Components of a drug eluting stent (DES)
Abstract: Drug eluting stents have stent struts, polymer used to anchor the drug and the drug itself. Polymer coating of the drug eluting stent (DES) reduces the expandability of the DES.
Drug eluting stents were introduced to reduce the chance of restenosis which was common with bare metal stents. Neointimal proliferation is the important cause of restenosis of bare metal stents. Hence drugs which can suppress neointimal proliferation, basically antineoplastic antibiotics, have been used to reduce restenosis in drug eluting stents. The important components of a drug eluting stent are:
- Stent platform: Stent platform is the metallic structure of the stent, which could be made of surgical grade stainless steel or cobalt-chromium. Platinum based stents are also available. The stent platform gives the radial strength to the stent. Various types of cell design like open cell design and closed cell design are used by various manufacturers. The stent platform remains in the vessel indefinitely though the drug and even the polymer may not. The stent platform changes the vascular geometry and influences the vasomotion of the vessel in the long run. Nickel allergy is a cause for concern in case of stent platforms containing nickel in those allergic to nickel. Newer bioresorbable vascular scaffolds do not have a metallic stent platform. They are made of bioresorbable material like polylactate.
- Polymer coating: Polymer coating anchors the drug to the stent for gradual release to the arterial wall. Stents with biodegradable polymer are available in which the polymer gets degraded gradually and disappears from the vessel wall in the long run.1,2 Material of the polymer can also cause local hypersensitivity phenomena (Kounis syndrome)3 which can lead to stent thrombosis in the worst case.
- Antiproliferative drug: The antiproliferative drug within the polymer is the active component of the drug eluting stent which is gradually released locally and prevents neointimal proliferation. Initial drugs used were paclitaxel and sirolimus. Various other drugs like biolimus, everolimus and zotarolimus have been used in drug eluting stents, with varying results.
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- Kounis NG, Hahalis G, Theoharides TC. Coronary stents, hypersensitivity reactions, and the Kounis syndrome. J Interv Cardiol. 2007;20:314-323.