From Science News Online - Biodegradable stents in your future?

[Guest guest]

Arne

---------------------------------

Science News Online

Week of June 9, 2007; Vol. 171, No. 23

Blending In: Dissolvable stents promise to protect arteries

Seppa

Biodegradable versions of the metal cylinders known as stents can

keep blocked coronary arteries propped open long enough to free up

blood flow, after which they disappear & #151;a potential advantage.

The new finding suggests that such dissolving stents might someday

replace rigid, permanent stents, which carry health risks (SN:

10/28/06, p. 277).

Doctors insert mesh stents into jammed arteries to keep them open. In

the new study, researchers implanted an experimental version of

biodegradable magnesium stents in 63 people with clogged coronaries.

The scientists chose magnesium because it's found in the body, poses

no allergy risk, and in alloy form is slowly dissolved by body

fluids, says study coauthor Raimund A. Erbel, an interventional

cardiologist at the West German Heart Center in Essen.

At checkups 4 months after implantation, the researchers found that

the stents had completely degraded and had been replaced by calcium

and a phosphorus compound. Moreover, new vessel-lining cells had

grown over the area, the team reports in the June 2 Lancet.

However, earlier checkups had revealed that the magnesium alloy began

degrading within 14 days & #151;too fast for practical use. Nearly half

the vessels getting the magnesium stents narrowed again so much that

the patients warranted an additional procedure, such as coronary

bypass surgery.

As a result, the new stent differed little in effectiveness from

angioplasty, in which a balloon-tipped catheter is inflated at a

coronary blockage to simply push it aside. Over the past 15 years,

doctors have increasingly used angioplasty to prepare a vessel for

stent insertion. Without a stent, a vessel opened by angioplasty can

soon collapse, a complication known as recoil.

Overall, the magnesium stent fared worse than did permanent stents,

which stay rigid enough to prevent collapse. But unless they're

coated with certain drugs, rigid stents can lead to renarrowing of

the vessel from aberrant tissue healing. Coated metal stents,

however, appear to carry the separate risk of triggering blood clots.

If biodegradable stents are to work, they will have to maintain

rigidity just long enough to allow healthy layers of cells to reline

a vessel and get past the recoil-risk stage, says interventional

cardiologist E. Cutlip of Harvard Medical School in Boston. If

so, they could provide better vessel flexibility than rigid stents

do. " This is a novel concept. As with most early techniques, it

raises a lot of questions, " he says.

Erbel and his team are testing an alloy of magnesium that may take

longer to dissolve and therefore reinforce vessels for several months.

Meanwhile, other groups are experimenting with biodegradable stents

coated with compounds that help prevent the aberrant healing that can

occur with rigid metal stents.

If you have a comment on this article that you would like considered

for publication in Science News, send it to editors@....

Please include your name and location.

ScienceNews.org needs your input

Take our quick, 1-minute survey, and tell us how to improve our Web

site.

You might win a free iPod!.

References:

Erbel, R., et al. 2007. Temporary scaffolding of coronary arteries

with bioabsorbable magnesium stents: A prospective, non-randomised

multicentre trial. Lancet 369(June 2):1869-1875. Abstract available

at http://dx.doi.org/10.1016/S0140-6736(07)60853-8.

Further Readings:

Harder, B. 2006. Vanishing devices: Doctors implant disappearing

stents, heart patches. Science News 170(Oct. 28):277. Available to

subscribers at http://www.sciencenews.org/articles/20061028/fob5.asp.

Morice, M-.C., et al. 2002. A randomized comparison of a

sirolimus-eluting stent with a standard stent for coronary

revascularization. New England Journal of Medicine 346(June

6):1773-1780. Available at

http://content.nejm.org/cgi/content/full/346/23/1773.

Moses, J.W., et al. 2003. Sirolimus-eluting stents versus standard

stents in patients with stenosis in a native coronary artery. New

England Journal of Medicine 349(Oct. 2):1315-1323. Available at

http://content.nejm.org/cgi/content/full/349/14/1315.

Ormiston, J., and M. Webster. 2007. Absorbable coronary stents.

Lancet 369(June 2):1839-1840.

Ormiston, J.A., M.W.I. Webster, and G. Armstrong. 2007.

First-in-human implantation of a fully bioabsorbable drug-eluting

stent: The BVS poly-L-lactic acid everolimus-eluting coronary stent.

Catheterization and Cardiovascular Interventions 69(January):128-131.

Abstract available at http://dx.doi.org/10.1002/ccd.20895.

Sources:

E. Cutlip

Harvard Clinical Research Institute

Harvard Medical School

Beth Israel Deaconess Medical Center

330 Brookline Avenue

Boston, MA 02215

Raimund A. Erbel

Department of Cardiology

West German Heart Center Essen

University Duisburg-Essen

Hufelandstr 55

D-45122 Essen

Germany

http://www.sciencenews.org/articles/20070609/fob5.asp

From Science News, Vol. 171, No. 23, June 9, 2007, p. 356.

Copyright © 2007 Science Service. All rights reserved.

---------------------------------

Interested in new developments in science and technology? Consider

subscribing to Science News. Visit Science News Online at

http://www.sciencenews.org/ for access to additional news articles and

subscription information.