Doctors generally try to treat strokes within six hours of symptoms. Now, researchers say treatments within the first 24 hours can be helpful.

New research is revolutionizing the way doctors approach the most common form of stroke.

This month, the American Heart Association (AHA) released new guidelines that could significantly change the number of patients eligible for life-saving treatment after a stroke.

Two major recent studies reached the conclusion that treating some people who experience a stroke long after the traditional six-hour window has closed may be key to saving and improving lives.

Dr. Edward Yu, director of neuromuscular services of neurology at Staten Island University Hospital in New York, said the studies add to a body of evidence about how long doctors initially have to treat stroke patients.

“It’s very exciting news — basically it shows that intervention for acute stroke care beyond the traditional six hours seems to really help and benefit patients,” he said.

Treating strokes before they permanently damage brain tissue is key in helping minimize disability in patients, or even death.

Strokes kill 140,000 Americans every year. It’s the number one cause of disability for people in the United States.

Here’s a look at how things have changed and what you need to know.

The new guidelines won’t affect all people who experience a stroke.

But they do encompass people who have the most common type of stroke, called an acute ischemic stroke.

This stroke is caused when a blood clot cuts off blood flow to part of the brain, resulting in damage and death of key brain tissue.

A medication called alteplase has been used to treat ischemic strokes since 1996. However, depending on the clot size and duration of stroke symptoms, guidelines around the use of this drug were “very, very rigid,” according to the AHA.

Now these guidelines have been somewhat relaxed, thanks in part to better imaging.

“The way we look at alteplase used to be green and red,” Dr. William J. Powers, guidelines writing group chair and chair of neurology at the University of North Carolina School of Medicine in Chapel Hill, said in a statement. “Green go, red stop. Now we’ve taken some of the reds and made them yellow.”

The AHA recommends using intravenous alteplase up to four and a half hours after symptom onset.

In addition, the AHA now recommends that some patients with large clots or those outside of the alteplase window be treated with a type of clot removal procedure called mechanical thrombectomy up to 24 hours after first showing signs of a stroke.

In this procedure, doctors thread a catheter with a special device that can grab and remove the clot.

The guideline change comes on the heels of the publication of the major DEFUSE 3 study, which was sponsored by the National Institutes of Health and led by Stanford University School of Medicine researchers.

That study found that people who were treated after the traditional six-hour window had better functionality and were more likely to survive to 90 days.

“These astounding results will have an immediate impact in the clinic and will help us save many lives,” Dr. Walter Koroshetz, director of the National Institute of Neurological Disorders and Stroke, said in a statement. “I really cannot overstate the size of this effect.”

For years, doctors have believed that once a person with an ischemic stroke has had symptoms for six hours or more, there’s little reason to remove the clot, because the brain tissue may already be permanently damaged.

However, the recent studies find that treating a stroke even 24 hours after a person had symptoms could significantly help their outcome.

“Removing blood clots from large arteries can mean the difference between stroke survivors being independent versus being dependent on others, which makes a big difference in their quality of life,” Dr. José Biller, a guidelines author and chair of neurology at Loyola University Chicago Stritch School of Medicine in Illinois, said in a statement.

In the study of 182 patients, about half underwent the CT scan and then rapid removal of the clot. The other half underwent traditional stroke treatment.

The Stanford-led study found that 45 percent of patients who underwent the new therapy achieved functional independence after their stroke. For the group that received the standard medical therapy, 17 percent were able to achieve this functional independence.

Additionally, 26 percent of the control group died within 90 days, compared to 14 percent of the treated group.

Another similar study published in the New England Journal of Medicine concluded that treating stroke patients even 24 hours after symptom onset could help them.

That study — which was funded by a manufacturer of clot-removing devices — examined how patients fared when they were treated 6 to 24 hours after exhibiting symptoms.

The researchers found that 49 percent of the 107 patients who had a thrombectomy had more independent functionality, compared to 13 percent of the 99 people in the control group.

“Overall, it’s exciting, it’s definitely significant, and it does help extend the window and extend the treatment for stroke care,” Yu said.

Part of the reason that the people who experienced a stroke could be helped is due to a breakthrough in technology to better identify brain tissue that’s salvageable.

The Stanford-led DEFUSE 3 study used new technology that can fit on a device the size of a phone to save lives.

Dye was used before a patient underwent a CT scan to better determine which brain tissue was dead and which was just damaged. The researchers looked at data from patients, who either had stroke symptoms for longer than six hours or who didn’t know when their symptoms occurred.

This technology can also be a help for people who experience a stroke while asleep or while alone. In those cases, it can be impossible to pinpoint the moment they started to exhibit symptoms.

While treating a stroke quickly is vital to saving a person’s functionality and their life, these newly studied stroke treatments may not be available at all hospitals.

In order to save more lives, the American Heart Association Stroke Council found hospitals should use telemedicine and video consultation so doctors can more quickly prescribe alteplase medication to bust up clots within an hour.

Ideally, the AHA wants half of eligible patients to be treated within 45 minutes with medication.

A consultation with stroke experts can also help identify which patients would benefit from mechanical clot removal. If a hospital doesn’t offer the procedure, a patient could quickly be moved to another hospital in order to undergo the procedure quickly.

“This is going to make a huge, huge difference in stroke care,” said Powers in a statement about the recent study.