Every year over 2 million people get coronary stents implanted. But what even is a stent, you might ask? A stent is a small, flexible mesh tube typically made up of metal alloys such as cobalt chromium or platinum chromium. It is used to prop open narrowed or weak arteries for better blood flow in patients.

In its early stages, a stent was a simple piece of metal. However, with advancements in technology, it has evolved into a sophisticated drug delivery system, largely due to polymer technology.

While metal stents were a major breakthrough in combating cardiac diseases, they also came with several disadvantages. Traditionally, stents were coated with heparin, a blood-thinning drug. Unfortunately, heparin did not adhere well to the metal surface and washed away over time, often leading to restenosis, or the re-narrowing of arteries.

Additionally, heparin’s animal origin and unstable coating caused allergic reactions in some patients, further limiting its effectiveness.

Another drawback of metal stents is their permanent nature. The body never fully accepts them, which can lead to complications. Even after healing, metal stents may cause low-grade inflammation that can later develop into thrombosis—blood clot formation occurring years after implantation.

Metal stents can also lock arteries into a rigid state, restricting natural expansion and contraction. Moreover, permanent stents complicate future medical procedures such as bypass surgery or additional stent implantation.

Fortunately, recent advancements have led to the development of polymer stents.

The word polymer originates from the Greek word poly, meaning “many.” A polymer is a long chain of repeating units called monomers. Polymers are versatile in structure and may be natural or synthetic. Most importantly, they are biocompatible, making them safe for use in medical procedures.

Polymers can also function as effective drug delivery systems. They are capable of holding large amounts of medication and releasing it slowly and steadily over time.

Currently, two types of polymer stents are available: biodegradable and biostable. Biodegradable polymers dissolve after fulfilling their purpose, while biostable polymers remain permanently in the body. Biodegradable stents have proven to be superior to metal stents, reducing scarring and tissue overgrowth from 30% to 5%.

Furthermore, these stents have demonstrated an 80% reduction in blood clots, highlighting their significant clinical advantages.

Over time, key polymers used in drug-eluting stents (DES) have continued to advance. In the first generation of DES, the Cypher stent was introduced, utilizing the polymer poly-(n)-butyl methacrylate. This stent was highly effective in preventing arterial reblockage.

Similarly, the Taxus stent was manufactured using the polymer Translute. It released 10% of the drug within the first ten days, while the remaining drug stayed embedded in the stent coating.

Newer polymer stents have also been developed. One example is the zotarolimus-eluting stent, which releases 98% of its drug within 14 days. Another advanced stent is Xience, made from a fluorinated copolymer.

Xience is non-inflammatory and releases medication in a slower, more controlled manner, making it one of the most effective stents available today.

Polymer stents have transformed stent implantation practices for decades to come. Previously, stent failure rates ranged from 25% to 30%. With the introduction of polymer stents, failure rates have dropped to approximately 5%, making the procedure safer than ever.

However, research continues. Scientists are now developing stents that respond to changes in body pH and temperature. The medical field is rapidly evolving, and procedures that once carried high risk are becoming increasingly safe.