Stent coatings and local drug delivery; state of the art.

The new enemy of percutaneous intervention is in-stent restenosis. He joins the old enemy, restenosis after balloon angioplasty, who, after 21 years of resistance, refuses to capitulate. Unlike restenosis after balloon angioplasty, in-stent restenosis is a consequence almost entirely of tissue hyperplasia, occurring principally around the points where the stent struts impinge upon the artery wall. Less common, but troublesome when it occurs, is subacute thrombosis, a complication not quite eliminated by modern stent deployment techniques and anti-platelet agents. These two factors are particularly limiting in diffuse disease, small vessels and arteries with poor run-off. Stenting, therefore, presents both the need and the opportunity for local drug delivery. Whilst the struts may create the problem, they may also present the solution, by carrying a coating or drug targeted at the thrombotic or hyperplastic responses occurring locally.