Grabbing and removing a clot blocking blood flow to the brain, rather than just administering clot-busting drugs, dramatically improves the likelihood that patients will recover from a stroke, according to two highly-anticipated studies released on Wednesday.

The larger of the studies found that the procedure nearly halved the death rate from stroke.

Because three previous studies had failed to show a benefit from procedures employing clot-removing devices, the latest research should renew interest in the devices and are likely to change stroke treatment, experts said.

The two studies used devices made by Covidien, which was acquired by Medtronic PLC last month and helped pay for one of the trials. Stryker Corp and privately-held Penumbra Inc also manufacture devices approved for clot removal.

The research echoes a large Dutch study published in December, called MR CLEAN, that also found a benefit from fishing a clot out of an artery. Taken together, they offer "a really persuasive signal that we're on to something," said Dr. Patrick Lyden, director of the Stroke Program at Cedars-Sinai Medical Center in Los Angeles, who was not involved in the studies.

Lyden, who helped develop clot-busting drugs, said he had been skeptical of the devices, but called the latest results "tremendous," adding, "it's a whole new world for us. Medical centers are going to have to gear up and be able to do this treatment quickly."

The two studies were reported at the American Heart Association/American Stroke Association International Stroke Conference in Nashville and released in summary form by the New England Journal of Medicine.

In one trial, called ESCAPE and conducted at 22 centers worldwide, 53 percent of 120 patients who had clot removal via a tube fed into a blood vessel of the brain were functionally independent 90 days later. Of the 118 who received only the standard clot-busting drug, 29 percent were.

While 19 percent of patients receiving drugs alone died within three months, only 10.4 percent of those whose clots were removed died.

The second study, called EXTEND-IA and based in Australia, found that 24 hours after treatment all of the oxygen-starved brain tissue in 35 patients whose clot was removed was getting blood again. That compared to 37 percent of the tissue in patients receiving only the clot-busting drug alteplase.

After three months, 71 percent of the clot-removal group had achieved functional independence compared to 40 percent given conventional care.

Both trials were stopped early because the benefits of extracting the clot were so pronounced.

One reason the results were better than previous ones was that doctors were selective in whom they tried the procedure on, said Dr. Michael Hill of Canada's University of Calgary, who led ESCAPE.

In particular, scans had to identify the blocked artery so physicians knew where to find the clot, and patients needed to have "collateral circulation," or some blood flow bypassing the clot.

Without collateral circulation, Hill said, "the brain dies very quickly, even in 15 minutes. You can't save those people."

Another possible reason for success was speed: many of the clots were removed within 84 minutes, an hour faster than in trials that failed to show a benefit.