Using advanced imaging technology, doctors may have substantially longer than the established six-hour window to treat stroke victims via a clot removal procedure, according to a new study that spurred the American Heart Association/American Stroke Association to revamp its stroke guidelines Wednesday.
Stoke prevalence, treatment in the United States
According to the Washington Post, stroke is the fifth-leading cause of death the United States. Each year, about 750,000 to 800,000 U.S. residents experience a stroke. In 2016, stroke led to 142,142 deaths.
Most strokes are ischemic, meaning they involve a clot or a mass in a blood vessel that blocks the supply of blood to part of the brain, potentially killing brain cells. Under established care guidelines, doctors have been treating stroke with clot-dissolving medication within the first few hours and have been removing blood colts—using devices such as stents—within six hours to save tissue that is threatened, but not yet dead, because of the lack of blood flow.
The study, published Wednesday in the New England Journal of Medicine, was called DEFUSE 3, funded by National Institute of Neurological Disorders and Stroke (NINDS), and conducted by researchers at Stanford University. It involved 182 patients at 38 medical centers. Patients had suffered the form of blockage in brain arteries that cause 50% to 60% of deaths and most significant disabilities, according to the Post.
About half of the study population was given blood pressure medication, blood thinners, and other medical interventions that make up typical care. The rest received typical care but also had images taken via an advanced imaging technology developed at Stanford and underwent a clot removal procedure called a thrombectomy. According to NBC News, the advanced imaging technology enabled physicians to assess CT and MRI scans to identify potentially salvageable tissue by examining areas of blood flow in the brain.
The researchers found that using the advanced imaging technology, the window doctors have for thrombectomy, beginning when symptoms start, can expand from six hours to up to 16 hours.
Specifically, the study found that the 90-day mortality rate was 14% among the patients in the thrombectomy group compared with 26% among those in the control group. In addition, 45% of those in the thrombectomy group were able to resume "functional independence" and did not experience severe disabilities. Meanwhile, the rate of severe side effects was comparable between the two groups, at 43% for the thrombectomy patients and 53% for the control group, according to the study.
Gregory Albers, director of the Stanford Stroke Center and lead author of the new study, said the imaging technology is key. Using the imaging, doctors were able to identify patients thought to have salvable tissue as long as 16 hours after stroke symptoms began. "We now know that it's not so much the amount of time elapsed since a stroke began, as the amount of remaining at-risk but salvageable brain tissue that determines who will benefit from stroke therapy," Albers said.
According to the New York Times, the new findings are particularly significant for cases when patients have a stroke while asleep—meaning they don't know when the event occurred—and for patients who must travel far to reach a medical center that can remove the clot.
The new study expands on the findings of the DAWN study, also published in the New England Journal of Medicine, which found that doctors could have up to 24 hours after a stroke occurs to intervene. The DAWN study was funded by a manufacturer of clot-removing devices.
The new study—as well as the earlier DAWN study—were ended early so that the findings could be shared with physicians, the Post reports.
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"The big news is that we were all wrong in how we were thinking about how strokes evolve," Albers said. "We are quadrupling the stroke treatment window today. … It's going to have a massive impact on how stroke is triaged and assessed."
That said, Albers noted that the findings should not be taken to lessen the sense of urgency in getting treatment for a stroke patient. He said clot-dissolving drugs—the first line of therapy—need to be given within four and a half hours of the onset of symptoms. "It's important to get both treatments," Albers said. "Clot-busting drugs are much better for smaller clots. Thrombectomy is for the bigger ones."
NINDS Director Walter Koroshetz in a release said, "These striking results will have an immediate impact and save people from life-long disability or death. I really cannot overstate the size of this effect."
AHA/ASA update guidelines
For the first time in five years, the American Heart Association/American Stroke Association on Wednesday announced new treatment guidelines for acute ischemic stroke patients that extend the timeframe for thrombectomies to up to 24 hours in certain cases.
The update also expands the population eligible for clot-busting medication, called alteplase, to include those who've had mild strokes, as well as those who have had a recent surgery or spinal tap. "The way we look at alteplase used to be green and red," William Powers, chair of the guidelines writing group and the chair of neurology at the University of North Carolina School of Medicine. "Green go, red stop. Now we've taken some of the reds and made them yellow."
In addition, the guidelines advice hospitals without stroke experts to use teleconferences to ensure alteplase can be quickly prescribed and that patients qualifying for thrombectomies can be more quickly identified (Bernstein, Washington Post 1/24; Grady, New York Times, 1/24; Emery, Reuters, 1/24; NIND release, 1/24; Charles, NBC News, 1/24; American Heart Association News, 1/24).
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Madhavi Kasinadhuni, Senior Consultant, and Jackie Kimmell, Analyst
The new guidelines will significantly impact all stroke programs. By expanding the time window for key stroke treatments, providers will need to prepare for greater volumes of surgical and transfer candidates.
For providers that already have the capability, this will considerably expand the patient population eligible for endovascular stroke surgery. With the previous guidelines, even the most advanced stroke centers performed just a few hundred surgeries a year since many patients—around 87-95% of all patients with ischemic stroke—could not receive treatment. The shorter window particularly affected treatment for those who had a stroke in their sleep and did not wake up before the six-hour window, or who could not be transferred to an appropriate facility quickly enough. With this expanded window, hospitals offering this treatment should prepare for greater volumes by ensuring continual specialist availability and making sure that the necessary surgical equipment, such as a biplane angiography suite, are continually available and not being used by other types of patients.
For all hospitals, the new guidelines offer even more aggressive targets for how quickly patients should be treated. The guidelines suggest a 20-minute time limit for performing brain imaging after patient arrival and suggest a 45-minute door-to-needle goal for providing patients with intravenous tissue plasminogen activator, IV-tPA. To achieve these goals, all hospitals should develop or critically evaluate their stroke protocols to limit the length of time between each step of the stroke pathway—from the moment the patient enters the hospital to their treatment and, if necessary, to their transfer to another facility. The guidelines also encourage hospitals without the necessary specialists to consider joining a stroke or telestroke network that can connect patients with nearby, or virtual, providers for evaluation.
The new guidelines also expand the recommended patient population eligible for IV-tPA from just those experiencing major strokes to all patients, even those experiencing minor strokes. This expansion will also increase the patient population eligible for non-surgical stroke care, which presents more opportunity for smaller hospitals, who may not have the staff or equipment to offer endovascular surgery, to help stroke patients.
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