Legionella occurrence in municipal and industrial wastewater treatment plants and risks of reclaimed wastewater reuse: Review

Wastewater treatment plants (WWTPs) have been identified as confirmed but until today underestimated sources of Legionella, playing an important role in local and community cases and outbreaks of Legionnaires' disease. In general, aerobic biological systems provide an optimum environment for the growth of Legionella due to high organic nitrogen and oxygen concentrations, ideal temperatures and the presence of protozoa. However, few studies have investigated the occurrence of Legionella in WWTPs, and many questions in regards to the interacting factors that promote the proliferation and persistence of Legionella in these treatment systems are still unanswered. This critical review summarizes the current knowledge about Legionella in municipal and industrial WWTPs, the conditions that might support their growth, as well as control strategies that have been applied. Furthermore, an overview of current quantification methods, guidelines and health risks associated with Legionella in reclaimed wastewater is also discussed in depth. A better understanding of the conditions promoting the occurrence of Legionella in WWTPs will contribute to the development of improved wastewater treatment technologies and/or innovative mitigation approaches to minimize future Legionella outbreaks.

Abstract TP7: Isolated Basal Ganglia Strokes Undergoing Thrombectomy Have High Rates of Good Clinical Outcomes

Background and Purpose: Isolated basal ganglia strokes are thought to have worse clinical outcomes as compared to mixed and cortical infarcts.

Methods: Review of a prospectively collected database of endovascular patients with anterior circulation Large vessel occlusion strokes from January 2014-June 2018. Only patients with an ASPECT score of 6 to 9 were included. Patients were dichotomized into 2 groups according to ASPECT region involvement: (i) isolated basal ganglia and (iBG) (ii) other stroke patterns. Baseline characteristics and Clinical outcomes were compared.

Results: 465 patients qualified for the study of which 324 (70%) were iBG strokes. Baseline characteristics were comparable between the 2 groups except for higher rates of hypertension (73.8%vs63.8%,p=0.03) and larger CTP core infarct (3.6 cc[0-13] vs 3[0-10.85], p<0.001) in the iBG group. There were no differences between groups in rates of successful reperfusion (mTICI 2b-3) (97.2% for iBG vs96.5%, p=0.66), any parenchymal hematomas (9.4%vs11.4%, p=0.49) and rates of good outcomes (mRS 0-2) (53.7% vs 50.4%, p=0.55). iBG patients had lower 90-day mortality rates (13.1%vs23.3, p=0.01). This persisted as non-statistically significant trend after adjusting for potential confounders (OR 0.54 95%CI [0.277-1.03],p=0.06)

Conclusions: iBG strokes carry similar procedural and clinical outcomes as other stroke patterns with a trend towards lower mortality.

Abstract 1: DAWN versus Modified Clinical-ASPECTS Mismatch Selection for Stroke Endovascular Therapyin the Early and Late Time Windows

Background and Purpose: Optimal patient selection for thrombectomy in large vessel acute ischemic stroke (LVOS) remain to be established. We evaluated the performance of imaging paradigms in a cohort of endovascularly-treated LVOS.

Methods: Review of a prospectively collected database of endovascular patients with anterior circulation LVOS, adequate CTP maps, and NIHSS ≥10 from January 2014-June 2018 in a clinical setting where no specific ASPECTS or CTP criteria defined treatment selection. Patients were assessed for thrombectomy eligibility by each 2 mismatch criteria: DAWN Clinical-Core Mismatch (DAWN-CCM): between age-adjusted NIHSS and CTP-derived ischemic core volume and modified Clinical-ASPECTS Mismatch (mCAM) defined as ASPECTS 6-10 and one of the following criteria: NIHSS ≥ 10 and 0-1 Cortical-ASPECTS (M1-6 area) Involvement (any age);NIHSS ≥ 10 and 0-2 Cortical-ASPECTS (M1-6 areas) Involvement (and age < 80 years old);NIHSS ≥ 20 and 0-3 Cortical-ASPECTS (M1-6 areas) Involvement (and age < 80 years old). Clinical outcomes were compared.

Results: 591 patients qualified. mCAM had a higher inclusion rate as compared to the DAWN-CCM criteria (89.8%vs83.9%). The proportions of selected patients were statistically different between groups (p=0.01). Both mCAM(+) and DAWN-CCM(+) patients had higher rates of 90-day good outcomes (modified Rankin scale 0-2) compared to non-selected counterparts (53.2%vs21.3%,p<0.0001 and 52.5%vs35.5%,p=0.09 respectively). mCAM(+) had lower rates of 90-day mortality than mCAM(-) patients (17.5% vs 29.8%,p=0.04). However there was no difference in mortality between DAWN-CCM (+) and DAWN-CCM(-) patients (17.7% vs 25%,p=0.15). The abilities of mCAM and CCM to predict good outcomes were similar as assessed by the c-statistic, Akaike and Bayesian information criterion. Sensitivity analyses for the early (within 6H after symptom onset) and late (6-24H) time windows yielded similar results.

Conclusion: mCAM and DAWN-CCM selection paradigms have similar inclusion rates and outcome discrimination ability. mCAM could represent a good substitute in centers where access to advanced imaging is more limited. Future studies are warranted.

Abstract WP8: Global Real World Evidence of Balloon Guided Stent Retriever Thrombectomy

Background and Aims: Balloon Guide Catheter (BGC) use during thrombectomy treatment in Stroke patients has been reported to have positive effects on revascularization, procedural characteristics, and clinical outcomes. We evaluate the use of BGC in an open-label large prospective TREVO Retriever Registry of real world patients to determine predictors of good ‘clinical’ outcomes.

Method: Consecutive Trevo Registry patients that had Balloon Guide Catheter (BGC) used during their thrombectomy procedure were identified; a subset of patients who fulfilled the criteria (ICA and/or MCA-M1/M2 occlusion with pre-morbid mRS 0-1, TLSW ≤6 hrs) within the cohort were also identified. Multivariate analysis was performed to identify the predictors of good outcomes in BGC thrombectomy patients.

Results: A total of 1031 BGC treated Trevo Registry patients (overall enrolled, n=2010) qualified for analysis, of which 605 patients fulfilling the subset criteria were identified. The mean age of BGC/stent retriever patients was 67.5 with a median (IQR) baseline NIHSS of 15(11-19). Occlusion location of the BCG group was ICA -20.4%, M1- 57.1%, M2/M3-20.3%, and Posterior 1.8%.

In the overall BGC cohort, the median (IQR) time to treatment was (4.2 (3.0,6.5)- hrs.) with conscious/local sedation used in 63.4% and general anesthesia used in 37.3% of cases. The median number of passes with Trevo stent retriever was 1 and revascularization (mTICI ≥ b) was achieved in 92.8% of cases. The sICH rate was low at 1.9% (20/1031) with a low rate of vessel perforation (0.2%). At 90 days post stroke, 56.0% of patients achieved functional independence (mRS 0-2) with 63.7% of the subset of “guidline “ BGC patients achieving functional independence at 90 days. Multivariate logistic regression showed age (aOR 0.97 [0.96, 0.99] P <0.001), Diabetes (aOR 0.67, [0.18,0.98] P =0.03), conscious sedation vs general anesthesia ( aOR 1.7 [1.2,2.3], P= 0.002, number of passes (aOR 0.76 [0.66-0.88],P <0.001), pre stroke mRS (aOR 0.54 [0.45-0.65], P <0.0010 and NIHSS (aOR 0.93 [0.91-0.95], P <0.001) as predictors of functional independence .

Conclusion: Data from Trevo Registry demonstrate the use of BGC in thrombectomy procedure is safe, and leads to a reduction of disability in ischemic stroke patients.

Abstract 112: Identifying Patients Who May Benefit From Thrombectomy in the Late Time Window: Predictors of Good Outcome Beyond Advanced Imaging

Background: The DAWN trial showed EVT effectiveness in the late time window (6-24 hrs), however, DAWN patients were carefully selected based on advanced perfusion imaging, CTP and MRI. Similar to the early window (0-6 hrs), simple imaging (CT) and other clinical variables may select patients for thrombectomy beyond 6 hours. We evaluated a largescale, real world practice for predictors that could identify patients who may benefit from EVT in the late time window.

Methods: Patients with LVO in the anterior circulation (M1, M2, ICA) from a prospective, single arm, multicenter, international registry (Trevo Retriever Registry) treated in the late window LSN to groin puncture (GP) (6-24 hrs) were included. Univariate and multivariate analyses assessed factors independently correlating with good outcome (90 day mRS 0-2). Furthermore, patients outcomes were compared based on their baseline imaging selection CT vs CTP and MRI.

Results: 549 patients were treated beyond 6 hours. The average age was 67, median/IQR ASPECTS 8(6-9), median/IQR NIHSS was 15 (9-20), median/IQR time LSN to GP (hr) was 9.7 (7.3-13.6) and IV-tPA rate were 22.8%. CT was the only imaging selection method in 15.9%, while additional advanced imaging was utilized in the remaining patients; CTP (70%), and MRI(14.1%). Good outcomes were observed in 51.4% of late window patients. Age (aOR 0.96, 95% CI 0.94-0.98, p<0.001), stroke severity by NIHSS (aOR 0.9, 95% CI 0.86-0.95, p<0.001) and ASPECTS (for each point increment in ASPECTS aOR 1.24, 95% CI 1.05-1.47, p=0.012) were independent pre-intervention predictors of good outcome in the late window. The addition of advanced imaging beyond CT, including CTP or MRI, did not confer higher correlation with good outcome (aOR 1.45, 95% CI 0.77-2.73, p=0.25). Good outcome was achieved in 56% of CT selected patients as compared to 53% patients selected by CTP or MRI.

Conclusion: Simple imaging and clinical variables can identify patients that could benefit from thrombectomy in the late window. Importantly, ASPECTS reliably predicted good outcome beyond 6 hours without adjunctive benefit from adding advanced perfusion imaging, a finding that may simplify patients selection to facilitate and generalize the intervention in the late window to wide, real world practice.

Abstract WP27: Sex-Related Differences in Disability Adjusted Life Years After Mechanical Thrombectomy for Acute Ischemic Stroke

Background: Randomized trials have shown that mechanical thrombectomy improves 3-month disability outcomes after acute ischemic stroke for both women and men. However post-stroke disability and reduced life expectancy (LE) persists beyond 3 months, and lifetime effects of thrombectomy might differ between men and women.

Methods: We analyzed patients treated with the Solitaire stent retriever in the TripleS database (pooled patient-level data from the SWIFT, STAR, and SWIFT-PRIME trials). Years of optimum life after thrombectomy were defined as disability adjusted life-year (DALYs), using the methodology of the World Health Organization Global Burden of Disease Project. For each patient, LE was calculated based on age and sex-specific values, and known degree of modification of LE by modified Rankin Scale (mRS) status at 3 months post-stroke. Years of optimum life lost due to disability were calculated by projecting mRS status at 3 months through the remaining LE.

Results: Among 389 patients treated with ET, 55% were female, and median NIHSS was 17 [8-28]. There were no differences between females vs. males in presenting deficit severity (NIHSS 17 vs. 17, p=0.21), occlusion location (69% vs. 64% M1, p=0.62), presenting infarct extent (ASPECTS 9 vs. 8, p=0.24), rate of substantial reperfusion (TICI 2b/3, 87% vs. 83%, p=0.37), onset to reperfusion time (277 vs. 306 mins, p=0.46). Women presented at advanced mean age compared to men (69 vs 64, p<0.001). Rates of functional independence at 90 days (53% vs. 56%, p=0.54) were similar in men and women. Without adjusting for age at presentation, years of optimal life (DALYs) following thrombectomy were similar between women and men (9.3 vs 9.6 years, p=0.48). After adjusting for differing ages at presentation, women had more years of optimal life (DALYs) following thrombectomy, 10.6 vs 8.5 years (p<0.001).

Conclusions: In age-standardized comparisons, women experience two more optimal years than men following mechanical thrombectomy for acute ischemic stroke. Greater life expectancies of women, coupled with similar disability outcome distributions, yield substantially greater years of optimal life after intervention.

Abstract 108: Mechanical Thrombectomy in Patients With Milder Strokes and Large Vessel Occlusions - A Multicenter and Matched Analysis

Background: In patients with acute ischemic strokes (AIS) and milder symptoms (NIHSS</=5) harboring a large vessel occlusion (LVO) best clinical management is unclear. To describe the safety and efficacy of immediate mechanical thrombectomy (MT) in patients with LVO and milder symptoms versus best medical management, including rescue MT.

Methods: Retrospective cohort study on consecutive patients for a descriptive analysis regarding clinical and safety outcomes. From local prospectively run databases of six international comprehensive stroke centers data was pooled. 300 Patients with LVO (distal internal carotid artery, MCA-M1 and/or M2 segments, or basilar artery with or without tandem occlusions) and milder symptoms were identified and divided into two groups for analysis: immediate MT (i-MT) or best medical management which included rescue MT after neurological deterioration (n/r-MT). Uni- and multivariate analysis were performed to compare baseline and outcome variables across the two groups. Additional comparisons were performed after patient-level matching for age, baseline NIHSS and occlusion site. The primary outcome was defined as good outcome (modified rankin scale [mRS] 0-2) at day 90. Secondary outcomes were, among others, modified shift analyses at day 90. Safety outcome was symptomatic intracranial hemorrhage (sICH) as defined by the European Cooperative Acute Stroke Study (ECASS) II and mortality at day 90.

Results: Compared to n/r-MT (n=220), patients with i-MT (n=80) were younger (65.3+/-13.5 vs. 69.5+/-14.1, p=0.021), had more often atrial fibrillation (44.8% vs. 28.2%, p=0.012), higher baseline NIHSS (4, 0-5 vs. 3, 0-5, p=0.005), more MCA-M1 (41.3% vs. 21.9%) and less MCA-M2 (28.8% vs. 49.3%, p=0.016) occlusions. The adjusted odds ratio for good outcome was 3.1 95% CI: 1.4-6.9 favoring i-MT. In the matched analysis, there was a 14.4% absolute difference in good outcome (84.4% vs. 70.1%, p=0.03) and a significant modified mRS shift (OR 2.29, 95% CI: 1.05-4.98) at day 90 favoring i-MT. There were no safety concerns.

Conclusions and Relevance: The observed benefit-safety profile favors immediate MT in patients with milder symptoms and LVO.

Abstract TP128: Multicenter Experience With Stenting for Carotid Webs

Background: Carotid web is a shelf-like lesion in the posterior aspect of the internal carotid bulb and represents an intimal variant of fibromuscular dysplasia. Carotid webs have been associated with recurrent strokes and traditionally treated with surgical excision. We report a multicenter experience of stenting in patients with symptomatic carotid webs.

Methods: Retrospective review of patients admitted to three comprehensive stroke centers identified to have a carotid web with otherwise negative stroke workup that underwent stenting. A carotid web was defined by the presence of a shelf-like/linear, smooth filling defect in the posterior aspect of the carotid bulb diagnosed by neck CT/MR angiography and confirmed with conventional angiography.

Results: Twenty patients with symptomatic (80% Stroke/20% TIA) carotid webs were stented. Median age was 48[41-61] years, 7(35%) were male, and 15(75%) Black. Median NIHSS was 11[2-16] while ASPECTS 8[7-8]. Eight (40%) received intravenous thrombolysis and 10 (50%) thrombectomy. All patients were stented on dual antiplatelets (aspirin and clopidogrel[17] or ticagrelor[3]) at a median 9[4-30]days after the last vascular event. Closed-cell stents were used in 75% of cases (XACT [14] and Wallstent [1]) while open-cell stents in 25% (Acculink[5]). No cases required angioplasty for residual stenosis had to be performed. DIstal embolic protection was used in 19 cases (SpiderFX[18] and Emboshield_NAV6[1]) while proximal protection in 1 (MoMa). No periprocedural events occurred with the exception of two cases of hypotension/bradycardia (one requiring 24-hour vasopressors). No parenchymal hematomas were observed but one patient developed vaginal hemorrhage requiring discontinuation of one antiplatelet at 2 months. Modified Rankin Scale 0-2 (independence) at 90 days was recorded in 95% of patients. Clinical follow-up post stent occurred for a median of 4 [2-12] months and no follow-up cerebrovascular events were noted. Follow-up vascular imaging was performed in 95% patients at a median of 3[2-12]months and were all unremarkable.

Conclusions: Stenting for symptomatic carotid web appears to be a valid, safe, and effective alternative to surgical piecemeal resection. Further studies are warranted.

Abstract TP29: Endovascular Therapy for Distal Occlusions in the Early and Late Window: an Extension in Location and Time

Background: Endovascular therapy (EVT) effectiveness is established in ischemic strokes with large vessel occlusion (LVO) in the terminal ICA and M1, which was extended up to 24 hrs by recent DAWN trial results. However this benefit is not as well established in more distal (M2) occlusions, especially late presenters (beyond 6 hrs). We evaluated thrombectomy outcomes in M2 occlusions as compared to ICA/M1 across early and late time windows.

Methods: In a prospective, multicenter, single arm, international registry (Trevo Retriever Registry), anterior circulation LVOs were stratified on clot location into M2 vs ICA/M1 and dichotimized into early vs late (0-6 vs 6-24 hrs). 90 day mRS (0-1 excellent, 0-2 good) were the primary outcomes; sICH and dissection were the secondary (safety) outcomes. Multivariate analyses identified pre-procedure variables independently correlating with good outcome in M2s.

Results: 1581 patients were identified (1265 ICA/M1, 316 M2). The M2 and ICA/M1 groups were similar (age in both 68.4), IV-tPA (69.1 vs 69.7%, p=0.8) and same median/IQR ASPECTS 8 (7-9). M2 patients had lower NIHSS (13 vs 16, p<0.001). Higher good and excellent outcomes were observed in M2s (65.8% and 51.3%) compared to ICA/M1 (57.9% and 42.8%) (p=0.01). Similar outcomes were maintained beyond 6 hrs (64.8% good, 45.9% excellent in M2s vs 53.8% and 38.4% in ICA/M1) (p=0.08). Fig 1 shows the probabilities of good outcome in M2 vs ICA/M1 in relation to time, illustrating no association with time (p=0.4). Similar safety profiles were seen: sICH (0% M2 vs 0.7% ICA/M1, p=1.0) and dissections (0.3% M2 vs 0.4% ICA/M1, p=0.22). Age (aOR 0.96, 0.94-0.98 95% CI, p<0.001) and NIHSS (aOR 0.94, 0.9-0.98 95% CI, p<0.001) correlated with good outcome in M2, while IV-tPA did not have adjunctive benefit (aOR 0.72, 0.42-1.24 95% CI, p=0.24).

Conclusion: Excellent and good outcomes may be achieved in distal LVO isolated to M2 similar to those with proximal occlusions. A benefit that can be reached up to 24 hrs.

Abstract 107: Real World Clinical and Radiographic Outcomes With and Without Intravenous tPA in Anterior Circulation Large Vessel Occlusion Mechanical Thrombectomy Patients Treated Within 8 Hours

Background and Aims: Intravenous tPA remains the standard of care, with MT currently indicated within 8 hours for IV tPA failures or patients with IV tPA contraindications. Whether LVO patients should receive IV tPA treatment or instead be triaged directly to MT therapy is currently unknown but greatly debated. The Trevo Registry is a real world, multi-center, international study of mechanical thrombectomy (MT) patients treated from 0-24 hours. Evaluation of the Trevo Registry clinical and procedurals outcomes of MT patients treated with or without IV tPA could provide insight into the benefit of IV tPA in MT patients. We hypothesized that in MT patients treated within 8 hours, pretreatment with intravenous tPA would lead to better clinical outcomes compared to patients who did not receive IV tPA.

Method: Consecutively enrolled patients treated within 8 hours with ICA, M1, or M2 occlusions were selected for analysis. Univariate and multivariable regressions were conducted to identify clinical and radiographic independent variables that correlate best with the dependent variable of functional outcome: mRS 0-2, with a focus on intravenous tPA treatment.

Results: A total of 1183 Trevo Registry patients (overall enrolled, n=2010) qualified for analysis, of whom 380 were not treated with IV tPA. Demographics were similar, however atrial fibrillation (46.3% vs 27.2%) and previous ischemic stroke (14.1% vs 7.5%) were higher in the no IV tPA group. The median time to treatment was similar (3.8 vs. 3.6 hrs). First pass mTICI ≥ 2B (63.6% vs 66.4%) and final revascularization (91.1% vs 92.8%) were similar between no IV tPA and IV tPA groups.Unadjusted, there were similar rates of functional outcome (90 day mRS 0-2; 60.9% vs. 62.5%). After adjustment, patients who did not receive IV-tPA had similar rates of good outcome (aOR 1.08, 95% CI [0.87-1.34]. P=0.58) as well as reduction (shift) in disability (aOR 1.08, 95% CI [0.87-1.34]. P=0.49). Safety outcomes (mortality, sICH) were similar between both groups.

Conclusion: In the Trevo Registry of MT patients treated within 8 hours, patients who did not receive IV tPA had similar endovascular and clinical outcomes as patients pretreated with IV tPA. The added benefit of IV tPA for MT patients should be further investigated.

A control system for ultrasound devices utilized for inactivating E. coli in wastewater

Sonochemical processes applied to wastewater treatment have an influence on the behavior of ultrasonic systems. This is especially due to the load characteristic of the sonochemical process itself and the temperature increase caused by internal damping within the converter. Hence, a controlling device is needed to guarantee the operation in resonance and to keep the vibration amplitude constant. This paper presents a digital control system for the operation of weak to strong damped ultrasonic devices and its application for inactivating Escherichia coli in wastewater. In an experimental investigation, the electric data during a sonochemical process to inactivate E. coli in wastewater is taken into account to analyze the efficacy of the treatment process and the reaction of the vibration system to the process. Frequency response measurements depict that the resonance frequency changes with the sonicated medium and the vibration amplitude decreases with driving current. In addition to a common continuous operation of the system, different pulsed modes are investigated. The experiments prove the common dependencies between inactivation and power level or treatment time. Additionally, it is pointed out that the control of the sonochemical device is of utmost importance to guarantee an efficient treatment of water, because fast process changes, especially in pulsed operation modes, need to be controlled to a steady state as fast as possible. Although a water treatment efficiency increase using pulsed modes was not proved, it is shown, that the performance of the control unit is capable of using different driving modes in water treatment.

Analyses of thrombi in acute ischemic stroke: A consensus statement on current knowledge and future directions

Limited data exist on clot composition and detailed characteristics of arterial thrombi associated with large vessel occlusion in acute ischemic stroke. Advances in endovascular thrombectomy and related imaging modalities have created a unique opportunity to analyze thrombi removed from cerebral arteries. Insights into thrombus composition, etiology, physical properties and neurovascular interactions may lead to future advancements in acute ischemic stroke treatment and improved clinical outcomes. Advances in imaging techniques may enhance clot characterization and inform therapeutic decision-making prior to treatment and reveal stroke etiology to guide secondary prevention. Current imaging techniques can provide some information about thrombi, but there remains much to evaluate about relationships that may exist among thrombus composition, occlusion characteristics and treatment outcomes. Improved pathophysiological characterization of clot types, their properties and how these properties change over time, together with clinical correlates from ongoing studies, may facilitate revascularization with thrombolysis and thrombectomy. Interdisciplinary approaches covering clinical, engineering and scientific aspects of thrombus research will be key to advancing the understanding of thrombi and improving acute ischemic stroke therapy. This consensus statement integrates recent research on clots and thrombi retrieved from cerebral arteries and provides a rationale for further analyses, including current opportunities and limitations.

Abstract TP14: Predictors of Good Outcome after Endovascular Therapy for Acute Posterior Circulation Stroke

Background and Purpose: Endovascular therapy (ET) is increasingly utilized in acute ischemic stroke treatment and is now considered the gold standard approach for select patient populations. Prior studies have demonstrated that eventual patient outcome depend on both patient specific factors as well as procedural considerations. However, these factors remain unclear for acute basilar artery occlusion stroke. We sought to determine prognostic factors of good outcome after ET for acute posterior circulation stroke

Methods: We reviewed our prospectively collected endovascular databases at two tertiary care academic institutions for patients with acute posterior circulation strokes from September 2005 to September 2015. Baseline characteristics, procedural data and outcomes were evaluated. A good outcome was defined as a modified Rankin Scale score of 0 to 2 at 3 months. The association between clinical and procedural parameters and functional outcome was assessed.

Results: A total of 214 qualified for the study. Smoking status, creatinine levels, baseline National Institutes of Health Stroke Scale score (NIHSS), anesthesia modality (conscious sedation vs general anesthesia), procedural length and reperfusion status were significantly associated with outcomes in the univariate analysis Multivariate logistic regression indicated that only smoking (odds ratio, 2.49; 95% confidence interval 1.16-5.36; P=0.019), low NIHSS (odds ratio, 0.92; 95% confidence interval 0.88-0.96; P<0.001), and successful reperfusion (mTICI 2b-3) (odds ratio, 13.65; 95% confidence interval 1.71-108.76; P=0.014), were independent predictors of good outcomes.

Conclusion: Our study suggests that baseline NIHSS, smoking and reperfusion status are independent predictors of good outcomes after ET for acute posterior circulation stroke.

Abstract 32: Per Protocol versus Intent-to-treat Analysis in a Non-inferiority, Randomized Trial of the Safety and Efficacy of the Penumbra 3D Stent Retriever as an Adjunct to Aspiration in Acute Ischemic Stroke

Introduction: The relative treatment effects for a stent retriever when used as an adjunct to aspiration versus aspiration alone remain unclear. The aim of this study was to demonstrate the safety and efficacy of the Penumbra stent retriever, 3D, when used in conjunction with the Penumbra Aspiration System (3D/PS), was non-inferior to the Penumbra Aspiration System (PS) alone. It remains controversial if a Per Protocol (PP) or an Intent-To-Treat (ITT) analysis is more appropriate for this study design.

Hypothesis: PP and ITT analyses are comparable for a non-inferiority design trial.

Materials and Methods: Patients presenting with symptoms of ischemic stroke within 8 hours of onset who had evidence of a LVO (diameter ≥2.5mm) and a NIH Stroke Scale ≥8 were assigned 1:1 to either treatment group. The primary endpoint for effectiveness was angiographic revascularization of the occluded target vessel at immediate post-procedure where the 3D/PS is non-inferior to PS by no more than 15%. Key secondary endpoints were 90 day functional independence as defined by a modified Rankin score 0-2, all-cause mortality and the incidence of symptomatic intracerebral hemorrhage. A Core Laboratory assessed imaging data.

Results: The trial was terminated in June 2016 after the DSMB voted unanimously that recruiting additional subjects was judged to be both not feasible and unable to alter conclusions. A total of 198 patients were randomized at 25 sites: 98 to the 3D/PS and 100 to the PS alone group. The results indicate the 3D/PS was non-inferior to the PS alone in safety and effectiveness (difference in TICI 2-3=2.6%, 95%CI -5.8 to 11%). PP and ITT analyses showed similar results (Table).

Conclusion: This is the first Class 1 evidence showing the similarity in safety and effectiveness of a stent retriever when used as an adjunct to aspiration versus aspiration alone in acute stroke from LVO. Both PP and ITT analyses showed similar results.

Abstract TP12: Comparison of 3D Stent Retriever to Solitaire in Patients with Small Ischemic Cores: An Analysis of the Penumbra 3D Trial

Introduction: A recent meta-analysis of four randomized controlled trials (RCTs) concluded that mechanical thrombectomy using Solitaire for large vessel ischemic stroke was effective with significantly reduced disability.

Hypothesis: Our hypothesis was that treatment with the Penumbra Aspiration System and the novel 3D Stent Retriever would demonstrate similar angiographic and functional outcomes compared to use of Solitaire.

Methods: The 3D trial was a RCT to compare the safety and effectiveness of the 3D Stent Retriever when used with the Penumbra Aspiration System (3D/PS) compared to the PS alone. Inclusion criteria for the 3D RCT included presentation with NIH Stroke Scale ≥ 8 and refractory to or not eligible for IV rtPA. Analysis compared reperfusion to mTICI 2b or 3 and functional independence (mRS 0-2 at 90 days) in a 3D Trial cohort with ASPECTS 8-10 vs the meta-analysis data reported by Campbell et al ( Stroke 2016).

Results: One hundred four (104) of 198 patients met analysis criteria. Baseline ASPECTS (median [IQR]) were similar between the 3D Trial ASPECTS 8-10 cohort (3D/PS, PS, combined: 9 [8,10]) and Campbell group (9 [7,10]). Substantial reperfusion (mTICI 2b or 3) was experienced in 84.6% (44/52) of 3D/PS and 75.0% (39/52) of PS alone cases, similar to the Campbell group (76.6%). When both arms were pooled, results (79.8%) were also similar to Campbell. With regards to functional independence, both 3D cohorts and pooled trial results showed similar rates compared with Campbell (Figure).

Conclusions: The novel 3D Stent Retriever + Penumbra System and the Penumbra Aspiration System alone showed similar reperfusion and functional outcomes compared to Solitaire.

Abstract 127: Predictors of Good Functional Outcomes in an Acute Ischemic Stroke Cohort with a Large Infarct Core Treated with Mechanical Thrombectomy: Signals to Treat?

Purpose: Mechanical thrombectomy has been demonstrated to provide benefits in the treatment of acute ischemic stroke (AIS). But whether to treat AIS patients with a large infarct core remains controversial. Although it is a common practice that patients with large infarct core are not offered endovascular treatment, previous data have consistently shown a proportion of these patients may benefit from IA intervention. The purpose of this study is to identify predictors of good outcomes in an AIS cohort with a large infarct volume previously treated with mechanical thrombectomy.

Hypothesis: We hypothesize that among AIS patients with a large infarct volume, younger patients (≤66 years) who present with lower NIHSS scores will show good functional outcomes (mRS 0-2) at 90 days if treated with mechanical thrombectomy.

Methods: Univariable and multivariable analyses were preformed to identify factors that predict good functional outcomes in AIS patients with ASPECTS 0-5 who were treated with the Penumbra System. Five previous prospective, multicenter trials (PIVOTAL, PICS, RetroSTART, START, SEPARATOR 3D) were included in this study. Patients who presented with symptoms of AIS were analyzed for association between presenting demographics and modified Rankin scale (mRS) score at 90 days in univariate and multivariate analyses.

Results: Data for 614 patients with a median age of 69 years and an NIHSS score of 18 met study criteria. Of these, the 90-day mRS 0-2 rate and mortality were, respectively, 40.23% and 25.41%. Among those with ASPECTS 0-5 (N=93), 17.20% had good functional outcome. An age of ≤66 years was significantly associated with good outcome (p<0.0001) among those with ASPECTS 0-5. Within this age group who had ASPECTS 0-5, a baseline NIHSS score of ≤ 20 (p= 0.0088) with a target vessel location at the MCA (p=0.0210) were also strong predictors of good outcome if treated by mechanical thrombectomy.

Conclusion: These data demonstrate that age ≤66 years, baseline NIHSS score of ≤ 20 with a target vessel location in the MCA are important predictors of good outcomes in an AIS cohort with a large infarct core who are eligible for mechanical thrombectomy.