Mechanical Thrombectomy Outcomes May Be Worse at Low-Volume Stroke Centers

HONOLULU, HI—The number of centers delivering endovascular therapy for acute ischemic stroke is growing, with an increasing number of procedures performed at lower-volume hospitals. Now, new data show that patients treated at these lower-volume centers may have worse outcomes, at least in the short term.

The likelihood of having a good outcome—defined as being discharged home or to an acute rehabilitation facility—was greater for patients treated at centers performing a higher number of mechanical thrombectomy procedures each year, both in Florida (OR per 10 additional procedures 1.1; 95% CI 1.1-1.2) and in the broader US population (OR 1.3; 95% CI 1.2-1.4), Sunil Sheth, MD (UT Health McGovern School of Medicine, Houston, TX), reported here at the International Stroke Conference.

Acknowledging some limitations of the study, including the lack of information on some hospital and patient-specific factors that can influence outcomes of strokes caused by large-vessel occlusions and the use of discharge disposition as an outcome measure, Sheth said that “the findings support the idea that the results of the recent thrombectomy trials may not be generalizable to every clinical setting.”

Challenges in Expanding Access

The study, published simultaneously online in Stroke, with lead author Hamidreza Saber, MD (Wayne State University School of Medicine, Detroit, MI), highlights the difficulty in determining the best way to organize stroke systems of care to accommodate increased demand for endovascular therapy following the publication of several trials in recent years supporting the safety and efficacy of the treatment.

“With the wave of clinical trials that came out in the last few years, endovascular therapy has really changed the way that we approach acute ischemic stroke care,” Sheth said.  “But this has caused a real challenge to stroke systems around the country and really around the world, and that challenge is: how do we make sure that everyone has access to this treatment and gets the appropriate screening and testing for it? And more specifically, how do you structure those systems of care so that this can happen?”

Several options have been proposed, including a hub-and-spoke model directing patients to comprehensive stroke centers; a trip-and-treat model that brings physicians capable of performing mechanical thrombectomy to community hospitals; establishment of thrombectomy-capable centers that can perform endovascular therapy without being constrained by the requirements of a comprehensive stroke center; and use of mobile stroke units to help with prehospital triage. There has also been some talk about allowing interventional cardiologists to perform the procedures to fill the gap, although the stroke community has largely resisted that approach.

Sheth said a few issues need to be considered when thinking about what’s best. On the one hand, endovascular therapy was shown to be superior to medical therapy alone when performed at high-volume, tertiary care centers with advanced neuroimaging, neurosurgery, neurological intensive care, and nursing. On the other hand, any delay in treatment worsens a patient’s outlook.

“So there’s a push to disseminate these treatments out to the community into local hospitals where patients may get treated faster,” Sheth said.

Better Outcomes at Higher-Volume Centers

The current study was designed to explore how endovascular therapy has expanded in response to the positive trials and whether there are differences in outcomes between centers with lower versus higher procedural volumes.

The investigators delved into Florida state databases on discharges from hospitals and emergency rooms and into the National Inpatient Sample to identify patients with acute ischemic stroke who were treated with endovascular therapy. The analysis included 3,890 patients treated in Florida between 2006 and 2016 and 42,505 patients treated across the United States between 2012 and 2016.

In Florida and nationwide, the number of procedures performed increased over time, with a large jump in 2015 followed by a plateau. There were also increases in the number of hospitals performing mechanical thrombectomy and in the number of procedures performed at centers with lower volumes. Looking at the Florida data, for example, roughly 87% of procedures were performed at the eight highest-volume centers in 2008, but that proportion fell to 45% by 2016. At the end of the study period, about one-quarter of procedures were done at centers with an annual volume of less than 20.

The association between a greater likelihood of a good outcome at discharge and higher annual volumes remained after adjustment for several potential confounders, including age, sex, race, Charlson index, use of IV thrombolytics, and annual hospital stroke volume.

In a secondary analysis, lower annual volume was also associated with a greater likelihood of dying in the hospital, both in Florida and nationally.

“While improved endovascular stroke therapy outcomes at higher-volume centers are logical and consistent with prior studies . . . , these findings should not be extrapolated to imply that all stroke systems of care should focus on concentrating endovascular stroke therapy treatments at only a few high-volume centers rather than disseminating [the] treatments more widely. In some regions, distance, cost, and time make such transfers impractical,” the authors say.

“Further, although our analyses attempted to control for important variables affecting outcome, patients receiving [treatment] at lower-volume community hospitals may differ in important ways from those at higher-volume centers, and in ways for which we are unable to adjust,” Sheth et al caution. “As such, further data are needed to address this issue.”

Building Better Systems of Care

In a question-and-answer session after his presentation, Sheth reflected on the uncertainty about how best to organize systems to expand access to endovascular stroke therapy.

“In terms of how to build better systems of care, I think that’s a really tough question, and I think it depends on a lot of things, not least of which are the local geographies,” Sheth said. “Florida and many of the states that we looked at in the nationwide database are a mix of urban and rural populations, and some centers may be the only [one] for miles and miles for these patients. So I think the question of should these procedures be done at lower-volume centers is an open one and in many settings, if that is the best that they have, then that may be the right way to do it.”

Asked about the best strategy to make endovascular therapy available to more of the population, Philip Meyers, MD (NewYork-Presbyterian /Columbia University Irving Medical Center, New York), said he didn’t have the answer.

“It’s become a big political issue as well as a social and human welfare issue, so I don’t know how it’s going to turn out,” he told TCTMD. Meyers said he had initially hoped that a system of comprehensive stroke centers akin to what has been developed for trauma care would be rolled out, but that hasn’t transpired as different physician groups continue the debate.

“I think the data ultimately support that thrombectomy done sooner is better if you can get that done at a quality place,” Meyers said. “So then it depends on what is quality? How do you define it? Should somebody be sent a long way to a better center, or should they be treated locally? And those are very difficult questions to answer.”

It appears that there is now an acceptance of the need to allow hospitals that don’t meet the requirements of comprehensive stroke centers to perform endovascular therapy, as the Joint Commission, in collaboration with the American Heart Association/American Stroke Association (AHA/ASA), has developed a new certification for “thrombectomy-capable” stroke centers. Of note, there is a volume threshold listed in the requirements for this designation: performance of mechanical thrombectomy and postprocedural care for at least 15 patients in the past 12 months or at least 30 over the past 2 years.

“There is a need for thrombectomy capability in places where it’s not otherwise available, and you can’t blanket the US with comprehensive stroke centers, so if it’s possible to have these procedures performed and then the patients cared for in a quality manner so that outcomes are good for stroke patients treated at smaller, noncomprehensive stroke centers, then I think it’s a good thing,” Meyers said. “But I think these kinds of data speak to the need for ongoing monitoring.”

AHA/ASA spokesperson Karen Furie, MD (Lifespan, Providence, RI), agreed. The thrombectomy-capable designation “could be a strategy to enable centers in other parts of the country that may not have all of the components of a comprehensive stroke center but are able to perform mechanical thrombectomy with adequate quality to allow patients access to that,” Furie said, adding that such an approach may be more relevant for patients in rural areas.

But, Furie said, the field should keep an eye on outcomes as access continues to be expanded.

“While it’s incredibly exciting that we have such an effective treatment, there still needs to be consideration of whether in the real world the same results are achievable at all hospitals capable of doing the procedure,” she told TCTMD. “And so, further monitoring, certification, perhaps mandatory reporting of outcomes, those are all things that should be under consideration moving forward to ensure that patients are getting the same high-quality care that they received in the clinical trials.”