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Coronary stents are among the most common therapies worldwide. Despite significant improvements in the biocompatibility of these devices throughout the last decades, they are prone, in as many as 10–20% of cases, to short- or long-term failure. In-stent restenosis is a multifactorial process with a complex and incompletely understood pathophysiology in which inflammatory reactions are of central importance. This review provides a short overview for the clinician on the cellular types responsible for restenosis with a focus on the role of endothelial progenitor cells. The mechanisms of restenosis are described, along with the cell-based attempts made to prevent it. While the focus of this review is principally clinical, experimental evidence provides some insight into the potential implications for prevention and therapy of coronary stent restenosis.

Background : Coronary artery calcification is a predictor of adverse outcomes after percutaneous coronary intervention (PCI). Intravascular lithotripsy (IVL) is a promising tool for the treatment of calcified lesions. The aim of this study was to assess the effectiveness and safety of IVL. Methods : A single-center observational study of PCI procedure, with assessment of the outcomes of patients undergoing PCI using IVL, was performed. Angiographic procedural success was used as the primary effectiveness endpoint. The primary safety endpoint was defined as a composite of cardiac death, myocardial infarction and target vessel revascularization within 30 days. Results : A total of 111 patients were included. Indications for PCI spanned the spectrum of chronic (53.2%) and acute coronary syndromes (43%). Lesion preparation before IVL was performed with non-compliant (42%), cutting or OPN (14.4%) balloons and with atherectomy techniques in 11% of procedures. Intravascular imaging was used in 21.6% of procedures. The primary effectiveness endpoint was achieved in 100% and the primary safety endpoint in 3.6% of procedures. Peri-procedural complications were minimal and successfully resolved. Conclusions : IVL was an effective and safe technique for the treatment of calcified coronary lesions. These findings contribute to the growing body of evidence supporting the use of IVL in the management of these challenging scenarios.

Coronary stents belong to the most commonly implanted devices worldwide. A number of different types of stent exist, with very different mechanical and biochemical characteristics that influence their interactions with vascular tissues. Inappropriate inflammatory reactions are the major cause of the two major complications that follow implantation of stents in a percentage as high as 5–20%. It is therefore important to understand these reactions and how different they are among different generations of stents.

In patients undergoing percutaneous coronary intervention, the second-generation drug-eluting stents (DES) are considered the gold standard of care for revascularization. By reducing neointimal hyperplasia, drug-eluting coronary stents decrease the need for repeat revascularizations compared with conventional coronary stents without an antiproliferative drug coating. It is important to note that early-generation DESs were associated with an increased risk of very late stent thrombosis, most likely due to delayed endothelialization or a delayed hypersensitivity reaction to the polymer. Studies have shown a lower risk of very late stent thrombosis with developing second-generation DESs with biocompatible and biodegradable polymers or without polymers altogether. In addition, research has indicated that thinner struts are associated with a reduced risk of intrastent restenosis and angiographic and clinical results. A DES with ultrathin struts (strut thickness of 70 µm) is more flexible, facilitates better tracking, and is more crossable than a conventional second-generation DES. The question is whether ultrathin eluting drug stents suit all kinds of lesions. Several authors have reported that improved coverage with less thrombus protrusion reduced the risk of distal embolization in patients with ST-elevation myocardial infarction (STEMI). Others have described that an ultrathin stent might recoil due to low radial strength. This could lead to residual stenosis and repeated revascularization of the artery. In CTO patients, the ultrathin stent failed to prove non-inferiority regarding in-segment late lumen loss and showed statistically higher rates of restenosis. Ultrathin-strut DESs with biodegradable polymers have limitations when treating calcified (or ostial) lesions and CTOs. However, they also possess certain advantages regarding deliverability (tight stenosis, tortuous lesions, high angulation, etc.), ease of use in bifurcation lesions, better endothelialization and vascular healing, and reducing stent thrombosis risk. In light of this, ultrathin-strut stents present a promising alternative to existing DESs of the second and third generation. The aims of the study are to compare ultrathin eluting stents with second- and third-generation conventional stents regarding procedural performance and outcomes based on different lesion types and specific populations.

Introduction: The frequency, characteristics and clinical implications of Strut fractures (SFs) remain incompletely understood., Methods and Results: A total of 185 (160 patients) newer-generation drug-eluting stents (DES) were imaged. SFs were found in 21 DES (11.4%) and were classified in four patterns: one single stacked strut (41%); two or more stacked struts (23%); deformation without gap (27%); transection (9%). In multivariable analysis, calcific and bifurcation lesions were associated with SF in DES (OR: 3.5 [1.1-11] and 4.0 [2.2-7.2], p < 0.05). Device eccentricity and asymmetry as well as optical coherence tomography (OCT) features of impaired strut healing were also associated with SF. The prevalence of fractures was similar in a set of 289 bioresorbable scaffolds (BRS). In a separate series of 20 device thromboses and 36 device restenoses, the prevalence of SF was higher (61.2% of DES and 66.7% of BRS, p < 0.001 for both), with a higher frequency of complex SF patterns ( p < 0.0001). In logistic regression analysis, fractures were a correlate of device complications ( p < 0.0001, OR = 24.9 [5.6-111] for DES and OR = 6.0 [1.8-20] for BRS)., Discussion: The prevalence of OCT-diagnosed SF was unexpectedly high in the setting of elective controls and it increased by about three-fold in the setting of device failure. Fractures were associated with increased lesion complexity and device asymmetry/eccentricity and were more frequent in the setting of device failure such as restenosis and thrombosis.

Coronary stents belong to the most commonly implanted devices worldwide. A number of different types of stent exist, with very different mechanical and biochemical characteristics that influence their interactions with vascular tissues. Inappropriate inflammatory reactions are the major cause of the two major complications that follow implantation of stents in a percentage as high as 5-20%. It is therefore important to understand these reactions and how different they are among different generations of stents.