Let me give you a very brief overview of the development in the history of stents before coming to the practical aspects.
In the 1960’s Dr Dotter described the conceptual aspect of angioplasty ie using a device like a catheter to dilate a narrowed artery. Dr Andreas Gruntzig in 1977 performed the first angioplasty procedure in an awake patient and in 1986, the first human coronary stent was inserted in France.
Though the initial coronary stents were largely stainless steel wire meshes, in 1999 the first drug coated stent was inserted by Dr Sousa and in 2002-2004 the first generation stents i.e Cypher and Taxus were approved and brought into general use. Further improvements in technology lead to second and third generation drug coated stents and in 2011 the bio-absorbable stent was introduced.
Currently the latest generation stents are largely made of alloys such as chromium-cobalt or platinum-chromium. These have a layer of drugs coated on them and are stuck onto the stents using “polymers”.
Some stents have non-absorbable polymers and healing takes a bit longer. Some stents have fully absorbable polymers(bio-degradable) and once the drug has been released completely it becomes a “bare metal stent”. There are yet other stents where the drug is stored in small “reservoirs” and is designed to release the drug slowly.
Some stents have special coating inside to “capture” special cells floating in the blood stream and have the theoretical advantage of healing faster. There are stents with no polymer at all, where the drug is sprayed onto the surface. Having a polymer that disappears, along with faster healing inside the stent helps to shorten the duration one has to take blood-thinning agents and is suitable especially for elderly patients and those needing surgical procedures.
There are also stents which continue to expand after they have been implanted. These can conform to the contours of the blood vessel. There are also stents designed to fit blood vessels with large branches.
Of course, the latest developments have been the fully absorbable stents which in theory have the advantage of staying in the vessel when its necessary to keep the vessel open and disappearing in two to three years when the blood vessel has a much larger lumen. However the bio-absorbable family of stents are currently not available for general use. Metallic absorbable stents made of magnesium are available though they maynot be suitable for all blood vessels.
Stents have also become much thinner over time, with stent struts, ranging from 60 micron as compared to the older generation stainless steel stents which are about 140 microns. There are also different designs of stents making some more strong and yet others, more flexible.
In short, different kinds of stents with different properties designed for specific situations are now available making angioplasty quite versatile and the choice of procedure in the vast majority of cases.
