It’s another case of a beautiful idea colliding with some ugly facts.
The beautiful idea is the notion that clearing the blocked artery of a stroke patient with a device snaked right up to the blockage would salvage threatened brain cells and prevent a lot of disability.
A lot of stroke patients in the U.S. are already getting this endovascular (within-the-artery) treatment because the Food and Drug Administration approved the devices without clinical proof that they work. Medicare has begun paying for the treatment.
But now come those ugly facts. Three studies have now found no difference in outcome between patients who got the endovascular treatment along with an intravenous dose of a clot-busting drug called tPA, or Alteplase, and other patients who got only tPA.
“There wasn’t really clear evidence that endovascular therapy added to tPA … was better overall than tPA as the standard treatment,” Dr. Joseph Broderick told MedPage Today. “It was hard to detect a signal of benefit in the studies that were presented.”
Broderick, who led the largest of the three studies, was referring to disappointing results presented this week at the International Stroke Conference in Honolulu. He’s research director of the neurological institute at the University of Cincinnati.
Stroke specialists will be chewing on the findings for months and perhaps years to come. But the first guess about why the artery-clearing devices didn’t improve outcomes is that patients didn’t get the treatments in time.
After all, the endovascular procedure can’t be started until after intravenous tPA is tried first, and that can be as long as four-and-a-half hours after the first symptoms of stroke.
“Even a one-hour delay in the time to treatment negates the benefit” of a higher rate of artery clearance, Dr. Mark Chimowitz of the Medical University of South Carolina notes in an editorial accompanying online publication of the three studies in the New England Journal of Medicine.
Chimowitz was referring to an Italian study of 362 stroke patients called SYNTHESIS Expansion.
Dr. Brian Silver of the Rhode Island Hospital Stroke Center agrees that the disappointing outcomes were probably due to the passage of too much time. “It’s not sufficient to just open up the (blood) vessel, it has to be done early on,” Silver says in an interview with MedPage Today.
There was a hint in Broderick’s study, called IMS-III, that outcomes might be better if tPA can be started within two hours of stroke onset and endovascular treatment within 90 minutes of that.
But that kind of speed is almost impossible to achieve consistently in the real world. It takes time to gather the specialized personnel needed to do the fancy imaging tests and then perform the delicate endovascular procedure safely. Not to mention that many stroke patients aren’t lucky enough to live close to a center that can muster the effort quickly.
Speaking of fancy imaging, a third study, nicknamed MR RESCUE, tested whether CT or MRI scans could identify patients most likely to benefit from endovascular treatment, based on the amount of brain tissue at risk from the blockage but not yet dead. Many of these patients have large blood clots in a major artery of the brain, and tPA doesn’t always dissolve these blockages.
But alas, even patients who seemed to have the most favorable scans “had the same level of disability at 90 days, whether or not they had undergone the clot-removal procedure or had received standard therapy,” says the National Institute of Neurological Disorder and Stroke, which funded the MR RESCUE study.
So what’s next? Given the enormous toll of strokes, there will be more studies to figure out how to improve outcomes for patients who aren’t being rescued with tPA alone. Some will involve new clot-busting drugs and devices.
But Broderick tells MedPage Today that some of these studies “are not paying enough attention to how quickly the therapy is delivered.” And none is big enough by itself to provide good answers.
And many worry that it will be difficult to recruit stroke patients (and their doctors) into studies that randomly assign them to receive tPA alone or in combination with endovascular treatment. That’s because the endovascular devices are so widely used.
Maybe, Chimowitz says, Medicare will have to declare a moratorium on paying for endoscular therapy until “these urgently needed trials” are carried out. That ought to stir up some lively debate.