Cranial accelerometry: The ECG of ischemic strokes?

Large-vessel occlusion (LVO) strokes represent a minority of acute ischemic stroke presentations; however, they lead to a disproportionate majority of morbidity and mortality from stroke presentations.1, 2 Standard of care for treatment of LVO includes endovascular therapy (EVT) such as thrombectomy or catheter-directed thrombolysis—a treatment offered at comprehensive stroke centers. These centers are less widely available than primary stroke centers, often leading to a need for secondary transfer for LVO patients after initial presentation.3 Developing prehospital screening tools to optimize delivery of patients with LVO stroke to centers capable of mechanical thrombectomy has been an area of significant research investment and, when implemented, has the potential to reduce number of secondary transfers and reduce time to endovascular intervention.4, 5 Much of the research in this area has focused on the development of new diagnostic scores, which prehospital providers can use to identify LVO patients using combinations of historical features and clinical examination findings. Utilization of a prehospital LVO scale of some type has been incorporated into national guidelines, although no one scale has been demonstrated to be superior, and the selection of scale varies at a regional level.5-7 One of the challenges of these scales is their relatively high specificity and low sensitivity and their susceptibility to atypical clinical presentations.8, 9 The concern with overtriage of LVO strokes is causing unnecessarily long transport times and the risk of overwhelming comprehensive stroke centers, while undertriage may result in longer times to ultimate treatment when LVO strokes are missed. Clearly, the ideal prehospital triage tool would have high sensitivity and specificity for LVO stroke and would outperform the available LVO screens. Apart from assessment scales, other methods for prehospital LVO detection under investigation include deployment of mobile stroke units to perform CTA, telemedicine, transcranial doppler, and EEG.10, 11 In the study by Paxton et al.,12 the authors have demonstrated a novel method of prehospital stroke assessment using cranial accelerometry in combination with the LAMS examination. In this preliminary clinical trial, they noted significantly improved sensitivity and specificity utilizing this device compared to the LAMS score alone. Improved ability to detect LVO in the prehospital setting could have significant impacts in prehospital stroke management, especially in rural areas, where diverting to a comprehensive stroke center requires significantly increased transport times.13 Prolonged transport times present multiple challenges—including taking an EMS unit out of their primary service area for a longer period of time, reducing available resources for other emergency patients, and potentially increasing the time to treatment for patients that screen falsely positive for LVO. Reducing the number of false positives on prehospital LVO detection would minimize both of these challenges, while minimizing false negatives results in lower need for secondary transfers (which also take EMS units out of their service area and increases the time to EVT for patients who need it). Use of cranial accelerometry in conjunction with prehospital stroke examination could therefore lead to more efficient utilization of EMS resources and improve patient outcomes by shortening time to treatment in patients with the highest risk of morbidity and mortality. Clinical trials are often especially challenging in the prehospital environment, due to a wide variety of barriers that do not play a role in hospital-based trials. These include the local variability in EMS protocols, heterogenous levels of training of EMS personnel (BLS, ALS, intermediate), limited resources available in the prehospital setting, and limited time, due to the urgent nature of EMS transport. All these factors may limit the interventions and assessments that can be performed by EMS. Critically important for feasibility, Paxton et al. demonstrated that cerebral accelerometry can be performed in a variety of EMS systems, spanning across different population densities and geographic areas. By training both paramedics and EMTs, they demonstrated that this technique can be utilized by all levels of EMS providers. Their second iteration device was reliably able to obtain data on 86.3% of patients. While this is a robust performance, it does suggest the need for a backup stroke triage protocol for patients in which data capture fails. Accordingly, EMS will still need to be trained on an existing, human-collected LVO screening protocol. The authors' findings could be relevant for use in diverse prehospital settings. With the demonstrated enhanced performance of CA-LAMS technique of stroke assessment compared to use of stroke scales alone in the study by Paxton et al., there is a need for both validation and implementation studies—to demonstrate the effective use of this technique within a triage algorithm, where results are used to determine transport destination, and to follow patient outcomes. Optimally, further clinical trials would focus on systems located in rural and medically underserved areas, rather than areas with hospitals in close proximity. Rural areas will likely receive the most benefit from a triage system that reduces the need for longer distance transfers with longer transport times, and they often face increased barriers in terms of financial resources and staffing, which could raise challenges in implementation of these protocols. Special attention will need to be given to the cost of this potential new prehospital treatment, so that its cost of use is not prohibitive in the areas where it could have the most benefit. This includes the price of the device itself, maintenance and support fees, and the personnel training hours required to be proficient in its use. Addition of any device to a medical system comes with both up-front and persistent expenses that may be difficult for smaller EMS systems to support. Further clinical studies with this device will be crucial to demonstrate that the benefit of use to the system outweighs the cost to all who participate. Prehospital triage guidelines for specific disease states have been crucial for patient care throughout several decades. These special situations require triage based on prehospital examination (such as trauma), but also based on clinical testing with well-established devices (such as field ECG screening for STEMI). STEMI protocols demonstrate a clear example of prehospital providers utilizing a medical device to appropriately triage patients to the appropriate destination. This has proved to be widely successful and easily implemented and has significantly improved patient outcomes across the country, in diverse geographic settings.14 Though in its infancy, cranial accelerometry could potentially serve as the ECG of ischemic strokes—an easily utilized device that when combined with clinical examination and history accurately screens for severe pathology to deliver the appropriately selected patient to their destination therapy. The authors declare no conflicts of interest.