Citation: StatPearls Publishing. 2019 01.Published: ; 2019Full author list: Omeh DJ; Shlofmitz E.UI/PMID: 31424723.Subject(s): IN PROCESS -- NOT YET INDEXEDInstitution(s): MedStar Heart & Vascular InstituteActivity type: Journal Article.Medline article type(s): ReviewOnline resources: Click here to access onlineAbbreviated citation: StatPearls Publishing. 2019 01.Abstract: Restenosis is the reduction in the diameter of the vessel lumen after angioplasty. Despite advances in stent technology, restenosis continues to be the most frequent cause of target lesion failure following percutaneous coronary intervention (PCI). Following the introduction of bare-metal stents (BMS) in the mid-1990s for the treatment of coronary artery disease, a new clinical entity emerged called in-stent restenosis (ISR), which is restenosis in an implanted coronary stent. Angiographically, ISR is more than 50% stenosis within or immediately adjacent to a previously stented region. Clinical restenosis occurs when there is a recurrence of clinical manifestations of ischemia in the setting of ISR, often requiring a repeat revascularization procedure. In-segment restenosis is often defined as restenosis anywhere between 5 mm from the proximal and distal edges of the stent. Recurrent in-stent restenosis is defined as the failure of at least two revascularization procedures at the stent segment. In plain-old balloon (no-stent) angioplasty (POBA), mechanisms of restenosis involve vessel remodeling and elastic recoil. In contrast, restenosis in-stent angioplasty involves excessive tissue proliferation called neointimal proliferation, or by a new atherosclerotic process called neoatherosclerosis. The patterns of in-stent restenosis have been described as either diffuse (lesion over10 mm in length) or focal (lesion less than10 mm in length) according to the Mehran classification criteria. Clinically, coronary vessel restenosis will present as recurrence of angina or acute coronary syndrome. ISR is associated with significant morbidity. In a prospective cohort study of 10004 patients who underwent routine control angiography 6 to 8 months after coronary stenting, the presence of restenosis at follow-up angiography was predictive of 4-year mortality. Efforts to reduce the incidence of restenosis and treatment options for in-stent restenosis have evolved remarkably over the last two decades. Advancement in the stent platforms (e.g. thin-strut, and biodegradable), eluting drugs (biolimus A9 and zotarolimus, designed specifically for intracoronary use), and intravascular imaging modalities improving implant technique has led the interventional cardiologist to treat patients who were previously limited to surgical revascularization (i.e. left main stem, multivessel disease, complex bifurcations and complex and severely calcified lesions). As a result, real-world registries, including more complex patients and lesions, show a higher rate of ISR when compared to the reports from randomized trials.Abstract: Copyright (c) 2019, StatPearls Publishing LLC.