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Evidence that mobile stroke units (MSUs) could provide better care than standard management by EMS was extended to seven U.S. metropolitan areas in the BEST-MSU study, providing greater impetus to examine their cost-effectiveness in justifying a path to reimbursement.

Stroke patients transported in MSUs suffered significantly less disability measured on a utility-weighted modified Rankin Scale (mRS) at 90 days, the weighting reflecting low patient preference for disability requiring constant care over death. Moreover, patients were more likely to reach mRS 0-1, deemed complete recovery (55.0% vs 44.4%, OR 2.43, P<0.001).

Fully one in three alteplase-eligible patients transported in MSUs got their tissue plasminogen activator (tPA) bolus within the "golden hour" from symptom onset, consistent with other studies on these specialized ambulances.

In comparison, only 3% of eligible stroke patients on standard EMS transportation received tPA as quickly, reported James Grotta, MD, of Memorial Hermann-Texas Medical Center in Houston, during a late-breaking scientific session at the American Stroke Association's International Stroke Conference (ISC).

The proportion of eligible patients getting tPA within 4.5 hours was 97.1% in the MSU group and 79.1% among those receiving standard care (P<0.001).

"On the one hand, that MSUs can enable very early administration of thrombolysis and result in better functional outcomes for stroke patients could be considered neither controversial nor surprising," commented Anthony Kim, MD, MAS, of the University of California San Francisco.

"But on the other hand, these highly anticipated results are inspiring and game-changing nonetheless, and provide a clear imperative to work on implementing MSU programs more broadly," he added.

The biggest barrier to the dissemination of MSUs is convincing CMS and other payers to make pathways for reimbursement. Each MSU in the study was a 12-foot ambulance equipped with a portable CT scanner, a point-of-care laboratory, and telemedicine technology.

Grotta predicted that such an expensive program would be cost-effective in the right regions, though the healthcare resource utilization part of the study is ongoing and will be reported this summer, he said.

"The primary barriers to MSU implementation now will not be uncertainties about clinical impact, but about how to fund the required investments in equipment and personnel necessary to develop viable and sustainable MSU programs where they make sense, since MSUs have largely been funded with research and philanthropy dollars rather than general operating budgets or, more importantly, insurance," Kim noted.

BEST-MSU was conducted with MSU teams meeting EMS on-site at stroke calls and alternating by week, loading each tPA-eligible stroke patient on the MSU or making a note that the person would have qualified but leaving them to standard EMS management. There were 1,515 stroke calls from 2014 to 2020 and 1,047 people deemed tPA eligible and included in the analysis.

The majority of participants were enrolled in Houston. The other sites included Los Angeles, Northern California, New York City, Aurora and Colorado Springs, Memphis, and Indianapolis.

"We have seen a great proliferation of MSUs in the United States and around the world. While each locale is different, I think these results will inspire many more places to launch their own programs," said M. Shazam Hussain, MD, of Cleveland Clinic.

"We launched our MSU in Cleveland very close to the launch of Houston's program and our experience has been very similar. We have shown in our prior publications about [how] great the time to treatment is on MSU, and with the tight link between time and outcome for acute stroke treatment, this is exactly what we had expected," according to Hussain.

Whether MSUs work in rural areas is a lingering question that has not been explored by Grotta and colleagues. During an ISC press conference, he estimated that a catchment area of 350,000-500,000 people would be needed to keep an MSU busy.

"The most important thing is the MSU has to be tailored to the community. It requires a community that is willing to collaborate with EMS agencies. So a balkanization of EMS organizations where you can only treat patients that are managed by one EMS agency, that's going to limit what you can do. Given our positive data, it would behoove EMS agencies and hospitals to work together," said Grotta.

He estimated that for every 100 patients treated on an MSU rather than standard management, 27 will have less final disability and 11 more will be disability-free.

Ultimately, this hinges on prehospital care: patients, caregivers, and bystanders need to recognize the signs of stroke and call 911 immediately, Grotta urged.

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