sentences:  By the late 1990s it was generally acknowledged among cardiologists that the incidence of in-stent restenosis was between 15 and 30%, and possibly higher in certain subgroups of individuals.Stent manufacturers experimented with (and continue to experiment with) a number of chemical agents to prevent the neointimal hyperplasia that is the cause of in-stent restenosis.One of the first products of the new focus on preventing late events (such as in stent restenosis and late thrombosis) was the heparin-coated Palmaz-Schatz stent.