The Stockholm Stroke Triage Project: Outcomes of Endovascular Thrombectomy Before and After Triage Implementation

Stroke Evaluation in the Interventional Suite Using Dual-Layer Detector Cone-Beam CT: a First-in-human Prospective Cohort Study (the Next Generation X-ray Imaging System Trial)

PURPOSE

Cone-beam CT in the interventional suite could be an alternative to CT to shorten door-to-thrombectomy time. However, image quality in cone-beam CT is limited by artifacts and poor differentiation between gray and white matter. This study compared non-contrast brain dual-layer cone-beam CT in the interventional suite to reference standard CT in stroke patients.

METHODS

A prospective single-center study enrolled consecutive participants with ischemic or hemorrhagic stroke. The hemorrhage detection accuracy, per-region ASPECTS accuracy and subjective image quality (Likert scales for gray-white matter differentiation, structure perception and artifacts) were assessed by three neuroradiologists blinded to clinical data on dual-layer cone-beam CT 75 keV monoenergetic images compared to CT. Objective image quality was assessed by region-of-interest metrics. Non-inferiority for hemorrhage detection and ASPECTS accuracy was determined by the exact binomial test with a one-sided lower performance boundary prospectively set to 80% (98.75% CI).

RESULTS

27 participants were included (74 years ± 9; 19 female) in the hyperacute or acute stroke phase. One reader missed a small bleeding, but all hemorrhages were detected in the majority analysis (100% accuracy, CI lower boundary 86%, p = 0.002). ASPECTS majority analysis showed 90% accuracy (CI lower boundary 85%, p < 0.001). Sensitivity was 66% (individual readers 67%, 69%, and 76%), specificity was 97% (97%, 96%, 89%). Subjective and objective image quality were inferior to CT.

CONCLUSION

In a small single-center cohort, dual-layer cone-beam CT showed non-inferior hemorrhage detection and ASPECTS accuracy to CT. Despite inferior image quality, the technique may be useful for stroke evaluation in the interventional suite.

TRIAL REGISTRATION NUMBER

NCT04571099 (clinicaltrials.gov). Prospectively registered 2020-09-04.

Evaluation of a prehospital endovascular therapy stroke bypass program

INTRODUCTION

Prehospital stroke endovascular therapy bypass transports patients with suspected large vessel occlusion directly to an endovascular therapy capable center. Our objective was to determine if an endovascular therapy bypass protocol improved access to stroke treatments. Secondary objectives were to determine safety, effectiveness, and rate of subsequent interfacility transfers.

METHODS

Endovascular therapy bypass in 2018 was implemented in Eastern Ontario, for patients with a Los-Angeles-Motor-Scale ≥ 4 (positive large vessel occlusion screen) with a 90-min transport time if < 6 h from last seen well. A before-after health record review was conducted from Dec 1, 2017 to Nov 30, 2019. A piloted data form was used to extract demographics, times, primary outcomes (endovascular therapy and intravenous (IV) tissue plasminogen activator (tPA) rate), and secondary outcomes (redirect to closer hospital, airway intervention, and subsequent interfacility transfer). We present descriptive statistics and odds ratios (OR) with 95% confidence intervals (CI) from multivariable logistic regression.

RESULTS

We included 379 stroke patients (165 pre and 214 post-implementation). The endovascular therapy rate between groups was similar (14.1% vs 15.1%). The bypass had an OR of 0.98 (95% CI 0.54-1.78) for receiving endovascular therapy. IV tPA was given to 25.4% of patients pre vs 27.4% post-implementation (OR 1.06, 95% CI 0.65-1.74). No patients became unstable during transport, only one patient had an intubation attempt. The inappropriate bypass (false positive) rate was 12.7% pre vs 12.8% post-implementation (positive predictive value 87%). The bypass protocol had an OR of 1.06 (95% CI 0.58-1.95) for subsequent interfacility transfer with a mean of 2.7 h at the community site before transfer.

CONCLUSIONS

Endovascular therapy stroke bypass with 90-min transport radius and Los-Angeles-Motor-Scale ≥ 4 was safe and well executed by paramedics. Our study did not show any difference in endovascular therapy rate from its implementation. The IV tPA rate was similar between groups despite potentially bypassing thrombolysis capable centers.

Portable cerebral blood flow monitor to detect large vessel occlusion in patients with suspected stroke

BACKGROUND

Early detection of large vessel occlusion (LVO) facilitates triage to an appropriate stroke center to reduce treatment times and improve outcomes. Prehospital stroke scales are not sufficiently sensitive, so we investigated the ability of the portable Openwater optical blood flow monitor to detect LVO.

METHODS

Patients were prospectively enrolled at two comprehensive stroke centers during stroke alert evaluation within 24 hours of onset with National Institutes of Health Stroke Scale (NIHSS) score ≥2. A 70 s bedside optical blood flow scan generated cerebral blood flow waveforms based on relative changes in speckle contrast. Anterior circulation LVO was determined by CT angiography. A deep learning model trained on all patient data using fivefold cross-validation and learned discriminative representations from the raw speckle contrast waveform data. Receiver operating characteristic (ROC) analysis compared the Openwater diagnostic performance (ie, LVO detection) with prehospital stroke scales.

RESULTS

Among 135 patients, 52 (39%) had an anterior circulation LVO. The median NIHSS score was 8 (IQR 4-14). The Openwater instrument had 79% sensitivity and 84% specificity for the detection of LVO. The rapid arterial occlusion evaluation (RACE) scale had 60% sensitivity and 81% specificity and the Los Angeles motor scale (LAMS) had 50% sensitivity and 81% specificity. The binary Openwater classification (high-likelihood vs low-likelihood) had an area under the ROC (AUROC) of 0.82 (95% CI 0.75 to 0.88), which outperformed RACE (AUC 0.70; 95% CI 0.62 to 0.78; P=0.04) and LAMS (AUC 0.65; 95% CI 0.57 to 0.73; P=0.002).

CONCLUSIONS

The Openwater optical blood flow monitor outperformed prehospital stroke scales for the detection of LVO in patients undergoing acute stroke evaluation in the emergency department. These encouraging findings need to be validated in an independent test set and the prehospital environment.

Clinical Judgment vs Triage Scales for Detecting Large Vessel Occlusions in Suspected Acute Stroke

This cohort study examines clinical judgment of large vessel occlusions compared with triage scales in a sample of patients admitted to the emergency department with suspicion of acute stroke.

Long-term effect of field triage on times to endovascular treatment for emergent large vessel occlusion

BACKGROUND

Delays to endovascular therapy (EVT) for stroke may be mitigated with direct field triage to EVT centers. We sought to compare times to treatment over a 5.5 year span between two adjacent states, one with field triage and one without, served by a single comprehensive stroke center (CSC).

METHODS

During the study period, one of the two states implemented severity-based triage for suspected emergent large vessel occlusion, while in the other state, patients were transported to the closest hospital regardless of severity. We compared times to treatment and clinical outcomes between these two states. We also performed a matched pairs analysis, matching on date treated and distance from field to CSC.

RESULTS

639 patients met the inclusion criteria, 407 in State 1 (with field triage) and 232 in State 2 (without field triage). In State 1, scene to EVT decreased 6% (or 8.13 min, p=0.0004) every year but no decrease was observed for State 2 (<1%, p=0.94). Cumulatively over 5.5 years, there was a reduction of 43 min in time to EVT in State 1, but no change in State 2. Lower rates of disability were seen in State 1, both for the entire cohort (all OR 1.22, 95% CI 1.07 to 1.40, p=0.0032) and for those independent at baseline (1.36, 95% CI 1.15 to 1.59, p=0.0003).

CONCLUSIONS

Comparing adjacent states over time, the implementation of severity-based field triage significantly reduced time to EVT.

Impact of prehospital stroke triage implementation on patients with intracerebral hemorrhage

Background

Little is known about how prehospital triage using large vessel occlusion (LVO) stroke prediction scales affects patients with intracerebral hemorrhage (ICH).

Objectives

We aimed to investigate whether the Stockholm Stroke Triage System (SSTS) implemented in 2017 has affected timing and outcomes of acute ICH neurosurgery, and to assess system triage accuracy for ICH with a neurosurgical indication or LVO thrombectomy.

Design

Observational cohort study.

Methods

In the Stockholm Region, we compared surgical timing, functional outcome, and death at 3 months in patients transported by code-stroke ground ambulance who had ICH neurosurgery, 2 years before versus 2 years after SSTS implementation. We also calculated triage precision metrics for treatment with either ICH neurosurgery or thrombectomy.

Results

A total of 36 patients undergoing ICH neurosurgery were included before SSTS implementation and 30 after. No significant difference was found in timing of neurosurgery [median 7.5 (4.9-20.7) versus 9.1 (6.1-12.5) h after onset], distribution of functional outcomes (median 4 versus 4), and death at 3 months [3/29 (9%) versus 5/35 (17%)] before versus after implementation, respectively. The SSTS routed a larger proportion of patients subsequently undergoing ICH neurosurgery directly to the comprehensive stroke center: 13/36 (36%) before versus 18/30 (60%) after implementation. Overall system triage accuracy for ICH neurosurgery or thrombectomy was high at 90%, with 92% specificity and 65% sensitivity.

Conclusion

The SSTS, initially designed for prehospital LVO stroke triage, routed more patients with neurosurgical indication for ICH directly to the comprehensive stroke center. This did not significantly affect surgical timing or outcomes.

Dual-Layer Detector Cone-Beam CT Angiography for Stroke Assessment: First-in-Human Results (the Next Generation X-ray Imaging System Trial)

BACKGROUND AND PURPOSE

In patients with stroke, IV cone-beam CTA in the angiography suite could be an alternative to CTA to shorten the door-to-thrombectomy time. However, image quality in cone-beam CTA is typically limited by artifacts. This study evaluated a prototype dual-layer detector cone-beam CT angiography versus CTA in patients with stroke.

MATERIALS AND METHODS

A prospective, single-center trial enrolled consecutive patients with ischemic or hemorrhagic stroke on initial CT. Intracranial arterial segment vessel conspicuity and artifact presence were evaluated on dual-layer cone-beam CTA 70-keV virtual monoenergetic images and CTA. Eleven predetermined vessel segments were matched for every patient. Twelve patients were necessary to show noninferiority to CTA. Noninferiority was determined by the exact binomial test; the 1-sided lower performance boundary was prospectively set to 80% (98.75% CI).

RESULTS

Twenty-one patients had matched image sets (mean age, 72 years). After excluding examinations with movement or contrast media injection issues, all readers individually considered dual-layer cone-beam CT angiography noninferior to CTA (CI boundary, 93%, 84%, 80%, respectively) when evaluating arteries relevant in candidates for intracranial thrombectomy. Artifacts were more prevalent compared with CTA. The majority assessment rated each individual segment except M1 as having noninferior conspicuity compared with CTA.

CONCLUSIONS

In a single-center stroke setting, dual-layer detector cone-beam CTA virtual monoenergetic images are noninferior to CTA under certain conditions. Notably, the prototype is hampered by a long scan time and is not capable of contrast media bolus tracking. After excluding examinations with such scan issues, readers considered dual-layer detector cone-beam CTA noninferior to CTA, despite more artifacts.

Prehospital stroke management and mobile stroke units

PURPOSE OF REVIEW

Delayed presentation at the hospital contributes to poorer patient outcomes and undertreatment of acute stroke patients. This review will discuss recent developments in prehospital stroke management and mobile stroke units aimed to improve timely access to treatment within the past 2 years and will point towards future directions.

RECENT FINDINGS

Recent progress in research into prehospital stroke management and mobile stroke units ranges from interventions aimed at improving patients' help-seeking behaviour, to the education of emergency medical services team members, to the use of innovative referral methods, such as diagnostic scales, and finally to evidence of improved outcomes by the use of mobile stroke units.

SUMMARY

Understanding is increasing about the need for optimizing stroke management over the entire stroke rescue chain with the goal of improving access to highly effective time-sensitive treatment. In the future, we can expect that novel digital technologies and artificial intelligence will become relevant in effective interaction between prehospital and in-hospital stroke-treating teams, with beneficial effects on patients' outcomes.

Does Weekends Effect Exist in Asia? Analysis of Endovascular Thrombectomy for Acute Ischemic Stroke in A Medical Center

BACKGROUND

Discussing the quality measurements based on interrupted time series in ischemic stroke, delays are often attributed to weekends effect. This study compared the metrics and outcomes of emergent endovascular thrombectomy (EST) during working hours versus non-working hours in the emergency department of an Asian medical center.

METHODS

A total of 297 patients who underwent EST between January 2015 and December 2018 were retrospectively included, with 52.5% of patients presenting during working hours and 47.5% presenting during nights, weekends, or holidays.

RESULTS

Patients with diabetes were more in non-working hours than in working hours (53.9% vs. 41.0%; p=0.026). It took longer during nonworking hours than working hours in door-to -image times (13 min vs. 12 min; p=0.04) and door-to-groin puncture times (median: 112 min vs. 104 min; p=0.042). Significant statistical differences were not observed between the two groups in neurological outcomes, including successful reperfusion and complications such as intracranial hemorrhage and mortality. However, the change in National Institute of Health Stroke Scale (NIHSS) scores in 24 hours was better in the working-hour group than in the nonworking-hour group (4 vs. 2; p=0.058).

CONCLUSION

This study revealed that nonworking-hour effects truly exist in patients who received EST. Although delays in door-to-groin puncture times were noticed during nonworking hours, significant differences in neurological functions and mortality were not observed between working and non-working hours. Nevertheless, methods to improve the process during non-working hours should be explored in the future.

Prehospital stroke mimics in the Stockholm Stroke Triage System

Introduction

In 2017, Stockholm implemented a new prehospital stroke triage system (SSTS) directing patients with a likely indication for thrombectomy to the regional comprehensive stroke center (CSC) based on symptom severity and teleconsultation with a physician. In Stockholm, 44% of patients with prehospital code stroke have stroke mimics. Inadvertent triage of stroke mimics to the CSC could lead to inappropriate resource utilization.

Aims

To compare the characteristics between (1) triage-positive stroke mimics and stroke (TP mimics and TP stroke) and (2) triage-negative stroke mimics and stroke (TN mimics and TN stroke) and to (3) compare the distribution of stroke mimic diagnoses between triage-positive and triage-negative cases.

Methods

This prospective observational study collected data from October 2017 to October 2018, including 2,905 patients with suspected stroke who were transported by code-stroke ambulance to a Stockholm regional hospital. Patients directed to the CSC were defined as triage-positive. Those directed to the nearest stroke center were defined as triage-negative.

Results

Compared to individuals with TP stroke (n = 268), those with TP mimics (n = 55, median 64 vs. 75 years, P < 0.001) were younger and had lower NIHSS score (median 7 vs. 15, P < 0.001). Similarly, those with TN mimics (n = 1,221) were younger than those with TN stroke (n = 1,361, median 73 vs. 78 years, P < 0.001) and had lower NIHSS scores (median 2 vs. 4, P < 0.001). Functional paresis was more common in those with TP mimics than in those with TN mimics, 18/55 (32.7%) vs. 82/1,221 (6.7%), P < 0.001. Systemic infection was less common in those with TP mimics than in those with TN mimics, 1/55 (1.8%) vs. 160/1,221 (13.1%), P < 0.011. There was a trend toward “syncope, hypotension, or other cardiovascular diagnosis” being less common in those with TP mimics than in those with TN mimics, 1/55 (1.8%) vs. 118/1,221 (9.7%), P < 0.055.

Conclusions

In the SSTS, those with triage-positive and triage-negative stroke mimics were younger and had less severe symptoms than patients with stroke. All patients with TP mimics who had hemiparesis but overall exhibited less severe symptoms against true stroke but more severe symptoms than those with TN mimics were triaged to the nearest hospital. Over-triage of functional paresis to the CSC was relatively common. Meanwhile, a large majority of cases with minor symptoms caused by stroke mimics was triaged correctly by the SSTS to the nearest stroke center.

Analysis and modelling of mistriage in the Stockholm stroke triage system

INTRODUCTION

The Stockholm Stroke Triage System (SSTS) is a prehospital triage system for detection of patients eligible for endovascular thrombectomy (EVT). Assessment of hemiparesis combined with ambulance-hospital teleconsultation is used to route patients directly to the thrombectomy centre. Some patients are not identified and require secondary transport for EVT (undertriage) while others taken to the thrombectomy centre do not undergo EVT (overtriage). The aims of this study were to characterize mistriaged patients, model for and evaluate alternative triage algorithms.

PATIENTS AND METHODS

Patients with suspected stroke transported by priority 1 ground ambulance between October 2017 and October 2018 (n = 2905) were included. Three triage algorithms were modelled using prehospital data. Decision curve analysis was performed to calculate net benefit (correctly routing patients for EVT without increasing mistriage) of alternative models vs SSTS.

RESULTS

Undertriage for EVT occurred in n = 35/2582 (1.4%) and overtriage in n = 239/323 (74.0%). Compared to correct thrombectomy triages, undertriaged patients were younger and had lower median NIHSS (10 vs 18), despite 62.9% with an M1 occlusion. In overtriaged patients, 77.0% had a stroke diagnosis (29.7% haemorrhagic). Hemiparesis and FAST items face and speech were included in all models. Decision curve analysis showed highest net benefit for SSTS for EVT, but lower for large artery occlusion (LAO) stroke.

DISCUSSION

Undertriaged patients had lower NIHSS, likely due to better compensated proximal occlusions. SSTS was superior to other models for identifying EVT candidates, but lacked information allowing comparison to other prehospital scales.

CONCLUSION

Using prehospital data, alternative models did not outperform the SSTS in finding EVT candidates.

European Stroke Organisation (ESO) guidelines on mobile stroke units for prehospital stroke management

The safety and efficacy of mobile stroke units (MSUs) in prehospital stroke management has recently been investigated in different clinical studies. MSUs are ambulances equipped with a CT scanner, point-of-care lab, telemedicine and are staffed with a stroke specialised medical team. This European Stroke Organisation (ESO) guideline provides an up-to-date evidence-based recommendation to assist decision-makers in their choice on using MSUs for prehospital management of suspected stroke, which includes patients with acute ischaemic stroke (AIS), intracranial haemorrhage (ICH) and stroke mimics. The guidelines were developed according to the ESO standard operating procedure and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) methodology. The working group identified relevant clinical questions, performed systematic reviews and aggregated data meta-analyses of the literature, assessed the quality of the available evidence and made specific recommendations. Expert consensus statements are provided where sufficient evidence was not available to provide recommendations based on the GRADE approach. We found moderate evidence for suggesting MSU management for patients with suspected stroke. The patient group diagnosed with AIS shows an improvement of functional outcomes at 90 days, reduced onset to treatment times and increased proportion receiving IVT within 60 min from onset. MSU management might be beneficial for patients with ICH as MSU management was associated with a higher proportion of ICH patients being primarily transported to tertiary care stroke centres. No safety concerns (all-cause mortality, proportion of stroke mimics treated with IVT, symptomatic intracranial bleeding and major extracranial bleeding) could be identified for all patients managed with a MSU compared to conventional care. We suggest MSU management to improve prehospital management of suspected stroke patients.