at 52,158 patients across 51 trials. At a median 3.8 years follow up, all DES demonstrated superior efficacy compared to BMS, resulting in lower rates of revascularization procedures. Among DES, newer-generation devices had substantially improved safety outcomes, specifically in regards to stent thrombosis, recurrent MIs, or death. In another 2016 trial, 9,013 patients who received either DES or BMS to treat coronary artery disease were followed at 6 years in order to determine differences in rates of all-cause mortality (death from any cause) as well as frequency of repeat revascularization, stent thrombosis, and quality of life measures. At 6 years, there were no significant differences in all-cause mortality or quality of life measures. However, rates of repeat revascularization and stent thrombosis were significantly lower in those who received DES as opposed to BMS. Adverse effects Risks Like all invasive medical procedures, stent placement carries certain risks. Risks associated with cardiac catheterization procedures include bleeding, allergic reaction to the X-ray contrast agents used to visualize the coronary arteries, and myocardial infarction. With PCI, the requirement for emergency CABG has markedly decreased since the days of balloon angioplasty, such that in some communities, coronary stenting is permitted in hospitals without on-site cardiac surgery facilities. This remains controversial in the United States because of the rare but unpredictable risk of coronary artery perforation. Rarely, a type of allergic reaction to the drug may occur; episodes of fatality have been reported. Stent thrombosis One of the most feared complications of coronary stenting is stent thrombosis. This occurs when a new clot forms within the stent and occludes blood flow, causing another heart attack. Treatment for stent thrombosis is emergent revascularization; however, this is only achieved in two thirds of patients. Accordingly, stent thrombosis carries a 30-day mortality risk of 10-25%. The mechanisms responsible for clot formation are multifactorial, including patient factors (smoking, diabetes, hematologic disorders, etc.), choice of stent, and post-procedural factors (duration of antiplatelet therapy, adherence to follow-up). Although drug-eluting stents continue to represent a major medical advance for angioplasty, there is no evidence to suggest reduced frequency of thrombosis with DES compared to older BMS. What is more, while thrombosis occurs immediately (<24 hours) with BMS, DES have been associated with stent thrombosis up to 3 years after implantation, a phenomenon not seen prior. Explanations may lie in the very nature that these new stents are designed to function. A stent represents