Coronary Stents

Coronary stents are tiny spring like structures implanted in coronary arteries to maintain their lumen after balloon angioplasty. They help to prevent immediate recoil and closure of the vessel after angioplasty. Sometimes when there is a tear in the layers of the vessel known as dissection, the stents help to seal off the tear. Use of stents allow us to achieve better luminal diameter than plain old balloon angioplasty (POBA).

Coronary stents are made up of various materials. The popular bare metal stents are the stainless steel stents and cobalt chromium stents. Cobalt chromium stents are superior to stainless steel stents and of course, costlier. Drug coated stents are a recent introduction. Drug coating is usually done using polymers attached to the metallic stent struts. The two important drugs used are sirolimus and paclitaxel. Both these drugs prevent the regrowth of tissue into the stents, an important cause of restenosis. A new introduction is the use of biodegradable polymers for drug coating. A disadvantage of drug coated stents is the delay in endothelialisation of the stented region of the vessels. This has been reported to cause very late stent thrombosis. Stents with biodegradable polymers might offer an advantage of lesser delayed stent thrombosis.

Stent thrombosis is a dreaded complication which can lead to myocardial infarction due to sudden blockage of a vessel by a blood clot. This can be prevented to a certain extent by giving regular treatment with antiplatelet drugs. Dual antiplatelet drug treatment using aspirin and clopidogrel has been recommended to prevent stent thrombosis. Since bare metal stents get endothelialized earlier, a shorter duration of dual antiplatelet therapy is recommended for them. In contrast dual antiplatelet therapy has to be taken for at least one year or longer with drug eluting stents.