Article In Brief
Stroke specialists discuss strategies to make endovascular thrombectomy (EVT) more accessible to many patients who don't have access to the therapy.
Fewer than one-fifth of Americans have ready access to hospitals that offer endovascular thrombectomy (EVT), and in some parts of the country the availability of the clot-busting procedure is even more scant.
“Approximately 61 million (19.8 percent) of Americans have direct EVT-access within 15 minutes,” while 95 million (30.9 percent ) Americans are within 30 minutes of a center that offers the procedure, the study reported in the February 19 online edition of Stroke.
In addition to analyzing the availability of EVT around the US, the study also considered whether it would be more beneficial to add more EVT programs or to implement policies that allow emergency medical crews to bypass closer non-EVT centers to get to a center with EVT—even if that takes more time.
“Bypassing [closer non-EVT centers] showed more potential for maximizing direct EVT access,” the study concluded. “National and state efforts should focus on identifying gaps and tailoring solutions to improve EVT access.”
James C. Grotta, MD, FAAN, a study coauthor and director of stroke research and director of the Mobile Stroke Unit at Memorial Hermann Hospital in Houston, said EVT is not unlike some other new therapies and technologies that took off without much thought to the issue of access.
“We have this treatment (EVT) that is relatively new and very effective and requires specialized teams to carry it out, so now there is a tremendous amount of interest in reorganizing systems of care to improve the number of patients who can get treated,” Dr. Grotta told Neurology Today.
The study authors noted that EVT “improves clinical outcomes, reduces disability and saves lives for patients with acute ischemic stroke (AIS) due to anterior circulation large vessel occlusion (LVO).”
Several clinical trials showed that EVT is effective if done within six hours of the last known point of wellness, though two recent trials known as DAWN and DEFUSE 3, have shown that EVT is efficacious and safe up to 24 hours in selected patients.
“Current stroke care algorithms largely prioritize initial transport of stroke patients to the closest hospital equipped with the ability to administer IV-tPA. Therefore, the majority of patients only have access to EVT through inter-hospital transfers (drip and ship model), which are associated with significant treatment delays and worse outcomes,” the paper said.
How EVT Access Was Measured
To study access, the researchers used 2017 claims data for Medicare and Medicaid to identify stroke centers that were EVT-capable. Of 1,941 stroke centers nationwide, 713 (37 percent) reported having done one or more EVTs for acute ischemic stroke. The researchers used geomapping techniques and 2010 census data to determine that 19.8 percent of the US population have direct access (within 15-minutes travel time) and 30.9 percent of the population could reach a center within 30 minutes.
Ready access to EVT varies greatly among states. Eight states have greater than 25 percent EVT coverage within 15 minutes, 34 states have 10 to 25 percent coverage, and nine states have less than 10 percent coverage, the study reported. Among the higher-access states were Arizona, California, Florida, Nevada, and North Dakota. Among the lower-access states were Alabama, Arkansas, Iowa, Mississippi, and New Hampshire.
The researchers then used mathematical models to ask the question of how EVT access could be improved. Would it be better to open more EVT centers, which they referred to as flipping? Or would it be better to make changes in emergency transportation systems to allow ambulances to bypass the closest non-EVT center to instead take patients who appear to have LVO to a center that offers EVT?
The researchers found that converting the top 10 percent of non-EVT centers to EVT centers would increase the direct coverage level from 19.8 percent to 27.1 percent. In comparison, using the bypass approach would increase access to EVT by 36.5 percent nationwide, with better or less results in some regions.
“Overall, for the majority of states bypassing resulted in better coverage than flipping,” the researchers concluded.
The study had several limitations, including the fact that the researchers used the criterion of “one or more” EVT claims to determine if a center was EVT-capable. The study did not consider volume of EVT procedures, outcomes, or costs of adding an EVT center at a hospital. They also did not consider the details of any given region or community, such as geography, traffic, availability of specialists who perform EVT, or the risk for stroke in the community. The makeup and size of a community's ambulance system could also influence whether the flipping or bypass model is better. The Mobile Stroke Unit in Houston, for example, is equipped to do CTs (which can detect LVO) and start tPA en route to the hospital.
“One size by all means does not fit all,” said Dr. Grotta. But he said every community should give thought to how to best improve access to EVT because “this treatment (EVT) is extremely effective so there is an urgency to address this question.”
Volume Influences Outcomes
David S. Liebeskind, MD, FAAN, professor of neurology at University of California Los Angeles and director of the UCLA Comprehensive Stroke Center, said that while the new study provided a useful theoretical look at how to improve access to EVT, any real-time local or state planning needs to engage all the stakeholders, including doctors, hospitals, community members, and public health officials. He said outcomes should be a key focus because there is a correlation between the number of EVTs done at a hospital and patient outcomes, with higher volume associated with better outcomes.
“Everyone at the onset of stroke thinks the treatment should be straight forward and easy... that as long as you do your part (with EVT) the patient will do fine,” said Dr. Liebeskind, president of the Society of Vascular and Interventional Neurology. “But many stroke cases are complex and require expertise at all phases of care, not just in the endovascular suite.”
Dr. Liebeskind said EVT centers tend to be financially desirable to hospitals, but he said market forces don't necessarily lead to an efficient distribution of resources or a system that “gets the right patient to the right center at the right time.”
He said there are more than 20 EVT centers in Los Angeles County, yet there are some pockets of the community that have limited access, whether due to geography or traffic congestion at peak times of day.
Dr. Liebeskind said that advances in telemedicine—including the potential to perform EVT procedures remotely—could help improve access issues in rural or more remote communities.
Johanna T. Fifi, MD, FAAN, associate professor of neurology, neurosurgery and radiology and associate director of the Cerebrovascular Center at Mt. Sinai Hospital in New York City, said her hospital system has devised a model of care in which a team of EVT providers covers four different sites, including the main hospital and three others in its network.
“Our team travels to the patient,” she said. “That model leads to our providers being very experienced. We do it (EVT) more often so our team is more experienced.”
She said that the model also produces good outcomes by measure of the time it takes to get stroke patients into the procedure.
“We find it's basically faster,” than transferring the patient to the comprehensive stroke center, said Dr. Fifi, who added that a student researcher presented some of the results at the International Stroke Conference last month in Los Angeles.
Dr. Fifi said that while New York City overall has adopted a model of care that allows for ambulances to bypass a non-EVT center in favor of an EVT center based on a clinical assessment scale, she does not think that the bypass model favored in the new study is perfect.
“No matter what, you are going to have some transfers” of stroke patients from one center to another, Dr. Fifi said. “You can't say you are going to do bypassing and expect no transfers.”
M. Shazam Hussain, MD, director of the Cerebrovascular Center at the Cleveland Clinic, said that while it makes sense to say emergency responders should strive to identify patients who probably have LVO and could benefit if they are taken to an EVT center, “what you really want to do is identify whether it's a severe stroke or a not a severe stroke. More severe strokes, regardless of the reason, need to be treated in larger, more equipped centers.”
The Cleveland Clinic, a 12-hospital network, offers EVT at its main campus and three network hospitals, Dr. Hussain said, and some other hospitals in the area offer it as well.
Dr. Hussain said that a downside to adding more EVT centers to improve access in underserved areas is that “you end up diluting the number of patients at each center,” which could affect quality. But the bypass model, has some downsides as well, such as tying up emergency responders, and potentially delaying other critical treatments, such as thrombolysis, he said.
In organizing the ideal design and distribution of stroke care, “so much comes down to regional and local factors,” he said. “Trying to mandate something so broadly across the country would be impossible.”
Dr. Grotta receives consulting fees from Frazer Ltd., which manufactures mobile stroke units, and grant support from Genentech, which markets tPA. Dr. Liebeskind disclosed that he receives consulting fees from Imaging Core Lab for Cerenovus, Genentech, Medtronic, and Stryker. Dr. Fifi had no disclosures.