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We read with interest the comments by Leira and Savitz1 in the June 2018 issue of Stroke regarding ischemic stroke triage, administration of intravenous tissue plasminogen activator (IV tPA), and mechanical thrombectomy. Although the topic is timely and the authors’ insights clearly expressed, we disagree with both the concluding statements and the supporting arguments that lead to these inferences. Current evidence does not suggest that advances in mechanical thrombectomy are occurring at the expense of IV tPA only treated patients, and primary stroke centers (PSCs) are not at an existential risk. We offer the following thoughts:
Endovascular therapy (ET) is now the standard of care for emergent large vessel occlusion (ELVO) acute ischemic stroke following the overwhelmingly positive outcomes from multiple randomized trials that compared ET with IV tPA or best medical management.2–8 It is one of the most effective therapies available in modern medicine.2–8 It was estimated that only 10–15% of patients with acute ischemic stroke were eligible for ET.9–11 In the past year, the number of eligible patients has increased further due to the demonstrated efficacy of treatment for selected patients in the extended time window.9–11 However, the aphorism that time is brain still holds true: the faster a patient is recanalized, the greater the chance of a good outcome.
Leira and Savitz are correct to affirm that access to ET is limited by availability, resource allocation, and stroke systems of care, which are currently geared to evaluate patients for thrombolysis. We agree that reorganization of the system at several levels is required to distribute thrombectomy access more evenly across the population while maintaining access to thrombolysis for those most likely to benefit. However, suggesting that initiatives such as bypassing PSCs for those centers where more effective therapies are available challenges the principles of beneficence and justice, is unfair, and should be further discussed.
Data from several studies have shown that transfer between hospitals leads to delays, imaging deterioration, and worse thrombectomy outcomes.12–14 Transfer of patients prior to treatment appears to incur a minimum of 1 hour and often 2 or more hour delays in initiation of ET.12 15 In certain geographic regions, stroke triage in the field to distinguish ELVO patients and redirect them to centers with ET capability has been proposed. This has been implemented in several cities and counties across the USA. Initial data from an Ohio county show an increase in ET utilization and improvement in both IV tPA times and ET times after initiation of a bypass protocol.16 Similar data from Rhode Island show that this improvement may be in part due to the faster IV tPA times in comprehensive centers versus PSCs.17 This implies that proper patient triage decreases delays in thrombolysis.
Advances in prehospital screening tools
The rapid triage and transport of ELVO patients directly to appropriate facilities requires screening tools. Prehospital clinical stroke severity scales have been implemented in several regions across the USA. The sensitivity of prehospital stroke scales used by emergency medical services (EMS) for detection of ELVO ranges from 49% to 91% and specificity from 40% to 94%.18 To improve the accuracy of prehospital ELVO detection, prehospital technologies, such as portable, non-invasive ELVO detection devices and mobile CT scanners, have emerged akin to field electrocardiography for acute myocardial infarction.19 In a recent study, Kellner et al evaluated the accuracy of a volumetric impedance phase shift spectroscopy (VIPS) portable visor device. This instrument was able to detect severe strokes, including ELVO, with a sensitivity of 93% and specificity of 92%.20 In preliminary feasibility studies, the use of mobile stroke units, equipped with CT scanners, has resulted in a significant reduction in time to treatment and improved triage of patients to appropriate facilities.21 In these mobile stroke units, IV tPA can be administered prior to or during transportation. It is also possible to perform CT angiography in the mobile stroke unit, providing an effective way to identify ELVO patients suitable for transport directly to ET capable sites.21
Complete stroke system of care
We recognize that current enthusiasm for mechanical thrombolysis in ELVO patients may risk alienating PSCs, as suggested by Leira and Savitz. Nonetheless, PSCs are anything but superfluous. The initiation of an ELVO triage protocol does not obviate the need for PSCs. Many minor stroke patients will be appropriately routed to the nearest PSC. Indeed, creative solutions involving PSCs such as the ‘scan, treat, and ship’ protocol proposed by Leira and Savitz are evolving to better preserve patient distribution within the community stroke infrastructure. Although triage tools will improve, there will be false negatives as well as false positives, and growing pains are to be expected. Arrangement of acute stroke ready hospitals, PSCs, and comprehensive stroke centers (CSCs) should be coordinated into a hub and spoke model with focus on local efficiencies, accurate evaluation, and rapid transport. These designs can, and should, vary based on local geography and resources. A travel time limit for EMS diversion past a PSC, and to a CSC, is critical to any bypass protocol. Therefore, some rural areas may never have direct access to ET. By contrast, urban areas with PSCs and CSCs in close proximity would require appropriate triage and workflow.
Conclusions
Implementation of thoughtful protocols allowing for field triage of ELVO patients using appropriate tools has the power to improve stroke care for all stroke patients.
References
Footnotes
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial, or not-for-profit sectors.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Commissioned; internally peer reviewed.