius Scarlet Blue, immunohistochemistry for von Willebrand factor (VWF). Patients included were assigned to SE or no SE group. The differences in histological composition and clinical characteristics were compared, and logistic regression was conducted for predictors of SE.

RESULTS

Fifty-four patients were included, of which 19 were identified as having an SE. For patients with SE, there was more history of stroke or transient cerebral ischemia (TIA) (57.9 % vs. 28.6 %, p = 0.035), more occlusion located in terminal internal carotid artery (ICA) (63.2 % vs. 25.7 %, p = 0.007), relatively more contact aspiration used as frontline strategy (68.4 % vs. 45.7 %, p = 0.110), and less eTICI2c-3 recanalization achieved (52.6 % vs. 91.4 %, p = 0.003). As for histologic composition, the clots in SE group showed a higher proportion of erythrocyte fractions (42.9 % vs. 26.8 %, p = 0.045), while the other components were comparable with the non-SE group. Multivariate analysis suggested that a history of stroke or TIA (OR 6.45, 95 %CI 1.41-29.44, p = 0.016) and ICA occlusion (OR 8.05, 95 %CI 1.80-36.10, p = 0.006) could independently predict SE.

CONCLUSION

History of TIA or stroke and occlusion in the terminal ICA were found to be independent predictors for SE. Thrombus with a higher erythrocyte fractions might be more fragile. Further studies are needed.

Sub-angiographic peripheral emboli in high resolution DWI after endovascular recanalization

Background and aim

To analyze the incidence of peripheral emboli after successful mechanical thrombectomy (MT) of intracranial large vessel occlusions (LVO).

Methods

We performed a prospective analysis of patients with intracranial LVO who underwent successful MT and received a 1.5 T MRI including diffusion-weighted imaging (DWI) in standard- and high-resolution as well as susceptibility-weighted imaging (SWI) on the day following the intervention. Reperfusion grade was assessed on post-thrombectomy digital subtraction angiography (DSA) using the expanded thrombolysis in cerebral infarction (eTICI) scale. Punctuate DWI lesions distal to the DWI core lesion were classified as peripheral emboli. DWI lesions outside the primary affected vascular territory were classified as emboli into new territories. Additionally, SWI and post-thrombectomy DSA were analyzed and correlated to findings on DWI.

Results

Twenty-eight patients undergoing successful MT met the inclusion criteria. In 26/28 patients (93%), a total of 324 embolic lesions were detected in DWI representing 2.1% of the cumulated ischemic core volume. 151 peripheral emboli were detected in standard-resolution DWI, 173 additional emboli were uncovered in high-resolution DWI. Eight out of nine patients with an eTICI 3 reperfusion had embolic lesions (29 DWI lesions). 9.6% (31/324) of peripheral emboli were observed in vascular territories not affected by the LVO. SWI lesions were observed in close proximity to 10.2% (33/324) of DWI lesions.

Conclusions

Peripheral emboli are frequent after MT even after complete reperfusion. These emboli occur rather in the vascular territory of the occluded vessel than in other territories. A large proportion of peripheral emboli is only detected by high-resolution DWI.

Electronic supplementary material

The online version of this article (10.1007/s00415-020-09719-1) contains supplementary material, which is available to authorized users.

Mechanical Thrombectomy in Ischemic Stroke Patients With Alberta Stroke Program Early Computed Tomography Score 0-5

Supplemental Digital Content is available in the text.

Background and Purpose—

If anterior circulation large vessel occlusion acute ischemic stroke patients presenting with ASPECTS 0–5 (Alberta Stroke Program Early CT Score) should be treated with mechanical thrombectomy remains unclear. Purpose of this study was to report on the outcome of patients with ASPECTS 0–5 treated with mechanical thrombectomy and to provide data regarding the effect of successful reperfusion on clinical outcomes and safety measures in these patients.

Methods—

Multicenter, pooled analysis of 7 institutional prospective registries: Bernese-European Registry for Ischemic Stroke Patients Treated Outside Current Guidelines With Neurothrombectomy Devices Using the SOLITAIRE FR With the Intention for Thrombectomy (Clinical Trial Registration—URL: https://www.clinicaltrials.gov. Unique identifier: NCT03496064). Primary outcome was defined as modified Rankin Scale 0–3 at day 90 (favorable outcome). Secondary outcomes included rates of day 90 modified Rankin Scale 0–2 (functional independence), day 90 mortality and occurrence of symptomatic intracerebral hemorrhage. Multivariable logistic regression analyses were performed to assess the association of successful reperfusion with clinical outcomes. Outputs are displayed as adjusted Odds Ratios (aOR) and 95% CI.

Results—

Two hundred thirty-seven of 2046 patients included in this registry presented with anterior circulation large vessel occlusion and ASPECTS 0–5. In this subgroup, the overall rates of favorable outcome and mortality at day 90 were 40.1% and 40.9%. Achieving successful reperfusion was independently associated with favorable outcome (aOR, 5.534; 95% CI, 2.363–12.961), functional independence (aOR, 5.583; 95% CI, 1.964–15.873), reduced mortality (aOR, 0.180; 95% CI, 0.083–0.390), and lower rates of symptomatic intracerebral hemorrhage (aOR, 0.235; 95% CI, 0.062–0.887). The mortality-reducing effect remained in patients with ASPECTS 0–4 (aOR, 0.167; 95% CI, 0.056–0.499). Sensitivity analyses did not change the primary results.

Conclusions—

In patients presenting with ASPECTS 0–5, who were treated with mechanical thrombectomy, successful reperfusion was beneficial without increasing the risk of symptomatic intracerebral hemorrhage. Although the results do not allow for general treatment recommendations, formal testing of mechanical thrombectomy versus best medical treatment in these patients in a randomized controlled trial is warranted.

Association Between Thrombus Density and Reperfusion Outcomes Using Different Thrombectomy Strategies: A Single-Center Study and Meta-Analysis

Background: For patients with acute ischemic stroke (AIS), the thrombus density on non-enhanced CT (NECT) indicates the composition of the thrombus, a characteristic that impacts the efficacy of mechanical thrombectomy (MT). A previous meta-analysis suggested a correlation between higher thrombus density and successful reperfusion, but some new studies have drawn different conclusions. This single-center study and meta-analysis aimed to detect the association between thrombus density and reperfusion outcomes based on various thrombectomy strategies.

Methods: We reviewed AIS patients who underwent MT at our center between July 2015 and May 2019. Thrombus density was recorded as mean Hounsfield Unit (HU) value on 1-mm reconstructed NECT, and expanded Thrombolysis In Cerebral Infarction (eTICI) scale was used to evaluate the reperfusion grade. The difference in thrombus density was examined according to reperfusion outcomes. Then, we systematically searched relevant literature on this issue. The random effect model was used to calculate standardized mean difference (SMD), and subgroup analysis was conducted according to MT strategies employed, including stent retriever (SR), contact aspiration (CA), Solumbra (a combination of SR and aspiration), and multiple thrombectomy modalities.

Results: Sixty-four patients with anterior circulation AIS were included in our single-center study with 57 (89.1%) achieving successful reperfusion (eTICI2b-3). Retrospective analysis showed no significant difference in thrombus density between eTICI2b-3 and eTICI0-2a reperfusion (65.27 vs. 62.19, p = 0.462). As for systematic review, 11 studies were included in qualitative analysis, among which 6 had data available for meta-analysis. Pooled result showed that a comparable thrombus density between eTICI2b-3 and eTICI0-2a reperfusion (SMD 0.14, 95%CI −0.28 to 0.57, p = 0.50). Interestingly, in the SR subgroup, eTICI2b-3 reperfusion showed a significant higher thrombus density (SMD 0.53, 95%CI 0.10 to 0.96, p = 0.02), while an inverse trend was observed in the CA subgroup (SMD −0.48, 95%CI −0.88 to −0.07, p = 0.02).

Conclusions: Although the pooled result of meta-analysis did not show a significant association between thrombus density and successful reperfusion, subgroup analysis implicated that the SR technique might be prone to retrieve high-density thrombus, while the CA subgroup showed an opposite tendency. Further studies are needed to confirm these results and to investigate its role in the optimization of thrombectomy strategy.

Mechanical thrombectomy for basilar artery occlusion: efficacy, outcomes, and futile recanalization in comparison with the anterior circulation

BACKGROUND

Performing mechanical thrombectomy (MT) in patients with basilar artery occlusion (BAO) is currently not evidence-based.

OBJECTIVE

To compare patients' outcome, relative merits of achieving recanalization, and predictors of futile recanalization (FR) between BAO and anterior circulation large vessel occlusion (ACLVO) MT.

METHODS

In the multicenter BEYOND-SWIFT registry (NCT03496064), univariate and multivariate (displayed as adjusted Odds Ratios, aOR and 95% confidence intervals, 95%-CI) outcome comparisons between BAO (N=165) and ACLVO (N=1574) were performed. The primary outcome was favorable outcome at 90 days (modified Rankin Scale, mRS 0-2). Secondary outcome included mortality, symptomatic intracranial hemorrhage (sICH) and FR. The relative merits of achieving successful recanalization between ACLVO and BAO were evaluated with interaction terms.

RESULTS

MT in BAO was more often technically effective and equally safe in regards to mortality and sICH when compared to ACLVO. When adjusting for baseline differences, there was no significant difference between BAO vs ACLVO regarding rates of favorable outcome (aOR 0.986, 95%-CI 0.553 - 1.758). However, BAO were associated with increased rates of FR (aOR 2.146, 95%-CI 1.267 - 3.633). Predictors for FR were age, stroke severity, maneuver count and intracranial stenting. No significant heterogeneity on the relative merits of achieving successful recanalization on several outcome parameters were observed when comparing BAO and ACLVO.

CONCLUSIONS

In selected patients, similar outcomes can be achieved in BAO and ACLVO patients treated with MT. Randomized controlled trials comparing patient selection and interventional strategies seem warranted to avoid FR.

TRIAL REGISTRATION NUMBER

NCT03496064.

Correlation of imaging and histopathology of thrombi in acute ischemic stroke with etiology and outcome

Mechanical thrombectomy has become the stand of care for patients with large vessel occlusions, yet major improvements in thrombectomy speed, efficacy, and completeness can still be achieved. High rates of clot fragmentation and failure to remove the clot resulting in poor neurological outcomes suggest that in order to further advance the field of stroke intervention we must turn our attention towards understanding the science of clot. Accurately identifying the composition of the occlusive clot prior to intervention could significantly influence the success of the revascularization strategy used to treat them. Numerous features of thromboemboli could be studied and characterized, including quantitative histomorphometry and diagnostic imaging characteristics. Each of these features might logically predict superior thrombectomy outcomes with one device or another. This article aims to review the current literature on histopathological composition of acute ischemic stroke clots, with a particular focus on the correlation between clot composition and diagnostic imaging, stroke etiology and revascularization outcomes.

A canine model of mechanical thrombectomy in stroke

Purpose

To develop a preclinical model of stroke with a large vessel occlusion treated with mechanical thrombectomy.

Materials and methods

An ischemic stroke model was created in dogs by the introduction of an autologous clot into the middle cerebral artery (MCA). A microcatheter was navigated to the clot and a stent retriever thrombectomy was performed with the goal to achieve Thrombolysis in Cerebral Ischemia (TICI) 2b/3 reperfusion. Perfusion and diffusion MRI was acquired after clot placement and following thrombectomy to monitor the progression of restricted diffusion as well as changes in ischemia as a result of mechanical thrombectomy. Post-mortem histology was done to confirm MCA territory infarct volume.

Results

Initial MCA occlusion with TICI 0 flow was documented in all six hound-cross dogs entered into the study. TICI 2b/3 revascularization was achieved with one thrombectomy pass in four of six animals (67%). Intra-procedural events including clot autolysis leading to spontaneous revascularization (n=1) and unresolved vasospasm (n=1) accounted for thrombectomy failure. In one case, iatrogenic trauma during microcatheter navigation resulted in a direct arteriovenous fistula at the level of the cavernous carotid. Analysis of MRI indicated that a volume of tissue from the initial perfusion deficit was spared with reperfusion following thrombectomy, and there was also a volume of tissue that infarcted between MRI and ultimate recanalization.

Conclusion

We describe a large animal stroke model in which mechanical thrombectomy can be performed. This model may facilitate, in a preclinical setting, optimization of complex multimodal stroke treatment paradigms for clinical translation.