Candidates For Thrombectomy Research Articles

Overview of imaging choices for thrombectomy patients

Neuroimaging Predictors for the Outcome of Acute Interventions-Marc Fisher, M.D. Boston MA USA Brain imaging plays a key role in the diagnosis and management of acute ischemic stroke. All patients are imaged with either CT or MRI to exclude a hemorrhage and vessel imaging is necessary to identify patients with large vessel occlusion that are candidates for thrombectomy. The extent of ischemic injury early after stroke onset can also be estimated by various CT and MRI approaches. On routine CT imaging, the ASPECTS score provides information about the extent of ischemic injury and is widely used to identify thrombectomy candidates in the early time window after stroke onset.

Rescan Time Delays in Ischemic Stroke Imaging: A Retrospective Observation and Analysis of Causes and Clinical Impact.

Delays to reperfusion negatively impact outcomes of patients with ischemic stroke, yet current guidelines recommend selective sequential imaging for thrombectomy candidates. We aimed to quantify and analyze time delays associated with rescanning in sequential acute stroke imaging. This was a retrospective cohort study of consecutive patients with acute ischemic stroke who underwent imaging for treatment decision-making from January 1, 2017, to June 30, 2020. Rescan time delay was defined as ≥10-minute difference between initial NCCT and CTA ± CTP. Mean rescan time delays in comprehensive and primary stroke centers were compared. Bivariate and multivariable regression analyses assessed clinical and imaging factors associated with rescanning time delays and early outcomes. A total of 588 patients with acute ischemic were included in statistical analyses. Rescanning occurred in 27.9% (164/588 patients), with a mean time delay of 53.7 (SD, 43.4) minutes. For patients presenting at primary compared with comprehensive stroke centers, rescan time delays were more common (59.6% versus 11.8%, P < .001), with longer delays (65.4 [SD, 45.4] minutes versus 23.6 [SD, 14.0] minutes, P < .001). Independent predictors of rescan time delays included primary stroke center presentation, intravenous thrombolysis administration, black race, admission NIHSS ≥10, baseline independent ambulation, and onset-to-comprehensive stroke center arrival in ≥6 hours. Protocols for early simultaneous comprehensive CT (NCCT + CTA + CTP) were associated with lower odds of time delays (OR = 0.34; 95% CI, 0.21-0.55). Rescanning was associated with lower odds of home discharge (OR = 0.53; 95% CI, 0.30-0.95). A sequential approach to CT-based imaging may be significantly associated with prolonged acute stroke evaluations. Adoption of early simultaneous comprehensive CT could minimize treatment delays and improve outcomes.

'Drip-and-ship' intravenous thrombolysis and outcomes for large vessel occlusion thrombectomy candidates in a hub-and-spoke telestroke model

BackgroundRandomized trials have not demonstrated benefit from intravenous thrombolysis among patients undergoing endovascular thrombectomy (EVT). However, these trials included primarily patients presenting directly to an EVT capable hub center. We...

Mechanical Thrombectomy Improves Outcome for Large Vessel Occlusion Stroke after Cardiac Surgery

BackgroundStroke is a feared complication of cardiac surgery. Modern clot-retrieval techniques provide effective treatment for large vessel occlusion (LVO) strokes. The purpose of this study was to 1) report the incidence of LVO stroke after cardiac surgery at a large academic center, and 2) describe outcomes of postoperative LVO strokes. MethodsAll patients experiencing stroke within 30 days after undergoing cardiac surgery at a single center in 2014-2018 were reviewed. LVOs were identified through review of imaging and medical records, and their characteristics and clinical courses were examined. ResultsOver the study period, 7,112 cardiac surgeries, including endovascular procedures, were performed. Acute ischemic stroke within 30 days after surgery was noted in 163 patients (2.3%). Among those with a stroke, 51/163 (31.3%) had a CTA or MRA, and 15/163 (9.2%) presented with LVO stroke. For all stroke patients, the median time from surgery to stroke was 2 days (interquartile range, IQR, 0–6 days), and for patients with LVO, the median time from surgery to stroke was 4 days (IQR 0–6 days). The overall rate of postoperative LVO was 0.2% (95% CI 0.1–0.4%), though only 6/15 received thrombectomy. LVO patients receiving thrombectomy were significantly more likely to return to independent living compared to those managed medically (n = 4/6, 66.6% for mechanical thrombectomy vs. n = 0/9, 0% for medical management, P = .01). Of the 9 patients who did not get thrombectomy, 6 may currently be candidates for thrombectomy given new expanded treatment windows. ConclusionsThe rate of LVO after cardiac surgery is low, though substantially elevated above the general population, and the majority do not receive thrombectomy currently. Patients receiving thrombectomy had improved neurologic outcomes compared to patients managed medically. Optimized postoperative care may increase the rate of LVO recognition, and cardiac surgery patients and their caregivers should be aware of this effective therapy.

Editors' Note: Association of Initial Imaging Modality and Futile Recanalization After Thrombectomy

In “Association of Initial Imaging Modality and Futile Recanalization After Thrombectomy,” Meinel et al. reported that the rate of futile recanalization (defined as 90-day modified Rankin Scale (mRS) score 4–6 despite successful recanalization) among patients enrolled in the BEYOND-SWIFT multicenter, retrospective observational registry was significantly higher in patients selected for thrombectomy based on a CT scan as compared with patients selected for thrombectomy based on an MRI. Siegler and Thon cautioned that these findings should not dissuade against (1) use of a CT scan to determine eligibility for thrombectomy because this could lead to unnecessary delays in care or (2) performance of thrombectomy after CT scans because the imaging modality itself does not directly affect outcome and 40% of patients selected for thrombectomy based on a CT scan had a good 90-day mRS score (which represents a 22%–27% absolute increase compared with patients treated with medical management in the DAWN and DEFUSE-3 trials). Meinel et al agreed that it is imperative to avoid delays before thrombectomy and reinforced that their findings should not influence the selection of imaging modality for potential thrombectomy candidates. They also pointed out that implementation of high-speed MRI protocols should be considered to obtain more detailed information than a CT scan can provide while avoiding lengthy delays between imaging and groin puncture. In “Association of Initial Imaging Modality and Futile Recanalization After Thrombectomy,” Meinel et al. reported that the rate of futile recanalization (defined as 90-day modified Rankin Scale (mRS) score 4–6 despite successful recanalization) among patients enrolled in the BEYOND-SWIFT multicenter, retrospective observational registry was significantly higher in patients selected for thrombectomy based on a CT scan as compared with patients selected for thrombectomy based on an MRI. Siegler and Thon cautioned that these findings should not dissuade against (1) use of a CT scan to determine eligibility for thrombectomy because this could lead to unnecessary delays in care or (2) performance of thrombectomy after CT scans because the imaging modality itself does not directly affect outcome and 40% of patients selected for thrombectomy based on a CT scan had a good 90-day mRS score (which represents a 22%–27% absolute increase compared with patients treated with medical management in the DAWN and DEFUSE-3 trials). Meinel et al agreed that it is imperative to avoid delays before thrombectomy and reinforced that their findings should not influence the selection of imaging modality for potential thrombectomy candidates. They also pointed out that implementation of high-speed MRI protocols should be considered to obtain more detailed information than a CT scan can provide while avoiding lengthy delays between imaging and groin puncture.

Abstract P149: Regional Transfer Protocols Can Improve Transfer Times and Reduce Length of Stay for Thrombectomy Candidates Seen on Telestroke

Introduction: Our telestroke (TS) network instituted a regional transfer protocol (RTP) that allows for stroke patients in need of higher level of care to be pre-accepted and transferred to the nearest appropriate comprehensive stroke center (CSC). We studied the impact of the RTP on resource utilization and time metrics in patients transferred for evaluation of intra-arterial thrombectomy (IAT). Before the RTP, all potential IAT patients were transferred to one central CSC. After the RTP was initiated, the network had the capability to transfer to two additional CSCs within the same health system that are strategically located in the Houston area. Methods: We identified patients evaluated via TS in spoke emergency rooms that were subsequently transferred for IAT evaluation from 1/1/2016 to 12/31/2017 - one year prior and one year after the RTP. Baseline demographic characteristics, transfer and IAT metrics, and outcomes were compared for the two time periods. Results: Of 220 patients, 102 patients were transferred pre-RTP, and 120 were transferred to the three CSCs post-RTP. There were no significant differences in baseline characteristics, except fewer patients received tPA post-RTP (Table 1). In total, 30 patients (29%) pre-RTP and 42 patients (35%) post-RTP underwent IAT (p=0.38). Post-RTP, there was a trend toward faster travel times (median 40 vs 32 minutes, p=.07) and transfer initiation times to hub arrival times (median 109 vs 100.5 minutes, p=0.09). Door to groin puncture times were not statistically different between the two time periods. Post-RTP patients had a significantly shorter length of stay (median 6 vs 5 days, p=0.03). Conclusions: Regional transfer protocols can potentially help reduce transfer times and length of stay for stroke patients at CSCs that were initially seen by TS at community hospitals; however, larger sample size is needed to study its impact on other IAT-related metrics and clinical outcomes.

IAT-TiMeS: Intra-Arterial Thrombectomy Transfer Metric Study in Texas

ObjectiveWe aim to report intra-arterial thrombectomy transfer metrics for ischemic stroke patients that were transferred to hub hospitals for possible intra-arterial thrombectomy in multiple geographic regions throughout the state of Texas and to identify potential barriers and delays in the intra-arterial thrombectomy transfer process. MethodWe prospectively collected data from 8 participating Texas comprehensive stroke/thrombectomy capable centers from 7 major regions in the State of Texas. We collected baseline clinical and imaging data related to the pre-transfer evaluation, transfer metrics, and post-transfer clinical and imaging data. ResultsA total of 103 acute ischemic stroke patients suspected/confirmed to have large vessel occlusions between December 2016 to May 2019 that were transferred to hubs as possible intra-arterial thrombectomy candidates were enrolled. A total of 56 (54%) patients were sent from the spoke to the hub via ground ambulance with 47 (46%) patients traveling via air ambulance. The median spoke arrival to hub arrival time was 174 min, median spoke arrival to departure from spoke was 131 min, and median travel time was 39 min. The spoke arrival time to transfer initiation was 68 min. CT-perfusion obtained at the spoke and earlier initiation of transfer were statistically associated with shorter transfer times. ConclusionTransfer of intra-arterial thrombectomy patients in Texas may take over 4 h from spoke arrival to hub arrival. This time may be shortened by earlier transfer initiation and acceptance.

Only a Minority of Thrombectomy Candidates Are Admitted During Night Shift: A Rationale for Diurnal Stroke Care Planning.

Background: Widespread quick access to mechanical thrombectomy (MT) for acute ischemic stroke (AIS) is one of the main challenges in stroke care. It is unclear if newly established MT units are required 24 h/7 d. We explored the diurnal admission rate of patients with AIS potentially eligible for MT to provide a basis for discussion of daytime-adapted stroke care concepts.Methods: Data collected from the Baden-Württemberg Stroke Registry in Germany were assessed (2008–2012). We analyzed the admission rate of patients with AIS stratified by the National Institutes of Health Stroke Scale (NIHSS) score at admission in 3-h intervals. An NIHSS score ≥10 was considered a predictor of large vessel occlusion. The average annual admission number of patients with severe AIS were stratified by stroke service level and calculated for a three-shift model and working/non-working hours.Results: Of 91,864, 22,527 (21%) presented with an NIHSS score ≥10. The average admission rates per year for a hospital without Stroke Unit (SU), with a local SU, with a regional SU and a stroke center were 8, 52, 90 and 178, respectively. Approximately 61% were admitted during working hours, 54% in the early shift, 36% in the late shift and 10% in the night shift.Conclusions: A two-shift model, excluding the night shift, would cover 90% of the patients with severe AIS. A model with coverage during working hours would miss ~40% of the patients with severe AIS. To achieve a quick and area-wide MT, it seems preferable for newly implemented MT-units to offer MT in a two-shift model at a minimum.

Contraindications to intravenous thrombolysis in prehospital triage of thrombectomy candidates.

The existence of contraindications to intravenous thrombolysis (IVT) is considered a criterion for direct transfer of patients with suspected acute stroke to thrombectomy-capable centers in the prehospital setting. Our aim was to assess the utility of this criterion in a setting where routing protocols are defined by the Madrid - Direct Referral to Endovascular Center (M-DIRECT) prehospital scale. This was a post hoc analysis of the M-DIRECT study. Reported contraindications to IVT were retrospectively collected from emergency medical services reports and categorized into late window, anticoagulant treatment and other contraindications. Final diagnosis and treatment rates were compared between patients with and without reported IVT contraindications and according to anticoagulant treatment or late window categories. The M-DIRECT study included 541 patients. Reported IVT contraindications were present in 227 (42.0%) patients. Regarding final diagnosis no significant differences were found between patients with or without reported IVT contraindications: ischaemic stroke (any) 65.6% vs. 62.1%, ischaemic stroke with large vessel occlusion (LVO) 32.2% vs. 28.3%, hemorrhagic stroke 15.4% vs. 15.6%, stroke mimic 18.9% vs. 22.3% respectively. Amongst patients with LVO, endovascular thrombectomy (EVT) was performed less often in the presence of IVT contraindications (56.2% vs. 74.2%). M-DIRECT-positive patients had higher rates of LVO and EVT compared with M-DIRECT-negative patients independent of reported IVT contraindications. Reported IVT contraindications alone do not increase EVT likelihood and should not be considered to determine routing in urban stroke networks.

Assessment of Collateral Circulation Using Perfusion CT in Middle Cerebral Artery Thrombectomy-Treated Patients

Introduction: The prognostic value of leptomeningeal collateral circulation in thrombectomy-treated patients remains unclear. We evaluated the construct validity of assessing leptomeningeal collateral circulation using a new regional perfusion CT source image-based approach, the Perfusion Acquisition for THrombectomy Scale (PATHS). We also compared the prognostic value of PATHS with a further 6 scales based on various techniques: CT-angiography, perfusion CT, and digital subtraction angiography. Additionally, we studied the relationship between the scores for the different scales. Patients and Methods: We performed a retrospective study of consecutive patients with stroke and M1/terminal carotid occlusion treated with thrombectomy in our center. Leptomeningeal collateral circulation was prospectively evaluated using 7 scales: Tan and Miteff (CT Angiography); Calleja, Cao, American Society of Intervention and Therapeutic Neuroradiology/Society of Interventional Radiology, and PATHS (perfusion); and Christoforidis (Digital Subtraction Angiography). Correlations were studied using the Spearman method. Results: The study population comprised 108 patients. All scales predicted the modified Rankin Scale at 3 months (P ≤ .02) and all but 1 (Christoforidis) correlated with 24-hour brain infarct volume (P ≤ .02). These correlations were higher with PATHS (rho = −0.47, P < .001 for 3-month modified Rankin Scale; rho = −0.35, P < .001 for follow-up infarct volume). The multivariate analysis showed PATHS to be an independent predictor of modified Rankin Scale at 3 months less than equal to 2. A crosscorrelation analysis revealed a better correlation between scales that used the same techniques. Conclusions: PATHS can be used to assess leptomeningeal collateral circulation. PATHS had better prognostic value than other scales; therefore, it might be considered for assessment of leptomeningeal collateral circulation in candidates for thrombectomy. The moderate correlation between scales suggests that scores are not interchangeable.

Stroke Outcomes and Palliation in Interhospital Transfer Thrombectomy Candidates with Large Vessel Occlusion Following Extension of the Interventional Treatment Window (2153)

Stroke Outcomes and Palliation in Interhospital Transfer Thrombectomy Candidates with Large Vessel Occlusion Following Extension of the Interventional Treatment Window (2153)

Bypassing the Closest Stroke Center for Thrombectomy Candidates: What Additional Delay to Thrombolysis Is Acceptable?

Background and Purpose- Patients with acute ischemic stroke who have large vessel occlusion benefit from direct transport to a comprehensive stroke center (CSC) capable of endovascular therapy. To avoid harm for patients without large vessel occlusion from delayed access to intravenous thrombolysis (IVT), it has been suggested to only redirect patients with high likelihood of large vessel occlusion for whom the additional delay to intravenous thrombolysis (IVT) caused by transport to the CSC is below a certain threshold. However, which threshold achieves the greatest clinical benefit is unknown. Methods- We used mathematical modeling to calculate additional-delay-to-IVT thresholds associated with the greatest reduction in disability-adjusted life years in abstracted 2-stroke center and multiple-stroke center scenarios. Model parameters were extracted from recent meta-analyses or large prospective cohort studies. Uncertainty was quantified in probabilistic and 2-way univariate sensitivity analyses. Results- Assuming ideal treatment time performance metrics, transport to the nearest CSC was the preferred strategy irrespective of additional delay-to-IVT when the transfer time between primary stroke center and CSC was <40 minutes (95% credible interval: 25-66 minutes); otherwise, the optimal additional delay-to-IVT-threshold ranged from 28 to 139 minutes. In multiple-stroke center scenarios, optimal additional-delay-to-IVT thresholds were 30 to 54 minutes in urban and 49 to 141 minutes in rural settings; use of optimal thresholds as compared with a 15 minute-threshold saved 0 to 0.11 and 0 to 0.37 disability-adjusted life years per triage case, respectively. Assuming slower treatment times at primary stroke centers and CSCs yielded longer permissible additional delays. Conclusions- Our results suggest that patients with acute ischemic stroke with suspected large vessel occlusion should be redirected to a CSC if the additional delay to IVT is <30 minutes in urban and 50 minutes in rural settings.

Evaluation of Patients with High National Institutes of Health Stroke Scale as Thrombectomy Candidates Using the Kentucky Appalachian Stroke Registry

Introduction: Mechanical thrombectomy has become standard of care for emergent large vessel occlusive stroke. Estimates of incidence for thrombectomy eligibility vary significantly. National Institutes of Health Stroke Scale (NIHSS) of 10 or greater is highly predictive of large vessel occlusion. Using our Kentucky Appalachian Stroke Registry (KApSR), we evaluated temporal trends in stroke admissions with NIHSS ≥10 to determine patient characteristics among that group along with effects and needs in thrombectomy utilization. Methods: Using the KApSR database that captures patients throughout the Appalachian region in our stroke network, we evaluated patients admitted with ischemic stroke with NIHSS ≥10. We recorded demographics, comorbidities, treatment (thrombectomy, decompressive craniectomy), and county of origin. Change in NIHSS from admission to discharge was used as an indicator of inpatient outcome. Results: Between 2010 and 2016, 1,510 patients were admitted with NIHSS ≥10. 87.2% had high blood pressure, 69.6% had dyslipidemia, and 41.7% used tobacco. There were significant sex differences in the types of patients presenting with NIHSS ≥10 with females being older on average and having more atrial fibrillation and obesity. There was an increase in thrombectomy utilization from 2010 to 2016, but only 7.5% of the potentially eligible patients underwent the procedure. In comparison to the period 2010–2014, the 2015–2016 period had higher rates of obesity and tobacco abuse. Conclusion: Among patients with significant burden of ischemic stroke, the most common coexisting medical condition was high blood pressure. Patients who underwent thrombectomy had significantly better inpatient clinical improvement. These data support the need to maximize utilization of thrombectomy along with need to devote increased resources on modifiable stroke risk factors.

Incidence of Unreliable Automated Computed Tomography Perfusion Maps

IntroductionDespite the increasing national adoption of automated computed tomography perfusion (CTP) to select thrombectomy patients 6 hours after last known well, reliability issues have been anecdotally reported. Unreliable diagnostic tests add time and confusion to a process that requires efficiency. Our study aims to critically assess an automated CTP program in a contemporary cohort of patients presenting with large vessel occlusion (LVO) in the extended time window by evaluating the rate of unreliable automated CTP maps and whether this influences clinical outcomes. MethodsA retrospective review of consecutive thrombectomy candidates undergoing CTP imaging in the extended time window was performed. All automated CTP maps using RAPID software (iSchemaView, Menlo Park, CA) were assessed for reliability. Clinical outcomes were compared between patients with and without reliable RAPID reports. ResultsNinety-nine consecutive thrombectomy candidates underwent automated CTP imaging from February 2017 to December 2018. Of these, 78 (79%) had LVO determined by CT angiographyand were included in the study population. Automated CTP maps were unreliable in 13% of cases as a result of motion artifact (n = 3) and contrast bolus flow issues (n = 7). Heart failure was more frequent in patients with unreliable studies. Clinical outcomes did not significantly differ between patients with and without unreliable studies. ConclusionsThirteen percent of CTP maps generated by automated software were unreliable, with an increased frequency among patients with heart failure. Given the rate of unreliable automated CTP maps, further studies are warranted to not only establish the true necessity of currently available CTP software, but also more reliable methods to select patients for thrombectomy presenting in the extended time window.

Arrival times of patient with ischemic stroke at emergency room: Comparison of two time periods a study in South India

Intravenous thrombolysis and endovascular thrombectomy are the proven treatments for ischemic stroke. These treatments are time-based. This study aims at finding changes in the arrival times of patients with ischemic stroke between two time periods This is a retrospective analysis of prospectively collected stroke registry data. The study compared arrival times of patients with ischemic stroke at Emergency Room between two time periods: 2008-2010 (T-I) vs. 2016-2018 (T-II). Patients with first ever new stroke were included. TOAST criteria were applied to determine the stroke sub type. There were 549 and 451 patients in T-I and T-II periods respectively. Clinical differences between T-II vs. T-I were elderly age 60.76+14.35 vs. 58.30+13.64 p<005); and less severe stroke (NIHSS: 6.53+5.82 vs. 10.7+3.0 p<0001). During T-II period more patients arrived in the window period for iv thrombolysis (100 vs. 56 p<0.0001) and more patients received iv thrombolysis (91 vs. 40 p<0.0001). Number of patients with proximal occlusive disease who arrived in the window period (<6 h) for possible endovascular treatment were (T-II vs. TI) 20 vs. 15 (p<0.14) and 4 patients received the therapy in T-II. Patients who could be possible candidates for thrombectomy in 7-24 h were (T-II vs. T-I) 29 vs. 29 (p<0.43). This study suggests that there is increased awareness of stroke and stroke treatment in this part of India. More patients utilized thrombolysis treatment.

Electronic Alberta Stroke Program Early CT score change and functional outcome in a drip-and-ship stroke service

BackgroundDebate continues as to whether patients with acute ischemic stroke with (suspected) large vessel occlusion benefit from direct referral versus secondary transportation.AimsTo analyze the change in early infarct signs, collaterals,...

Dismantling the ability of CT and MRI to identify the target mismatch profile in patients with anterior circulation large vessel occlusion beyond six hours from symptom onset.

Patients with large vessel occlusion and target mismatch on imaging may be thrombectomy candidates in the extended time window. However, the ability of imaging modalities including non-contrast CT Alberta Stroke Program Early Computed Tomographic Scoring (CT ASPECTS), CT angiography collateral score (CTA-CS), diffusion-weighted MRI ASPECTS (DWI ASPECTS), DWI lesion volume, and DWI volume with clinical deficit (DWI + NIHSS), to identify mismatch is unknown. We defined target mismatch as core infarct (DWI volume) of < 70mL, mismatch volume (tissue with TMax >6s) of ≥ 15mL, and mismatch ratio of ≥ 1.8. Using experimental dismantling design, ability to identify this profile was determined for each imaging modality independently (phase 1) and then with knowledge from preceding modalities (phase 2). We used a generalized mixed model assuming binary distribution with PROC GLIMMIX/SAS for analysis. We identified 32 patients with anterior circulation occlusions, presenting > 6h from symptom onset, with National Institute of Health Stroke Scale of ≥ 6, who had CT and MR before thrombectomy. Sensitivities for identifying target mismatch increased modestly from 88% for NCCT to 91% with the addition of CTA-CS, and up to 100% for all MR-based modalities. Significant gains in specificity were observed from successive tests (29, 19, and 16% increase for DWI ASPECTS, DWI volume, and DWI + NIHSS, respectively). The combination of NCCT ASPECTS and CTA-CS has high sensitivity for identifying the target mismatch in the extended time window. However, there are gains in specificity with MRI-based imaging, potentially identifying treatment candidates who may have been excluded based on CT imaging alone.

Benefit from revascularization after thrombectomy according to FLAIR vascular hyperintensities-DWI mismatch.

We tested whether FLAIR vascular hyperintensities (FVH)-DWI mismatch could identify candidates for thrombectomy most likely to benefit from revascularization. We retrospectively reviewed 100 patients with proximal MCA occlusion from 18 stroke centers randomized in the IV-thrombolysis plus mechanical thrombectomy arm of the THRACE trial (2010-2015). We tested the associations between successful revascularization on digital subtraction angiography (modified Thrombolysis in Cerebral Infarction 2b/3) and 3-month favorable outcome (modified Rankin Scale score ≤ 2), stratified on FVH-DWI mismatch status, with secondary analyses adjusted on National Institutes of Health Stroke Scale (NIHSS) and DWI lesion volume. FVH-DWI mismatch was present in 79% of patients, with a similar prevalence at 1.5T (80%) and 3T (78%). Successful revascularization (74%) was more frequent in patients with FVH-DWI mismatch (63/79, 80%) than in patients without (11/21, 52%), p = 0.01. The OR of favorable outcome for revascularization were 15.05 (95% CI 3.12-72.61, p < 0.001) in patients with FVH-DWI mismatch and 0.83 (95% CI 0.15-4.64, p = 0.84) in patients without FVH-DWI mismatch (p = 0.011 for interaction). Similar results were observed after adjustment for NIHSS (OR = 12.73 [95% CI 2.69-60.41, p = 0.001] and 0.96 [95% CI 0.15-6.30, p = 0.96]) or for DWI volume (OR = 12.37 [95% CI 2.76-55.44, p = 0.001] and 0.91 [95% CI 0.16-5.33, p = 0.92]) in patients with and without FVH-DWI mismatch, respectively. The FVH-DWI mismatch identifies patients likeliest to benefit from revascularization, irrespective of initial DWI lesion volume and clinical stroke severity, and could serve as a useful surrogate marker for penumbral evaluation. • The FVH-DWI mismatch, defined by FLAIR vascular hyperintensities (FVH) located beyond the boundaries of the DWI lesion, is associated with large penumbra. • Among stroke patients with proximal middle cerebral artery occlusion referred for thrombectomy, those with FVH-DWI mismatch are most likely to benefit from revascularization. • FVH-DWI mismatch provides an alternative to PWI-DWI mismatch in order to select patients who are candidates for thrombectomy.

Abstract TP65: Perfusion Artifacts May Overestimate Thrombectomy Eligibility in Patients With Acute Large Vessel Occlusion

Background: Automated computed tomography perfusion (CTP) is effective at identifying salvageable penumbra in patients with acute ischemic stroke due to large vessel occlusion (LVO). Perfusion imaging is now recommended for the selection of thrombectomy candidates in the extended window (&gt;6 hours) which may incorporate the penumbra mismatch ratio (T max &gt;6s:rCBF&lt;30%) &gt;1.7. However automated perfusion output may include artifactual findings that are discordant with a patient’s symptoms and vessel imaging, overestimating the tissue at risk. Hypothesis: Artifactual findings on automated CTP penumbral assessment (T max &gt;6s) will misclassify thrombectomy eligibility in some patients. Methods: We reviewed a retrospective multi-site consecutive cohort of patients undergoing CTP for suspected acute ischemic stroke ≤24 hours from onset (6/2017-12/2017). The primary outcome was the volume of any discordant T max &gt;6s abnormality on RAPID automated perfusion CT imaging, calculated by two independent readers using manual assessment (ImageJ, NIH). The discordant penumbral volume was compared to the automated output and corrected mismatch ratios were generated. Results: Of 410 consecutive patients who underwent CTP, 60 (14.6%) had acute LVO of the anterior circulation and were included. The median age was 78 years (IQR 64-84), 36 (60.0%) were female, and 25 (41.7%) were White. Fifteen patients (26.3%) had T max &gt;6s abnormalities that were discordant with the clinical symptoms or anticipated vascular distribution, with strong inter-rater agreement (r 2 =0.927). The median difference between manual and automated T max &gt;6s volumes was 18.4cc (IQR 10.80-35.77) accounting for 11.3% of the automated volume (IQR 7.8-46.7%). Following manual recalculation of the T max &gt;6s volume, 1 patient was reclassified as having an “unfavorable” mismatch ratio (1.7%, 95%CI 0.2-11.5%). Conclusion: About one quarter of patients had discordant penumbral imaging on automated CTP, which may lead to misclassification of thrombectomy eligibility. While artifactual findings are reliably identified by trained raters, our results emphasize the need to evaluate CTP results with knowledge of the patient’s clinical symptoms and vascular imaging.

Abstract WP66: CT and Multiphase CTA Alone Can Identify Thrombectomy Candidates Beyond 6 Hours

Introduction: Current stroke guidelines recommend CT Perfusion (CTP) or MRI to identify thrombectomy candidates beyond 6 hours from stroke onset. The efficacy of more readily available NCCT and CTA in the identification of such patients is unknown. In this study, we compared the accuracy of arterial phase CTA only (sCTA) and multi-phase CTA (mCTA) with MRI in patients beyond 6 hours from onset. Methods: We retrospectively reviewed 45 consecutive patients, presenting 6 to 24 hours from stroke onset, with known ICA or M1 occlusions. All patients had pre-treatment CTA and MRI, with diffusion weighted (DWI) and perfusion weighted imaging (PWI). MRI images were processed using RAPID. Five experienced readers independently scored ASPECTS (0-10), sCTA collateral score (0-5), and whether patients would have met DAWN or DEFUSE-3 MRI imaging criteria. After a one-month delay, grading was repeated by the same readers using NCCT and mCTA. The sensitivity and specificity for DAWN and DEFUSE-3 eligibility was examined for both sCTA and mCTA. We also examined the median DWI volume based on the combination of NCCT ASPECTS and collateral score, for both sCTA and mCTA. Results: Sensitivity and specificity for DAWN eligibility was 91.4% and 74.8% for sCTA; 87.2% and 76.8% for mCTA. For DEFUSE-3, sensitivity and specificity was 92.3% and 46.3% for sCTA; 94.5% and 57.5% for mCTA. The higher specificity for DAWN is likely due to the more restrictive imaging criteria used in that trial. For DWI volume, the results are summarized in the graph, and show that the combination of mCTA collateral score and NCCT ASPECTS is significantly more correlated with DWI volume than sCTA (p=.0018). Conclusions: In conclusion, the combination of NCCT ASPECTS and mCTA collateral score has high sensitivity and moderate specificity for identifying patients who meet DAWN or DEFUSE-3 criteria. NCCT ASPECTS and Multi-phase CTA collateral score are significantly more correlated with DWI volume than single-phase.