For patients with ischemic stroke who live in rural areas, flying a team to provide endovascular treatment (EVT) at the nearest primary stroke center did not yield significant clinical benefit compared with transferring the patients to a comprehensive stroke center, a new study shows.
The adjusted odds ratio (OR) of a good outcome was 1.26 for use of a flying intervention team (FIT) in comparison with transferring patients to an intervention center, but the difference was not statistically significant. A good outcome was defined as a Modified Rankin Scale (mRS) score of 0 to 2 after 3 months.
Still, “With the deployment of the FIT, more patients received thrombectomy, the treatment was started 1.5 hours earlier, and clinical results trended towards a better outcome after 3 months than if patients had interhospital transfer,” study author Gordian Hubert, MD, senior physician and TEMPiS telestroke network coordinator at the Munich Harlaching Clinic, in Munich, Germany, told Medscape Medical News.
He presented the results of his study at the European Stroke Organisation Conference (ESOC) 2021, which was held online.
Intervening in Rural Areas
EVT is an effective treatment for ischemic stroke but should be administered as quickly as possible for maximum benefit, the researchers note. Expertise in administering EVT is less common in rural areas than in cities, but transferring patients to intervention centers can result in treatment delays and worse outcomes.
Transporting an intervention team by helicopter to a primary stroke center was previously shown to reduce time to treatment by 90 minutes, compared with transferring the patient, the researchers write. The current study sought to determine whether this treatment strategy was associated with improved functional outcomes.
For the prospective cohort study, patients were recruited from February 2018 through January 2021. Fifteen primary stroke centers that were participating in a telestroke network took part in the study. Eligible patients were candidates for EVT and had experienced occlusion of the intracranial internal carotid artery, M1, proximal M2, or the basilar artery.
Two FITs were available for 50% of the study period. Patients were treated by FIT at the nearest primary stroke center or were transferred to a comprehensive stroke center for EVT, depending on whether an FIT was available.
The study’s primary endpoint was mRS score at 3 months. Secondary endpoints included clinical and safety outcomes during hospitalization and within 3 months after stroke onset.
In all, 134 patients underwent treatment by FIT, and 210 patients were transferred to a comprehensive stroke center. The treatment arms were well matched on demographic characteristics. The population’s mean age was approximately 76 years, and about 52% of patients were women. The mean baseline NIH Stroke Scale score was 13.
The percentage of patients who were women was higher In the FIT group (57%) than in the transfer group (47%), however.
EVT was performed for 84% of patients in the FIT group and for 65% of patients in the transfer group (P < .001). The median time from decision to treatment was 62 minutes for the FIT group and 148 minutes for the transfer group (P < .001).
The rate of successful recanalization was 94% in the FIT group and 88% in the transfer group, but the difference between groups was not statistically significant. The median time from onset to recanalization was 240 minutes in the FIT group and 338 minutes in the transfer group (P < .001).
There was a shift toward increased probability of good functional outcome at 3 months, as measured by mRS, in the FIT group, but it did not reach statistical significance. In the FIT group, the adjusted OR of a good outcome after 3 months was 1.26 (P = .385).
Safety outcomes were similar between groups. The rate of death within 3 months was 23% in the FIT group and 23% in the transfer group. The rates of in-hospital complications (such as symptomatic intracranial hemorrhage and new ischemic stroke) and of periprocedural complications (such as intracranial vessel perforation and distal embolization) were similar between groups.
Because many patients did not receive EVT, the investigators performed a subgroup analysis that included only patients who underwent this treatment. As in the primary analysis, there was a trend toward a better outcome in the FIT group, but it did not reach statistical significance. For patients in the FIT group, the adjusted OR of a good outcome after 3 months was 1.64 (P = .112).
“The amount of difference in outcome between the two groups is in line with previous publications that looked at the effect of time delay until thrombectomy,” said Hubert. The lack of a significant difference between treatment arms was most likely the result of low patient numbers, he added. “We will have to continue to gather data and do more analyses,” he said.
The investigators plan to continue the FIT project and have applied to extend it for another 3 years. “After this time, we will be able to do more analyses also looking into subgroups,” said Hubert. “I would also be happy to see other groups setting up this system of care, so that we learn more about generalizability in the future.”
“A Great Idea”
“This was a really ambitious study and was underpowered for its primary outcome measure,” said S. Claiborne Johnston, MD, PhD, professor of neurology at the University of Texas at Austin, who commented on the findings for Medscape Medical News. The data support the idea that timely EVT is effective, he added. “Increasing rates of EVT and the time to recanalization will be associated with better outcomes,” he said.
The imbalances in the numbers of participants enrolled in the two treatment arms indicate that not everyone who could have benefited from FIT received to it, said Johnston. This suggests that the patients who underwent treatment by an FIT differed from those who were transferred. “A fairer way to analyze the data would have been to look at overall differences in outcomes for those eligible during weeks of coverage vs weeks without coverage, regardless of whether the flying team was deployed,” said Johnston.
A larger randomized trial likely would confirm the trends toward better outcomes seen in this study. “The key question then would be whether this is a cost-effective intervention,” said Johnston. “There are lots of things that are feasible, but are they worth the investment? That requires more data.”
Imaging Criteria, Experience
The study was the first reasonably large study of FIT and demonstrates the feasibility of this approach, said James C. Grotta, MD, director of stroke research at the Clinical Institute for Research and Innovation at Memorial Hermann–Texas Medical Center, Houston, Texas, who commented on the findings for Medscape Medical News.
Another important strength of the study is that it addresses the poor distribution of trained interventionists to carry out thrombectomy, said Grotta. Several studies have found an association between better outcomes and more experienced interventionists. “So, bringing a skilled, experienced interventionist to a low-volume center will probably result in better outcomes than treatment by a local interventionist who does only a few cases per year,” he said.
Patients were treated at around 4 to 6 hours after stroke onset, said Grotta. “The benefit of EVT in patients at 4 to 6 hours becomes more dependent on appropriate selection by imaging, which takes into account collateral status,” he said. The dropout rate of patients whose collaterals became insufficient over that 4- to 6-hour period and who therefore did not meet imaging criteria could account for the larger number of patients who underwent EVT in the FIT group, he said.
“The most appropriate analysis would be to compare all patients with alarm within a certain time, say, 4 hours of onset, who met criteria for presumed large-vessel occlusion [LVO] at that time, regardless of whether they went on to receive EVT, without including the false alarms (meaning probable non-LVO patients) and not just the ones who would do well with or without FIT (such as those with good imaging),” Grotta said. The results of such an analysis would likely be more favorable for FIT, he added.
In addition, the investigators should perform a power analysis to see how many patients would be required for there to be an absolute 10% increase in the proportion of patients achieving an mRS of 0 to 2 with FIT, said Grotta.
“I think this is a great idea to speed stroke treatment into rural areas,” he continued. “It deserves further study in other networks and geographic or population regions, taking into consideration the patient selection and statistical power issues I raised.”
The study was funded by the Bavarian Ministry of Health and the Björn-Steiger-Foundation. Hubert and Johnston have disclosed no relevant financial relationships. Grotta was the primary investigator of the BEST-MSU study of mobile stroke units.
European Stroke Organisation Conference (ESOC) 2021.
Follow Erik Greb on Twitter: @MedscapeErik.