Large Vessel Occlusion Stroke Detection in the Prehospital Environment

Abstract

Purpose of Review Endovascular therapy for acute ischemic stroke secondary to large vessel occlusion (LVO) is time-dependent. Prehospital patients with suspected LVO stroke should be triaged directly to specialized stroke centers for endovascular therapy. This review describes advances in LVO detection among prehospital suspected stroke patients. Recent Findings Clinical prehospital stroke severity tools have been validated in the prehospital setting. Devices including EEG, SSEPs, TCD, cranial accelerometry, and volumetric impedance phase-shift-spectroscopy have recently published data regarding LVO detection in hospital settings. Mobile stroke units bring thrombolysis and vessel imaging to patients. Summary The use of a prehospital stroke severity tool for LVO triage is now widely supported. Ease of use should be prioritized as there are no meaningful differences in diagnostic performance amongst tools. LVO diagnostic devices are promising, but none have been validated in the prehospital setting. Mobile stroke units improve patient outcomes and cost-effectiveness analyses are underway.

Comparison of Prehospital Assessment by Paramedics and In-Hospital Assessment by Physicians in Suspected Stroke Patients: Results From 2 Prospective Cohort Studies

“…Future research should address this, ideally also taking into account efficacy of other aLVO triage modalities, such as mobile stroke units, telemedicine, dry-electrode electroencephalography, or transcranial doppler systems. 22 Strengths of this study include the large sample size of unselected stroke code patients from multiple ambulance regions with several primary stroke centers and thrombectomy-capable stroke centers. In addition, prehospital assessments were performed by paramedics in the field and implemented in regular workflow, representing the real-world setting, and making results well generalizable for routine practice.…”

Cost-effectiveness of Direct Transfer to Angiography Suite of Patients With Suspected Large Vessel Occlusion

“…Given the comparable performance of these (0.57–0.67), each emergency medical service region should choose an easy-to-use tool and monitor adherence and accuracy of the prehospital scale. 40 In addition, our model with published input parameters may be used in other settings to assess the cost-effectiveness of the DTAS strategy at different decision thresholds (i.e., $100,000 per QALY in the United States, 41 €22,000–€33,000 per QALY in Denmark 42 ). Future work should confirm the economic benefit of the DTAS strategy in other settings.…”

Large vessel occlusion prediction scales provide high negative but low positive predictive values in prehospital suspected stroke patients

“…Several devicebased approaches are under development to address the diagnostic limitations of LVO prediction scales, including by some of the current authors, but no devices have examined M2 occlusions in large numbers nor completed prehospital validation studies. [32][33][34] Alternatively, broadening our definition of successful triage to include not only M2 occlusions but also intracranial haemorrhage results in high PPVs but low sensitivities. This may be reassuring to prehospital systems of care decision makers.…”

“…As noted above, M2s have comprised a significant proportion of LVOs in studies with prehospital suspected stroke patients (33% in our study and over 40% in two others) so the development of prehospital diagnostic tests that are sensitive for them while retaining specificity would be beneficial. Several device-based approaches are under development to address the diagnostic limitations of LVO prediction scales, including by some of the current authors, but no devices have examined M2 occlusions in large numbers nor completed prehospital validation studies 32–34…”

“…EMS systems already using the CPSS as a binary initial stroke screen could also adopt it as a high NPV LVO triage prediction scale without having to incorporate an additional stroke scale. The limitations of these neurological examination-based tests support the need for further investigation of alternative approaches to prehospital LVO stroke identification, such as Mobile Stroke Units and portable LVO stroke diagnostic devices 34. In the meantime, implementation of LVO prediction scales still may benefit correctly classified patients more than prehospital systems that do not attempt prehospital LVO stroke triage.…”