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Functional Outcomes of Patients ≥85 Years With Acute Ischemic Stroke Following EVT: A HERMES Substudy

Originally published 2022;53:2220–2226



Observational studies have shown endovascular treatment (EVT) for acute ischemic stroke to be effective in the elderly, despite resulting in poorer outcomes and higher rates of mortality compared with younger patients. Randomized data on the effect of advanced age on outcomes following EVT are, however, lacking. Our aim was to assess the EVT effect for ischemic stroke in patients aged ≥85 years and the influence of age on outcome in a large, randomized trial dataset.


Data were from the HERMES (Highly Effective Reperfusion Evaluated in Multiple Endovascular Stroke Trials) collaboration, a meta-analysis of 7 randomized trials published between January 1, 2010, and May 31, 2017, that tested the efficacy of EVT. A possible multiplicative interaction effect of age on the relationship between treatment and outcome was investigated. Ordinal logistic regression tested the association between EVT and 90-day functional outcome (modified Rankin Scale, primary outcome) in patients ≥85 years. Multivariable binary logistic regression was performed to compare primary and secondary outcomes (modified Rankin Scale score of 0–2/5–6) of patients ≥85 years versus those <85 years.


We included 1764 patients in the analysis, of whom 77 (4.4%) were ≥85 years old. A significant interaction of age and treatment on poor outcome (modified Rankin Scale score of 5–6, P=0.020) and mortality (P=0.031) was observed, with older adults having worse functional outcomes at 90 days compared with younger patients (adjusted common odds ratio, 0.20 [95% CI, 0.13–0.33]). However, a benefit of EVT was observed in the ≥85-year-old patient subgroup (common odds ratio, 4.20 [95% CI, 1.56–11.32]). Age ≥85 years was not significantly associated with differing rates of symptomatic intracerebral hemorrhage or reperfusion (adjusted odds ratio, 1.92 [95% CI, 0.71–5.15] and adjusted odds ratio, 0.91 [95% CI, 0.40–2.06], respectively).


Patients ≥85 years old with independent premorbid function more often achieve good functional outcomes and have lower rates of mortality when treated with EVT compared with conservative management, with an observed treatment effect modification of age on outcome. EVT should therefore not be withheld in this subgroup.

See related article, p 2227

Due to improvements in health care and standards of living, the older population (aged ≥65 years) now comprises the fastest-growing age group worldwide.1 With increasing age, however, comes an increase in comorbidities, in particular those of cardiovascular and cerebrovascular nature. Seventeen percent of all stroke patients are ≥85 years,2 and patients in this age group have been observed to have longer hospital stays,3 more severe disability,4 and higher rates of mortality.4 As such, age represents an important unmodifiable risk factor for all types of stroke, including acute ischemic stroke (AIS).5,6

Endovascular treatment (EVT) has been shown to be an effective and safe treatment for AIS due to large vessel occlusion, and its benefit is maintained across a wide range of subgroups, including patients ≥80 years of age.7 However, although data from the HERMES (Highly Effective Reperfusion Evaluated in Multiple Endovascular Stroke Trials) collaboration showed that the effect size of EVT on functional outcome is even larger in this patient subgroup compared with younger patients, elderly patients still experienced overall worse outcomes and higher rates of mortality.7 Several confirmatory observational studies and systematic reviews on the effect of EVT in octogenarians have since been published,8–12 with few targeting nonagenarian patient populations.13–16 The latter group accounts for ≈7% of all AIS patients6 and was underrepresented in the large EVT trials, partly due to upper age limits in the exclusion criteria. Furthermore, even within the subgroup of the elderly, incremental increases in age appear to play a role, with nonagenarians faring worse than octogenarians with respect to complications such as symptomatic intracerebral hemorrhage (sICH), despite similarities in baseline characteristics other than age.16

A recent survey demonstrated that, despite the limited evidence, the majority of stroke physicians would offer EVT to patients ≥80 years (including nonagenarians).17 A randomized trial involving only the very elderly undergoing EVT is unlikely to occur, however. With this study, we, therefore, aim to assess the effect of age on outcome following EVT in detail using an existing large randomized clinical trial dataset. Because the original HERMES study performed an a priori determined subgroup analysis on patients ≥80 years of age, we chose a cutoff of 85 years for the current study. The main goal of the investigation was to assess whether the EVT effect is maintained in patients ≥85 years old. As a secondary aim, we sought to compare clinical outcomes following EVT of patients according to age (≥85 years versus <85 years).


The data that support the findings of this study are available from the corresponding author upon reasonable request.

Patient Sample and Study Design

The HERMES collaboration pooled individual patient data of 7 randomized controlled trials that established EVT as a safe and effective treatment for patients with AIS due to large vessel occlusion (n=1764).7 Of the trials, only ESCAPE (Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion With Emphasis on Minimizing CT to Recanalization Times),18 EXTEND-IA (Extending the Time for Thrombolysis in Emergency Neurological Deficits–Intra-Arterial),19 and MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands)20 included patients ≥85 years. Detailed methodology and inclusion criteria of the individual trials, as well as the HERMES meta-analysis, are published elsewhere.7,18–24 In brief, patients who were randomized to the intervention arm underwent EVT, whereas those randomized to the control arm received standard medical care (including, where available, stroke unit care and specialized rehabilitation under the dedicated management of health care professionals with stroke expertise). Intravenous alteplase was administered to eligible patients in both arms. Patient consent was obtained unless the local ethics boards allowed for deferral of consent.

Outcome Measures

The primary outcome of interest was ordinal 90-day modified Rankin Scale (mRS). Secondary outcomes were binarized good functional outcome, defined as an mRS score of 0 to 2 at 90 days, binarized poor outcome, defined as an mRS score of 5 to 6 at 90 days, and successful expanded Thrombolysis in Cerebral Infarction score, defined as expanded Thrombolysis in Cerebral Infarction 2b/3 (binary; patients who underwent EVT only). The safety outcomes were mortality at 90 days and sICH at 24 hours. The presence of sICH was determined using the individual definitions of the participating trials.18–24

Statistical Analyses

Baseline characteristics of patients aged ≥85 years were compared with those <85 years using descriptive statistics, stratified by treatment allocation. Adjusted logistic regression with a multiplicative interaction term (age×treatment allocation) was performed to test for an interaction effect of age (≥85 versus <85 years) on the relationship between treatment (EVT versus control) and outcomes. Multivariable binary logistic regression models tested the association between patient age (≥85 versus <85 years) and outcomes. Analyses were adjusted for treatment arm (EVT versus control; binary), patient sex (binary), baseline National Institutes of Health Stroke Scale score (continuous), administration of intravenous alteplase (binary), baseline Alberta Stroke Program Early CT Score (continuous), occlusion location (internal carotid artery versus M1 segment of the middle cerebral artery versus M2 segment of the middle cerebral artery; categorical), and time from onset to randomization (continuous). Finally, within the subgroup of patients ≥85 years, univariable (due to the low n) ordinal logistic regression was used to measure the effect of EVT on 90-day mRS compared with conservative treatment. The results are presented in comparison to those from patients <85 years.

To properly account for clustering effects within and across studies as well as treatment groups, all statistical modeling includes random effects for study effect, as well as for the age×treatment interaction.

Missing data (including loss to follow-up) were minimal (<5%) for all outcomes and predictor variables employed in the reported analyses, and hence no imputation was employed except for covariates in statistical modeling, for which simple imputation (median or mean) was used to avoid an undesirable reduction to complete-case analysis.

Unadjusted and adjusted (common) odds ratios are reported with 95% CIs. All statistical tests were 2-sided, and a conventional significance threshold (alpha=0.05) was used for interpretation. Analyses were performed with SAS software, version 9.4 (SAS Institute, Cary, NC), and R, version 3.3 (R Foundation for Statistical Computing, Vienna, Austria).

We used the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) cohort checklist when writing our report.25


Patient Population

The HERMES collaboration included 1764 patients, of whom 77 (4.4%) were ≥85 years of age. Compared with their younger counterparts, patients 85 years and older had higher systolic blood pressure, higher rates of atrial fibrillation, and higher Alberta Stroke Program Early CT Scores at baseline (Table 1). Patients ≥85 years undergoing EVT also less often received intravenous alteplase (73.8% versus 88.3%, P=0.013) and were more likely to have suffered from a prior stroke (26.2% versus 10.4%, P=0.004) and diabetes (28.6% versus 14.4%, P=0.024), whereas those in the control arm had higher rates of hypertension (82.9% versus 57.9%, P=0.003; Table 1). Older adults were also more often female, although this was only significant in the control arm (EVT: 57.1% ≥85 years versus 46.8% <85 years, P=0.207, control: 80.0% ≥85 years versus 46.0% <85 years, P<0.001; Table 1).

Table 1. Baseline Characteristics of Patients Aged ≥85 Years at the Time of Onset Versus Those of <85 Years, Stratified According to Treatment Arm

Age ≥85 y mean±SD (N) [median] (IQR)Age <85 y mean±SD (N) [median] (IQR)P valueAge ≥85 y mean±SD (N) [median] (IQR)Age <85 y mean±SD (N) [median] (IQR)P value
Age, y87.3±2.2 (42) [86.8] (85.4–89.0)64.4±12.8 (829) [66.9] (56.0–75.0)<0.001*88.6±2.7 (35) [89.0] (86.2–90.0)64.8±13.0 (855) [67.0] (57.0–75.0)<0.001*
Female sex57.1% (24/42)46.8% (388/829)0.20780.0% (28/35)46.0% (393/855)<0.001*
Systolic blood pressure, mm Hg153.4±23.3 (42) [153.5] (137.5–162.3)144.6±23.5 (825) [143.0] (129.0–159.0)0.018*155.1±31.1 (35) [156.0] (130.0–173.5)144.9±24.1 (850) [144.0] (129.0–160.0)0.016*
Hypertension, % (n/N)69.0% (29/42)52.8% (436/825)0.05682.9% (29/35)57.9% (494/853)0.003*
Hyperlipidemia, % (n/N)38.1% (16/42)35.3% (284/804)0.74242.9% (15/35)40.2% (336/836)0.729
Diabetes, % (n/N)28.6% (12/42)14.4% (119/825)0.024*17.1% (6/35)17.6% (150/852)1.000
Atrial fibrillation, % (n/N)62.2% (23/37)31.7% (198/625)<0.001*63.6% (21/33)31.2% (202/647)<0.001*
Prior stroke, % (n/N)26.2% (11/42)10.4% (85/820)0.004*20.0% (7/35)10.0% (85/852)0.081
Blood glucose, mg/dL137.5±48.0 (41) [124.2] (111.6–140.4)132.3±77.4 (800) [119.0] (105.5–140.4)0.672126.0±24.9 (34) [123.0] (106.5–139.8)130.3±58.8 (828) [119.0] (103.6–140.1)0.674
NIHSS at baseline17.8±4.9 (42) [17.0] (14.0–21.0)17.0±4.8 (822) [17.0] (14.0–20.0)0.29616.4±4.4 (35) [17.0] (13.5–19.5)16.9±5.3 (851) [17.0] (13.0–21.0)0.556
ASPECTS at baseline8.4±1.6 (42) [8.5] (8.0–10.0)7.5±1.8 (818) [8.0] (7.0–9.0)0.004*8.3±1.5 (34) [9.0] (8.0–9.0)7.5±2.0 (841) [8.0] (7.0–9.0)0.015*
Intravenous alteplase delivered, % (n/N)73.8% (31/42)88.3% (732/829)0.013*91.4% (32/35)90.8% (776/855)1.000
Occlusion location, % (n/N)0.2050.140
 ICA15.8% (6/38)26.8% (209/781)44.1% (15/34)26.7% (212/794)
 M168.4% (26/38)65.3% (510/781)52.9% (18/34)65.2% (518/794)
 M215.8% (6/38)7.8% (61/781)2.9% (1/34)7.9% (63/794)
 Other0.0% (0/38)0.1% (1/781)0.0% (0/34)0.1% (1/794)
Collateral grade, % (n/N)0.1280.369
 00.0% (0/38)1.0% (6/601)3.2% (1/31)1.1% (7/619)
 115.8% (6/38)14.1% (85/601)19.4% (6/31)16.5% (102/619)
 260.5% (23/38)43.3% (260/601)29.0% (9/31)43.0% (266/619)
 323.7% (9/38)41.6% (250/601)48.4% (15/31)39.4% (244/619)
Onset to randomization219.6±128.9 (42) [177.5] (132.5–275.5)201.0±90.2 (825) [181.0] (142.0–239.0)0.201196.1±78.4 (35) [192.0] (134.5–230.0)201.9±85.3 (852) [184.0] (140.0–249.3)0.685
Onset to intravenous alteplase administration117.7±51.2 (31) [114.0] (80.0–138.0)123.0±48.9 (724) [115.0] (85.0–155.0)0.553121.6±74.4 (32) [101.0] (77.0–143.0)128.1±59.3 (776) [120.0] (85.0–162.3)0.544

ASPECTS indicates Alberta Stroke Program Early CT Score; EVT, endovascular treatment; ICA, internal carotid artery; IQR, interquartile range; M1, M1 segment of the middle cerebral artery; M2, M2 segment of the middle cerebral artery; and NIHSS, National Institutes of Health Stroke Scale.

* Statistically significant.

Interaction Analysis of the Effect of Age on the Relationship Between Treatment and Outcome

There was a significant interaction effect of age on the relationship between treatment allocation and poor outcome (mRS score 5–6, P=0.020) and mortality at 90 days (P=0.031) such that the beneficial effect of EVT on mortality and poor outcome was more pronounced in patients ≥85 years of age (Tables S1 through S3). In a subsequent subgroup analysis involving only patients ≥85 years, we observed a positive effect of EVT on outcome compared with conservation management, with an unadjusted common odds ratio of 4.20 (95% CI, 1.56–11.32; Figure [A]). The common odds ratio for the effect of EVT on outcome in the younger cohort was 1.90 (95% CI, 1.60–2.26; Figure [B]).


Figure. Distribution (in percentage) of modified Rankin Scale (mRS) scores at 90 d in the intervention and control (CTL) arms. A, Patients ≥85 y; (B) patients <85 y. EVT indicates endovascular treatment.

Outcomes in Patients ≥85 Years Versus <85 Years

Older adults had worse ordinal mRS at 90 days compared with younger patients (adjusted common OR [95% CI, 0.13–0.33]; Table 2). Only 18.2% of patients ≥85 years achieved good functional outcome (mRS 0–2) compared with 40.8% in the younger patient subgroup (adjusted odds ratio, 0.28 [95% CI, 0.15–0.53]; Table 2). Although mortality at 90 days was significantly higher in the older population compared with those <85 years (41.6% versus 14.8%, adjusted odds ratio, 5.18 [95% CI, 3.11–8.66]; Table 2), patients ≥85 years who received EVT had significantly lower rates of mortality compared with those ≥85 years in the control arm (31.0% versus 54.3%, Figure [A]). No significant differences in the rates of successful reperfusion (EVT arm) or sICH were observed between the 2 age groups (Table 2).

Table 2. Primary, Secondary, and Safety Outcomes for Patients Aged ≥85 Years Compared With Those <85 Years Old

Outcome% (n/N)UnadjustedAdjusted
≥85 y<85 ycOR*95% CIP valuecOR*95% CIP value
mRS at 90 d0.230.14–0.36<0.0010.200.13–0.33<0.001
mRS score 0–2 at 90 d18.2% (14/77)40.8% (667/1664)0.310.17–0.57<0.0010.280.15–0.53<0.001
mRS score 5–6 at 90 d57.1% (44/77)23.2% (386/1664)4.772.92–7.77<0.0015.623.38–9.34<0.001
Mortality at 90 d41.6% (32/77)14.8% (248/1674)4.222.58–6.91<0.0015.183.11–8.66<0.001
sICH at 24 h6.5% (5/77)3.5% (58/1649)1.720.65–4.530.2721.920.71–5.150.198
eTICI 2b/3 postprocedure75.0% (27/36)75.5% (523/693)0.900.40–2.030.8080.910.40–2.060.813

cOR indicates common OR; eTICI‚ expanded Thrombolysis in Cerebral Infarction score; mRS‚ modified Rankin Scale; OR‚ odds ratio; and sICH‚ symptomatic intracerebral hemorrhage.

*cOR derived from ordinal logistic regression.


This study observed a nominal, quantitative interaction effect of age on the relationship between treatment (EVT) and outcomes in the higher mRS range (mortality, mRS 5–6). In other words, there was a differential effect of EVT by age, indicating that EVT is at least if not more effective in the elderly subpopulation. Although patients ≥85 years experienced substantially worse outcomes and higher rates of mortality following AIS due to large vessel occlusion compared with younger patients, the positive effect of EVT effect on outcome was maintained; within the subgroup of patients ≥85 years, those who underwent EVT had better functional outcomes and lower rates of mortality at 3 months compared with those who received standard therapy alone.

These results are in line with those from previous studies involving elderly patients undergoing EVT.12,26–28 A key strength of the current study, however, is that the data are derived from randomized clinical trials with robust control groups, as opposed to the primarily observational studies found in the literature. The disadvantage of trial data lies in its potentially limited applicability to clinical practice. In their systematic review and meta-analysis of 17 studies involving the effect of EVT in octogenarians (n=860), however, Hilditch et al. observed rates of functional outcome (27%) and mortality (34%)8 within close range of those from the current study (24% and 31%, respectively).

The observed effect size of EVT on outcome for patients ≥80 years in the HERMES collaboration7 was smaller than that which was observed for those 85 years and older from the same cohort (common odds ratio 3.68 [95% CI, 1.95–6.92] versus 4.20 [95% CI, 1.56–11.32], respectively), the latter albeit with larger confidence intervals due to the smaller overall sample size. The seemingly paradoxical finding that elderly patients have significantly worse functional outcomes despite larger EVT effect sizes compared with younger populations is again reflected in the interaction effect. This is partly explained by the different risk factors observed for the elderly population. For example, frailty and the increased risk of (post-treatment) complications in the older population make the likelihood of survival without successful reperfusion quite low. Younger patients with generally more favorable baseline characteristics, on the other hand, are more likely to survive even in the absence of successful reperfusion.12

It is important to note that the rates of sICH and reperfusion did not differ according to age group, which further points toward EVT being a safe and effective treatment option for the elderly. As noted above, the relatively poor outcomes observed in elderly patient populations are likely due to other prognostic factors, such as baseline disability (although the majority of patients included in the HERMES meta-analysis were prestroke independent, MR CLEAN being the only study to include patients with a prestroke mRS score ≥2 (n=46)20) or increased susceptibility in the post-treatment hospitalization phase.29 Nevertheless, approximately 1 out of 4 patients ≥85 years old will achieve a good outcome following EVT, suggesting that age alone should not exclude patients from thrombectomy.


This study has several limitations. First, patients ≥85 years were underrepresented in trials that did include them, potentially leading to selection bias. Indeed, in this study, older patients had better Alberta Stroke Program Early CT Scores, indicating potentially more stringent selection criteria for EVT for this subgroup. As a result, it is unclear whether the results of this study are applicable to the corresponding patient population seen in clinical practice. Second, due to the small sample size, we were unable to adjust for potentially confounding factors; the presented results regarding the effect of EVT in the ≥85-year-old subgroup are derived from univariable analyses. Third, we were unable to assess the effect of preexisting disability on outcome, with is presumably more prevalent with increasing age. Fourth, information on additional standards of care during the post-acute phase (eg, discharge destination) is lacking. As a result, we are unable to comment on events that occurred from the time of treatment to 90-day follow-up, which may influence outcomes. Finally, while the mRS is the standard outcome measure in stroke studies, each level is a rather broad category that may require more granularity with respect to quality of life and disability, particularly within the elderly population. Despite these limitations, we believe the results of this study will be of value to physicians faced with the often-complex treatment decision-making processes involving patients suffering from AIS.


Patients ≥85 years old with independent premorbid function more often achieve good functional outcomes when treated with EVT compared with conservative management, with a number needed to treat of 8 for 90-day mRS score of 0 to 2, an observed treatment effect modification of age on outcome, and no differences in sICH and reperfusion rates. EVT should therefore not be withheld in this subgroup on the basis of age alone.

Article Information


We would like to thank the HERMES collaboration (Highly Effective Reperfusion Evaluated in Multiple Endovascular Stroke Trials) investigators.

Supplemental Material

Tables S1–S3

Nonstandard Abbreviations and Acronyms


acute ischemic stroke


Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion With Emphasis on Minimizing CT to Recanalization Times


endovascular treatment


Extending the Time for Thrombolysis in Emergency Neurological Deficits–Intra-Arterial


Highly Effective Reperfusion Evaluated in Multiple Endovascular Stroke Trials


Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands


modified Rankin Scale


symptomatic intracerebral hemorrhage

Disclosures No authors received any payments for work on the submitted manuscript. Dr Ospel reports support from the University of Basel Research Foundation, Julia Bangerter Rhyner Foundation, and Freiwillige Akademische Gesellschaft Basel. Dr Saver reports being an employee of the University of California; serving as an unpaid site investigator in multicenter trials run by Medtronic and Stryker for which the University of California (UC) Regents received payments on the basis of clinical trial contracts for the number of subjects enrolled; receiving funding for services as a scientific consultant regarding trial design and conduct to Medtronic, Stryker, Cerenovus and Rapid Medical. The UC Regents have patent rights in endovascular retrievers. Dr Dippel reports that his institution has received honoraria for his speaking from Stryker and grant funding from the Dutch Heart Foundation, AngioCare BV, Medtronic/EV3, MEDAC Gmbh/ LAMEPRO, Penumbra, Stryker, and Top Medical/ Concentric. Dr Majoie reports grants paid to the institution from the Netherlands Cardiovascular Research Committee (CVON)/Dutch Heart Foundation, the European commission, Stichting Toegepast Wetenschappelijk Instituut voor Neuromodulatie (TWIN) foundation, and Stryker. Dr Majoie is shareholder of Nicolab, a company that focuses on the use of artificial intelligence for medical image analysis. Dr Jovin reports receiving grants from Stryker Neurovascular and consultant fees for Anaconda, VizAI, FreeOx Biotech, Corindus, Cerenovus, Route92, Blockade Medical, and Medtronic. Dr Bracard reports grants from the French Ministry of Health during the conduct of the THRACE study (Trial and Cost Effectiveness Evaluation of Intra-Arterial Thrombectomy in Acute Ischemic Stroke), and personal fees from General Electric Medical Systems and nonfinancial support from Microvention Europe outside the submitted work. Dr Guillemin reports grants from the French Ministry of Health during the conduct of the THRACE study. Dr Campbell reports that his institution received a grant to support the EXTEND-IA trial (Extending the Time for Thrombolysis in Emergency Neurological Deficits–Intra-Arterial) from Covidien/Medtronic. Dr Campbell reports grant funding from the National Health and Medical Research Council of Australia and Medtronic and fellowships from the National Heart Foundation of Australia, National Stroke Foundation of Australia, and Royal Australasian College of Physicians. Dr Mitchell reports that his institution received grants from Medtronic and Stryker; he received consultant fees from Stryker and Microvention. Dr White reports grants from UK National Institutes for Health Research, Microvention Terumo, Stryker, Medtronic, and Penumbra; received consultation fees from Microvention Terumo. Dr Muir has received consultant fees from Boehringer Ingelheim, Bayer and Daiichi-Sankyo. Dr Brown reports receiving consulting fees from Medtronic/Covidien and personal fees from the University of Calgary. Dr Demchuk reports receiving grant support and personal fees from Medtronic and has a patent with Circle Cardiovascular Imaging on stroke imaging software. Dr Hill reports unrestricted grant funding for the ESCAPE trial (Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion With Emphasis on Minimizing CT to Recanalization Times) to University of Calgary from Covidien/Medtronic, and active/in-kind support consortium of public/charitable sources (Heart and Stroke Foundation, Alberta Innovates Health Solutions, Alberta Health Services) and the University of Calgary (Hotchkiss Brain Institute, Departments of Clinical Neurosciences and Radiology, and Calgary Stroke Program); grant funding from Boehringer Ingelheim, NoNo, Inc, and Stryker. Personal fees from Merck, nonfinancial support from Hoffmann-La Roche Canada. In addition, Dr Hill has a submitted patent for triaging systems in ischemic stroke and owns stock in Calgary Scientific, a company that focuses on medical imaging software. Dr Goyal reports receiving an unrestricted institutional grant from Medtronic; he received a grant from Stryker and consulting fees from Stryker, Microvention, Mentice; he holds patent rights in systems and methods for acute stroke diagnosis with GE Healthcare. The other author reports no conflicts.


*R.V. McDonough and J.M. Ospel contributed equally.

This manuscript was sent to Steven M. Greenberg, Guest Editor, for review by expert referees, editorial decision, and final disposition.

Supplemental Material is available at

For Sources of Funding and Disclosures, see page 2225.

Correspondence to: Mayank Goyal, MD, Departments of Radiology and Clinical Neurosciences, University of Calgary, Foothills Medical Centre, 1403 29th St NW, Calgary, AB T2N 2T9, Canada. Email


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