Magnesium Stent Gradually Absorbed by Blood Vessels; Longer Studies Needed
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Reviewed By Louise Chang, MD
May 31, 2007 -- Researchers report promising results from a preliminary study of a new, biodegradable heart stent.
The stent, made of magnesium, widens blocked or narrowed heart arteries and then fades away within a few months.
The coronary arteries supply blood to heart muscle. Blocked or narrowed coronary arteries make heart attacks more likely. Heart disease is the No. 1 cause of death for U.S. men and women.
Other types of heart stents are in use, but they have issues that the biodegradable stent is designed to avoid, researchers report in The Lancet.
But it's too soon to count on the biodegradable stent as the latest, greatest treatment for people with heart disease, states an editorial also published in The Lancet.
Stents are tiny mesh tubes. Doctors insert them into blocked or narrowed coronary arteries to hold those arteries open.
Some stents are made of bare metal. Other stents are coated with drugs that release over time.
Permanent stents can have complications. Bare metal stents can get clogged. Drug-coated stents are designed to help avoid that problem, but recent research shows they can cause a blood clot to form in the opened artery.
In light of those issues with permanent stents, several research teams are developing biodegradable stents.
Biodegradable, also called absorbable, stents are intended to last long enough to widen the blocked or narrowed artery, then gradually dissolve.
Now, a different biodegradable stent is spotlighted in the June 2 edition of The Lancet. The stent, made of magnesium, is designed to last for four months before fading away.
Biodegradable Magnesium Heart Stent
The doctors studying the biodegradable magnesium stent included Raimund Erbel, MD, of the cardiology department at the West German Heart Center in Essen, Germany.
They implanted the absorbable stents into 63 patients and monitored them for a year. It was the stent's first test in humans.
None of the patients died or had heart attacks during the yearlong follow-up period.
However, about 45% of the patients required that their stented artery be reopened within a year of getting the stent. That includes 24% of the group who got the stented artery reopened within four months, the time span when the stent was still supposed to be present.
The stent's developers are tweaking the stent's design to make it last a little longer and to add a drug coating, note Erbel and colleagues.
The researchers stress that longer studies are needed, since a year might not be enough to see how the patients fare over time.
The editorialists agree. They write that no one knows exactly how long heart stents are needed, "but it probably ranges from a few weeks to six months."
The editorialists included John Ormiston, MD, of Mercy Angiography and Auckland City Hospital in Auckland, New Zealand.
The stent study was funded by Biotronik, the German company developing the absorbable magnesium heart stent. Several of the researchers consulted for Biotronik, according to The Lancet.
Editorialist Ormiston worked on a different study of a biodegradable stent made by Abbott Vascular, a branch of the health care company Abbott.
SOURCES: Erbel, R. The Lancet, June 2, 2007; vol 369: pp 1869-1875. Ormiston, J. The Lancet, June 2, 2007; vol 369: pp 1839-1840. WebMD Medical Reference provided in collaboration with Cleveland Clinic: "Heart Disease: Treatment With Angioplasty and Stents." WebMD Health News: "Can Drug-Coated Stents Beat Bypass?" News release, The Lancet.
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