Here, we present real-world data of a prehospital transport strategy adjusted for suspected aLVO stroke patients in rural areas (ʻaLVO-dispatch strategyʼ) that results in faster access not only to EVT but also to IVT compared to highly realistic modeled alternative transport strategies.

While the time from stroke onset to emergency call is difficult to influence [11, 12], the time that lapses from emergency call to recanalization therapy (IVT and EVT) can be positively affected by optimizing the prehospital workflow. A number of factors significantly impact the prehospital time: (i) the initial dispatch of rescue means based on the emergency call, (ii) the stroke patient transport strategy based on preclinical assessment at the scene, and (iii) the mode of transport to the target hospital based on the distance between the scene and the hospital and the availability of specific emergency transport. The two common allocation strategies for aLVO stroke patients both have significant advantages and disadvantages: the MS strategy is known for fast arrival at the CSC and thus fast access to EVT, but the delayed or even aborted initiation of IVT reduces its benefits. On the other hand, the DnS strategy allows for faster access to IVT, but is associated with delayed EVT. In fact, the recent RACECAT trial comparing MS and DS strategies in suspected LVO stroke patients in non-urban areas in Catalonia (Spain) showed no significant difference in 90-day disability [7]. It is noteworthy that in this comparison, despite long transport distances, transport to CSC was almost exclusively carried out ground-based, resulting in travel times to the next CSC > 60 min in more than half of the study population. While the assumed treatment times for MS ʻgroundʼ and DnS ʻgroundʼ in our example were remarkably consistent with those observed in the RACECAT trial (see Fig. 2), the use of the secondary requested helicopter as part of the MS ʻairʼ strategy would already shorten the prehospital time in the case of transport to a CSC by 14 min compared to ground-based transport, enabling IVT after 133 min and EVT after 193 min instead of 147 min and 207 min, respectively. Nevertheless, the time to IVT would still be delayed by 16 min with the MS ʻairʼ strategy compared to the DnS strategy.

To further optimize the prehospital workflow, parallel dispatch of ground EMS and HEMS in the case of aLVO stroke suspicion by the dispatcher (aLVO-guided dispatch) could save time on site as the helicopter is immediately available for transport without the need of a subsequent request. Emergency rescue data from a German air-rescue study showed that parallel activation of EMS and HEMS shortens the on-scene time: while the median on-scene time was 53 min in the case of secondary request of helicopter, the median on-scene time with parallel activation only amounted to 28 min [13]. Since only 10% of cases in this study accounted to “neurological emergencies”, there is a lack of real-world data investigating the parallel activation of EMS and HEMS in patients with aLVO stroke.

Based on our case, we compared different prehospital strategies with the aLVO-guided dispatch strategy. The calculated time differences between the different strategies could be clinically highly relevant, as a recent post hoc analysis of the RACECAT trial demonstrated that time differences very similar to those observed in our comparison led to significant differences in clinical outcome [14]. Overall, it can be assumed that the time benefit of the aLVO-guided dispatch strategy would further increase with greater transport distance since not only the driving distance to the CSC but also the flight distance from the helicopter base to the emergency scene increases. The parallel activation of HEMS warrants that the helicopter approach to the scene starts at the earliest possible time point and does not extend the on-scene time, as in the case of secondary helicopter request in the MS ʻairʼ strategy. Despite long transport distances, the aLVO-guided dispatch strategy would ensure timely administration of IVT. This finding appears particularly important in light of a recent meta-analysis showing that the benefit of IVT in combination with EVT versus EVT alone is linearly time-dependent, with a statistically significant benefit demonstrated only when the time from symptom onset to IVT administration was less than 140 min [15]. These results once again emphasize the need to initiate IVT as early as possible also in aLVO stroke patients to obtain the greatest possible clinical benefit, which is best enabled by the aLVO-guided dispatch strategy.

Moreover, the aLVO-guided dispatch strategy could be beneficial for patients with intracerebral hemorrhage (ICH), who, particularly in the case of cortical lobar hemorrhage, can present with the same symptoms as aLVO stroke patients and therefore cannot be distinguished by the dispatcher. These patients benefit from immediate access to neurosurgical care [16], which in our region is only available at CSCs. The aLVO-guided dispatch strategy could overcome the reported negative effects of long-distance ground transport to the CSC in patients with ICH from the RACECAT trial [17], not only because transport times are significantly shorter with helicopter but also because the constant presence of physicians in the helicopter allows improved medical support during patient transfer compared to the limited medical support provided by EMS.

This study has limitations. Since it is not possible to observe the timelines of different transport strategies on a single case basis, we applied modeling as a means to compare prehospital transport strategies. Modeling generally involves assumptions rather than real-time data. We were able to calculate highly realistic prehospital transport times for alternative transport strategies based on real-world emergency ambulance travel times and helicopter flight times. The default on-scene time of 30 min represents the median on-scene time in stroke rescue missions in our federal state (and is also exactly in line with the on-scene time of the present case) [18]. The default door-in-door-out time of 60 min for the DnS strategy represents an optimally functioning system. The real-world door-in-door-out times in our region [19], as well as in other countries [20, 21], considerably exceed this benchmark, so our modeled data might underestimate the time advantage of the aLVO-guided dispatch strategy relative to the DnS strategies. It should be noted that cross-border transport is not considered in our study as it is not regularly performed due to organizational matters and insurance regulations. Despite this, in our case, ambulance transport to the nearest foreign CSC (ambulance travel time from emergency scene: 24 min) would not have a time advantage over the aLVO-guided dispatch strategy.

There are also limitations associated with the aLVO-guided dispatch strategy itself. The aLVO-guided dispatch strategy requires the detection of suspected aLVO stroke patients in emergency calls. Detection of suspected aLVO stroke over the phone might be challenging, and the limited reliability of stroke detection by dispatchers could influence the success of this strategy [22]. The development of an aLVO-query specifically tailored for dispatchers is an important cornerstone of the LESTOR study [10]. The aLVO-query aims to recognize a combination of arm paresis and correspondent cortical sign as cortical symptoms have proved to be a reliable indicator for LVO [23]. A poor specificity of the aLVO-query could potentially lead to inefficient use or even overload of HEMS carrying the risk of disadvantaging other time-critical emergencies. Nevertheless, aLVO stroke and its mimics are a rare occasion, particularly in sparsely populated rural areas.

The availability and costs of HEMS could also pose a challenge to the aLVO-guided dispatch strategy. In Germany, helicopters are evenly distributed throughout the country [24], so the rare unavailability of helicopters is most often due to unfavorable weather conditions or limited night-flying capability. In our region, there are helicopters that have full night-flying capability and are able to land at unmarked landing sites even at night. The deployment of HEMS is checked regularly for transport distances of more than 40–50 km or in areas that are difficult to access on roads. Using helicopter transport for shorter distances might overstretch the HEMS system. In addition, since the number of available helicopters may be limited in other countries, prolonged helicopter approach times must be considered when selecting the fastest means of transport. A recent simulation study in Finland showed that helicopter transport of stroke patients was faster only when the estimated ground transport time exceeded 40 min, provided that the helicopter was dispatched in parallel [9]. Moreover, helicopter deployment is more expensive than ground transportation. Therefore, the LESTOR trial is accompanied by a cost-effectiveness analysis, which offsets the costs of helicopter missions against the savings resulting from the faster initiation of therapy.