Developing an Absorbable Heart Stent
Novel Design Could Prevent Blood Clot Formation That Plagues Current Stents
March 26, 2007 (New Orleans) -- The first stent designed to be absorbed by
the heart's arteries could overcome a potentially fatal flaw associated with
those currently used to prop open clogged arteries, researchers report.
The biodegradable stent, which dissolves over time, appears to prevent the
formation of blood clots -- a major concern with the popular drug-coated stents
now in use, says Patrick Serruys, MD, a professor of interventional cardiology
at Erasmus University in the Netherlands.
In the first small study to test the device, "early results indicated it
is safe, effective, and easy to deploy," he tells WebMD.
None of the 26 people implanted with the new stent died, developed a blood
clot, or needed a repeat procedure to open a reblocked artery. One person
suffered a mild heart attack.
The study, funded by Abbott Laboratories, a maker of stents, was presented
at the annual meeting of the American College of Cardiology.
Clots Plague Drug-Coated Stents
Stents coated with drugs to keep arteries from reclogging after being opened
in a balloon angioplasty procedure have revolutionized heart care.
In a simple angioplasty, a tiny balloon at the end of a long tube is
threaded through an artery in the groin. The doctor shimmies the probe up
through the patient's leg and into the arteries of the heart, inflating the
balloon at the spot where the vessel has narrowed.
The balloon stretches open the walls of the vessel. Then the balloon is
deflated and removed. In about 25% or 30% of patients, the arteries close up
To keep the vessel open, doctors now often add a stent to the end of the
balloon catheter. The mesh-like metal tubes prop open clogged arteries and
restore blood flow. Stents bring the rate of renarrowing down to about 15% to
In recent years, stents have been coated with a polymer that slowly releases
a powerful drug to keep scar tissue from forming.
Unfortunately, the drug also slows the healing process. That's a problem
because until the stented blood vessel heals, there's a risk of blood clotsup
to two years later that can trigger heart attacks.
Of the 1 million Americans implanted with stents each year, about 80% to 90%
now get drug-coated devices, according to the American Heart Association.
Stent Made of Biodegradable Polyester
The new stent is made of a biodegradable material that slowly releases the
drug everolimus to prevent blood vessels from reclogging. Everolimus is not FDA
approved for use in the U.S.
Serruys says its design eliminates two possible causes of blood clots: the
metal scaffold and the polymer coating.
There are other potential advantages as well. Because the stent is absorbed
over time, it may be easier to take MRI or CT images of the stented vessel so
doctors can monitor for problems. Also, it will be easier to perform new
stenting procedures on the same vessel, he says.