Types of Polymer Stents

Stents are tubes surgeons insert into collapsed or narrowed arteries. They are designed to increase blood flow through a problem portion of an artery. There are two general types of stents: Metal stents and polymer stents. Metal stents are the oldest type. There are three different general types of polymer stent. Each type is designed to help solve a different problem.

Bioabsorbable Stents

• There are a couple of types of bioabsorbable stent. A purely polymer stent allows a vessel to heal before the stent naturally decomposes and absorbs into the body. A fully bioabsorbable stent leaves no material in the vessel where it was placed.

  The second type of bioabsorbable stent uses a bioabsorbable polymer coating over a permanent metal or polymer substructure. This stent delivers a substance to the stented area or changes the properties of the underlying stent over time.

Drug Delivery

• Polymer stents can deliver drugs as they decompose. As the polymer decomposes, drugs embedded in the polymer release medication. The quantity of medication in the polymer and the rate of decomposition of the material control the dosage.

  Drugs impregnated into the polymer can include drugs to decrease the risk of thrombosis or reduce problems with clots forming around the stent.

Gene Delivery

• Although still in clinical testing, polymer stents similar to drug-delivery stents may be able to deliver genetic therapy materials to stented blood vessels. A stent impregnated with adenovirus can deliver reporter genes to stented areas in rabbits, according to recent studies reported by the American Heart Association. The principle behind the delivery of genetic material in these experimental stents is similar to stents designed to deliver drugs. As the stents decompose, they release adenovirus in the polymer material into the area around the stents.