The benefit from endovascular therapy (EVT) for treatment of stroke due to intracranial large vessel occlusion is time dependent (1, 2). In patients who qualify for EVT in the neuro-interventional hospital, each 30 min increase of CT-to-reperfusion time is associated with a nearly 10% decreased chance to achieve a favorable outcome (3). Moreover, with each second of delay between arrival to groin puncture, the patient loses 2.2 h of healthy life-time (4).

Therefore, an efficient workflow should be paramount to reduce in-hospital treatment times (3, 5). The European recommendations on organization of interventional care in acute stroke (EROICAS) advise that imaging to treatment time (image-to-groin) should be <30 min and always <90 min (6). The Guidelines of the American Heart Association (AHA) recommend achieving a door-to-imaging time of <20 min but do not specify time goals in EVT patients (7). A multi-society (including the European Stroke Organization and World Stroke Organization) consensus statement proposed that 75% of patients being evaluated for EVT should have a door-to-imaging time of 30 min or less with high volume centers expected to achieve this in 12 min (8).

Telestroke networks have been shown to facilitate access of ischemic stroke patients to EVT by means of a drip-and-ship model with comparable results regarding safety and outcome (7, 9, 10). Furthermore, the transfer in the network itself is safe with medical interventions necessary in only a minority of patients (11). In contrast to patients who are directly admitted via ambulance, patients who are transferred from remote hospitals can be announced prior to arrival at the angiography site, leaving the staff with considerable time for preparation. However, due to potential long distances of travel between the community hospital and the stroke center and the possibility of transfer delays, patient admission to the angiography site might vary considerably (11, 12).

The objective of our study was to test whether the implementation of a semi-automated pre-notification procedure can lead to faster in-hospital treatment times of stroke patients who are transferred for EVT in a telestroke network.

Our study demonstrates that standardized team prenotification of all team members who are involved into acute treatment decision making and treatment of patients with acute ischemic stroke considered for EVT results in faster treatment times. Particularly, door-to-imaging times and image-to-groin were decreased with a resulting reduction of door-to-groin time by nearly 15 min. Time-reduction was particularly observed during on-call periods, though this interaction was not statistically significant. As a side effect, overall awareness for acute ischemic stroke as a medical emergency increased at our hospital.

Treatment times were in line with proposed time metrics from guidelines and with treatment time targets of trials with focus on rapid treatment work-flow (7, 8, 17). However, despite implementation of the EVT-call, the door-to-groin puncture time in our cohort was still longer compared to the average door-to-groin puncture time of patients transferred via a primary stroke center in the German stroke registry (median door-to-groin time: 44 min [IQR 30–67]) (18). Potential reasons for delay in our hospital are the relatively high rate of periinterventional intubation during the study period (62.1%) and repeated imaging after arrival at our center as a standardized procedure. In patients from the German stroke registry who received repeated imaging, door-to-groin times were comparable to our data (door-to-image time: 15 min [10–23]; image-to-angio time: 22 min [15–36]; angio-to-groin time: 20 min [15–31]) (18). Moreover, door-to-groin puncture times were significantly delayed in patients who received repeated imaging in a recent report from the Amsterdam stroke registry (19).

It is debatable whether repeated imaging is required for stroke patients transferred from primary stroke centers for EVT. However, in our cohort, nearly 40% of transferred patients did not receive EVT due to extensive early ischemic changes or vessel recanalization, probably secondary to long distances and transfer times in our network (11, 20, 21). In the Amsterdam stroke registry, EVT was not performed in 55% of patients who received repeated imaging—mostly due to recanalization in patients who had improved clinically (19). Novel one-stop management strategies with flat panel detector CT and CT perfusion strategies in the angiography suite may enable significant decrease of door-to-groin puncture times in patients who receive repeated imaging, but need to be tested in larger patient cohorts treated at different EVT centers (22).

Rates of periinterventional intubation may have prolonged treatment times in our center. Treatment times until groin puncture tended to be delayed in patients who received EVT under general anesthesia in the randomized GOLIATH and AnSTROKE trials (23). Whereas, randomized trial data do not point to a detrimental effect of periinterventional general anesthesia, analyses of large study cohorts suggest a negative impact on favorable outcome (23). Regardless of the direct effects of general anesthesia on functional outcome, avoidance of periinterventional intubation has potential to further reduce door-to-groin times. Furthermore, our own data has shown that prolonged general anesthesia after EVT is associated with worse functional outcome, therefore we have adapted our standard operational procedure targeting timely extubation after EVT (24).

Our faster treatment times did not translate into better outcomes measured by mRS at 3 months. It is possible that our patient population is too small to show this effect. Despite this, there is no doubt that faster treatment times generally translate into improved clinical outcomes in stroke treatment, it can be challenging to show this association outside of randomized controlled trials (25). Furthermore, only 28.2% of our patients reached a mRS of 0–2 at 3 months and 29.4% were deceased. A generally poorer outcome of stroke patients who are transferred for EVT has been described previously and may be linked to an overall lower rate of actually performed EVTs, mostly due to already progressed cerebral ischemia (11, 12, 26, 27).

Though a numerically greater time benefit of the EVT-call was observed during on-call periods (Figure 4), this interaction was not statistically significant. This may be due to overall low numbers but was unexpected. Admission on weekends was independently associated with longer door-to-groin puncture times in comprehensive stroke center patients in the German stroke registry (odds ratio 1.61; 95% CI 1.37–1.97) (18). However, despite delay of door-to-groin puncture times during on call periods, groin-to-reperfusion times and functional outcomes were unchanged in a recent study (28).

Treatment times had already decreased in 2016 compared to 2014 and 2015, potentially as a result of positive trial results with, thereafter, clear criteria for EVT (1). Though the focus of the current study was on EVT patients transferred from primary stroke centers or telestroke centers, we have recently established an intravenous thrombolysis call (IVT-call) in 2019 to decrease door-to-needle times, which also resulted in decreased median door-to-groin puncture times of directly admitted patients. As presented, the effect of the EVT-call on reduced treatment times was robust after its transfer into clinical routine even during the COVID-19 pandemic. Door-to-image times in our center remained unchanged during the first COVID-19 wave in Germany (29).

The EVT-call at our hospital is semi-automated and phone-based and delivered by a central dispatcher. To avoid an intermediary person and possible delay of information, other forms of delivery like a paging system or a secured messaging system could enhance our pre-notification procedure.

Our study is limited by its monocentric design. However, as the EVT-call itself is simple if expected transfer times are known or can be calculated, widespread external validity is likely. Centers with different patient workflow and in-hospital logistics may need to find individual solutions, e.g., presence of all team members on patient arrival may be difficult to accomplish in smaller teams. Technical solutions like electronic image analysis and smartphone image transfer may help to fasten treatment times in such scenarios. Apart from in-hospital workflow after patient arrival at the EVT center, patient selection in remote hospitals or preclinical patient selection of EVT patients and methods to speed-up transport to the intervention center are of critical importance and not addressed in this study (30, 31). The rate of intubation of patients before transfer was significantly higher before implementation of the EVT call. However, since the decision to intubate lies in the discretion of the treating physicians at the transferring hospital and is therefore not effected by our in-hospital procedures, we do not think that one can assume a causal relationship. Finally, it is difficult to determine to what extent further improvement of treatment times after implementation of the EVT-call simply resulted from increased routine. However, since most other parameters were similar before and after implementation of the EVT-call, we think that the significant faster treatment times can be mainly derived from our procedure.

We have demonstrated that team prenotification with an EVT-call, which informs all team members about impending arrival and expected arrival time of patients who are potentially eligible for EVT, can decrease in-hospital treatment times and—potentially—improve functional outcomes of acute stroke patients. Door-to-groin puncture time reduction of 15 min translates into nearly 3 months healthy life-time gain, on average, emphasizing its clinical relevance (4). Several aspects that could further decrease treatment times (e.g., necessity for repeated imaging, periinterventional general anesthesia) and methods to effectively select patients in the preclinical or early clinical setting need to be analyzed in future studies.

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

The studies involving human participants were reviewed and approved by Ethikkommission an der Technischen Universität Dresden. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements.

L-PP and VP contributed to the study design. MK, SW, VP, and L-PP were involved in statistical analyses. L-PP, SW, KH, JG, CH, VP, and JL were involved in data collection. L-PP, KB, JB, SW, TS, MK, HT, JR, and VP were involved in drafting the manuscript and revising it critically for important intellectual content. Each author has made substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data. All authors have given final approval of the version to be published.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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