Current status of drug-eluting stents

Liquid Metal-Based Flexible Bioelectrodes for Management of In-Stent-Restenosis: Potential Application

Although vascular stents have been widely used in clinical practice, there is still a risk of in-stent restenosis after their implantation. Combining conventional vascular stents with liquid metal-based electrodes with impedance detection, irreversible electroporation, and blood pressure detection provides a new direction to completely solve the restenosis problem. Compared with conventional rigid electrodes, liquid metal-based electrodes combine high conductivity and stretchability, and are more compliant with the implantation process of vascular stents and remain in the vasculature for a long period of time. This perspective reviews the types and development of conventional vascular stents and proposes a novel stent that integrates liquid metal-based electrodes on conventional vascular stents. This vascular stent has three major functions of prediction, detection and treatment, and is expected to be a new generation of cardiovascular implant with intelligent sensing and real-time monitoring.

Evolutionary perspective of drug eluting stents: from thick polymer to polymer free approach

BACKGROUND

Introduction of Bare Metal Stents (BMS) was itself a revolutionary step in the history of the medical industry; however, Drug Eluting Stents (DES) maintained its superiority over BMS in every aspect from restenosis rate to late lumen loss. The reason behind the magnanimous position of the DES in the stent market is the degree of improvement with which it evolves. New and better stents come into the market every year, surpassing their predecessors by many folds.

LITERATURE REVIEW

This review paper discusses the journey of DES with supporting clinical trials in detail. In the first generation, there were stainless-steel stents with thicker coatings. Although they had superior results compared to BMS, there was still room for improvement. Afterward came the second-generation stents, which had superior metal platforms with thinner struts and thin coatings. The drugs were also changed from Paclitaxel and Sirolimus to Zotrolimus and Everolimus. These stents performed best; however, there was an issue of permanent coating, which remained intact over the stent surface after complete drug elution and started to cause issues in longer-term studies. Hence, an improved version of DES was introduced to these permanent coatings called the third generation of drug eluting stents, which initially utilized biodegradable polymer and ultimately moved towards polymer free drug coatings. This generation has introduced a unique amalgam of technologies to achieve its polymer free coatings; however, researchers have numerous prospects of growth in this field. This review paper highlights the major coups of stent technology evolution from BMS to DES, from thick polymeric coatings to thin coatings and from durable polymers to polymer free DES.

CONCLUSION

In conclusion, though the medical industry promptly accepted BMS as the best treatment option for cardiovascular diseases; however, DES has provided even better results than BMS. In DES, the first and second generation has ruled the technology for many years and are still on the shelves. Still, the issues aroused due to durable polymer shifted the attention towards biodegradable drug eluting stents, the third generation growing rapidly. But the scientific community has not restricted themselves and is investigating bioresorbable stents that completely eliminate the polymer intervention in drug eluting stent technology.

Interim Results of the Basket of Real-World Randomised Clinical PRISM Trials for M’Sure-S, a Next-Generation Sirolimus-Eluting Stent, Versus Eliminator, an Everolimus-Eluting Stent

Objective: This study compared sirolimus-eluting stents (SES) with everolimus-eluting stents (EES) in coronary artery disease patients. Methods: A total of 1,174 patients were enrolled in the study; 290 patients (25.28%) were treated with EES and 884 patients (74.72%) were treated with SES. The trial (PRISM) was a randomised (in a 3:1 ratio), multicentre, single-blind, all-comers, single-arm, non-inferiority trial comparing SES and EES-implanted patients with coronary artery disease. The primary endpoint was a composite of safety parameters (including major adverse cardiac events [MACE], cardiac death, and myocardial infarction) and efficacy (parameters concerned to quantitative coronary angiogram). An intention-to-treat analysis was performed at 9 and 18-month follow-ups. Results: The baseline characteristics were similar for both EES and SES groups. At the 9-month follow-up, MACE occurred in 5.86% and 2.43% of patients in the EES and SES groups, respectively. At the 18-month follow-up, this differential remained almost the same (i.e., 5.17 % of patients treated with the EES versus 2.14% treated with the SES). The rate of definite stent thrombosis at 9-month follow-up was lower in the SES group (11 patients [1.24%]) compared to the EES group (9 patients [3.10%]). At 18-month follow-up, the rate was 2.14% (19 patients) in the SES group and 4.13% (12 patients) in the EES group. When censoring the patients at the time of stent thrombosis, no significant differences between the two stent groups were found. Conclusion: In this real-world trial, at 9 and 18-month follow-ups, SES (M’Sure-S) exhibited a better safety and efficacy profile when compared to EES in terms of MACE rates and definite stent thrombosis. However, the difference was not statistically significant and SES was found to be non-inferior to EES.

Revolution of Drug-Eluting Coronary Stents: An Analysis of Market Leaders

Percutaneous coronary intervention with drug-eluting stents (DES) is a well-established and widely-accepted treatment approach in patients with coronary artery disease. Although the underlying principle of DES remains constant for different stents available on the market, certain factors may offer variations with respect to deliverability (ease of placement), efficacy (preventing restenosis), and safety (thrombosis rates). These factors may include the type of drug (sirolimus, everolimus, biolimus, zotarolimus, novolimus, paclitaxel, docetaxel), type of stent platforms (stainless steel, platinum, cobalt-chromium, cobalt-nickel, platinum-chromium), type of polymers (permanent, biodegradable, polymer-free), thickness of stent struts (thick, thin, ultra-thin), type of coating (abluminal, conformal), and type of stent design (open-cell, closed-cell, combination of open-closed cell). In this context, we present a review on characteristic features of several of the most widely used coronary stents worldwide. Furthermore, the advancements of completely biodegradable stents are discussed. In addition, the future directions for the development of creating an ideal or perfect DES are debated.

Feasibility and Efficacy of Herculink Elite ((TM)) Biliary Stent Implantation in Large Coronary Arteries (≥ 5 mm) and Venous Conduits: An Observational Study

BACKGROUND AND OBJECTIVES

Percutaneous coronary intervention (PCI) in patients with lesions of large calibre coronary arteries (≥ 5 mm) and saphenous venous grafts (≥ 5 mm) can be challenging. There are no separate guidelines available to treat these vessels with PCI. Standard coronary stents of 4 mm diameter are used to treat these lesions conventionally but carry the risk of under deployment, distortion of stent architecture and future stent thrombosis even if they are subsequently expanded beyond 5 mm.

METHODS AND RESULTS

Biliary stents (Herculink Elite™) provide a better alternative to standard coronary stents in these patients. These stents are of larger diameter (5-7 mm) and can be safely delivered over a 6 French sheath. In our case series, we demonstrate the use of intravascular ultrasound examination to confirm that biliary stents provide improved stent strut apposition within the coronary artery associated with extremely low repeat revascularisation rates.

CONCLUSION

Our paper highlights that PCI of lesions in patients with large calibre coronary arteries can successfully be achieved using biliary stents.

Biodegradable polymer biolimus-eluting stent versus durable polymer everolimus-eluting stent in patients with acute myocardial infarction

BACKGROUND

There are limited data about long-term outcomes for biodegradable polymer biolimus-eluting stent (BES) versus durable polymer everolimus-eluting stent (EES) in patients undergoing percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI). We sought to compare the two-year efficacy and safety of BES versus EES in AMI patients.

METHODS

A total of 707 consecutive patients with ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction who underwent PCI with BES (n=171) or EES (n=536) between July 2008 and June 2012 were enrolled in this study. The efficacy endpoint (target vessel failure; a composite of cardiac death, target vessel-related myocardial infarction, and target vessel revascularization) and the safety endpoint (a composite of all cause death, myocardial infarction, and stent thrombosis) at two years were compared in crude and propensity score-matched cohorts.

RESULTS

After two years, target vessel failure occurred in 13 patients treated with BES and 49 patients treated with EES (7.6% versus 9.1%; adjusted hazard ratio [HR], 1.09; 95% confidence interval [CI], 0.58-2.04; p=0.78). The rates of composite safety endpoint at two years were not different between two groups (BES 7.6% versus EES 10.8%; adjusted HR, 0.87; 95% CI, 0.47-1.62; p=0.66). The rates of stent thrombosis did not differ between two groups (BES 0.6% versus EES 1.3%; adjusted HR, 0.63; 95% CI, 0.06-6.20; p=0.69). These findings were substantiated by similar results in the propensity score-matched cohort.

CONCLUSIONS

In the treatment of patients with AMI, BES showed similar efficacy and safety compared to those of EES for up to two years.

Short-term inhibition of DPP-4 enhances endothelial regeneration after acute arterial injury via enhanced recruitment of circulating progenitor cells

BACKGROUND

Endothelial injuries regularly occur in atherosclerosis and during interventional therapies of the arterial occlusive disease. Disturbances in the endothelial integrity can lead to insufficient blood supply and bear the risk of thrombus formation and acute vascular occlusion. At present, effective therapeutics to restore endothelial integrity are barely available. We analyzed the effect of pharmacological DPP-4-inhibition by Sitagliptin on endogenous progenitor cell-based endothelial regeneration via the SDF-1α/CXCR4-axis after acute endothelial damage in a mouse model of carotid injury.

METHODS AND RESULTS

Induction of a defined endothelial injury was performed in the carotid artery of C57Bl/6 mice which led to a local upregulation of SDF-1α expression. Animals were treated with placebo, Sitagliptin or Sitagliptin+AMD3100. Using mass spectrometry we could prove that Sitagliptin prevented cleavage of the chemokine SDF-1α. Accordingly, increased SDF-1α concentrations enhanced recruitment of systemically applied and endogenous circulating CXCR4+ progenitor cells to the site of vascular injury followed by a significantly accelerated reendothelialization as compared to placebo-treated animals. Improved endothelial recovery, as well as recruitment of circulating CXCR4+ progenitor cells (CD133+, Flk1+), was reversed by CXCR4-antagonization through AMD3100. In addition, short-term Sitagliptin treatment did not significantly promote neointimal or medial hyperplasia.

CONCLUSION

Sitagliptin can accelerate endothelial regeneration after acute endothelial injury. DPP-4 inhibitors prevent degradation of the chemokine SDF-1α and thus improve the recruitment of regenerative circulating CXCR4+ progenitor cells which mediate local endothelial cell proliferation without adversely affecting vessel wall architecture.

Drug-eluting metallic stents in urology

Drugeluting metal stents (DESs) have been extensively used in coronary and vascular disease. This type of stents has been proven to provide significantly lower restenosis rates due to the reduction of neo-intimal hyperplasia in comparison to the traditionally used bare metal stents (BMSs). The latter stents have been evaluated for more than a decade in urological practice in an attempt to provide permanent relief of urethral or ureteral obstruction. Although the initial results were promising, long-term experience revealed significant complications, which are mainly attributed to stent-related hyperplastic reaction compromising stent patency. The favorable experience of vascular DESs led to the application of DESs in both the urethra and ureter of animal models. These experimental results demonstrated a reduction of hyperplastic reaction of DESs in comparison to BMSs. Nevertheless, clinical data are currently not available. Considering the fact that DESs are under continuous development, the use of DESs in urology holds promise for the future and seems to be an intriguing field.

Biodegradable stents in gastrointestinal endoscopy

Biodegradable stents (BDSs) are an attractive option to avoid ongoing dilation or surgery in patients with benign stenoses of the small and large intestines. The experience with the currently the only BDS for endoscopic placement, made of Poly-dioxanone, have shown promising results. However some aspects should be improved as are the fact that BDSs lose their radial force over time due to the degradable material, and that can cause stent-induced mucosal or parenchymal injury. This complication rate and modest clinical efficacy has to be carefully considered in individual patients prior to placement of BDSs. Otherwise, the price of these stents therefore it is nowadays an important limitation.

Comparison of newer-generation drug-eluting with bare-metal stents in patients with acute ST-segment elevation myocardial infarction: a pooled analysis of the EXAMINATION (clinical Evaluation of the Xience-V stent in Acute Myocardial INfArcTION) and COMFORTABLE-AMI (Comparison of Biolimus Eluted From an Erodible Stent Coating With Bare Metal Stents in Acute ST-Elevation Myocardial Infarction) trials

OBJECTIVES

This study sought to study the efficacy and safety of newer-generation drug-eluting stents (DES) compared with bare-metal stents (BMS) in an appropriately powered population of patients with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

Among patients with STEMI, early generation DES improved efficacy but not safety compared with BMS. Newer-generation DES, everolimus-eluting stents, and biolimus A9-eluting stents, have been shown to improve clinical outcomes compared with early generation DES.

METHODS

Individual patient data for 2,665 STEMI patients enrolled in 2 large-scale randomized clinical trials comparing newer-generation DES with BMS were pooled: 1,326 patients received a newer-generation DES (everolimus-eluting stent or biolimus A9-eluting stent), whereas the remaining 1,329 patients received a BMS. Random-effects models were used to assess differences between the 2 groups for the device-oriented composite endpoint of cardiac death, target-vessel reinfarction, and target-lesion revascularization and the patient-oriented composite endpoint of all-cause death, any infarction, and any revascularization at 1 year.

RESULTS

Newer-generation DES substantially reduce the risk of the device-oriented composite endpoint compared with BMS at 1 year (relative risk [RR]: 0.58; 95% confidence interval [CI]: 0.43 to 0.79; p = 0.0004). Similarly, the risk of the patient-oriented composite endpoint was lower with newer-generation DES than BMS (RR: 0.78; 95% CI: 0.63 to 0.96; p = 0.02). Differences in favor of newer-generation DES were driven by both a lower risk of repeat revascularization of the target lesion (RR: 0.33; 95% CI: 0.20 to 0.52; p < 0.0001) and a lower risk of target-vessel infarction (RR: 0.36; 95% CI: 0.14 to 0.92; p = 0.03). Newer-generation DES also reduced the risk of definite stent thrombosis (RR: 0.35; 95% CI: 0.16 to 0.75; p = 0.006) compared with BMS.

CONCLUSIONS

Among patients with STEMI, newer-generation DES improve safety and efficacy compared with BMS throughout 1 year. It remains to be determined whether the differences in favor of newer-generation DES are sustained during long-term follow-up.

Clinical outcomes of everolimus- and zotarolimus-eluting stents in patients with acute myocardial infarction for small coronary artery disease

BACKGROUND AND PURPOSE

There were limited data about comparison of zotarolimus-eluting stents (ZES) and everolimus-eluting stents (EES) in patients with small coronary artery disease (CAD), especially in patients with acute myocardial infarction (AMI). The objective of this study was to compare the clinical outcomes of ZES and EES in patients with AMI for small CAD.

METHODS AND SUBJECTS

A total 1565 AMI patients treated with Endeavor-ZES (n=651) (Medtronic CardioVascular, Santa Rosa, CA, USA) or Xience V/Promus-EES (n=914) (Abbott Vascular, Temecula, CA/Boston Scientific, Natick, MA, USA) for small CAD (stent diameter ≤ 2.75 mm) in KAMIR (Korea Acute Myocardial Infarction Registry) were enrolled. After propensity score matching to adjust for baseline clinical and angiographic characteristics, we compared a total 1302 patients (651 ZES and 651 EES) about major adverse cardiac events (MACE) at 1-year. Subgroup analysis about 1-year clinical outcomes was undertaken in patients who were discharged alive.

RESULTS

Baseline clinical and angiographic characteristics were similar between the two groups after propensity score matching. Total MACE did not differ between the two groups before (9.8% vs. 8.2%, p=0.265) and after (9.8% vs. 9.4%, p=0.778) propensity score matching. The EES group showed lower rate of 1-year cardiac death (5.4% vs. 3.3%, p=0.041), target lesion failure (TLF; 6.9% vs. 4.3%, p=0.022), and stent thrombosis (1.4% vs. 0.4%, p=0.042) compared with the ZES group. However, there were no differences in 1-year cardiac death, TLF, and stent thrombosis in propensity score matched populations. Other various 1-year clinical outcomes showed no difference between the two groups. Subgroup analysis in patients who were discharged alive showed similar outcomes between the two groups at 1-year follow-up.

CONCLUSION

In-this propensity score matched analysis, EES and ZES showed no significant difference in clinical outcomes at 1-year follow-up in patients with AMI for small CAD.

The decline effect in cardiovascular medicine: is the effect of cardiovascular medicine and stent on cardiovascular events decline over the years?

The term decline effect is referred to a diminution of scientifically discovered effects over time. Reasons for the decline effect are multifaceted and include publication bias, selective reporting, outcomes reporting bias, regression to the mean, scientific paradigm shift, overshadowing and habituation, among others. Such effects can be found in cardiovascular medicines through medications (e.g., aspirin, antithrombotics, proton pump inhibitor, beta-blockers, statins, estrogen/progestin, angiotensin converting enzyme inhibitor etc.), as well as with interventional devices (e.g., angioplasty, percutaneous coronary intervention, stents). The scientific community should understand the various dimensions of the decline effects, and effective steps should be undertaken to prevent or recognize such decline effects in cardiovascular medicines.

New-generation drug-eluting stents: focus on Xience V® everolimus-eluting stent and Resolute® zotarolimus-eluting stent

Compared to bare metal stent angioplasty, first-generation drug-eluting stents (DES) have markedly reduced the incidence of in-stent restenosis. However, given the increased concerns over late and very late stent thrombosis, newer-generation DES were developed. To date, these DES have virtually replaced the use of first-generation DES worldwide. In this review article, we carefully consider the pre-clinical and clinical trials that have been performed with currently available, european conformity-marked and Food and Drug Administration-approved new-generation Resolute(®) and Xience V(®) DES.

Drug-eluting stent restenosis: effect of drug type, release kinetics, hemodynamics and coating strategy

Restenosis following stent implantation diminishes the procedure's efficacy influencing long-term clinical outcomes. Stent-based drug delivery emerged a decade ago as an effective means of reducing neointimal hyperplasia by providing localized pharmacotherapy during the acute phase of the stent-induced injury and the ensuing pathobiological mechanisms. However, drug-eluting stent (DES) restenosis may still occur especially when stents are used in complex anatomical and clinical scenarios. A DES consists of an intravascular metallic frame and carriers which allow controlled release of active pharmaceutical agents; all these components are critical in determining drug distribution locally and thus anti-restenotic efficacy. Furthermore, dynamic flow phenomena characterizing the vascular environment, and shear stress distribution, are greatly influenced by stent implantation and play a significant role in drug deposition and bioavailability within local vascular tissue. In this review, we discuss the performance of DES and the interaction of the different DES components with the hemodynamic milieu emphasizing on the inhibition of clinical restenosis.

Bivalirudin inhibits periprocedural platelet function and tissue factor expression of human smooth muscle cells

AIM

A major concern of stent implantation after percutaneous coronary intervention (PCI) is acute stent thrombosis. Effective inhibition of periprocedural platelet function in patients with coronary artery disease (CAD) leads to an improved outcome. In this study, we examined the periprocedural platelet reactivity after administrating bivalirudin during PCI compared to unfractionated heparin (UFH) administration. Further, the effect of bivalirudin on induced tissue factor (TF) expression in smooth muscle cells (SMC) was determined.

METHODS

Patients with CAD (n = 58) and double antithrombotic medication were treated intraprocedural with UFH (n = 30) or bivalirudin (n = 28). Platelet activation markers were flow cytometrically measured before and after stenting. The expression of TF in SMC was determined by real-time PCR and Western blotting. The thrombogenicity of platelet-derived microparticles and SMC was assessed via a TF activity assay.

RESULTS

Bivalirudin significantly diminished the agonist-induced platelet reactivity post-PCI. Compared to UFH treatment, the adenosine diphosphate (ADP) and thrombin receptor-activating peptide (TRAP)-induced thrombospondin expression post-PCI was reduced when bivalirudin was administrated during intervention. In contrast to UFH, bivalirudin reduced the P-selectin expression of unstimulated and ADP-induced platelets post-PCI. Moreover, bivalirudin inhibited the thrombin-, but not FVIIa- or FVIIa/FX-induced TF expression and pro-coagulant TF activity of SMC. Moreover, bivalirudin reduced the TF activity of platelet-derived microparticles postinduction with TRAP or ADP.

CONCLUSIONS

Bivalirudin is better than UFH in reducing periprocedural platelet activation. Moreover, thrombin-induced TF expression is inhibited by bivalirudin. Thus, bivalirudin seems to be a better anticoagulant during PCI than UFH.

Chemical surface alteration of biodegradable magnesium exposed to corrosion media

The understanding of corrosion processes of metal implants in the human body is a key problem in modern biomaterial science. Because of the complicated and adjustable in vivo environment, in vitro experiments require the analysis of various physiological corrosion media to elucidate the underlying mechanism of "biological" metal surface modification. In this paper magnesium samples were incubated under cell culture conditions (i.e. including CO(2)) in electrolyte solutions and cell growth media, with and without proteins. Chemical mapping by high-resolution electron-induced X-ray emission spectroscopy and infrared reflection microspectroscopy revealed a complex structure of the formed corrosion layer. The presence of CO(2) in concentrations close to that in blood is significant for the chemistry of the oxidised layer. The presence of proteins leads to a less dense but thicker passivation layer which is still ion and water permeable, as osmolality and weight measurements indicate.

Gastrointestinal stent update

The use of self-expanding metallic stents in the upper gastrointestinal tract, placed under radiologic imaging or endoscopic guidance, is the current treatment of choice for the palliation of malignant gastrointestinal outlet obstructions. Advances in metallic stent design and delivery systems have progressed to the stage where this treatment is now considered a minimally invasive therapy. Metallic stent placement will broaden further into the field of nonsurgical therapy for the gastrointestinal tract. To date, metallic stents placed in the esophagus, gastric outlet, colorectum, and bile ducts are not intended to be curative, but rather to provide a palliative treatment for obstructions. The evolution of metallic stent technology will render such procedures not only palliative but also therapeutic, by enabling local drug delivery, and the use of biodegradable materials will reduce procedure-related complications.