What are Biodegradable-Polymer Drug Eluting Stents?

Riya Gilja

Over a million procedures using heart stents are conducted annually in the U.S. To open the vessel, doctors perform angioplasty in which they insert a balloon-tipped catheter into the artery. The currently used stents are metal. A stent is collapsed to a tiny diameter and put over the balloon. When the catheter gets to the blockage, the balloon is inflated to open the vessel. The stent then expands and locks into place. The scaffold it forms holds open the vessel. Clots can form in the stent. Most metal stents are coated with drugs to reduce the risk of clots. Patients with heart conditions are also on Aspirin for lifetime and take a blood-thinning drug, such as clopidogrel (Plavix).

Another type of stent is a Biodegradable-polymer drug eluting stents.The new stent is made of a cornstarch-based material called poly-l-lactic acid completely resorbs in about three years, (hence why they are called biodegradable).  They are currently approved in European countries as well as Turkey.   According to a new study with 50 patients by Dr.Kosuga’s MD, PhD Medical director of cardiology at Shiga Center for Adults in Moriyama City, Japan, this particular stent also aids in opening clogged coronary arteries. His team followed 44 men and six women. The average age of the clients was 61. Together, the patients got 84 stents. The follow-up was 10 years. The results are described as ”excellent” by researcher Kosuga, MD, PhD,  Rates of major complications, including heart attacks,  were similar to those for metal stents in use now, showing that the new stents possess no new health risk. The biodegradable stents will eventually replace the current metal stents as Kosuga predicts. Dr.Igaki, PhD, invented and developed the new stent. No country has approved these stents for coronary arteries.

A U.S.-based expert states that the study findings are positive. However, he doesn’t expect the new stents to be on the market anytime soon. “The timeline for U.S. approval would be at least five or six years,” says Kirk Garratt, MD, an interventional cardiologist and clinical director of interventional cardiovascular research at Lenox Hill Hospital in New York.Garratt says. With the metal stents, “We think the blood clot risk falls off fairly steeply after two or three years. It’s not clear if the risk ever goes to zero,” Garratt says. Regardless, it looks like investment in biodegradable-polymer drug eluding stents looks promising.

Biodegradable stents are already used in nine European Union countries and Turkey to treat peripheral artery disease. No countries yet have approved the re-absorbable stents developed by Igaki for heart arteries. Biodegradable stents cost more, Kosuga tells WebMD. “The cost of manufacturing is about 10% higher than that of the metallic stent,” he says. These stents actually look safe,” says Vincent Bufalino, MD, a spokesman for the American Heart Association and director of cardiology at Advocate Cardiovascular Institute in Chicago. The new report, in WebMD, ”gives us some comfort and a long view of these patients. However the rate of re-narrowing found, 16%, is about twice that of metal drug-coated stents.” If the biodegradable stent becomes obtainable, it could decrease the need for the blood-thinning drugs and be more cost effective.