Drug-eluting stent safety

Coronary Bifurcation Stenting: Review of Current Techniques and Evidence

BACKGROUND

Coronary bifurcation stenting constitutes 20% of all PCI performed. Given the extensive prevalence of bifurcation lesions, various techniques have sought to optimally stent the bifurcation to improve revascularization while also decreasing rates of stent thrombosis and lesion recurrence. Advanced techniques, such as planned two-stent approaches, have been shown to have improved outcomes but also require fluoroscopy and procedure time, posing an economic argument as well as a patient-outcome one.

OBJECTIVE

Because of the many strategies posited in the literature, it becomes essential to objectively evaluate evidence from randomized controlled trials and meta-analyses to help determine the optimal stenting strategy.

METHODS

We reviewed the clinical evidence on the efficacy of coronary bifurcation stenting.

RESULTS

In this paper, we review the most recent randomized controlled trials and meta-analyses on the efficacy of various stenting techniques and advances in stenting technologies published to gauge the current state of understanding and chart where the field is heading.

CONCLUSION

Bifurcation stenting is a maturing problem in the field of interventional cardiology that is adapting to the needs of the patients and advances in technology.

Protective Layer Development for Enhancing Stability and Drug-Delivery Capabilities of DES Surface-Crystallized Coatings

Carrier-free drug-eluting stents (DES)-based crystalline coatings are gaining prominence because of their function, skipping many limitations and clinical complications of the currently marketed DES. However, their usage has been humbled by inflexibility of the crystalline coating and limited mechanical and physical properties. This study reports for the first time the development of a protective top coating for enhancing the merits and delivery capabilities of the crystalline coating. Flexible and water-soluble polysaccharide top coating was developed and applied onto rapamycin (RM) crystalline carpet. The top coating prevented crystalline coating delamination during stent crimping and expansion without affecting its release profile. Crystalline coating strata and its interfaces with the metallic substrate and top coating were fully studied and characterized. The crystalline top-coated stents showed significant physical, mechanical, and chemical stability enhancement with ∼2% RM degradation after 1 year under different storage conditions. Biocompatibility study of the top-coated stents implanted subcutaneously for 1 month into SD rats did not provoke any safety concerns. Incorporating RM into the top coating to develop a bioactive protective coating for multilayer release purposes was also investigated. The developed protective coating had wide applicability and may be further implemented for various drugs and implantable medical devices.

Crystalline paclitaxel coated DES with bioactive protective layer development

Drug eluting stents (DES) based on polymeric-carriers currently lead the market, however, reports on clinical complications encourage the development of safer and more effective DES. We recently reported on carrier-free DES based on rapamycin crystalline coating as a potential therapeutic solution. Here, we report for the first time surface crystallization of paclitaxel (PT) onto metallic stents. The physicochemical principles of crystallization and key process parameters were extensively studied for fabrication of controllable and homogeneous crystalline coatings on stent scaffolds. Stents loaded with nearly 100μg PT were chosen as a potential therapeutic device with a multilayer coating of 4-7μm thickness. In vitro PT release from these coated stents shows constant release for at least 28days with 10% cumulatively released. The effect of fast dissolving top coating on the physical stability of the coated stent was determined. The top coating enhances the mechanical stability of the crystalline coating during deployment and expansion simulations. Also, incorporating PT in the protective top coating for developing bioactive top coating for multilayer controlled release purpose was intensively studied. This process has wide applications that can be further implemented for other drugs for effective local drug delivery from implantable medical devices.

MicroRNAs for Restenosis and Thrombosis After Vascular Injury

Percutaneous revascularization revolutionized the therapy of patients with coronary artery disease. Despite continuous technical advances that substantially improved patients' outcome after percutaneous revascularization, some issues are still open. In particular, restenosis still represents a challenge, even though it was dramatically reduced with the advent of drug-eluting stents. At the same time, drug-eluting stent thrombosis emerged as a major concern because of incomplete or delayed re-endothelialization after vascular injury. The discovery of microRNAs revealed a previously unknown layer of regulation for several biological processes, increasing our knowledge on the biological mechanisms underlying restenosis and stent thrombosis, revealing novel promising targets for more efficient and selective therapies. The present review summarizes recent experimental and clinical evidence on the role of microRNAs after arterial injury, focusing on practical aspects of their potential therapeutic application for selective inhibition of smooth muscle cell proliferation, enhancement of endothelial regeneration, and inhibition of platelet activation after coronary interventions. Application of circulating microRNAs as potential biomarkers is also discussed.

IL-10 Accelerates Re-Endothelialization and Inhibits Post-Injury Intimal Hyperplasia following Carotid Artery Denudation

The role of inflammation on atherosclerosis and restenosis is well established. Restenosis is thought to be a complex response to injury, which includes early thrombus formation, acute inflammation and neo-intimal growth. Inflammatory cells are likely contributors in the host response to vascular injury, via cytokines and chemokines secretion, including TNF-alpha (TNF). We have previously shown that IL-10 inhibits TNF and other inflammatory mediators produced in response to cardiovascular injuries. The specific effect of IL-10 on endothelial cell (ECs) biology is not well elucidated. Here we report that in a mouse model of carotid denudation, IL-10 knock-out mice (IL-10KO) displayed significantly delayed Re-endothelialization and enhanced neo-intimal growth compared to their WT counterparts. Exogenous recombinant IL-10 treatment dramatically blunted the neo-intimal thickening while significantly accelerating the recovery of the injured endothelium in WT mice. In vitro, IL-10 inhibited negative effects of TNF on ECs proliferation, ECs cell cycle, ECs-monocyte adhesion and ECs apoptosis. Furthermore, IL-10 treatment attenuated TNF-induced smooth muscle cells proliferation. Our data suggest that IL-10 differentially regulate endothelial and vascular smooth cells proliferation and function and thus inhibits neo-intimal hyperplasia. Thus, these results may provide insights necessary to develop new therapeutic strategies to limit vascular restenosis during percutaneous coronary intervention (PCI) in the clinics.

Antibody-targeted drug delivery to injured arteries using layered double hydroxide nanoparticles

Targeted local delivery of a nanoparticle-based, antibody-targeted, and low molecular weight heparin (LMWH) delivery system successfully reduces restenosis and thrombus formation in an animal model. An antibody recognizing cross-linked fibrin (XLF) D-dimer is successfully conjugated to layered double hydroxide nanoparticles. Use of the anti-XLF-conjugated LMWH-carrying layered double hydroxide nanoparticles shows successful targeting of the nanoparticles (red) to the injured artery wall (green), resulting in decreased neointimal thickening and thrombus formation.

Use of autologous blood-derived endothelial progenitor cells at point-of-care to protect against implant thrombosis in a large animal model

Titanium (Ti) is commonly utilized in many cardiovascular devices, e.g. as a component of Nitinol stents, intra- and extracorporeal mechanical circulatory assist devices, but is associated with the risk of thromboemboli formation. We propose to solve this problem by lining the Ti blood-contacting surfaces with autologous peripheral blood-derived late outgrowth endothelial progenitor cells (EPCs) after having previously demonstrated that these EPCs adhere to and grow on Ti under physiological shear stresses and functionally adapt to their environment under flow conditions ex vivo. Autologous fluorescently-labeled porcine EPCs were seeded at the point-of-care in the operating room onto Ti tubes for 30 min and implanted into the pro-thrombotic environment of the inferior vena cava of swine (n = 8). After 3 days, Ti tubes were explanted, disassembled, and the blood-contacting surface was imaged. A blinded analysis found all 4 cell-seeded implants to be free of clot, whereas 4 controls without EPCs were either entirely occluded or partially thrombosed. Pre-labeled EPCs had spread and were present on all 4 cell-seeded implants while no endothelial cells were observed on control implants. These results suggest that late outgrowth autologous EPCs represent a promising source of lining Ti implants to reduce thrombosis in vivo.

Comparison of chronic-stage histopathological findings among 3 coronary stents implanted in the same patient

A 73-year-old woman suffering from anterior thoracic pain on exertion presented to our hospital. We performed coronary angiography and noted three stenotic legions in each coronary artery. For each angiographic finding, we implanted a bare metal stent (BMS), sirolimus-eluting stent (SES) and paclitaxel-eluting stent (PES) into the right coronary artery, left anterior descending and left circumflex coronary arteries, respectively. Nine months later, she died of lung disease, and we could compare the histopathological findings among the three coronary stents. In the drug-eluting stents, very thin intima, infiltration of inflammatory cells, and fibrin deposition were observed, while thick intima and no inflammatory findings were observed in the BMS. Fibrin deposition was more marked in the PES than in the SES. This report shows marked differences in the subsequent pathological course among three stents in the same patient.

Increased serum vWF and sVCAM-1 levels are associated with late or very late angiographic stent thrombosis after sirolimus-eluting stent implantation

BACKGROUND

This study sought to examine whether circulatory levels of endothelial dysfunction biomarkers [vascular cell adhesion molecule (sVCAM-1), intercellular adhesion molecule (sICAM-1), sE-selectin, von Willebrand factor (vWF), tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1)] are associated with occurrence of late or very late stent thrombosis (ST) after percutaneous coronary intervention with sirolimus-eluting stent implantation, and to assess the possible influence of genetic variants of these proteins on ST.

METHODS

Serum levels of sVCAM-1, sICAM-1, sE-selectin, vWF, t-PA and PAI-1 were measured, and polymorphisms of vWF (-1234C/T, -1185A/G and -1051G/A), t-PA (insertion/deletion) and PAI-1 genes (4G/5G) were determined in 41 patients who experienced at least one episode of late or very late ST. Eighty-two patients without ST randomly selected from the same study period served as controls.

RESULTS

Serum levels of vWF, sVCAM-1 and sICAM-1 were significantly increased in patients with ST than in controls (all P<0.01). No significant difference was observed in the genotype and allele distribution of the vWF, t-PA and PAI-1 gene polymorphisms. Multivariable logistic regression analysis showed that vWF, sVCAM-1, discontinuation of clopidogrel therapy and left ventricular ejection fraction of less than 50% were independent determinants of late ST.

CONCLUSION

Increased serum vWF and sVCAM-1 levels are associated with late ST, suggesting that endothelial dysfunction contributes to the development of late or very late ST.

Prevention of the renarrowing of coronary arteries using drug-eluting stents in the perioperative period: an update

The management of patients scheduled for surgery with a coronary stent, and receiving 1 or more antiplatelet drugs, has many controversies. The premature discontinuation of antiplatelet drugs substantially increases the risk of stent thrombosis (ST), myocardial infarction, and cardiac death, and surgery under an altered platelet function could also lead to an increased risk of bleeding in the perioperative period. Because of the conflict in the recommendations, this article reviews the current antiplatelet protocols after positioning a coronary stent, the evidence of increased risk of ST associated with the withdrawal of antiplatelet drugs and increased bleeding risk associated with its maintenance, the different perioperative antiplatelet protocols when patients are scheduled for surgery or need an urgent operation, and the therapeutic options if excessive bleeding occurs.

Drug-eluting stent with improved durability and controllability properties, obtained via electrocoated adhesive promotion layer

Drug-eluting stents (DES) have become an accepted technology in intravascular intervention. Manufacturing methodologies of DES are based mainly on mechanical processes, which tend to generate coatings that have poor stability properties; these were recently related as a potential hazard. A novel approach for significantly increasing the adhesion of polymer coatings onto DES is presented. The method is based on the electrochemistry of diazonium salts. These substances are organic compounds with the characteristic structure of R-N(2) (+) X(-), where R is an organic residue and X(-) is an anion. The objective of this article is to study the properties of a selected diazonium salt 4-(1-dodecyloxy)-phenyldiazonium tetrafluoroborate, referred as C(12)-phenyldiazonium. This material was found to be a superior adhesive promoter for polymeric coatings applied onto metallic stents. C(12)-phenyldiazonium was synthesized and electrocoated on metallic stents and plates. The multilayer films of C(12)-phenyldiazonium were further characterized through electrochemical (cyclic voltammetry, impedance spectroscopy), physical (light and scanning electron microscopy, X-ray photoelectron spectroscopy, peeling tests), and chemical methodology (high pressure liquid chromatography). Further biocompatibility properties of the electrocoated basecoat were evaluated using in vitro and in vivo models. Synthesized C(12)-phenyldiazonium was successfully electrocoated onto metallic surfaces. Electrochemical tests demonstrated its efficient and controllable electrocoating. C(12)-phenyldiazonium was found to increase polymeric coating stability as was reflected by a standard adhesion test. Electrocoated metallic stents spray-coated with a second polymeric film showed improved durability following incubation in physiological buffer. Furthermore, this improvement in durability exhibits stabilized drug release. In addition, biocompatibility evaluations have demonstrated basecoat's inert properties.

Treatment of stenoses of vertebral artery origin using short drug-eluting coronary stents: improved follow-up results

BACKGROUND AND PURPOSE

Recent studies on stent placement of significant stenoses at the origin of the vertebral artery reported excellent immediate results. Long-term outcomes, however, were disappointing due to high restenosis rates and stent breakage. In the present study, we evaluated the application of a short drug-eluting balloon-expandable coronary stent for the endovascular treatment of these frequent lesions.

MATERIALS AND METHODS

In a period of 23 months, 48 patients (12 women, 36 men) with a mean age of 68 years (range, 46-82 years) harboring 52 significant ostial vertebral artery stenoses underwent treatment with short (8 mm) balloon-expandable paclitaxel-eluting coronary stents. Stents were deployed as closely as possible so that the proximal end was just at the origin of the vertebral artery, with high inflation pressure applied. Patients were under continuous medication with acetylsalicylic acid and clopidogrel before and after the treatment. Follow-up clinical assessment and angiography were performed in all patients.

RESULTS

Periprocedural complications were not encountered. Stenosis severity was reduced from 62 +/- 2% (mean +/- standard error of the mean) preprocedurally to 15 +/- 2% postprocedurally. Follow-up angiography at 7.7 +/- 0.6 months revealed a mean stenosis degree of 24 +/- 3%. None of the patients developed posterior circulation symptoms related to the treated segment during the follow-up period. Recurrent stenosis (>50%) at follow-up was found in 6 (12%) lesions.

CONCLUSIONS

Stent placement of significant ostial vertebral artery stenosis by using short drug-eluting stents is safe and yields good midterm patency rates and excellent protection from posterior circulation ischemia.

Distinct phosphodiesterase-4D variants integrate into protein kinase A-based signaling complexes in cardiac and vascular myocytes

Numerous cAMP-elevating agents regulate events required for efficient migration of arterial vascular smooth muscle cells (VSMCs). Interestingly, when the impact of cAMP-elevating agents on individual migration-related events is studied, these agents have been shown to have distinct, and sometimes unexpected, effects. For example, although cAMP-elevating agents inhibit overall migration, they promote VSMC adhesion to extracellular matrix proteins and the formation of membrane extensions, which are both events that are essential for and promote migration. Herein, we extend previous observations that identified phosphodiesterase-4D3 (PDE4D3) as an integral component of a PKA/A kinase-anchoring protein (AKAP) complex in cultured/hypertrophied rat cardiac myocytes to the case for nonhypertrophied cardiac myocytes. Moreover, we show that while rat aortic VSMCs also express PDE4D3, this protein is not detected in PKA/AKAP complexes isolated from these cells. In contrast, we show that another PDE4D splice variant expressed in arterial vascular myocytes, namely, PDE4D8, integrates into PKA/AKAP-based signaling complexes in VSMCs. Consistent with the idea that a PDE4D8/PKA/AKAP complex regulates specific VSMC functions, PKA and PDE4D8 were each recruited to leading-edge structures in migrating VSMCs, and inhibition of PDE4D8 recruitment to pseudopodia of migrating cells caused localized changes in actin dynamics. Our data are presented in the context that cardiac myocytes and arterial VSMCs may use distinct PDE4D variants to regulate selected pools of targeted PKA activity and that disruption of this complex may allow selective regulation of cAMP-dependent events between these two cardiovascular cell types.

The development of peptide-based interfacial biomaterials for generating biological functionality on the surface of bioinert materials

Biomaterials used in implants have traditionally been selected based on their mechanical properties, chemical stability, and biocompatibility. However, the durability and clinical efficacy of implantable biomedical devices remain limited in part due to the absence of appropriate biological interactions at the implant interface and the lack of integration into adjacent tissues. Herein, we describe a robust peptide-based coating technology capable of modifying the surface of existing biomaterials and medical devices through the non-covalent binding of modular biofunctional peptides. These peptides contain at least one material binding sequence and at least one biologically active sequence and thus are termed, "Interfacial Biomaterials" (IFBMs). IFBMs can simultaneously bind the biomaterial surface while endowing it with desired biological functionalities at the interface between the material and biological realms. We demonstrate the capabilities of model IFBMs to convert native polystyrene, a bioinert surface, into a bioactive surface that can support a range of cell activities. We further distinguish between simple cell attachment with insufficient integrin interactions, which in some cases can adversely impact downstream biology, versus biologically appropriate adhesion, cell spreading, and cell survival mediated by IFBMs. Moreover, we show that we can use the coating technology to create spatially resolved patterns of fluorophores and cells on substrates and that these patterns retain their borders in culture.