Clinical trial eyes dissolving coronary stents
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Medical investigators on Long Island and beyond have embarked on a clinical trial to determine if a coronary stent that slowly dissolves into a vessel can effectively protect the heart and enhance the free flow of blood.
Stenting has led to the expansion of cardiology departments in the nation's hospitals over the past two decades. More than 500,000 conventional stents are implanted annually. Former President George W. Bush received one in a procedure last month when a blockage was found in a coronary artery.
Conventional stents are tiny, metallic, mesh-like scaffolds that prop open vessels encumbered by biological goo -- plaque, dead cells and clotted blood -- that can lead to a heart attack or stroke. The new one under study is made of a disappearing, biodegradable polymer that leaves behind no traces of its existence other than an opened and possibly more pliable vessel.
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"Unlike metallic stents that stay within the vessels permanently, this stent completely dissolves within about two years after implantation," said Dr. Luis Gruberg, a professor of medicine at Stony Brook University School of Medicine and director of interventional cardiology research.
The new stent's ability to vanish over time, doctors say, is as close as science comes to magic.
Being free of a permanent implant allows a vessel the possibility to regain some of its natural flexibility. At the same time, the medication impregnated in the dissolving stent helps prevent re-clogging.
Gruberg said if the Food and Drug Administration approves the new stent, patients will have an option that frees them from having a lifelong implant.
The device is implanted via a balloon-tipped catheter, as are conventional stents. The catheter is threaded through a blood vessel in the groin to reach the blockage. When the balloon is inflated, the stent expands and is locked in place.
Stony Brook is one of four sites on Long Island and five in New York City participating in the nationwide ABSORB III clinical trial. The device was developed by California-based Abbott Vascular, a division of pharmaceutical giant Abbott Laboratories, which is based in Illinois.
The study is a randomized, controlled, double-blind trial, which means some patients will receive a conventional stent, while others are implanted with a dissolving one. It's expected that more than 2,000 patients will be tested.
Stents of any kind, doctors say, are most effectively used in patients suffering heart attacks or severe coronary artery blockage.
Many cardiologists are looking forward to the new stent.
"It's a game-changer," said Dr. Samin Sharma, director of clinical and interventional cardiology at The Mount Sinai Medical Center in Manhattan, which is also participating in the trial.
Optimistic on approval
Sharma predicts the stent will transform the way heart attacks and severe coronary blockages will be treated within the next few years. He said the device could be approved in the United States by 2015.
"We expect to enroll up to 50 patients into this trial within the next six to seven months," Sharma said.
Sharma, who also sees heart patients in India, said he has already implanted Abbott's stent in dozens of patients there, where the device is approved.
Richard Rapoza, an Abbott vice president, said the device has a long and storied past, having been under development since the early 2000s.
He calls the stent a flexible artery-support scaffold made of a naturally dissolvable material called a polylactide. The chemical compound is nearly identical to that used in biodegradable sutures and absorbable bone screws.
One goal of the study, Rapoza said, is to determine if a vessel regains some of its flexibility and motion once the stent dissolves. Going into the trial, scientists are theorizing that a treated vessel can reclaim some of that flexibility as it copes with bloodstream turbulence once the stent is gone.
Dr. Richard Shlofmitz, chairman of cardiology at St. Francis Hospital, said he is cautiously optimistic about the future of biodegradable stents.
"The concept is very innovative," he said. "But in medicine one has to have some restraint and not get too excited about new studies and techniques."
The device, which is technically known as a bioresorbable vascular scaffold, is the first to be tested in the United States, but not the first to be studied globally. Last year, scientists in Japan reported 10-year results for another dissolvable device called the Igaki-Tamai stent.
The Japanese device, which is made of a cornstarch compound, completely dissolved into the artery wall and left behind no permanent foreign material, reducing the likelihood of an in-stent blood clot -- which can cause a heart attack or stroke.
Developments involving absorbable stents come as a scathing report surfaced late last month, accusing some doctors of unnecessarily implanting conventional stents.
Dr. Ralph Brandis, president of the American College of Cardiology, said the report unduly tarnished an entire field of medicine without regard to the giant advances both stenting and coronary bypass surgery have made in saving patients' lives.