Abstract TP317: Hyperglycemia Strongly Predicts Large Ischemic Infarct Growth Despite Full Endovascular Reperfusion

Introduction: Ischemic infarct core grows at variable rates despite early reperfusion. The purpose of this study was to determine the predictors of infarct growth despite full recanalization of a large vessel occlusion in acute ischemic stroke.

Method: Patients with acute ischemic stroke due to ICA or MCA occlusion who received endovascular therapy with Thrombolysis in Cerebral Infarction scale (TICI) scores of 2b or greater were subsequently selected between July 2012 and May 2016. The Alberta Stroke Program Early CT Score (ASPECT) was measured on the initial CT or MRI upon arrival and subsequently on the 24-hour scan. The infarct growth (delta d) was measured as initial ASPECT minus 24-hour ASPECT. Large and small infarct growth was defined as delta d of >= to3 and < 3 respectively. The relationship between the infarct growth and baseline variables of blood glucose level(BG), time of symptoms onset to recanalization time and baseline ASPECT score were assessed using statistical analysis.

Results: Total of 76 patients were included. 32% had large infarct growth (25/76). The initial ASPECT score was not significantly different between the the 2 subgroups of large and small delta d (7.5 vs 6, P= 0.97). Baseline BG level was significantly higher in the group with larger infarct growth (160 vs 128, P=0.006). The baseline BG level of more than 150 was found as the threshold between the 2 subgroups (P=0.0003). No association was found between the infarct growth and history of diabetes (P= 0.7).

Conclusion: Our data suggests that infarct growth occurs in relatively high percentage of ischemic stroke patients despite early full reperfusion of the large vessel occlusion. We showed that baseline blood glucose level particularly levels of higher than 150 is significantly associated with larger infarct growth. Therefore, it can be used as a strong predictive value in early recognition of this patient population.

Multiparametric Magnetic Resonance Imaging for Prediction of Parenchymal Hemorrhage in Acute Ischemic Stroke After Reperfusion Therapy

Background and Purpose—

Patients with acute ischemic stroke are at increased risk of developing parenchymal hemorrhage (PH), particularly in the setting of reperfusion therapies. We have developed a predictive model to examine the risk of PH using combined magnetic resonance perfusion and diffusion parameters, including cerebral blood volume (CBV), apparent diffusion coefficient, and microvascular permeability (K2).

Methods—

Voxel-based values of CBV, K2, and apparent diffusion coefficient from the ischemic core were obtained using pretreatment magnetic resonance imaging data from patients enrolled in the MR RESCUE clinical trial (Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy). The associations between PH and extreme values of imaging parameters were assessed in univariate and multivariate analyses. Receiver-operating characteristic curve analysis was performed to determine the optimal parameter(s) and threshold for predicting PH.

Results—

In 83 patients included in this analysis, 20 developed PH. Univariate analysis showed significantly lower 10th percentile CBV and 10th percentile apparent diffusion coefficient values and significantly higher 90th percentile K2 values within the infarction core of patients with PH. Using classification tree analysis, the 10th percentile CBV at threshold of 0.47 and 90th percentile K2 at threshold of 0.28 resulted in overall predictive accuracy of 88.7%, sensitivity of 90.0%, and specificity of 87.3%, which was superior to any individual or combination of other classifiers.

Conclusions—

Our results suggest that combined 10th percentile CBV and 90th percentile K2 is an independent predictor of PH in patients with acute ischemic stroke with diagnostic accuracy superior to individual classifiers alone. This approach may allow risk stratification for patients undergoing reperfusion therapies.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00389467.

Cost-Effectiveness of Solitaire Stent Retriever Thrombectomy for Acute Ischemic Stroke: Results From the SWIFT-PRIME Trial (Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke)

BACKGROUND AND PURPOSE

Clinical trials have demonstrated improved 90-day outcomes for patients with acute ischemic stroke treated with stent retriever thrombectomy plus tissue-type plasminogen activator (SST+tPA) compared with tPA. Previous studies suggested that this strategy may be cost-effective, but models were derived from pooled data and older assumptions.

METHODS

In this prospective economic substudy conducted alongside the SWIFT-PRIME trial (Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke), in-trial costs were measured for patients using detailed medical resource utilization and hospital billing data. Utility weights were assessed at 30 and 90 days using the EuroQol-5 dimension questionnaire. Post-trial costs and life-expectancy were estimated for each surviving patient using a model based on trial data and inputs derived from a contemporary cohort of ischemic stroke survivors.

RESULTS

Index hospitalization costs were $17 183 per patient higher for SST+tPA than for tPA ($45 761 versus $28 578; P<0.001), driven by initial procedure costs. Between discharge and 90 days, costs were $4904 per patient lower for SST+tPA than for tPA ($11 270 versus $16 174; P=0.014); total 90-day costs remained higher with SST+tPA ($57 031 versus $44 752; P<0.001). Higher utility values for SST+tPA led to higher in-trial quality-adjusted life years (0.131 versus 0.105; P=0.005). In lifetime projections, SST+tPA was associated with substantial gains in quality-adjusted life years (6.79 versus 5.05), cost savings of $23 203 per patient and was economically dominant when compared with tPA in 90% of bootstrap replicates.

CONCLUSIONS

Among patients with acute ischemic stroke enrolled in the SWIFT-PRIME trial, SST increased initial treatment costs, but was projected to improve quality-adjusted life-expectancy and reduce healthcare costs over a lifetime horizon compared with tPA.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01657461.

Atypical case of perimesencephalic subarachnoid hemorrhage

Perimesencephalic subarachnoid hemorrhage (PM-SAH) refers to intracranial hemorrhage located in the perimesencephalic cistern. The etiology remains mainly unclear, although venous leakage or rupture has been postulated. We report an interesting case of a 57-year-old healthy man who presented initially with PM-SAH with worsening of subcortical lesions on follow-up neuroimaging. Histopathological examination demonstrated cerebral amyloid angiopathy with perivascular inflammation.

Coil embolization through the Marathon microcatheter: Advantages and pitfalls

Due to technical limitations, small, distal, and tortuous intracranial pathology is sometimes out of reach of the current armamentarium of microcatheters designed for intracranial coil embolization. The Marathon microcatheter (Medtronic, Minneapolis, Minnesota, USA), designed specifically for the delivery of Onyx, is longer and more flexible than most coil delivery catheters. We report on nine patients (three with arteriovenous fistula, three with arteriovenous malformation, two with intracranial aneurysm, and one with tumor) where Marathon was used to deliver commercially available platinum coils. We also conducted laboratory compatibility testing and conclude that the Marathon can be used as a coil delivery catheter for Barricade coils (Blockade Medical, Irvine, California, USA) with diameter less than 0.012 in.

Heads Up! A Novel Provocative Maneuver to Guide Acute Ischemic Stroke Management

BACKGROUND

A common dilemma in acute ischemic stroke management is whether to pursue recanalization therapy in patients with large vessel occlusions but minimal neurologic deficits. We describe and report preliminary experience with a provocative maneuver, i.e. 90-degree elevation of the head of bed for 30 min, which stresses collaterals and facilitates decision-making.

METHODS

A prospective cohort study of <7.5 h of acute anterior circulation territory ischemia patients with minimal deficits despite middle cerebral artery (MCA) or internal carotid artery (ICA) occlusive disease.

RESULTS

Five patients met the study entry criteria. Their mean age was 78.4 years (range 65-93). All presented with substantial deficits (median NIHSS score 11, range 5-22), but improved while in supine position during initial imaging to normal or near-normal (NIHSS score 0-2). MRA showed persistent M1 MCA occlusions in 4, critical ICA stenosis or occlusion in 1, and substantial perfusion-diffusion mismatch in all. To evaluate the potential for eventual collateral failure, patients were placed in a head of bed upright posture. Mean arterial pressure and heart rate were unchanged. Two showed no neurologic worsening and were treated with supportive care with excellent final outcome. Three showed worsening, including recurrent hemiparesis and aphasia at the 6th, recurrent aphasia at the 23rd, and recurrent hemineglect at the 15th upright minute. These 3 underwent endovascular recanalization therapies with successful reperfusion and excellent final outcome.

CONCLUSION

The 'Heads Up' test may be a useful, simple maneuver to assess the risk of collateral failure and guide the decision to pursue recanalization therapy in acute cerebral ischemia patients with minimal deficits despite persisting large cerebral artery occlusion.

Solitaire™ with the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke (SWIFT PRIME) trial: protocol for a randomized, controlled, multicenter study comparing the Solitaire revascularization device with IV tPA with IV tPA alone in acute ischemic stroke

Rationale

Early reperfusion in patients experiencing acute ischemic stroke is critical, especially for patients with large vessel occlusion who have poor prognosis without revascularization. Solitaire™ stent retriever devices have been shown to immediately restore vascular perfusion safely, rapidly, and effectively in acute ischemic stroke patients with large vessel occlusions.

Aim

The aim of the study was to demonstrate that, among patients with large vessel, anterior circulation occlusion who have received intravenous tissue plasminogen activator, treatment with Solitaire revascularization devices reduces degree of disability 3 months post stroke.

Design

The study is a global multicenter, two-arm, prospective, randomized, open, blinded end-point trial comparing functional outcomes in acute ischemic stroke patients who are treated with either intravenous tissue plasminogen activator alone or intravenous tissue plasminogen activator in combination with the Solitaire device. Up to 833 patients will be enrolled.

Procedures

Patients who have received intravenous tissue plasminogen activator are randomized to either continue with intravenous tissue plasminogen activator alone or additionally proceed to neurothrombectomy using the Solitaire device within six-hours of symptom onset.

Study Outcomes

The primary end-point is 90-day global disability, assessed with the modified Rankin Scale (mRS). Secondary outcomes include mortality at 90 days, functional independence (mRS ≤ 2) at 90 days, change in National Institutes of Health Stroke Scale at 27 h, reperfusion at 27 h, and thrombolysis in cerebral infarction 2b/3 flow at the end of the procedure.

Analysis

Statistical analysis will be conducted using simultaneous success criteria on the overall distribution of modified Rankin Scale (Rankin shift) and proportions of subjects achieving functional independence (mRS 0–2).

Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis of individual patient data from five randomised trials

BACKGROUND

In 2015, five randomised trials showed efficacy of endovascular thrombectomy over standard medical care in patients with acute ischaemic stroke caused by occlusion of arteries of the proximal anterior circulation. In this meta-analysis we, the trial investigators, aimed to pool individual patient data from these trials to address remaining questions about whether the therapy is efficacious across the diverse populations included.

METHODS

We formed the HERMES collaboration to pool patient-level data from five trials (MR CLEAN, ESCAPE, REVASCAT, SWIFT PRIME, and EXTEND IA) done between December, 2010, and December, 2014. In these trials, patients with acute ischaemic stroke caused by occlusion of the proximal anterior artery circulation were randomly assigned to receive either endovascular thrombectomy within 12 h of symptom onset or standard care (control), with a primary outcome of reduced disability on the modified Rankin Scale (mRS) at 90 days. By direct access to the study databases, we extracted individual patient data that we used to assess the primary outcome of reduced disability on mRS at 90 days in the pooled population and examine heterogeneity of this treatment effect across prespecified subgroups. To account for between-trial variance we used mixed-effects modelling with random effects for parameters of interest. We then used mixed-effects ordinal logistic regression models to calculate common odds ratios (cOR) for the primary outcome in the whole population (shift analysis) and in subgroups after adjustment for age, sex, baseline stroke severity (National Institutes of Health Stroke Scale score), site of occlusion (internal carotid artery vs M1 segment of middle cerebral artery vs M2 segment of middle cerebral artery), intravenous alteplase (yes vs no), baseline Alberta Stroke Program Early CT score, and time from stroke onset to randomisation.

FINDINGS

We analysed individual data for 1287 patients (634 assigned to endovascular thrombectomy, 653 assigned to control). Endovascular thrombectomy led to significantly reduced disability at 90 days compared with control (adjusted cOR 2.49, 95% CI 1.76-3.53; p<0.0001). The number needed to treat with endovascular thrombectomy to reduce disability by at least one level on mRS for one patient was 2.6. Subgroup analysis of the primary endpoint showed no heterogeneity of treatment effect across prespecified subgroups for reduced disability (pinteraction=0.43). Effect sizes favouring endovascular thrombectomy over control were present in several strata of special interest, including in patients aged 80 years or older (cOR 3.68, 95% CI 1.95-6.92), those randomised more than 300 min after symptom onset (1.76, 1.05-2.97), and those not eligible for intravenous alteplase (2.43, 1.30-4.55). Mortality at 90 days and risk of parenchymal haematoma and symptomatic intracranial haemorrhage did not differ between populations.

INTERPRETATION

Endovascular thrombectomy is of benefit to most patients with acute ischaemic stroke caused by occlusion of the proximal anterior circulation, irrespective of patient characteristics or geographical location. These findings will have global implications on structuring systems of care to provide timely treatment to patients with acute ischaemic stroke due to large vessel occlusion.

FUNDING

Medtronic.

Analysis of Workflow and Time to Treatment and the Effects on Outcome in Endovascular Treatment of Acute Ischemic Stroke: Results from the SWIFT PRIME Randomized Controlled Trial

Purpose To study the relationship between functional independence and time to reperfusion in the Solitaire with the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke (SWIFT PRIME) trial in patients with disabling acute ischemic stroke who underwent endovascular therapy plus intravenous tissue plasminogen activator (tPA) administration versus tPA administration alone and to investigate variables that affect time spent during discrete steps. Materials and Methods Data were analyzed from the SWIFT PRIME trial, a global, multicenter, prospective study in which outcomes were compared in patients treated with intravenous tPA alone or in combination with the Solitaire device (Covidien, Irvine, Calif). Between December 2012 and November 2014, 196 patients were enrolled. The relation between time from (a) symptom onset to reperfusion and (b) imaging to reperfusion and clinical outcome was analyzed, along with patient and health system characteristics that affect discrete steps in patient workflow. Multivariable logistic regression was used to assess relationships between time and outcome; negative binomial regression was used to evaluate effects on workflow. The institutional review board at each site approved the trial. Patients provided written informed consent, or, at select sites, there was an exception from having to acquire explicit informed consent in emergency circumstances. Results In the stent retriever arm of the study, symptom onset to reperfusion time of 150 minutes led to 91% estimated probability of functional independence, which decreased by 10% over the next hour and by 20% with every subsequent hour of delay. Time from arrival at the emergency department to arterial access was 90 minutes (interquartile range, 69-120 minutes), and time to reperfusion was 129 minutes (interquartile range, 108-169 minutes). Patients who initially arrived at a referring facility had longer symptom onset to groin puncture times compared with patients who presented directly to the endovascular-capable center (275 vs 179.5 minutes, P < .001). Conclusion Fast reperfusion leads to improved functional outcome among patients with acute stroke treated with stent retrievers. Detailed attention to workflow with iterative feedback and aggressive time goals may have contributed to efficient workflow environments. (©) RSNA, 2016 Online supplemental material is available for this article.

Rapid learning curve for Solitaire FR stent retriever therapy: evidence from roll-in and randomised patients in the SWIFT trial

BACKGROUND

In light of recent positive trial data for endovascular therapy in acute ischemic stroke (AIS), stent retriever use by practitioners without prior experience with these devices may become more common.

OBJECTIVE

To assess the safety and efficacy of thrombectomy for AIS using Solitaire for patients treated in the roll-in period of the Solitaire With the Intention For Thrombectomy (SWIFT) trial, which represented the first clinical use of the device for these interventionalists.

METHODS

Prospectively collected demographic, clinical, and angiographic data on patients treated in the initial roll-in and subsequent randomized phases of the SWIFT study were collected and analyzed. Key statistical analyses were validated by an independent external statistician.

RESULTS

Patients in the roll-in period achieved equivalently high rates of reperfusion (55%) compared with those treated with the device in the randomized phase (61%). Rates of adverse events were comparable (13% vs. 9%). Rates of good neurological outcome were equivalent between the roll-in and randomized patients treated with Solitaire (63% vs. 58%). Including the roll-in patients strengthened the conclusions of the study, that reperfusion rates without symptomatic hemorrhage with Solitaire were greater than with Merci (59% vs. 24%, p<0.001).

CONCLUSIONS

Thrombectomy in AIS using the Solitaire stent retriever device can be performed safely and effectively when used by experienced neurointerventionalists without previous experience with the device.

TRIAL REGISTRATION NUMBER

The SWIFT study is registered with ClinicalTrials.gov, number NCT 01054560.

Safety and Efficacy of Solitaire Stent Thrombectomy: Individual Patient Data Meta-Analysis of Randomized Trials

BACKGROUND AND PURPOSE

Recent positive randomized trials of endovascular therapy for ischemic stroke used predominantly stent retrievers. We pooled data to investigate the efficacy and safety of stent thrombectomy using the Solitaire device in anterior circulation ischemic stroke.

METHODS

Patient-level data were pooled from trials in which the Solitaire was the only or the predominant device used in a prespecified meta-analysis (SEER Collaboration): Solitaire FR With the Intention for Thrombectomy as Primary Endovascular Treatment (SWIFT PRIME), Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion With Emphasis on Minimizing CT to Recanalization Times (ESCAPE), Extending the Time for Thrombolysis in Emergency Neurological Deficits-Intra-Arterial (EXTEND-IA), and Randomized Trial of Revascularization With Solitaire FR Device Versus Best Medical Therapy in the Treatment of Acute Stroke Due to Anterior Circulation Large Vessel Occlusion Presenting Within Eight Hours of Symptom Onset (REVASCAT). The primary outcome was ordinal analysis of modified Rankin Score at 90 days. The primary analysis included all patients in the 4 trials with 2 sensitivity analyses: (1) excluding patients in whom Solitaire was not the first device used and (2) including the 3 Solitaire-only trials (excluding ESCAPE). Secondary outcomes included functional independence (modified Rankin Score 0-2), symptomatic intracerebral hemorrhage, and mortality.

RESULTS

The primary analysis included 787 patients: 401 randomized to endovascular thrombectomy and 386 to standard care, and 82.6% received intravenous thrombolysis. The common odds ratio for modified Rankin Score improvement was 2.7 (2.0-3.5) with no heterogeneity in effect by age, sex, baseline stroke severity, extent of computed tomography changes, site of occlusion, or pretreatment with alteplase. The number needed to treat to reduce disability was 2.5 and for an extra patient to achieve independent outcome was 4.25 (3.29-5.99). Successful revascularization occurred in 77% treated with Solitaire device. The rate of symptomatic intracerebral hemorrhage and overall mortality did not differ between treatment groups.

CONCLUSIONS

Solitaire thrombectomy for large vessel ischemic stroke was safe and highly effective with substantially reduced disability. Benefits were consistent in all prespecified subgroups.

Abstract TP81: Faster Start of IV tPA Does not Decrease the Need for Endovascular Thrombectomy in Acute Ischemic Stroke

Background: Recent patient series have shown IV tPA to more often lyse cerebral thrombi when started sooner after symptom onset in patients with acute ischemic stroke due to large vessel occlusion (AIS-LVO). This association has been attributed to less fibrin-cross-linking and less compaction of thrombi. We sought to determine if this phenomenon would make endovascular thrombectomy less often needed among AIS-LVO patients treated hyperacutely with IV tPA.

Methods: In a prospectively maintained registry, we identified patients receiving IV tPA at 2 academic medical centers from March 2005 - May 2015. Inclusion criteria were: 1) LVO seen on CTA or MRA before (or early during) infusion of IV tPA and 2) follow-up vessel imaging within 6h of IV tPA initiation, using CT, MR or catheter angiogram. Degree of thrombus lysis with IV tPA alone was rated using the arterial occlusive lesion (AOL) Scale.

Results: Among the 166 patients, average age was 72.4 (±13.4), 52.4% were female and pretreatment NIHSS was 13.9 (±8.4). Onset to needle time (OTN) was median 105 min (IQR 79-129) and door to needle time 44 min (27-65). Initial vessel imaging modality was MRA in 68.7% and CTA in 31.3%. Early post-tPA vessel imaging modality was catheter angiogram in 63.8%, MRA in 33.7% and CTA in 2.4%. Time from tPA initiation to recanalization assessment was faster when post-tPA vessel imaging was catheter angiogram vs MRA/CTA, 72 min (45.5-116.5) vs 232 min (185-283), p<0.001. In cases assessed with early post-treatment catheter angiogram, IV tPA yielded complete recanalization in 17%, partial in 6.6%, and none in 76.4%. In cases assessed with MRA/CTA, IV tPA yielded complete recanalization in 30%, partial in 35%, and none in 35%. Recanalization within the 6h window was visualized more often when imaged with later CTA/MRA than with earlier catheter angiogram (p<0.001). Among patients going directly to catheter angiography, OTN for IV tPA was not different between recanalizers and non-recanalizers, 106 vs 98 min, p = 0.53.

Discussion: Among large vessel acute ischemic stroke patients, the rate of complete recanalization with IV tPA alone is only 1 in 6, and faster OTN time is not associated with increased recanalization. All AIS-LVO patients should proceed to thrombectomy as swiftly as possible.

Abstract WMP6: Earlier Treatment is Associated with Higher Reperfusion Rates and Better Outcomes in the SWIFT PRIME Trial

Background: Previous randomized trials of endovascular therapy for stroke have shown better rates of functional independent outcome (mRS 0-2 at 90 days) with earlier initiation of endovascular therapy. In these trials no information was available to assess the volume of salvageable brain tissue prior to intervention or tissue reperfusion post- intervention. We sought to determine the associations between times to treatment, mismatch volume, reperfusion rates and functional independent outcome (FIO) in patients with the Target mismatch (TMM) profile in SWIFT PRIME.

Methods: Patients with TMM on CT or MR perfusion, as determined by an automated software package (RAPID), were included in the analysis. We compared the rate of FIO and factors associated with FIO in patients randomized early (<3h) vs. late (>3h) from stroke symptom onset (SSO). Age, NIHSS, core volume, mismatch volume and successful reperfusion at 27 h (>90% reduction in perfusion lesion volume on CT or MR Perfusion) were included in univariate and a multivariate logistic regression analysis.

Results: A total of 131/195 patients had TMM. FIO was 62.3% (33/53) in the early vs. 43.6% (34/78) in the late group, p=0.0498. In the Solitaire arm, FIO was 72.4% (21/29) in early group vs. 55.0% (22/40) in the late group. In the tPA arm FIO was 50.0% (12/24) in the early group vs. 31.6% (12/38) in the late group. There was no significant difference in age, baseline NIHSS, core volume, or mismatch volume among the overall early vs late groups but successful reperfusion at 27h occurred in 76% of the early vs. 55% of the late group (p<0.05). The rate of successful reperfusion at 27h was 92% (early) vs. 81% (late) for Solitaire; p=0.28 and 61% (early) vs. 27% (late) for tPA; p=0.032). The 27 hour CTA or MRA TICI 2b-3 rates were 92% (early) vs. 84% (late) for Solitaire group and 71% (early) vs. 38% (late) for tPA group.

Conclusions: Earlier lytic and stent-retriever thrombectomy interventions are associated with higher rate of FIO in patients with Target mismatch profiles in SWIFT Prime trial. This improved outcome is likely due to higher reperfusion rates that are achieved with earlier intervention, suggesting greater responsiveness of less organized and less compacted thrombi to fibrinolysis and potentially stent retrieval.

Abstract WP17: Effect of Solitaire Retriever-predominant Thrombectomy in Acute Ischemic Stroke: a Pooled, Individual Patient Data, Systematic Analysis

Introduction: Endovascular thrombectomy predominantly with the Solitaire stent retriever results in better outcomes among ischemic stroke patients with proximal, anterior circulation occlusions. The overall effect size and benefit in important subgroups are best estimated using pooled, individual participant-level data meta-analysis.

Methods: The SEER consortium pooled individual patient-level data from the 4 major randomized trials in which Solitaire retrievable stents were the predominant endovascular device, ESCAPE, SWIFT-PRIME, REVASCAT, and EXTEND-IA. A formal statistical analysis plan was pre-specified. The primary outcome is the modified Rankin Score at 90 days. Secondary outcomes include functional independence (mRS 0-2) and mortality at 90 days. Clinical sub-groups assessed are age, sex, NIHSS score, and target occlusion location. Full results will be presented at the meeting.

Results: Among 777 patients randomized (400 intervention, 377 control), mean age was 68 (sd 13), 51% were female, pretreatment NIHSS was median 17 (iqr 7), median ASPECTS score was 8 (iqr 2). More favorable outcomes over the entire mRS were observed with thrombectomy, CMH test p <0.001. Treatment benefit was homogenous across all subgroups of age, sex, baseline NIHSS, and target occlusion location. The rate of functional independence (mRS 0-2) at 90d was 55.0% endovascular vs. 31.5% control (RR = 1.7 CI95 1.4-2.1). The risk of death trended lower in the endovascular group (RR = 0.75 CI95 0.5-1.1). Among 128 patients ≥ 80 years of age, 37.8% (endovascular) vs. 18.5% (control) achieved an independent outcome (RR 2.0 CI95 1.1-3.8). Among 206 subjects with ICA occlusion, 45.9% (endovascular) vs. 18.9% (control) achieved an independent outcome (RR 2.4 CI95 1.5-3.8). Among 561 with MCA occlusions, 58.6% (endovascular) and 38.9% (control) achieved an independent outcome (RR 1.6 CI95 1.3-2.0).

Conclusions: Endovascular treatment for anterior circulation, large vessel occlusion ischemic stroke is a robust therapy in old and young, men and women, more and less severe deficits, and both ICA and MCA occlusions. The magnitude of benefit is large and consistent across trials; overall, 1 of every 4 treated patients achieves functional independence as a result of therapy.

Abstract WP19: Rate and Speed of Reperfusion Explains Variations in Treatment Effect Sizes Across Recent Trials of Endovascular Therapy for Acute Ischemic Stroke

Background: Five recent trials demonstrated benefit of endovascular treatment (ET) for large-vessel ischemic stroke. But, while all were positive, the trials differed in their estimates of benefit magnitude. We tested whether trial differences in rate and speed of successful accounted for their variations in effect size estimates.

Methods: We analyzed all 5 recent positive endovascular stroke trials, MR CLEAN, ESCAPE, EXTEND-IA, REVASCAT, and SWIFT-PRIME. An expanded analysis also included the 2 prior neutral trials, IMS-3 and MR RESCUE. Linear regression and correlation coefficients probed variable relations.

Results: Among the 5 positive trials, rates of substantial reperfusion ranged from 59%-88% and OTR from 241-355 minutes. Independent functional outcome rates ranged in the endovascular arms from 32.6% to 71.4%, and in the control arms from 19.1% to 40.0%. Absolute differences in functional independence between treatment arms ranged from 13.5% - 31.4%. In the 2 neutral trials, reperfusion rates were lower, OTR longer, and outcome differences much less. Linear regression demonstrated very strong relation of both trial reperfusion rate and trial reperfusion speed to trial magnitude of treatment benefit (Figure). Across all 7 trials, the correlation between reperfusion rate and treatment effect size was r= 0.98, and between reperfusion speed and treatment effect size was r=0.85. Among just the 5 positive trials, reperfusion rate correlation with treatment effect size was r=0.87, and between reperfusion speed and treatment effect size was r=0.89.

Conclusion: Achievement of successful reperfusion and speed of reperfusion are potent determinants of the degree of benefit with endovascular reperfusion therapy, and account for more than three-quarters of the variation in degree of treatment benefit in the 5 recent positive thrombectomy trials. To maximize patient benefit from endovascular intervention, open arteries fully and fast.

Abstract 200: Collaterals in SWIFT PRIME: Imaging Correlates and Ultimate Impact

Background: The overwhelming benefit of endovascular stroke therapy established in recent trials fueled by rapid workflow, modern devices and favorable noninvasive imaging profiles newly question the impact of collateral grade. We analyzed the SWIFT PRIME trial to evaluate the role of collaterals with respect to advanced imaging selection, the pace of infarct growth and ultimate clinical outcomes.

Methods: Conventional angiography of the endovascular arm in SWIFT PRIME (n=98) was reviewed by 3 independent readers that scored ASITN/SIR collateral flow grade, followed by consensus adjudications. Angiographic collaterals were scored only when available, prior to use of the Solitaire stent retriever. Statistical analyses investigated the relationship of collateral grade with clinical and imaging variables in the main trial dataset.

Results: 70 endovascular arm subjects (mean age 65.2±12.1 years, 35 (50%) women) had angiographic collaterals scored by 3 independent readers ( W =0.93). Pretreatment CT or MR perfusion imaging was obtained in 92% of cases, associated with a relatively wide range of angiographic collateral grades (1, n=6 (9%); 2, n=25 (36%); 3, n=37 (53%); 4, n=2 (3%)) with a preponderance (79%) of M1 occlusions. Worse collaterals were associated with prior myocardial infarction (33% (grade 1), 8% (grade 2), 3% (grades 3, 4); p=0.03) but unrelated to age, sex, or other co-morbidities or time from stroke onset. Baseline ASPECTS (median 9, r=0.20) trended higher (p=0.09) in those with more robust collaterals. Collaterals were unrelated to degree of TICI reperfusion, yet the presence of distal emboli at procedure end was linked with worse collaterals (p=0.008). More robust collaterals exhibited a potent and graded link with better day 90 mRS (r=- 0.3, p=0.03) and lower mean NIHSS at 27 hours (r=-0.3, p=0.03), whereas infarct growth at 27 hours was unrelated (r=-0.07, p=0.60).

Conclusions: Use of advanced noninvasive perfusion imaging enrolls patients with more robust collateral grades, yet a diverse range of collaterals may be seen. Even with rapid workflow, mismatch based selection and successful reperfusion, the degree of angiographic collaterals continues to be strongly associated with clinical outcomes at all timepoints.

Abstract WMP81: Collaterals and the Severity of Hypoperfusion in Acute Ischemic Stroke are Independent of Dehydration or Volume Status

Background: Systemic hemodynamic factors may affect blood flow to the brain, yet the influence of volume status and the use of fluid administration to improve perfusion in acute ischemic stroke remains unproven. We correlated the presence of dehydration and volume status defined by initial lab values with perfusion MRI and collaterals at angiography in middle cerebral artery (MCA) stroke patients.

Methods: Retrospective analysis of a consecutive series of isolated M1 MCA occlusions was conducted at an expert core lab to quantify acute Tmax volumes, Tmax hypoperfusion severity ratios and ASITN collateral grade on digital subtraction angiography (DSA). Blood urea nitrogen (BUN) and creatinine (Cr) measured during triage were correlated with hypoperfusion and ASITN/SIR grade. Statistical methods included correlations and ANOVA.

Results: 95 patients (median age 74 (24-101) years; 71 women; median NIHSS 16; median time to MRI, 4h06min) with acute stroke due to M1 occlusion (52 proximal, 43 distal) had contemporaneous BUN/Cr, perfusion MRI and DSA during a 6-year period. Dehydration was noted in 38% (BUN/Cr>20) and 71% (BUN/Cr>15) of patients. Tmax>6sec volumes were median 197 cc (IQR 102-347), with Tmax hypoperfusion severity ratios of 10/6 (median 0.80 (IQR 0.72-0.87)). DSA collateral grade was median 2 (IQR 2-3). Volume status or BUN/Cr was distinct from Tmax hypoperfusion severity at all thresholds, including Tmax>6s (r=0.143, p=0.166), Tmax 10/6 (r=0.114, p=0.271). Direct correlation between BUN/Cr and DSA collateral grade was also unapparent (r=0.034, p=0.744).

Conclusions: Dehydration and the degree of volume depletion may be common, but are not associated with the severity of collateral perfusion in acute M1 MCA occlusion. Collateral grade defined by DSA and the associated severity of hypoperfusion in the brain is unrelated to intravascular volume status.

Abstract WP36: The Role of Intravenous Thrombolysis in Patients With Acute Ischemic Stroke Treated With Mechanical Thrombectomy

Introduction: Mechanical thrombectomy (MT) improves clinical outcome of patients with acute ischemic stroke (AIS) and a large vessel occlusion. Approximately 90% of patients in the recent MT trials received intravenous thrombolysis (IVT) prior to MT.

Aim: To determine if IVT in combination with MT is superior to MT alone in patients with AIS and a large vessel occlusion.

Methods: A patient-level pooled analysis of the STAR and SWIFT studies, two large multicenter prospective studies on MT for AIS was utilized. Using multivariate logistic regression analysis, we compared mRS at follow-up, reperfusion rates, and complication rates (intracerebral hemorrhage and emboli to uninvolved territories) between patients who underwent MT following IVT, to those who underwent only MT. An independent core laboratory scored all radiological outcomes.

Results: Of 291 included patients, 160 (55%) underwent MT following IVT, and 131 (45%) underwent only MT. Of the patients treated with IVT, 116 were IVT failures (full tpa dose) and 44 received bridging therapy (mean tpa dose 0.62 mg/kg). Patients who received IVT less often had atrial fibrillation (33 vs. 47 %, p=0.016) and diabetes (14 vs. 24%, p=0.023), and had a lower mean ASPECTS (8.1 vs. 8.5, p=0.031) compared to thos who underwent only MT. There was no difference in baseline NIHSS (both median 17) or location of the occlusion between groups. We did not find a statistically significant association between use of IVT in addition to MT vs. MT alone for any of the outcomes. There were trends towards a lower risk of symptomatic intracerebral hemorrhage (adjusted OR 0.12, 95% CI 0.01-1.13), a higher risk of vasospasm (adjusted OR 1.81, 95% CI 0.86-3.80), and a higher chance of mRS 0-2 (adjusted OR 1.60, 95% CI 0.86-3.80) in patients who received MT following IVT, compared to MT alone.

Conclusions: We observed no statistically significant benefit or harm for the use of IVT in addition to MT in patients with AIS and a large vessel occlusion.

Abstract 2: Good Outcome After Successful Recanalization is Time Dependent in the Swift Prime Randomized Controlled Trial

Background and Purpose: The SWIFT PRIME trial demonstrated superior outcomes in patients presenting with disabling acute ischemic stroke (AIS) who underwent endovascular therapy vs. intravenous tissue plasminogen activator (t-PA) alone. We sought to understand the relationship between functional independence and time to reperfusion in study patients assigned to thombectomy.

Methods: SWIFT PRIME is a global, multi-center, prospective, randomized, open, blinded endpoint study comparing functional outcomes in AIS subjects treated with either IV t-PA alone or IV t-PA in combination with Solitaire stent retriever device. Among patients in whom substantial reperfusion (TICI 2b/3) was achieved, we analyzed the effect onindependent outcome (mRS 0-2) of time from stroke onset to reperfusion (OTR) and from qualifying imaging to reperfusion

Results: Among 83 patients undergoing thrombectomy, substantial reperfusion was achieved in 73 (88%). A marked effect of OTR was noted (Figure 1A). The rate of functional independence was 87% if reperfusion was achieved 150 minutes from symptoms onset. The absolute rate of good outcomes decreased by 10% over the next 60 minutes of delay in OTR and by 15% with every 60 minute delay there-after. Faster post-arrival workflow speed improved outcomes among patients presenting directly to study hospitals (Figure 1B).

Conclusions: Speed of reperfusion is a dominant determinant of functional outcome among patients treated with stent retrievers. In the early period after, every 6 minute delay in reperfusion causes 1 more out of 100 treated patients to not achieve functional independence.

Abstract WMP108: Endovascular Therapy in Children With Large Vessel Occlusion: a Clinical Series of Five Cases

Background & Purpose: Children were excluded from the recent positive mechanical thrombectomy trials and the literature on endovascular therapy in this population needs to be built. We report here case series of pediatric patients who received mechanical thrombectomy at our institution.

Methodology: Our prospectively collected UCLA acute stroke database from 2000 to present was retrospectively reviewed. Only patients <18 years old with large vessel occlusion who underwent acute endovascular therapy were included in this study. Demographic, clinical, pre- and post-intervention imaging, and the interventional procedure data were analyzed. The Pediatric National Institutes of Health Stroke Scale (PedNIHSS) score at presentation and at discharge, as well as pediatric-modified Rankin Scale (Ped-mRS) up-to 90 days were used.

Results: All five patients (ages 2-15) suffered an embolic stroke. Three of them had congenital heart disease and one had repeated episodes of syncope and bradycardia. No risk factors other than PFO were identified in the fifth patient. Occlusion sites were ICA-M1 (n=2), M1 (n=2), and M1-M2 (n=1). IV tPA was used in one case. Time from last known well to reperfusion ranged from 3h to 9h 28min and the patients’ initial collaterals were scored between grades 2 - 3. AOL score of 3 was achieved in all cases, TICI 2a in two and TICI 2b in three cases. Merci was used in two cases, Penumbra, Solitaire and Mindframe Capture were used each in one case. One patient developed intracerebral hemorrhage that required hemicraniectomy. The PedNIHSS score at discharge ranged from 0 to 8 and the Ped-mRS score up-to 90 days ranged from 0 to 4, with 80% of children having Ped-mRS ≤ 3.

Conclusion: Mechanical thrombectomy may be a safe and feasible treatment option in pediatric stroke patients with large vessel occlusion.

Abstract WMP13: Predictive Value of Rapid-assessed Cerebral Blood Volume and Cerebral Blood Flow Ct Perfusion Thresholds on Final Infarct Volume Following Successful Reperfusion: Analysis of The SWIFT PRIME Trial Data

Background and purpose: Advanced CT perfusion (CTP) imaging can estimate the size of the ischemic core, which can be used for selection of patients for endovascular therapy. The relative cerebral blood volume (rCBV) and cerebral blood flow (rCBF) thresholds chosen to identify ischemic core influence the accuracy of prediction. The purpose of this study was to analyze the accuracy of various rCBV and rCBF thresholds for predicting 27 hour infarct volume using RAPID automated analysis software.

Methods: Patients from the SWIFT PRIME study with baseline and 27 hour follow-up CT perfusion scans were included if they had complete reperfusion based on Tmax>6s perfusion maps obtained at 27 hours. Patients from both the tPA and endovascular groups were included. Infarct volume was determined on MRI (FLAIR images) or CT scans obtained 27 hours after symptom onset. The predicted ischemic core volume on rCBV and rCBF maps using thresholds ranging between 0.2 and 0.8 was compared with the actual infarct volume to determine the most accurate thresholds.

Results: Among the 47 subjects, the following baseline CTP thresholds most accurately predicted the actual 27 hour infarct volume: rCBV=0.34 (Median absolute error (MAE)=11.5 ml); rCBV=0.36, MAE=9.9 ml; rCBV=0.4, MAE=12.5 ml; rCBF=0.3, MAE=8.8 ml; rCBF=0.32, MAE=7.3; and rCBF=0.34, MAE=7.8.

Conclusions: Brain regions with rCBF ≤ .32 or rCBV ≤ .36 provided the most accurate prediction of infarct volume in patients who achieved complete reperfusion with median absolute errors less than 10 ml. Our data support the value of automated image analysis software as a tool for accurate prediction of ischemic core lesion volume.

Abstract 161: Prediction of Thrombolysis-induced Parenchymal Hemorrhage in Patients With Acute Ischemic Stroke: Use of MR Perfusion and Diffusion Biomarkers

Purpose: Ischemic stroke patients with low cerebral blood volume (CBV), low apparent diffusion coefficient (ADC) and increased microvascular permeability (K2) have increased risk of parenchymal hemorrhage (PH) after recanalization therapies. We have developed a predictive model to examine the risk of PH following revascularization therapies using combined MR perfusion and diffusion biomarkers.

Methods: Voxel-based values of rCBV, K2, and ADC from the infarction core were obtained using pre-treatment MRI data from patients enrolled in the Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy (MR RESCUE) clinical trial. Using histogram analyses the 10 th and 90 th percentile values were calculated for the rCBV, ADC, and K2 variables for each patient. The associations between PH and extreme values of CBV (10%rCBV), ADC (10%ADC), and K2 (90%K2) in each patient were assessed in univariate and multivariate analyses. Receiver operating characteristic (ROC) analysis was performed to determine the optimal parameter/s and threshold for predicting PH.

Results: In 83 patients included in this analysis, 20 (24%, 13 PH1, 7 PH2) developed PH. Univariate analysis showed significantly lower 10%rCBV and 10%ADC values and significantly higher 90%K2 values in patients with PH. After controlling for age, baseline NIHSS, infarct volume, and status of recanalization, multivariate logistic regression analysis identified 10%rCBV (p=0.002) and 90%K2 (p=0.03), but not 10%ADC (p=0.07), as independent predictors of PH. For 10%RCBV, ROC analysis showed the greatest AUC (0.87) at a threshold < 0.45 with sensitivity/specificity of 95%70%. For 90%K2, the greatest AUC (0.75) was obtained at a threshold of > 0.27 with sensitivity/specificity of 90%/60%. In a separate model, a combined K2-rCBV classifier remained the single independent predictor of PH (OR=33).

Conclusion: Our results suggest that combined increased permeability and decreased rCBV derived from MR perfusion can be used for risk stratification in patients with AIS before undergoing revascularization therapies.