The Intravascular Stent: A Concept in Evolution
Intravascular stents are used in general, as a means to mechanically solve the most common problems of percutaneous balloon angioplasty: elastic recoil and intimai dissection. The fact that intravascular stents become embedded in the arterial wall by tissue growth weeks to months following placement was first reported by Charles Dotter in 1969 . This favorable outcome occurs consistently with any stent design provided it has a reasonably low metal surface and does not obstruct flow. Endothelium grows over the fibrin coated metal surface until a continuous endothelial layer covers the stent surface, in days to weeks. Endothelium renders the thrombo-genic metal surface protected from thrombus deposition, which is likely to form with slow or turbulent flow. This is an important advantage of intravascular stenting over surgically implanted prosthetic bypass conduits which never endothelialize in patients, except for a few millimeters beyond the anastomoses. However, early stent failure may occur in situations of slow or turbulent flow, which compounds the thrombogenicity of the stent material. This is a definite risk before endothelization is complete. Understanding the series of events surrounding stent placement helps prevent stent failure. The following is a point-by-point discussion of these events.
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