alloys were used, namely cobalt-chrome and platinum chrome, with improved performance. Recently, bioresorbable stents have been developed in which the stent itself dissolves over time. As of 2009, materials that had been explored for use included magnesium, polylactic acid, polycarbonate polymers, and salicylic acid polymers. Resorbable stents have held the promise of providing an acute treatment that would eventually allow the vessel to function normally, without leaving a permanent device behind. One to three or more layers of polymer can be used in the coating, e.g., a base layer for adhesion, a main layer that holds and elutes (releases) the drug into the arterial wall by contact transfer, and sometimes a top coat to slow down the release of the drug and extend its effect. The first few drug-eluting stents to be licensed used durable coatings. The first generation of coatings appear to have caused immunological reactions at times, and some possibly led to thrombosis. This has driven experimentation and development of new coating approaches. The drug is mainly used to inhibit neointimal growth due to the proliferation of smooth muscle cells that would cause restenosis. Much of the neointimal hyperplasia seems to be caused by inflammation. Hence, immunosuppressive and antiproliferative drugs are used. Sirolimus, paclitaxel, and everolimus were previously used for other medical applications and have been included in licensed DES. Vascular stents are Class III medical devices that are intended for use as a mechanical radial support to enhance vessel patency over the intended design life of the device. Device properties and the intended use are dependent on results from extensive testing that involve mechanical tests on universal testing machines. Types of mechanical test include bend testing, fatigue testing, radial loading, tensile testing, and torsion testing. Depending on the type of vascular stent, its location and intended use, other tests may include crush resistance, kink resistance, corrosion, coating integrity, and more. History The first procedure to treat blocked coronary arteries was coronary artery bypass graft surgery (CABG), wherein a section of vein or artery from elsewhere in the body is used to bypass the diseased segment of coronary artery. In 1977, Andreas Grüntzig introduced percutaneous transluminal coronary angioplasty (PTCA), also called balloon angioplasty, in which a catheter was introduced through a peripheral artery and a balloon expanded to dilate the narrowed segment of artery. As equipment and techniques improved, the use of PTCA rapidly increased, and by the