New guidelines released Wednesday significantly expand the number of people eligible for lifesaving treatment after an ischemic stroke, which happens when a clot blocks blood flow to the brain.

In the past, surgery to remove a clot—known as thrombectomy—could only be performed within 6 hours. Now, many stroke victims will be able to get this procedure up to 24 hours after a stroke. In addition, clot-busting drugs may now be used for even mild strokes.

These new guidelines, issued by the American Heart Association and the American Stroke Association and published online Jan. 24 in the journal Stroke, will give more people the opportunity to make a full recovery, says Peter Panagos, M.D., the director of neurovascular emergencies and a professor of emergency medicine and neurology at the Washington University School of Medicine in St. Louis.

“The number one reason [we couldn’t offer stroke treatment] was that patients arrived [at the hospital] too late,” he says. “These are people with devastating strokes, and historically, we’ve had nothing to offer them.”

Stroke is the fifth most frequent cause of death in the U.S., according to the Centers for Disease Control and Prevention (CDC) and a leading cause of long-term disability, commonly leaving survivors with damage to the brain that can interfere with walking, eating, and/or speaking.

According to the American Heart Association, every 40 seconds, someone in the U.S. has a stroke, and every 4 minutes, someone dies from one.

Here’s what you need to know about the new rules, which are based on findings from more than 400 studies, as well as why they changed and what it means for consumers. 

Getting Treatment in Time

Ischemic strokes (which make up 87 percent of all strokes) occur when a clot forms in an artery that delivers blood to the brain. The clot deprives the brain of oxygen, which can damage or kill affected brain cells within minutes. Because this blockage continues to inflict damage as long as it's cutting off the brain’s oxygen supply, it’s vital to administer treatment that can dissolve the clot and restore blood flow as quickly as possible.

Because stroke patients are encouraged to call 9-1-1 right away, a 6-hour window—the limit for clot-removal surgery until today—may seem like plenty of time to seek help, but it often is not: People must recognize symptoms, get to the hospital, and be screened, diagnosed, and sometimes transferred to a larger hospital before treatment can begin.

In the new guidelines, the most important shift may be for people with a blockage in a major artery leading to the brain. These patients can often benefit from a thrombectomy, a surgical procedure in which doctors use a small tool to grab the clot and remove it. Now, they have the chance to receive this potentially life-altering procedure up to 24 hours after a stroke.

Thrombectomy was previously performed only within 6 hours of a stroke because there was not sufficient evidence to suggest it would be effective after that. But studies reviewed for the new guidelines showed that the procedure not only works long after the 6-hour window has passed but also may significantly increase the chance of recovery with little to no negative effects.

“These are not people who would recover and do well on their own—these are people with very bad, disabling strokes,” says William J. Powers, M.D., chair of the department of neurology at the University of North Carolina–Chapel Hill and of the large expert committee that developed the new guidelines. The shift, he says, represents “a major advance in our ability to treat people.”

The second major change in the guidelines extends the use of the clot-busting drug alteplase (tPA)—a first-line treatment for stroke given intravenously—to people suffering even mild strokes. Because tPA carries a risk of brain bleeding, it was not previously recommended for those with minor symptoms. But without treatment, “not all mild strokes get better,” says Powers. “Some of them get worse.”

Treating what appears to be a minor stroke early can help prevent any further deterioration, says Karen Furie, M.D., the chair of neurology at the Alpert Medical School of Brown University. 

New Guideline Winners

Three types of patients are expected to benefit most from the new 24-hour window for thrombectomy, Panagos says:

1) People who have strokes in their sleep, not noticing the symptoms until they wake up. When they arrive at the hospital, doctors count the hours from the last moment they are certain they were well, and assume the stroke began right after that. This put most in this group well outside the old treatment window.

2) Those who are incapacitated after a stroke and are unable to call for help right away. “You can’t control when you are found,” says Sarah Y. Song, M.D., M.P.H., an assistant professor of neurology at Rush University Medical Center in Chicago—but now even those found hours after a major stroke may be eligible for treatment.

3) Those who live far away from a hospital equipped to perform a thrombectomy, or who fail to recognize stroke symptoms in a timely way. The first group includes many people in rural areas, who may need to be assessed at their community hospital and then transferred to a large academic medical center.

Doctors will still have to use CT angiography and other advanced imaging to assess whether a thrombectomy will help a patient—especially one who is admitted many hours after a stroke occurs.  

What Consumers Must Know

“This is truly exciting news and will offer benefit to people who would not have been eligible for such treatments in the past. But it’s not a reason to delay care,” says Orly Avitzur, M.D., a neurologist and Consumer Reports’ medical director. “The advice we’ve always given still holds: If you suspect symptoms of a stroke, call 9-1-1 right away, so you can get to the emergency room quickly.”

The American Heart Association encourages everyone to be on the lookout for three signs of stroke: face drooping (lopsided smile, droopiness, or numbness on one side), arm weakness (does one arm drift down when you try to lift it?), or speech difficulty (slurring words or inability to speak). Any one of these should prompt an immediate call to 9-1-1.

Experts emphasize that in cases of suspected stroke, you should never drive yourself or someone else to the hospital—EMTs will know the best hospital for a stroke patient, and people who arrive at the hospital by ambulance get seen, evaluated, and treated more quickly. And even with the new guidelines, when it comes to stroke, those minutes count.