Walter Valesky, MD
With the increasing importance of endovascular therapy in acute ischemic stroke care, triage and emergency transport strategies have taken on renewed importance. Current recommendations advise preferential transport to a comprehensive stroke center (CSC) if a large vessel occlusion (LVO) is suspected based on prehospital screening and when the total transport time is less than 30 minutes. The study summarized here evaluated alternative triage strategies in comparison with the current American Heart Association (AHA) recommendations.1
A previously utilized decision-tree model referred to in a prior study2 was used to map outcomes of a suspected LVO to either a primary stroke center (PSC) and then transferred for thrombectomy or directly to an intervention center. A base scenario was applied to the model in which emergency medical services (EMS) was activated for a hypothetical patient with a suspected stroke within 4.5 hours of symptom onset with several time assumptions corresponding to “Get With the Guidelines” recommendations. LVO prevalence was estimated at 20% among suspected stroke patients based on prior studies,2-3 and prehospital assessment applied the rapid arterial occlusion evaluation (RACE) with an assumed sensitivity of 84% and specificity of 60% at a cutoff of 5 points.
United States Census tracts (county subdivisions totaling over 70,000) were used as start points (geographic input parameters) for transport modeling. Several transport strategies were then used: transport to nearest stroke center regardless of capabilities, which was considered the reference standard; transport according to AHA recommendations (as stated previously); variations of the AHA recommendations allowing for longer transport times by 30 and 60 minutes; unlimited allowable transport time to an intervention center (provided that time would not preclude intravenous thrombolytics); and mandatory transport to an intervention center. Effectiveness of each strategy was determined by the increased number of good outcomes (patients with a modified Rankin score of 0-2) and the increased number of patients transported to the intervention center compared to the reference standard.
When compared to the reference standard, a modified triage algorithm allowing for unlimited time for transport to an intervention center was optimal and would increase the number of good outcomes by 2.4% compared to 1.0% using the current AHA triage recommendations at the national level. The number needed to transport would be similar in the two strategies. The state level also showed improvement with a strategy allowing unlimited time compared to current recommendations. At the county level, an unlimited transport time strategy did not show as robust an improvement over current recommendations, but in 2,004 of 3,107 counties in the U.S., the optimal strategy allowed for longer transport time than currently recommended.
Although these results add to the literature of prehospital transport for acute ischemic stroke care, they highlight the fact that, to date, no randomized data exist to guide the current recommendations. As such, these and previous model-based studies assessing triage strategies are not beholden to real-world problems such as overburdened intervention centers or sub-optimal evaluation, treatment, and transfer at lower volume primary stroke centers. Therefore, although eye-opening, these findings should be interpreted with caution and may renew our interest in the pending RACECAT trial (NCT02795962), a randomized trial that will add valuable insight into this question of prehospital triage strategies for suspected LVO.
References:
1. https://www.heart.org/-/media/files/professional/quality-improvement/mission-lifeline/2_25_2020/ds15698-qi-ems-algorithm_update-2252020.pdf?la=en
2. Venema E, Lingsma HF, Chalos V, et al. Personalized Prehospital Triage in Acute Ischemic Stroke: A Decision-Analytic Model. Stroke. 2019;50:313-320.
3. Lakomkin N, Dhamoon M, Carroll K, et al. Prevalence of large vessel occlusion in patients presenting with acute ischemic stroke: a 10-year systematic review of the literature. J NeuroIntervent Surg. 2019;11:241-245.
