updated 10/24/2006 7:28:03 PM ET 2006-10-24T23:28:03

Scientists are developing a novel way to prop open clogged heart arteries: using a stent designed to dissolve once it finishes the job.

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Heart stents are tiny metal-mesh tubes that have been implanted in millions of people worldwide to hold arteries open after doctors push back the fatty deposits clogging them.

Stents are credited with preventing heart attacks while avoiding open-heart surgery. But they’re at the center of a heated controversy because doctors recently discovered that the most popular type, drug-coated ones, sometimes cause potentially fatal blood clots months or years after they’re inserted.

So a stent that could help an artery heal and then dissolve would be “a major milestone,” said Dr. John Ormiston of Auckland, New Zealand. He announced Tuesday that the first human experiment with just such a device is under way in his hospital and a few others in Europe.

Only 26 patients have been implanted in a study designed to test whether the new type of stent, made by Abbott Laboratories, is safe enough to be tried in larger experiments. Thirty days after receiving the device, all patients are faring well so far, Ormiston told a meeting of cardiologists.

Stent dissolves in about two years
It’s called a bio-absorbable stent, made of the same kind of material as certain dissolvable stitches but designed to last longer.

Animal studies suggest the body completes its breakdown of the device in about two years.

Here’s the issue: When a heart artery is clogged enough to risk a heart attack, doctors frequently use a balloon to push back the plaque so blood can flow freely again. Stents then are inserted to keep the newly widened artery from collapsing, and drug-coated ones prevent scar tissue from reclogging it.

But stents don’t need to be permanent, Ormiston contended. If an artery stays open for six months after being unclogged, it’s essentially healed, he said.

Test yourself“There’s not much sense in a permanent implant for a temporary problem,” he said. “I think patients like the concept of a device that goes away.”

The new absorbable stent is coated with a drug, just like today’s most-used versions, to prevent the reclogging. After the drug has permeated the artery walls, the stent should start dissolving.

In the spring, Ormiston is scheduled to announce how the first patients fared at that critical six-month time period, the first hint of whether the approach might really work.

His announcement came as cardiologists vehemently debated just how big a problem the blood-clot risk is for today’s devices. It apparently occurs because the drug coating allows the stent’s metal parts to remain exposed, acting as a clot magnet, instead of gradually being overgrown with a thin layer of cells.

The risk seems very rare, occurring in about one of every 500 or so patients, Harvard Medical School’s Dr. Donald Cutlip said at Tuesday’s meeting of cardiologists who specialize in stenting.

But given that about 6 million people worldwide have the drug-coated devices, critics say that could translate into thousands of heart attacks or deaths. The Food and Drug Administration will assess the risk, and how it compares to older bare-metal stents that have their own side effects, at a meeting in early December.

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