CINCINNATI—Every 30-minute delay in breaking up a blood clot from a stroke was associated with a 10 percent decrease in the probability of a good outcome, regardless of other factors such as stroke severity, according to new research led by a University of Cincinnati (UC) neurologist.
The study, presented today (Friday, Feb. 8) at the American Heart Association/American Stroke Association’s International Stroke Conference in Honolulu, was authored by Pooja Khatri, MD, director of acute stroke and associate professor of neurology and rehabilitation medicine at UC and a member of the UC Neuroscience Institute, one of four institutes affiliated with the UC College of Medicine and UC Health.
The study was funded by the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health (NIH).
Researchers studied patients who received both intravenous and endovascular therapy and had blood flow restored within seven hours of stroke onset. The patients were part of the Interventional Stroke Management (IMS) III trial, in which intravenous clot-busters and clot-busters plus endovascular therapy were compared, but neither approach proved superior.
Intravenous therapy delivers the clot-busting drug tPA through a vein in the arm and is the only emergency stroke treatment proven to improve outcomes. (UC researchers played a leading role in developing and testing tPA in the late 1980s and mid-1990s.) It must be given within 4.5 hours of symptom onset and has been shown to be time-dependent, with faster start of treatment leading to better recovery.
Endovascular therapy involves inserting a catheter directly into a blocked artery in the brain to deliver clot-busting drugs or use a device to remove the clot. This treatment is usually used after the 4.5-hour time window for intravenous clot-busting therapy has closed or for bigger or more stubborn clots.
Researchers examined data on the 240 IMS III patients who received both intravenous and endovascular therapy and had major clots in brain arteries. Among those patients, blood flow was restored in 182 patients within seven hours of stroke onset. Patients were evaluated for level of disability within 90 days after treatment.
The evaluations confirmed that a good clinical outcome was strongly time-dependent, with each 30-minute delay leading to a 10 percent decrease in the probability of a good outcome. Time proved critical for outcome regardless of other predictive factors, such as absence of a disability prior to stroke, stroke severity at presentation or the results of the patients’ scans before treatment.
"We have effective endovascular treatments for unblocking arteries, but as far as actually making stroke patients clinically better, we need to move a lot faster,” Khatri says. "There’s a window of time that we have during a stroke and if we pass that point, it’s the point of no return in terms of brain damage.
"For endovascular therapy to work, we may need to deliver it more quickly—and that is what future trials will need to test.”
Khatri says delays include patients not recognizing the signs of a stroke, family members driving patients to a hospital instead of calling emergency services (9-1-1), emergency departments being too slow in identifying or evaluating a stroke for treatment and delays in transferring patients to a hospital or facility with expertise in endovascular therapy.
"In the future, we may also be able to use MRI and CT scans to take images of a patient’s brain to identify whose treatment window is closing, those who have a little more time or those with the types of clots most likely to benefit from endovascular therapy. These approaches are under investigation,” she says.
"But even for those with favorable scans, we can’t get away from the fact that the clock is ticking and an acute stroke patient needs to be managed with the highest level of urgency.”