Distal M1 Research Articles

Stent-unsheathed effect predicts acute distal middle cerebral artery atherosclerotic disease-related occlusion

BackgroundThe differentiation of intracranial atherosclerosis (ICAS) and embolism is important. ObjectiveIn cases of ICAS, we observe a phenomenon that we call the “post-stent-deployment effect”; that is, all major branches are clearly visible beyond the occlusion segment when the stent is deployed at the site of occlusion. Our objective is to evaluates whether this post-stent-deployment effect can be used to differentiate ICAS from embolism in the distal M1 segment occlusion. MethodsWe conduct a retrospective study which reviewed consecutive patients with acute distal M1 segment and in whom recanalization was achieved by endovascular treatment. The post-stent-deployment effect was assessed in these patients. The sensitivity, specificity, positive predictive values (PPV), and accuracy of the post-stent-deployment effect for prediction of ICAS were assessed. ResultsFrom January 2015 to July 2018, a total of 80 patients were evaluated. The post-stent-deployment effect was more frequently observed in patients with ICAS than in those with embolism (100% vs 15.0%, P < .001). For identifying ICAS in distal M1 segment, the sensitivity, specificity, PPV, and accuracy of the post-stent-deployment effect were 100%, 85.0%, 69.0%, and 88.7%, respectively. ConclusionOur study finds that the sensitivity and accuracy of the post-stent-deployment effect in predicting distal M1 segment ICAS occlusion in patients with acute symptoms was high, and it may be useful in identifying ICAS lesion.

Bridging Therapy or IV Thrombolysis in Minor Stroke with Large Vessel Occlusion.

Whether bridging therapy (intravenous thrombolysis [IVT] followed by endovascular treatment) is superior to IVT alone in minor stroke with large vessel occlusion (LVO) is unknown. Multicentric retrospective observational study including, in intention-to-treat, consecutive IVT-treated minor strokes (National Institutes of Health Stroke Scale [NIHSS] ≤ 5) with LVO, with or without additional mechanical thrombectomy. Propensity-score (inverse probability of treatment weighting) was used to reduce baseline between-groups differences. The primary outcome was excellent outcome, that is, modified Rankin score 0 to 1 at 3 months follow-up. Overall, 598 patients were included (214 and 384 in the bridging therapy and IVT groups, respectively). Following propensity-score weighting, the distribution of baseline clinical and radiological variables was similar across the two patient groups. Compared with IVT alone, bridging therapy was not associated with excellent outcome (odds ratio [OR] = 0.96; 95% confidence interval [CI] = 0.75-1.24; p = 0.76), but was associated with symptomatic intracranial hemorrhage (OR = 3.01; 95% CI = 1.77-5.11; p < 0.0001). Occlusion site was a strong modifier of the effect of bridging therapy on outcome (pinteraction < 0.0001), with bridging therapy associated with higher odds of excellent outcome in proximal M1 (OR = 3.26; 95% CI = 1.67-6.35; p = 0.0006) and distal M1 (OR = 1.69; 95% CI = 1.01-2.82; p = 0.04) occlusions, but with lower odds of excellent outcome for M2 (OR = 0.53; 95% CI = 0.38-0.75; p = 0.0003) occlusions. Bridging therapy was associated with higher rates of symptomatic intracranial hemorrhage in M2 occlusions only (OR = 4.40; 95% CI = 2.20-8.83; p < 0.0001). Although overall outcomes were similar in intended bridging therapy as compared to intended IVT alone in minor strokes with LVO, our results suggest that intended bridging therapy may be beneficial in M1 occlusions, whereas the benefit-risk profile may favor IVT alone in M2 occlusions. ANN NEUROL 2020 ANN NEUROL 2020;88:160-169.

SAT-468 Anticoagulation Conundrum: A Case Of Embolic Stroke Due To Thyrotoxic Atrial Fibrillation

Background: Thyrotoxicosis is not incorporated into any of the atrial fibrillation (AF) CVA risk stratification methods, including CHADS2VASc, as neither the American College of Cardiology/American Heart Association nor the American College of Chest Physicians view it as an independent risk factor of CVA. However, the literature has reported numerous cases of patients with thyrotoxic AF and low CHADS2VASc scores who developed CVA. It is unclear which patients with thyrotoxic AF would benefit from prophylactic anticoagulation (AC). Clinical Case: A 50-year-old male without past medical history presented for palpitations. He was found to be in AF with rapid ventricular rate. Labs revealed thyrotoxicosis (TSH <0.010 [RR 0.34-5.6 μIU/mL], FT4 3.57 [RR 0.61-1.64 ng/dL], FT3 5.26 [RR 2.5-4.5 pg/mL], and TSI negative). He was started on methimazole but no AC, as his CHADS2VASc score was 0. A few hours after admission, he developed a right-sided facial droop and weakness & aphasia. CT head showed acute left MCA infarct. CTA head/neck revealed occlusive embolus in the distal left M1 segment. He underwent IR-guided embolectomy and received intra-arterial tPA. Echocardiogram did not show thrombi or atrial level shunt but showed right atrial dilation. After extensive work-up, etiology of CVA was determined most likely a cardioembolic source due to thyrotoxic AF. Patient was treated with PTU and steroids initially for two days due to recent contrast exposure (CTA and embolectomy) and poor neurologic status, in order to obtain the added benefit of decreased T4 to T3 peripheral conversion. Patient was started on AC two weeks after his CVA (given initial risk of hemorrhagic conversion due to large CVA burden), at which time his weakness and aphasia were slowly improving, but he remained with significant neurologic deficits. Discussion: The current thought that thyrotoxicosis is not an independent risk factor of CVA in patients with AF has led to recommendations against prophylactic AC for this specific group. Although recent research has suggested that patients with thyrotoxic AF are at a lower risk of CVA than patients with non-thyrotoxic AF, there have still been many reported cases of CVA in patients who have thyrotoxic AF but no other risk factors for CVA. This discrepancy in association between thyrotoxic AF and CVA needs to be clarified. Conclusion: This case of a middle-aged man with thyrotoxic AF who developed a debilitating CVA after being treated according to his CHADS2VASC score of 0 (he was not given prophylactic AC) mirrors multiple cases in the literature. It highlights the potential benefit of examining thyrotoxic patients with AF more closely in order to more effectively risk stratify them for CVA or further exploring the relationship between thyrotoxicosis and CVA. This may help to identify more patients who could benefit from AC and thus prevent devastating consequences of CVA.

Endovascular Therapy for Patients With Acute Ischemic Stroke During the COVID-19 Pandemic: A Proposed Algorithm.

Endovascular Therapy for Patients With Acute Ischemic Stroke During the COVID-19 Pandemic: A Proposed Algorithm.

CT Angiography in Evaluating Large-Vessel Occlusion in Acute Anterior Circulation Ischemic Stroke: Factors Associated with Diagnostic Error in Clinical Practice.

It is currently not completely clear how well radiologists perform in evaluating large-vessel occlusion on CTA in acute ischemic stroke. The purpose of this study was to investigate potential factors associated with diagnostic error. Five hundred twenty consecutive patients with a clinical diagnosis of acute ischemic stroke (49.4% men; mean age, 72 years) who underwent CTA to evaluate large-vessel occlusion of the proximal anterior circulation were included. CTA scans were retrospectively reviewed by a consensus panel of 2 neuroradiologists. Logistic regression analysis was performed to investigate the association between several variables and missed large-vessel occlusion at the initial CTA interpretation. The prevalence of large-vessel occlusion was 16% (84/520 patients); 20% (17/84) of large-vessel occlusions were missed at the initial CTA evaluation. In multivariate analysis, non-neuroradiologists were more likely to miss large-vessel occlusion compared with neuroradiologists (OR = 5.62; 95% CI, 1.06-29.85; P = .04), and occlusions of the M2 segment were more likely to be missed compared with occlusions of the distal internal carotid artery and/or M1 segment (OR = 5.69; 95% CI, 1.44-22.57; P = .01). There were no calcified emboli in initially correctly identified large-vessel occlusions. However, calcified emboli were present in 4 of 17 (24%) initially missed or misinterpreted large-vessel occlusions. Several factors may have an association with missing a large-vessel occlusion on CTA, including the CTA interpreter (non-neuroradiologists versus neuroradiologists), large-vessel occlusion location (M2 segment versus the distal internal carotid artery and/or M1 segment), and large-vessel occlusion caused by calcified emboli. Awareness of these factors may improve the accuracy in interpreting CTA and eventually improve stroke outcome.

Abstract 101: Predictors of Early Neurological Deterioration in Minor Strokes With Large Vessel Occlusion Treated With Intravenous Thrombolysis. A French Multicentric Observational Study (MINOR-STROKE)

Introduction: Whether thrombectomy added on intravenous thrombolysis (IVT), as compared to IVT alone, is beneficial in minor strokes with large vessel occlusion (LVO) is unknown. To identify predictors of early neurological deterioration (END) following IVT alone may help to select the best candidates for additional thrombectomy. Methods: MINOR-STROKE was a multicentric retrospective registry collecting data of IVT-treated minor strokes (NIHSS≤5) with LVO (internal carotid artery [ICA], M1, M2 or basilar artery; with central reading) treated with or without additional thrombectomy in 45 French stroke units. The patients initially intended for IVT alone, including those who eventually received thrombectomy due to END, were included in the present analysis. END was defined as a ≥4 points on NIHSS within 24hrs following admission. Thrombus length was measured centrally either on T2*-MRI, CT (hyperdense middle cerebral artery) or CT-angiography. Results: Overall, 799 patients were included: mean age 69 years, median NIHSS 3, occlusion located in ICA±M1/M2, proximal M1, distal M1, M2, or basilar artery in 20%, 7%, 19%, 50% and 4% of patients, respectively. Thrombus was visible in 78% of patients (median length 9mm, IQR 6-12mm). END occurred in 15% of patients and was associated with poor 3-month functional outcome (mRS&gt;2: 55% vs. 12% of patients with and without END, respectively). Only 15% of ENDs were due to intracranial haemorrhage. In multivariable analysis, a more proximal occlusion site (M2 [reference], distal M1: OR 2.1 [IC95% 1.1-4.1], proximal M1: OR 3.8 [1.6-9.1], ICA±M1/M2: OR 5.0 [2.6-9.6], basilar artery: OR 4.9 [1.1-4.1]; P &lt;0.001) and a longer thrombus (&lt;6mm [reference], [6-9mm[: OR 1.3 [IC95% 0.6-2.9], [9-12mm[: OR 1.8 [0.8-3.9] and ≥12mm: OR 2.7 [1.3-5.6]; P =0.036) were independently associated with END. END occurred in 33%, 19%, 14%, 7% and 27% of patients with ICA±M1/M2, M1 proximal, M1 distal, M2 and basilar artery, respectively, and in 8%, 10%, 14% et 23% of patients with thrombus length of &lt;6, [6-9[, [9-12[ and ≥12mm, respectively. Conclusion: Our study suggests that thrombus location and length are strong predictors of END in minor strokes with LVO. This may help to select the best candidates for additional endovascular therapy.

Abstract TP19: Thrombectomy in Medium Arteries Works for Distal Vessel Occlusions in Acute Ischemic Stroke - STRATIS

Background: Mechanical thrombectomy is established for large vessel occlusions in acute ischemic stroke, but the potential role in distal vessel occlusions of medium arteries is largely unknown. Such distal arterial segments have not been measured with respect to thrombectomy devices used during endovascular therapy. We conducted a systematic analysis of arterial size, segmental anatomy and stent retriever device performance during thrombectomy. Methods: The STRATIS angiography core lab adjudicated the exact location of the occlusion, proximal and distal device deployment, relationship to arterial bifurcations and anatomical nomenclature. Arterial diameters were measured at all of these sites. Statistical analyses examined the relationship between these variables, arterial recanalization and eTICI reperfusion. Results: Thrombectomy was performed with various device sizes, including Solitaire 4x40 in 36.3% (306/844), Solitaire 6x30 in 31.4% (265/844), Solitaire 4x20 in 26.4% (223/844), unspecified in 3.8% (32/844), Solitaire 6x20 in 1.3% (11/844) and Solitaire 4x15 in 0.8% (7/844). Arterial diameter at the occlusion site was median 2.17mm (1.40-3.59) in the distal M1, 1.67mm (0.81-2.98) in the proximal M2, 1.50mm (0.92-1.99) in the distal M2, 1.24mm (0.67-2.00) in the M3 and 1.88mm (1.49-1.94) in the P1. Considerable overlap was noted between arterial sizes at occlusion sites carrying different segmental arterial nomenclature or vessel names. During device deployment in STRATIS, median arterial diameter at the occlusion site was 2.4mm (IQR 1.9, 3.4), 2.9mm (IQR 2.2, 3.6) at the proximal stent marker and 1.4mm (IQR 1.2, 1.7) at the distal stent marker. Substantial eTICI reperfusion (2b-3) was achieved in all distal vessel occlusions (Table 1). Conclusions: Substantial reperfusion may be achieved with currently available mechanical thrombectomy devices for distal vessel occlusions in medium arteries.

Abstract WP24: Arterial Tortuosity is a Potent Determinant of Safety in Endovascular Therapy for Ischemic Stroke

Background: Subarachnoid hemorrhage (SAH) associated with vessel injury during endovascular therapy for acute ischemic stroke is a known complication. Arterial anatomy may predispose to increased risk of SAH and technical safety, yet factors such as clot location, arterial size and tortuosity have not been explored. We examined these anatomical factors with respect to SAH during thrombectomy. Methods: Arterial anatomy at the site of occlusion and mechanical thrombectomy during device deployment was detailed by the STRATIS core lab. Luminal diameters, arterial branching and segmental tortuosity were measured. Arterial tortuosity was quantified using the distance factor metric (DFM). Statistical analyses included descriptives of arterial anatomy, with univariate and multivariate modeling to predict SAH. Results: Arterial tortuosity in each segment from the proximal cerebral arteries to the site of occlusion was quantified in 790 subjects treated with mechanical thrombectomy in STRATIS. Cumulative arterial tortuosity to the site of vessel occlusion was greater in distal lesions (Table 1). SAH was clearly linked with more distal thrombectomy (p=0.017), with 19.0% of distal M2, 16.7% of M3, 7.3% of distal M1, 5.8% of proximal M2, 2.4% of distal ICA and 2.1% of proximal M1. Multivariate prediction of SAH revealed that arterial diameter was unrelated to SAH (p=0.30) when accounting for tortuosity, whereas the presence of tortuosity tripled the risk of SAH (OR 3, p&lt;0.05). Conclusions: This novel systematic analysis of arterial tortuosity and angiographic anatomy during mechanical thrombectomy establishes tortuosity as a determinant of SAH, providing insight for future techniques and innovative device designs.

Abstract 172: Bridging Therapy versus Intravenous Thrombolysis in Minor Stroke With Large Vessel Occlusion. A French Multicentric Observational Study (MINOR-STROKE)

Introduction: Whether bridging therapy (endovascular therapy [EVT] plus intravenous thrombolysis [IVT]) is superior to IVT alone in minor strokes with large vessel occlusion (LVO) is unknown. Methods: MINOR-STROKE was a multicentric retrospective cohort collecting data of IVT-treated minor strokes (NIHSS≤5) with LVO (ICA, M1 or M2; with central reading) treated with or without additional EVT in 45 French stroke units. Patients immediately intended for additional EVT -including those who eventually did not receive EVT- were analyzed in the bridging group, whereas patients initially intended for IVT alone -including those who eventually received rescue EVT- were analyzed in the IVT group. Propensity-score (inverse probability of treatment weighting) was used to reduce baseline between-groups differences. The primary outcome was excellent outcome defined as mRS 0-1 at 3 month. Results: Overall, 965 patients were included (237 and 728 in the bridging therapy and IVT groups, respectively). The distribution of all baseline clinical and radiological variables across the 2 groups were similar following propensity-score weighting. Compared with IVT alone, bridging therapy was not associated with better excellent outcome (OR=0.99; 95%CI 0.79-1.24; P =0.95), but was associated with higher risks of symptomatic intracranial haemorrhage (OR=2.39; 95%CI 1.51-3.80; P &lt;0.001). However, occlusion site was a strong modifier of the effect of bridging therapy on excellent outcome (P interaction &lt;0.0001), bridging therapy seeming beneficial in isolated ICA (OR=2.75; 95%CI 1.23 6.13; P =0.01) and proximal M1±ICA (OR=3.63; 95%CI 1.94-6.79; P &lt;0.0001), neutral for distal M1±ICA (OR=0.96; 95%CI 0.63-1.48; P =0.87) but deleterious for M2±ICA (OR=0.54; 95%CI 0.38-0.75; P &lt;0.001) occlusions. Bridging therapy was only associated with sICH in patients with M2 occlusions (OR=4.73; 95%CI 2.35-9.49; P &lt;0.0001). Conclusion: Overall, we observed similar outcomes with bridging therapy or IVT alone in minor strokes with LVO. However, our data suggest benefit of bridging therapy in patients with ICA or proximal M1 occlusion and potential harm through sICH in patients with M2 occlusion. Randomized trials are strongly commended to confirm these results.

ADAPT with New Catalyst 5 Reperfusion Catheter for Distal M2 Ischemic Stroke: Preliminary Experience

We sought to assess preliminary technical and clinical outcomes of Catalyst 5 (CAT 5) as front-line aspiration treatment for M2-M3 occlusion in acute ischemic stroke. Patients with symptomatic stroke and distal M2 or M3 occlusions were enrolled retrospectively. A direct aspiration first-pass technique was used as the first treatment option for absolute contraindication to intravenous fibrinolytic therapy. Time to recanalization, first attempt recanalization, and number of attempts were recorded. Successful recanalization was defined as a modified thrombolysis in cerebral infarction score ≥2b; incidence of procedure-related complications was recorded. National Institutes of Health Stroke Scale at discharge and modified Rankin Scale score at 90 days were evaluated by a dedicated neurologist. A total of 11 acute occlusions of distal M2-M3 segment were treated with a direct aspiration first-pass technique using CAT 5 (mean age 69.3 years). Tandem occlusion was present in 2 cases. Intracranial preocclusive mean vessel diameter was 1.9 mm. Overall modified thrombolysis in cerebral infarction score ≥2b was obtained in 72.7% of patients with mean time to recanalization of 36.4 minutes and a mean of 1.9 attempts. First-attempt recanalization with CAT 5 was obtained in 54% of patients with a mean time to recanalization of 29.2 minutes. A stent retriever with proximal aspiration was incorporated as a rescue device in 2 cases. Embolization of new territories was reported after CAT 5 aspiration in 1 patient. No intracranial hemorrhage was detected on follow-up computed tomography. The median National Institutes of Health Stroke Scale score at discharge was 3. At 90 days, a modified Rankin Scale score of 0-2 was achieved in 90.9% of patients. Preliminary experience using CAT 5 in distal occlusions demonstrates that it may be safe and effective in acute stroke treatment.

Left External Carotid Artery to the Middle Cerebral Artery Bypass with Radial Artery Graft and Clip Reconstruction of a Large Middle Cerebral Artery Fusiform Aneurysm: 3-Dimensional Operative Video.

This 16-yr-old boy presented with episodes of severe headaches, blurred vision, dizziness, and muffled hearing and was discovered to have a large fusiform aneurysm of the left middle cerebral artery (MCA), M1 segment, 20×12 mm in dimension. The lenticulostriate arteries were arising proximal and distal to the aneurysm, but the anterior temporal artery was arising from the aneurysm. The aneurysm culminated in the distal M1 segment, and M1 immediately branched into 3 M2 vessels, the lower one being the larger. Due to origin of the lenticulostriate arteries and the anterior temporal artery and patient's age, a bypass was preferred to a flow diversion stent. He underwent left frontotemporal craniotomy and orbital osteotomy, left cervical external carotid artery exposure followed by radial artery graft extraction. The Sylvian fissure was opened and intracranial ICA was exposed for proximal control. The distal M2 vessels traced back toward the aneurysm. The aneurysm was not clippable and a bypass to the larger inferior M2 branch was performed followed by aneurysm trapping. The radial artery graft bypass was placed from the left external carotid artery to the M2 segment of left MCA, followed by clip reconstruction and occlusion of the MCA aneurysm with the preservation of the anterior temporal branch and the lenticulostriate vessels. The patient had no postoperative complications. At the follow-up, one month after surgery, he was doing well, and his angiogram demonstrated patency of the bypass. This video shows the management of a complex fusiform M1 aneurysm with bypass and trapping. Informed consent was obtained from the patient prior to the surgery that included videotaping of the procedure and its distribution for educational purposes. All relevant patient identifiers have also been removed from the video and accompanying radiology slides.

Iodine-stained fragmented thromboembolism.

Iodine-stained fragmented thromboembolism (ISFT) is a rare phenomenon encountered in the immediate aftermath of mechanical thrombectomy or rarely as a complication of post-carotid stenting. The aim was to describe the imaging appearance and discuss its pathophysiology. This is a retrospective review of patients who underwent mechanical thrombectomy for acute stroke at a single institution over the period of one year. All patients underwent the standard acute stroke imaging protocol (CT head, CT angiogram (CTA) and CT brain perfusion) and when clinically appropriate followed by catheter angiogram and mechanical thrombectomy. ISFT was defined as an arterial luminal filling defect with Hounsfield density equal to or greater than iodine seen on the biplanar CT or conventional CT. The presence and location of ISFT were documented. Standard CT angiogram (CTA) or magnetic resonance angiogram (MRA) was performed 24-48 hours after the neurointerventional procedure to assess for recanalization, volume of infarction and the fate of the ISFT. ISFTs were identified in eight (five males and three females, age range 18-80 years) out of 49 patients in the following locations: distal M1 (n = 1), M2 (n = 4), M3 (n = 1), A1 (n = 1), distal A2 (n = 1). ISFT and vessel recanalization occurred in five patients on follow-up. ISFT and vessel occlusion persisted in two patients. ISFT is likely the result of mechanical disruption of a thromboembolus, and porosity of the thromboembolus fragment may transiently retain iodinated contrast. Recognition of this entity may be important to aid detection of residual thromboembolism and avoid misinterpretation as calcified thromboembolism.

Persistence of Gut Microbiota Dysbiosis and Chronic Systemic Inflammation After Cerebral Infarction in Cynomolgus Monkeys

Background: The bidirectional interaction between the gut and brain after stroke through the immune-mediated pathway has been studied. However, the long-term effects of gut microbiota and systemic immune homeostasis after cerebral ischemia remain unclear. We examined long-term changes in the gut microbiota and systemic inflammatory cytokines after cerebral infarction in cynomolgus monkeys.Methods: Twelve monkeys underwent successful distal M1 segment of the left middle cerebral artery occlusion (MCAO) and were randomly and equally assigned to the MCAO-1.5 m, MCAO-6 m, and MCAO-12 m groups, which were sacrificed 1.5, 6, and 12 months after cerebral infarction induction, respectively. Four monkeys that underwent a sham operation were sacrificed 12 months later. The gut microbiota and short-chain fatty acids (SCFAs) were analyzed by 16S rDNA sequencing and gas chromatography mass spectrometry, respectively. Histological examinations of the transverse colon were performed. Plasma D-lactate, zonulin, lipopolysaccharide (LPS), tumor necrosis factor (TNF-α), interferon (IFN)-γ, and interleukin (IL)-6 were detected by immunoassay kits.Results: The levels of the Bacteroidetes phylum and Prevotella genus were significantly increased, while the Firmicutes phylum as well as the Faecalibacterium, Oscillospira, and Lactobacillus genera were decreased after cerebral infarction. Gut-originating SCFAs were significantly decreased 6 and 12 months after cerebral infarction (P < 0.05). We observed intestinal mucosal damage, evaluated by Chiu's score. Plasma D-lactate, zonulin, LPS, TNF-α, IFN-γ, and IL-6 were significantly increased after cerebral infarction (P < 0.05). Additionally, the increases in plasma LPS, TNF-α, IFN-γ, and IL-6 after cerebral infarction coincided with overgrowth of the Bacteroidetes phylum (P < 0.001).Conclusion: Cerebral infarction induces persistent host gut microbiota dysbiosis, intestinal mucosal damage, and chronic systemic inflammation in cynomolgus monkeys.

Exploring the relationship between ischemic core volume and clinical outcomes after thrombectomy or thrombolysis.

To assess whether complete reperfusion after IV thrombolysis (IVT-R) would result in similar clinical outcomes compared to complete reperfusion after endovascular thrombectomy (EVT-R) in patients with a large vessel occlusion (LVO). EVT-R patients were matched by age, clinical severity, occlusion location, and baseline perfusion lesion volume to IVT-R patients from the International Stroke Perfusion Imaging Registry (INSPIRE). Only patients with complete reperfusion on follow-up imaging were included. The excellent clinical outcome rates at day 90 on the modified Rankin Scale (mRS) were compared between EVT-R vs IVT-R patients within quintiles of increasing baseline ischemic core and penumbral volumes. From INSPIRE, there were 141 EVT-R patients and 141 matched controls (IVT-R) who met the eligibility criteria. In patients with a baseline core <30 mL, EVT-R resulted in a lower odds of achieving an excellent outcome at day 90 compared to IVT-R (day 90 mRS 0-1 odds ratio 0.01, p < 0.001). The group with a baseline core <30 mL contained mostly patients with distal M1 or M2 occlusions, and good collaterals (p = 0.01). In patients with a baseline ischemic core volume >30 mL (internal carotid artery and mostly proximal M1 occlusions), EVT-R increased the odds of patients achieving an excellent clinical outcome (day 90 mRS 0-1 odds ratio 1.61, p < 0.001) and there was increased symptomatic intracranial hemorrhage in the IVT-R group with core >30 mL (20% vs 3% in EVT-R, p = 0.008). From this observational cohort, LVO patients with larger baseline ischemic cores and proximal LVO, with poorer collaterals, clearly benefited from EVT-R compared to IVT-R alone. However, for distal LVO patients, with smaller ischemic cores and better collaterals, EVT-R was associated with a lower odds of favorable outcome compared to IVT-R alone.

04:12 PM Abstract No. 168 M2 Frontal and Parietal Division Angles Impacting Success of Mechanical Thrombectomy

Vessel anatomy is the cornerstone of endovascular therapy, including in mechanical thrombectomy (MT). The horizontally orientated M1 segment of the MCA commonly terminates in a bifurcation. The M2 segment is made up of a frontal division coursing cephalic to supply the frontal convexity and a parietal division which appears as a continuation of the M1 coursing inferiorly to supply the temporoparietal lobes. We have demonstrated the rate of successful reperfusion following MT is significantly greater in parietal division than frontal division occlusions (unpublished work). Our current hypothesis is that the differences in success are due to a less obtuse angle of the frontal versus parietal division. A single-center retrospective study was conducted to identify isolated frontal and parietal M2 branch occlusions from September 2012 to April 2018. Occlusions involving the M1 segment, distal MCA (M3 and M4 divisions), ACA, ICA and posterior cerebral circulation were excluded. 3D renderings from preprocedural CT angiography of the head (MRA reformats were used for a single patient) were utilized to assess vessel anatomy. The angle between the conterminous segment of the distal M1 and of each M2 division were measured from the healthy non-occluded side. The angle between the M1 and parietal division was designated M1/parietal angle. A second angle between the M1 and frontal division was designated M1/frontal angle. Twenty nine out of 364 endovascularly treated cases had isolated parietal or frontal M2 occlusions. Of these, 23 met our criteria; 17 subjects were in the parietal cohort and 6 subjects in the frontal cohort. Mean age of patients was 67.7. There was a larger mean M1/parietal angle than M1/frontal angle in the parietal cohort (146.2° vs 116.3, p = <0.0001) and frontal cohort (147.7 vs 116.5, p = 0.013). A less obtuse angle of the frontal M2 division can account for an increased failure of recanalization. Although it may be difficult to determine the angle on the occluded side due to nonvisualization of the vessel, angle measurement on the healthy side correlates with success of mechanical thrombectomy.

Abstract 82: Thrombus Migration is a Common Phenomenon With IV TPA and May Have Negative Effects on Outcome When TPA Treatment is Given Before Endovascular Thrombectomy in Proximal Occlusions

Introduction: There is interest in understanding thrombus dynamics from IV TPA prior to endovascular thrombectomy (EVT) given the possible dichotomy amongst sites of occlusion for IV TPA benefit/harm. Kaesmacher et al reported beneficial 5+% rates of early TICI &gt; 2a reperfusion in distal M1 or M2 MCA occlusions with IV TPA. However in more proximal occlusions this was rare; and potentially harmful worsening of perfusion seen with change of occlusion site. We aimed to examine IV TPA related thrombus dynamics including migration further across both proximal and distal occlusions in a multicenter prospective cohort study INTERRSeCT. Methods: Acute ischemic stroke patients with intracranial occlusion who had baseline CTA and follow-up CTA or initial run angio in INTERRSeCT and IV TPA were reviewed. We evaluated change of occlusion site (COS) and classified patients into 4 categories: Complete Recanalization (CR) of primary occlusive lesion with no remaining thrombus; definite Thrombus Migration (dTM) with primary occlusion site moved to a distal artery and occlusion site patent on baseline CTA; probable Thrombus Migration (pTM) with COS evident but initial occlusion extent not visualized; or No Change of occlusion site (NC). Results: A total of 462 IV TPA patients were enrolled, 41% received EVT. Median time from TPA to follow-up imaging was 133 minutes. COS was seen in 50% of cases with CR in 15% and TM in 35% (dTM 12%, pTM 23%). Distal artery occlusion and longer interval of TPA to imaging were independent predictors for COS. In 62 proximal occlusion (ICA and proximal-mid M1 MCA) patients with follow-up imaging within 60 mins after TPA (receiving EVT in 94%), any TM showed a lower rate of 90-day mRS≤2 than NC (47% vs 78%, adjusted OR 0.21, 95%CI 0.04-0.87). No CR was seen in this early group. Conclusions: Thrombus migration is common after IV TPA. Thrombus instability from IV TPA may worsen clinical outcome in proximal occlusions despite early EVT initiation, possibly due to migration of thrombus to distal arteries accelerating infarction or more challenging thrombectomy due to thrombus dispersion. The benefit of IV TPA prior to EVT at comprehensive stroke centers for ICA or prox-mid M1 occlusions require more study in randomized clinical trials.

Abstract TP32: 3mmx20 Trevo Retriever vs. Penumbra 3 Max Distal Occlusion Acute Stroke Thrombectomy

Introduction: The optimal approach for distal intracranial occlusions in thrombectomy for acute ischemic stroke is unclear. We aim to compare our experience with 3mmx20 Trevo Retriever against the Penumbra 3max in small vessels. Methods: Retrospective review of a prospective thrombectomy databank for consecutive cases of use of 3mmx20 Trevo Retriever or Penumbra 3max for middle cerebral artery (MCA) mid or distal M2, M3, anterior cerebral artery (ACA A1, A2, A3) or posterior cerebral artery (PCA P1, P2) from Jan 2014-July 2018. Results: Of 1071 patients treated within the study period, 136 patients/144 different arteries underwent treatment with small devices (3mmTrevo n=92 vs 3Max n=52). There was no difference in the distal occlusion presentation: isolated distal occlusion, emboli to new or same distal territory, or multiple occlusions (p=0.11). The distribution of occlusions site was comparable (p=0.37). Demographics were comparable including age, gender, hypertension, atrial fibrillation, systolic blood pressure, last-normal to puncture. The use of intravenous alteplase was similar (p=0.47) as well as the use of balloon guide catheter (p=1.00). The approached vessel pre-clot diameter was comparable between the 3mmTrevo and 3Max groups (1.6±0.2mm vs 1.4±0.3;p=0.66), respectively. The frequency of superior vs inferior vs middle MCA division was similar (p=0.42) amongst arms. A trend for higher first-pass mTICI2b-3 reperfusion was noted in the 3mmTrevo (62% vs 44%;p=0.05) vs 3Max group. Rates of first-pass full reperfusion was comparable (42% vs 34%;p=0.38). Adjuvant therapy was used less frequently in the 3mm Trevo group (15% vs 31%;p=0.03) for comparable final mTICI3 rates (p=0.22). The number of passes (1.3±0.5 vs 1.3±0.6; p=0.9) and the frequency of arterial spasm (any spasm; p=1.00) were comparable between groups. 90-day rates of good outcomes (35/76 vs 21/43; p=0.84) were comparable amongst arms. Subarachnoid hemorrhage (p=0.37) and parenchymal hematomas (p=0.21) in the territory of approached vessel was similar. Conclusions: The 3mm Trevo may lead to enhanced rates of successful reperfusion as compared to 3Max thromboaspiration. Further studies are warranted.

Abstract WP4: Which Characteristics Determine the Decision to Proceed With Endovascular Therapy in Acute Stroke Patients: Results From an International Multidisciplinary Study

Introduction: The current management of acute ischemic stroke has changed recently with the publication of randomized trials using endovascular therapy (EVT). Rationale/Hypothesis: Limited information is however available on how physicians make decisions regarding patient selection for endovascular therapy (EVT) in the real-world. Methods: We conducted an international web-based cross-sectional survey of stroke physicians and interventionalists to assess the decision to offer EVT. Part 1 of the survey used hierarchical Bayes’ disaggregate discrete choice modelling to analyze ten pairs of patient scenarios, randomly generated from ten key patient characteristics to have respondents choose which scenario was best suited for EVT in their practice. Part 2 of the survey used mixed effects logistic regression modelling to analyze 22 randomly chosen patient scenarios, again randomly generated from several key patient and hospital level characteristics. Results: 607 physicians [mean age of 44 (SD 8.5) years, 83.5% men, 53.6% neurologists, 28.7% neuro-interventionists, 13.3% neurosurgeons, 4.7% other], from 38 countries participated. Using disaggregate discrete choice analysis, the most influential characteristic in deciding about EVT was the extent of ischemic change (ASPECTS)/volume of infarct core (26-28% of the choice). Patient age, premorbid status, baseline NIHSS score, and occlusion location (13-15% each) were the other relevant characteristics. Using mixed effects logistic regression, baseline stroke severity (NIHSS&gt; 15 vs. NIHSS 0-5, OR 6.7; 95% CI 4.8-9.5), ASPECTS (5-7 vs. 0-4, OR 9.4; 95% CI7.4-11.9) and occlusion location (distal M2 vs. ICA/M1, OR 012; 95% CI 0.08-0.17) were the most relevant characteristics in deciding about EVT. Time from stroke onset, sex, comorbidities, time of day (off hours vs. day time) were all less relevant in deciding about EVT in both analyses. Conclusion: Severity of stroke assessed clinically, and extent of brain infarction and location of thrombus assessed on imaging are the dominant characteristics that treating physicians use in the real world when deciding about EVT for patients with an acute ischemic stroke.

Effectiveness of Endovascular Recanalization Treatment for M2 Segment Occlusion: Comparison Between Intracranial ICA, M1, and M2 Segment Thrombectomy

Mechanical thrombectomy is common practice in proximal anterior vessel occlusion. However, it remains unclear whether peripheral artery occlusions should be treated as well. This retrospective study aimed to prove the effectiveness of endovascular recanalization treatment for the M2 segment by comparison of intracranial internal carotid artery (ICA), M1 segment, and M2 segment thrombectomy. All patients who received endovascular treatment for distal ICA, M1, or M2 segment occlusions between January 2010 and July 2017 at our center were re-analyzed with respect to reperfusion success, interventional and clinical parameters. Statistical analysis was performed by Mann Whitney test, Chi square test, and Spearman correlation analysis. A total of 261 patients (median age, 72 years), 100 with ICA, 137 with M1, and 24 with M2 segment occlusion, were included. Duration of endovascular treatment was significantly longer in ICA occlusions (median, 83 minutes, p < 0.001) compared to M1 (56 minutes) or M2 segment occlusions (49 minutes). Recanalization and reperfusion success and rate of endovascular complications did not differ between occlusion sites (AOL, p = 0.071; mTICI, p = 0.540; complications, p = 0.064). No significant difference in revascularization success was found between the different thrombectomy devices (direct thrombus aspiration, stent retrieving, or a sequential combined approach; p = 0.112). Successful M2 recanalization (mTICI 2b-3) correlated significantly with stronger posttherapeutic NIHSS reduction (r = 0.691, p < 0.001). We found endovascular treatment of M2 segment occlusions as safe and successful as endovascular therapy of the ICA or M1 segment, with stronger posttherapeutic NIHSS reduction after successful compared to insufficient M2 recanalization.

Association of Clinical, Imaging, and Thrombus Characteristics With Recanalization of Visible Intracranial Occlusion in Patients With Acute Ischemic Stroke

Recanalization of intracranial thrombus is associated with improved clinical outcome in patients with acute ischemic stroke. The association of intravenous alteplase treatment and thrombus characteristics with recanalization over time is important for stroke triage and future trial design. To examine recanalization over time across a range of intracranial thrombus occlusion sites and clinical and imaging characteristics in patients with ischemic stroke treated with intravenous alteplase or not treated with alteplase. Multicenter prospective cohort study of 575 patients from 12 centers (in Canada, Spain, South Korea, the Czech Republic, and Turkey) with acute ischemic stroke and intracranial arterial occlusion demonstrated on computed tomographic angiography (CTA). Demographics, clinical characteristics, time from alteplase to recanalization, and intracranial thrombus characteristics (location and permeability) defined on CTA. Recanalization on repeat CTA or on first angiographic acquisition of affected intracranial circulation obtained within 6 hours of baseline CTA, defined using the revised arterial occlusion scale (rAOL) (scores from 0 [primary occlusive lesion remains the same] to 3 [complete revascularization of primary occlusion]). Among 575 patients (median age, 72 years [IQR, 63-80]; 51.5% men; median time from patient last known well to baseline CTA of 114 minutes [IQR, 74-180]), 275 patients (47.8%) received intravenous alteplase only, 195 (33.9%) received intravenous alteplase plus endovascular thrombectomy, 48 (8.3%) received endovascular thrombectomy alone, and 57 (9.9%) received conservative treatment. Median time from baseline CTA to recanalization assessment was 158 minutes (IQR, 79-268); median time from intravenous alteplase start to recanalization assessment was 132.5 minutes (IQR, 62-238). Successful recanalization occurred at an unadjusted rate of 27.3% (157/575) overall, including in 30.4% (143/470) of patients who received intravenous alteplase and 13.3% (14/105) who did not (difference, 17.1% [95% CI, 10.2%-25.8%]). Among patients receiving alteplase, the following factors were associated with recanalization: time from treatment start to recanalization assessment (OR, 1.28 for every 30-minute increase in time [95% CI, 1.18-1.38]), more distal thrombus location, eg, distal M1 middle cerebral artery (39/84 [46.4%]) vs internal carotid artery (10/92 [10.9%]) (OR, 5.61 [95% CI, 2.38-13.26]), and higher residual flow (thrombus permeability) grade, eg, hairline streak (30/45 [66.7%]) vs none (91/377 [24.1%]) (OR, 7.03 [95% CI, 3.32-14.87]). In patients with acute ischemic stroke, more distal thrombus location, greater thrombus permeability, and longer time to recanalization assessment were associated with recanalization of arterial occlusion after administration of intravenous alteplase; among patients who did not receive alteplase, rates of arterial recanalization were low. These findings may help inform treatment and triage decisions in patients with acute ischemic stroke.