Medical Device Daily
Drug-eluting stent (DES) technology is the current state of the art in propping open, and keeping open, coronary and peripheral vessels. But DES doesn't equal the “Holy Grail“ in treating restenosis.
That goal most likely will be achieved with a stent device that, after placement, disappears from the vasculature, leaving in place no material that is foreign to the body.
Details concerning a version of such a stent were unveiled at this week's 17th annual International Symposium on Endovascular Therapy (ISET) in Miami Beach, Florida.
The product is the Lekton Magnesium Bioabsorbable Metal Stent from Biotronik (Berlin/Lake Oswego, Oregon), with Belgian researchers presenting data concerning its use in treating blocked lower leg arteries.
The Lekton is an absorbable bare-metal stent made of an alloy of 90% magnesium — a substance that occurs naturally in the body — and 10% rare earth elements. Bioabsorption of the stent begins in a week to 10 days, and tests have shown the stent is fully absorbed within 60 days, according to Marc Bosiers, MD, lead author of the study presented at ISET.
Typically, about 60% of narrowed below-the-knee arteries treated with standard stents remain open after six months, said Bosiers, head of the department of vascular surgery at A.Z. Sint-Blasius Hospital (Dendermonde, Belgium).
Lekton stents were implanted to treat 20 patients who suffered severely blocked arteries below the knees. Six months after treatment, 15 of 19 arteries (79%) remained open. One patient died of pneumonia unrelated to the procedure.
The stents were completely absorbed into the walls of the vessels without freeing particles into the bloodstream, Bosiers said. The absorption, he said, actually begins with implantation, with the body immediately beginning to cover the stent with a layer of cells.
Bosiers said that the Lekton is the first biosabsorbable metal stent tested in humans. He acknowledged that an absorbable polymer stent has been implanted in humans but said it doesn't appear to be as effective for propping open the arteries as a metal device.
“A stent is really only needed for a couple of weeks, to allow the blood vessel to reshape and get strong, and after that time it is useless,“ Bosiers said. “We believe the absorbable metal stent could be a major breakthrough, because it provides a temporary solution to a temporary problem.“
Koen DeLoose, a co-investigator in the study, told Medical Device Daily that the next step in the group's research is the launch of a randomized study of 120 patients to compare the use of percutaneous intervention alone against the Lekton absorbable metal stent.
“If results are as promising [in the larger study] as our results, at this moment, on our 20 patients,“ it will clearly support commercialization, he said.
DeLoose acknowledged the preliminary nature of the 20-patient study, but said, “at this moment, [the absorbable stent] looks very promising.“
He added: “When in the future it is possible to make a combination drug-eluting/absorbable stent, in my opinion it is the absolute future for small artery treatments.“
While he granted the need for such a stent in larger vessels, such as coronary arteries, he said that “the problem of restenosis is most important in arteries below the knee. The key point is to prove [the Lekton's] value in small-caliber vessels.“
At last October's annual Transcatheter Cardiovascular Therapeutics (TCT) conference in Washington, Biotronik released preliminary positive data for the Lekton in treating blocked coronary arteries in a 65-patient trial, reporting 50% absorption of the stent in all patients after three weeks. Study results should be released sometime this year, with larger studies to be launched in both U.S. and Europe also this year, Biotronik said at the TCT gathering (Medical Device Daily, Oct. 4, 2004).
In another study presented at ISET:
• Endologix (Irvine, California) reported clinical data suggesting that three years following treatment of abdominal aortic aneurysm (AAA) with the company's Powerlink System, patients from a premarket application study experienced decreases in aneurysm sac diameter and volume, and less angulation of the aorta.
The paper, “Sac Remodeling with the Powerlink Stent Graft for AAA,“ was presented by Rodney White, MD, professor of vascular surgery at Harbor-UCLA Medical Center (Torrance, California).
“These results are based on our retrospective study that investigated changes in aneurysm sac anatomy, including maximum diameter of the aneurysm, volume of the aneurysm sac, length from the renal arteries to the aortic bifurcation and angulation of the abdominal aorta, during a three-year period in patients treated with a Powerlink System,“ said White. “The design features of the Powerlink device, including its long main body, and single wire stent cage that provide for column strength, may positively influence the aortic sac remodeling that we found during this study.“
Endologix received approval last October to market the Powerlink in the U.S. Paul McCormick, president and CEO of Endologix, said, “In spite of the success of minimally invasive treatment of AAA, there remain 50,000 to 60,000 patients who still undergo the traditional surgery, many due to concerns about the long-term results of the stent graft procedure itself. With our Powerlink System, we are addressing the failings of first-generation endoluminal stent grafts in deliverability of the device, dependability of the clinical results and durability of the materials.“
He added: “If the data demonstrates that the Powerlink design induces this favorable remodeling, it may provide greater long-term benefit for the therapy permitting it to be applied to a larger patient population. Based on its design benefits, we are working to make the Powerlink System the standard of care.“