updated 9/29/2004 7:11:54 PM ET 2004-09-29T23:11:54

A tiny tent-like device implanted into the heart appears to block strokes caused by a common irregular heartbeat, sealing off a spot where dangerous blood clots form, German and U.S. researchers reported Wednesday.

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While more research is needed, stroke specialists said the implant could offer long-needed protection for thousands of patients with atrial fibrillation.

In early stage testing of 111 patients at very high risk of a stroke, the PLAATO device cut that risk by two-thirds, Dr. Yves Bayard of the CardioVascular Center in Frankfurt, Germany, told an international meeting of cardiovascular researchers in Washington.

These were “the worst imaginable patients,” yet the early signs of stroke protection “are overwhelming,” added Dr. Paul Kramer of Shawnee Mission, Kan., who helped lead the U.S. half of that study.

About 2.5 million Americans have atrial fibrillation, a type of irregular heartbeat most common among the elderly and on the rise as the population ages. It occurs when the top chambers of the heart, called the atria, speed up so fast that instead of pumping blood they quiver — literally looking like a bag of worms.

With each episode, blood can pool inside the heart and form clots that pose a risk of a major stroke. Some 15 percent of the nation’s 700,000 annual strokes are caused by atrial fibrillation.

The blood thinner warfarin can significantly lower that risk. But it is so hard to use, because of side effects and dosing difficulty, that many patients cannot take it.

The PLAATO device is “a new way of almost curing the problem,” said Dr. Mark Alberts, a neurologist at Chicago’s Northwestern Memorial Hospital and American Stroke Association spokesman who is watching the implant research.

How strokes happenIt is complicated to implant, Alberts said. But, he said, “It’s a viable option for patients who, for one reason or another, cannot take warfarin.”

In atrial fibrillation, 90 percent of stroke-causing blood clots form in a thumb-sized flap that hangs off the edge of the left atrium. This flap, called the left atrial appendage, serves no biological purpose. It is a leftover from fetal development, sort of a belly button of the heart.

PLAATO is a little metal cage covered with Gore-Tex that opens and closes. Doctors thread the closed cage into the left atrium and then expand it to cover the flap opening — almost like popping open a tent. Tiny hooks hold it in place until, in a few months, tissue grows over it to permanently seal the opening.

Among the first 111 patients implanted — 64 of them Americans — just two European patients suffered strokes within a year, Bayard said. That is far below the 5.5 percent of strokes expected in that patient population.

Researchers now are tracking an additional 92 newly implanted patients in Europe.

Those first studies were designed only to test whether the implant could be performed safely, so the stroke protection finding was something of a surprise. Manufacturer ev3 Inc. of Plymouth, Minn., hopes to begin a bigger U.S. study of the device’s effectiveness next year.

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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