Stent & balloon induced acute mechanical arterial injury during expansion is an important determinant of restenosis. The cellular signaling mechanism that result in platelet deposition, thrombus formation & smooth muscle cell proliferation begin in response to arterial injury. It has been shown that deep injury to the media & superficial injury to the endothelium occur during stent expansion. Stent implantation imparts extreme vascular strain & focal mechanical injury to the vessel wall ranging from denudation of the endothelial cell mono layer, to progressive laceration of the deeper vascular structures. The amount of injury infllicated by the stent and balloon is a function of stent geometry.