During this same time frame, the initial events of ISR occur, - primarily migration and proliferation of smooth muscle cells. The key event in rebuilding the endothelial layer over the stent struts is the recruitment of circulating endothelial progenitor cells (EPC), their adherence and attachment to the surface of the stent and vascular wall between the struts. The full coverage of the prothrombotic metal struts with new endothelial cells reduces the initially high risk of thrombosis. The repair processes are completed after 1 month when bare metal stents are used, and over 6 months after DES implantation.