Drug-Eluting Stents and Late Adverse Clinical Outcomes

Platinum chromium everolimus-eluting stents for the treatment of (complex) coronary artery disease; from SYNERGY™ to the MEGATRON™

INTRODUCTION

The introduction of drug-eluting coronary stents (DES) into clinical practice in 2002 represented a major milestone in the treatment of obstructive coronary artery disease. Over the years, significant advances in polymer coating and in antiproliferative agent technology have further improved the safety and clinical performance of newer-generation DES.

AREAS COVERED

Development of platinum chromium (PtCr) alloys with high radial strength and high radiopacity have enabled the design of new, thin-strut, flexible, and highly trackable stent platforms, while simultaneously improving stent visibility. These advances have facilitated complex percutaneous treatment of a diverse population of patients in clinical practice. This review will provide an overview of the evolution in PtCr everolimus-eluting stents from PROMUS Element™ to SYNERGY™ to the recently introduced SYNERGY MEGATRON™. The clinical data will be summarized and put into perspective, especially focusing on the role of the SYNERGY™ and MEGATRON™ platforms in the treatment of complex coronary artery disease and high-risk patients.

EXPERT OPINION

The SYNERGY™ stent demonstrates favorable clinical efficacy and safety outcome data, and whilst the clinical data on MEGATRON™ are sparse, early experience is promising. The specific overexpansion capabilities, visibility, and radial strength of the MEGATRON™ are attractive features for complex coronary interventions.

Management of Concomitant Severe Thermal Injury and ST-Elevation Myocardial Infarction

Acute coronary thrombosis is a known, but rare, contributor to morbidity and mortality in patients with thermal and electrical injuries. The overall incidence of myocardial infarction among burn patients is 1%, with an in-hospital post-infarction mortality of approximately 67%, whereas the overall mortality rate of the general burn patient population is from 1.4% to 18%. As such, early detection and effective peri-operative management are essential to optimize patient outcomes. Here, we report the details of the management of an adult male patient with a 65% total body surface area severe thermal injury, who developed an ST-elevation myocardial infarction (STEMI) in the resuscitation period. The patient was found to have 100% occlusion of his left anterior descending coronary artery, for which prompt coronary artery stent placement with a drug-eluting stent (DES) was performed. Following stent placement, the patient required dual antiplatelet therapy. The ongoing dual antiplatelet therapy required the development of a detailed peri-operative protocol involving pooled platelets, packed red blood cells, desmopressin (DDAVP™) and intraoperative monitoring of the patient's coagulation parameters with thromboelastography for three staged operative interventions to achieve complete debridement and skin grafting of his burn wounds.

Mobilization of progenitor cells and vessel healing after implantation of SYNERGY in acute coronary syndrome

This study was aimed to compare the vascular healing process of a SYNERGY stent with that of a PROMUS PREMIER stent in patients with acute coronary syndrome (ACS). In 71 patients with ACS, undergoing coronary stent implantation using the SYNERGY stent (n = 52) or PROMUS PREMIER stent (n = 19), we measured circulating CD34+/CD133+/CD45^null cells and CD34+/KDR+ cells and observed vascular healing at the stented sites using optical coherence tomography (OCT) and coronary angioscopy. On the day 7, circulating CD34+/CD133+/CD45^null cells increased in SYNERGY group (P < 0.0001), while it did not change in PROMUS group. The CD34+/KDR+ cells also increased in SYNERGY group (P < 0.0001) but less significantly in the PROMUS group (P < 0.05). The OCT-based neointimal thickness (P < 0.0005) and neointimal coverage rate (P < 0.05) at 12 months were greater in SYNERGY group, compared with PROMUS group. The coronary angioscopy-based neointimal coverage grade at 12 months was also greater in SYNERGY group (P < 0.001). In overall patients, the change in CD34+/KDR+ cells on the day 7 correlated with the OCT-based neointimal thickness at 12 months (R = 0.288, P < 0.05). SYNERGY stent seems to have potential advantages over PROMUS PREMIER stent for ACS patients in terms of vascular healing process at the stented sites.

Heart team 2.0: A decision tree for minimally invasive and hybrid myocardial revascularization

Recent years have seen an important shift in the target population for myocardial revascularization. Patients are increasingly presenting with more complex coronary artery disease (CAD), but also with multiple comorbidities and frailty. At the same time, minimally invasive strategies such as Minimally Invasive Direct Coronary Artery Bypass Grafting (MIDCAB) and Percutaneous Coronary Interventions (PCI) have been developed, which might be more appealing for this group of patients. As a result, the landscape of options for myocardial revascularization is evolving while adequate use of all resources is required to ensure optimal patient care. Heart Teams are confronted with the challenge of incorporating the new minimally invasive strategies into the decision process, yet current guidelines do not fully address this challenge. In this review, the current evidence regarding outcomes, indications, benefits, and risks of off-pump coronary artery bypass grafting (OPCAB), MIDCAB, PCI, and hybrid coronary revascularization (HCR) are discussed. Based on this evidence and on experiences from Heart Team discussions, a new decision tree is proposed that incorporates recent advances in minimally invasive revascularization strategies, thereby optimizing adequate delivery of care for each individual patient's needs. Introducing all important considerations in a logical way, this tool facilitates the decision-making process and might ensure appropriate use of resources and optimal care for individual patients.

Magmaris resorbable magnesium scaffold for the treatment of coronary heart disease: overview of its safety and efficacy

Introduction: Bioresorbable scaffold technology provides transient vessel support with drug-delivery capability without the long-term limitations of the permanent metallic drug-eluting stents (DES). The technology has the potential to overcome many of the safety concerns associated with metallic DES, such as hypersensitivity reactions, late stent thrombosis and progression of atherosclerosis within the stented segment (i.e. neoatherosclerosis). Areas covered: The sirolimus-eluting resorbable magnesium scaffold Magmaris is the only metallic CE-marked resorbable scaffold currently available. This magnesium scaffold is designed for providing a short-term lumen support (up to 3 months) before being completely bioresorbed, eliminating the permanent caging typical of the metallic DES. This review will focus on the device development and characteristics, currently available clinical efficacy and safety data, and potential future perspectives. Expert opinion: The first clinical studies testing this device in a small number of patients have shown promising results with good clinical and safety outcomes up to 3 years' clinical follow-up, supporting the use of Magmaris in simple coronary artery disease.

Perioperative Complications in Patients with Drug-Eluting Stents: A Three-Year Audit at Geelong Hospital

Drug-eluting stents are a recommended treatment for lesions in the coronary arteries. Stent insertion requires the patient remain on antiplatelet medication for a minimum of six months after insertion. A serious consequence of ceasing antiplatelet medication is late stent thrombosis leading to myocardial infarction in the territory of the drug-eluting stent. Continuing antiplatelet medication can lead to excessive bleeding at the time of surgery. Understanding the risk of complications attributable to bleeding or myocardial ischaemia will help in defining the optimal management of these patients at the time of noncardiac surgery.

This study is a retrospective database analysis and case note review of all patients with drug-eluting stents presenting for noncardiac surgical procedures over a three-year period in one centre.

Twenty-four patients with drug-eluting stents inserted presented for 43 noncardiac surgical procedures. Severe bleeding problems were encountered in one case. Three of 15 patients (20%) who ceased clopidogrel prior to surgery without alternative anti-thrombotic prophylaxis suffered myocardial infarction due to stent thrombosis. Four patients who received alternative anti-thrombotic prophylaxis did not suffer complications. All 19 patients who ceased clopidogrel remained on aspirin prior to surgery.

Patients treated with drug-eluting stents for coronary artery stenosis represent a challenging group of patients for subsequent perioperative management. The risk of myocardial infarction when clopidogrel is stopped prior to surgery is 20%, if alternative anti-thrombotic prophylaxis is not used. This risk persists beyond one year after insertion of drug-eluting stents. Some treatments appear to be effective in reducing the risk of myocardial infarction.

Coronary stents and vascular response to implantation: literature review

Drug-eluting stents (DESs) have minimized the limitations of bare-metal stents (BMSs) after percutaneous coronary interventions. Nevertheless, serious concerns remain about possible late complications of stenting, such as stent thrombosis (ST) and in-stent restenosis (ISR), although the introduction of second-generation DESs seems to have softened the phenomenon, compared to the first-generation ones. ST is a potentially catastrophic event, which has been markedly reduced by optimization of stent implantation, novel stent designs, and dual antiplatelet therapy. The exact mechanism to explain its occurrence is under investigation, and, realistically, multiple factors are responsible. ISR of BMSs has been previously considered as a stable condition with an early peak (at 6 months) of intimal hyperplasia, followed by a regression period beyond 1 year. On the contrary, both clinical and histologic studies of DESs have demonstrated evidence of continuous neointimal growth during long-term follow-up, named "late catch-up" phenomenon. The acknowledgment that ISR is a relatively benign clinical condition has been recently challenged by evidences which reported that patients with ISR can experience acute coronary syndromes. Intracoronary imaging is an invasive technology that allows identifying features of atherosclerotic plaque of stent implanted and of vascular healing after stenting; it is often used to complete diagnostic coronary angiography and to drive interventional procedures. Intracoronary optical coherence tomography is currently considered a state-of-the-art imaging technique; it provides, compared to intravascular ultrasound, better resolution (at least >10 times), allowing the detailed characterization of the superficial structure of the vessel wall. Imaging studies "in vivo," in agreement with histological findings, suggest that chronic inflammation and/or endothelial dysfunction may induce late de novo "neoatherosclerosis" inside both BMSs and DESs. So, neoatherosclerosis has become the prime suspect in the pathogenesis of late stent failure.

Nanostructured ultra-thin patches for ultrasound-modulated delivery of anti-restenotic drug

This work aims to demonstrate the possibility to fabricate ultra-thin polymeric films loaded with an anti-restenotic drug and capable of tunable drug release kinetics for the local treatment of restenosis. Vascular nanopatches are composed of a poly(lactic acid) supporting membrane (thickness: ~250 nm) on which 20 polyelectrolyte bilayers (overall thickness: ~70 nm) are alternatively deposited. The anti-restenotic drug is embedded in the middle of the polyelectrolyte structure, and released by diffusion mechanisms. Nanofilm fabrication procedure and detailed morphological characterization are reported here. Barium titanate nanoparticles (showing piezoelectric properties) are included in the polymeric support and their role is investigated in terms of influence on nanofilm morphology, drug release kinetics, and cell response. Results show an efficient drug release from the polyelectrolyte structure in phosphate-buffered saline, and a clear antiproliferative effect on human smooth muscle cells, which are responsible for restenosis. In addition, preliminary evidences of ultrasound-mediated modulation of drug release kinetics are reported, thus evaluating the influence of barium titanate nanoparticles on the release mechanism. Such data were integrated with quantitative piezoelectric and thermal measurements. These results open new avenues for a fine control of local therapies based on smart responsive materials.

Preclinical evaluation of a novel abluminal surface coated sirolimus eluting stent with biodegradable polymer matrix

BACKGROUND

Second generation of drug eluting stents (DES) has attempted to improve safety using abluminal sirolimus drug delivery with biodegradable polymers matrix. The present preclinical study was designed to investigate the safety and efficacy profile of Abluminus™ stents (SES). This is a new coronary stent with sirolimus and biodegradable polymer matrix coated on abluminal stent and balloon surface.

METHODS

SES were compared with two controls: bare metal stent (BMS) and BMS + polymer coated stents (PC). All devices (40 stents) were implanted in porcine coronary arteries with primary endpoint of endothelialization at 7 days and subsequent histological and morphometric evaluations at 7, 30 and 90 days.

RESULTS

Early endothelialization at seven days was complete in all stents. Histology at 30 days revealed minimum inflammation in all groups and increased at 90 days in PC group while it was absent at 180 days. Thirty day morphometry showed significantly reduction of neointimal area in Abluminus™ (SES 0.96±0.48 mm(2); BMS 1.83±0.34 mm(2); PC 1.76±0.55 mm(2); P<0.05); after 90 days neointimal area was 1.10±0.54 mm(2) for SES; 1.92±0.36 mm(2) for BMS; and 1.94±0.48 mm(2) for PC; P<0.05). Neointimal thickness at 30 and 90 days respectively was 0.15±0.07 and 0.18±0.10 mm for SES, 0.57±0.08 and 0.61±0.09 mm for BMS and 0.52±0.09 and 0.59±0.08 mm, P<0.001 for PC group.

CONCLUSIONS

The most significant experimental evidence appears to be earlier endothelialization at 7 days for SES which led to safety of the device. Efficacy of the device was also observed by a reduced neointimal thickness and minimized inflammatory score at all follow-ups. Termination of antiplatelet at 30 days has not shown any further complications. Polymer thickness was almost in negligible amount at 180 days with no inflammation.

Clinical utility of platinum chromium bare-metal stents in coronary heart disease

Coronary stents represent a key development for the treatment of obstructive coronary artery disease since the introduction of percutaneous coronary intervention. While drug-eluting stents gained wide acceptance in contemporary percutaneous coronary intervention practice, further developments in bare-metal stents remain crucial for patients who are not candidates for drug-eluting stents, or to improve metallic platforms for drug elution. Initially, stent platforms used biologically inert stainless steel, restricting stent performance due to limitations in flexibility and strut thickness. Later, cobalt chromium stent alloys outperformed steel as the material of choice for stents, allowing latest generation stents to be designed with significantly thinner struts, while maintaining corrosion resistance and radial strength. Most recently, the introduction of the platinum chromium alloy refined stent architecture with thin struts, high radial strength, conformability, and improved radiopacity. This review will provide an overview of the novel platinum chromium bare-metal stent platforms available for coronary intervention. Mechanical properties, clinical utility, and device limitations will be summarized and put into perspective.

In vivo Evaluation of Cenderitide-Eluting Stent (CES) II

The use of drug-eluting coronary stents has led to significant reduction in in-stent restenosis (ISR), but led to delayed endothelialization, necessitating the prolonged use of expensive anti-thrombotic drugs with their side-effects. Cenderitide (CD-NP) is a novel anti-proliferative chimeric peptide of semi-endothelial origin. Our previous work in vitro has demonstrated; that the smooth muscle cells were inhibited significantly more than endothelial cells which is the desirable feature of an anti-restenosis drug. This work reports the effects of implantation of a centeritide-eluting stent (CES) on ISR and endothelialization in an in vivo model. CESs were produced by coating bare metallic stents with CD-NP entrapped in biodegradable poly(ε-caprolactone) using an ultrasonic spray coater. A total of 32 stents were successfully implanted into 16 pigs, and all animal survived for 28 days. The plasma levels of CD-NP were significantly higher in the CES group than in the control group (bare metal stents and polymer-coated stent) at post-stenting, indicating the successful release of CD-NP from the stent in vivo. Furthermore, SEM analysis results showed the greater endothelial coverage of the stent struts, as well as between the struts in CES group. Moreover, histological results showed mild inflammation, and low fibrin score at 28 days. However, plasma cGMP (second messenger, cyclic 3',5' guanosine monophosphate) does not show a significant difference, and the CES is also unable to show significant difference in terms on neointimal area and stenosis, in comparison to BMS at 28 days.

In vitro evaluation of cenderitide-eluting stent I -an antirestenosis and proendothelization approach

Despite the success that drug-eluting stents (DESs) have achieved for minimizing in-stent restenosis (ISR), the antirestenotic agents used in DES have been implicated in delayed endothelial healing and impairment of endothelial functions. Cenderitide (CD-NP) is a novel antiproliferation chimeric peptide of semiendothelial origin; thus, this paper aims to demonstrate the selectivity aspect of this new peptide via in vitro evaluation on key players in ISR-smooth muscle cells (SMCs) and endothelial cells. The microbicinchoninic acid protein assay was used to investigate the CD-NP release from films and stents. Cenderitide-containing films blended with poly(ethylene glycol) and its copolymer exhibited higher release kinetics compared with neat poly(ε-caprolactone) (PCL) formulation. Cenderitide-eluting stents (CES) was produced by coating bare metallic stents with CD-NP entrapped PCL using an ultrasonic spray coater. The investigation of CD-NP on in vitro cells revealed that CD-NP inhibits human coronary smooth muscle cells (HCaSMCs) proliferation but exhibits no effects on human umbilical vein endothelial cells (HUVECs) proliferation. Moreover, CD-NP released up to 7 days displayed inhibitory effects on SMCs proliferation. The CES produced in this work shows that the released CD-NP inhibits HCaSMCs proliferation but did not hamper HUVECs proliferation in vitro, suggesting that it has potential to reduce ISR without retarding the endothelialization healing in vivo.

Gallic acid tailoring surface functionalities of plasma-polymerized allylamine-coated 316L SS to selectively direct vascular endothelial and smooth muscle cell fate for enhanced endothelialization

The creation of a platform for enhanced vascular endothelia cell (VEC) growth while suppressing vascular smooth muscle cell (VSMC) proliferation offers possibility for advanced coatings of vascular stents. Gallic acid (GA), a chemically unique phenolic acid with important biological functions, presents benefits to the cardiovascular disease therapy because of its superior antioxidant effect and a selectivity to support the growth of ECs more than SMCs. In this study, GA was explored to tailor such a multifunctional stent surface combined with plasma polymerization technique. On the basis of the chemical coupling reaction, GA was bound to an amine-group-rich plasma-polymerized allylamine (PPAam) coating. The GA-functionalized PPAam (GA-PPAam) surface created a favorable microenvironment to obtain high ECs and SMCs selectivity. The GA-PPAam coating showed remarkable enhancement in the adhesion, viability, proliferation, migration, and release of nitric oxide (NO) of human umbilical vein endothelial cells (HUVECs). The GA-PPAam coating also resulted in remarkable inhibition effect on human umbilical artery smooth muscle cell (HUASMC) adhesion and proliferation. These striking findings may provide a guide for designing the new generation of multifunctional vascular devices.

A comparative study of the effects of vitamin C, sirolimus, and paclitaxel on the growth of endothelial and smooth muscle cells for cardiovascular medical device applications

Antiproliferative drugs such as sirolimus (SIR) and paclitaxel (PAT) are currently released from stents and vascular grafts to inhibit the growth of smooth muscle cells (SMCs), thereby preventing neointimal hyperplasia. However, these drugs delay or impair the growth of endothelial cells (ECs) on implant surfaces causing late thrombosis. Hence, there is a need to use alternative drugs in these implants to encourage the growth of ECs and to inhibit the growth of SMCs. Vitamin C (L-ascorbic acid [L-AA]) is one such drug which has been shown to encourage EC growth and inhibit SMC growth when orally administered or added directly to the cell cultures. In this research, four sets of in vitro cell culture experiments were carried out to compare the effects of L-AA, SIR, and PAT on the growth of ECs and SMCs under similar conditions, and to compare the effects of different doses of L-AA to determine the optimal dose for promoting maximum EC growth and inhibiting SMC growth. The ECs and SMCs treated with different drugs were characterized for their viability and proliferation, and morphology using the quantitative resazurin assay (as well as qualitative fluorescence microscopy characterization) and phase contrast microscopy, respectively, for up to 7 days. Also, the phenotype of ECs was characterized using immunofluorescence microscopy. Both SIR and PAT significantly inhibited the EC growth while L-AA significantly encouraged EC growth even more than that of the controls with no drugs. Also, L-AA significantly inhibited SMC growth although the inhibitory effect was inferior to that of SIR and PAT. The L-AA dosage study demonstrated that 100 μg and 300 μg of L-AA showed maximum EC growth after 7 days when compared to other dosages (1 μg, 500 μg, and 1000 μg) of L-AA and controls investigated in this study. Also, the 100 μg and 300 μg L-AA doses significantly inhibited the SMC growth. Thus, this study demonstrates that L-AA is a promising drug for potential use in stents and vascular grafts, to promote their endothelialization and inhibit neointimal hyperplasia.

A novel platinum chromium everolimus-eluting stent for the treatment of coronary artery disease

The development of coronary stents represents a major step forward in the treatment of obstructive coronary artery disease since the introduction of percutaneous coronary intervention. The initial enthusiasm for bare metal stents was, however, tempered by a significant incidence of in-stent restenosis, the manifestation of excessive neointima hyperplasia within the stented vessel segment, ultimately leading to target vessel revascularization. Later, drug-eluting stents, with controlled local release of antiproliferative agents, consistently reduced this need for repeat revascularization. In turn, the long-term safety of first-generation drug-eluting stents was brought into question with the observation of an increased incidence of late stent thrombosis, often presenting as myocardial infarction or sudden death. Since then, new drugs, polymers, and platforms for drug elution have been developed to improve stent safety and preserve efficacy. Development of a novel platinum chromium alloy with high radial strength and high radiopacity has enabled the design of a new, thin-strut, flexible, and highly trackable stent platform, while simultaneously improving stent visibility. Significant advances in polymer coating, serving as a drug carrier on the stent surface, and in antiproliferative agent technology have further improved the safety and clinical performance of newer-generation drug-eluting stents. This review will provide an overview of the novel platinum chromium everolimus-eluting stents that are currently available. The clinical data from major clinical trials with these devices will be summarized and put into perspective.

Endoscopic resection of bladder cancer in patients receiving double platelet antiaggregant therapy

BACKGROUND

Approximately 5% of patients who have undergone coronary artery stenting require noncardiac surgery within a year of their cardiac intervention. European cardiological guidelines and recommendations from the U.S. Food and Drug Administration on platelet antiaggregant therapy following coronary artery stenting are for dual treatment with acetylsalicylic acid and clopidogrel, which should be continued for at least 12 months. The aim of this study was to evaluate the clinical course in patients receiving double platelet antiaggregant therapy who underwent transurethral resection of bladder cancer.

METHODS

Between September 2007 and April 2010, twelve patients receiving double antithrombotic therapy (clopidogrel+acetylsalicylic acid) underwent transurethral resection of bladder cancer. In two cases the operation was "urgent". The mean age of the patients was 71.25 years (range, 52-83 years). In nine cases the bladder cancer was newly diagnosed.

RESULTS

The patients' preoperative mean hemoglobin concentration was 11.4 g/dl (range=5.2-13.4 g/dl), and on the first postoperative day it was 10.2 g/dl (range=9.6-12.6 g/dl). The mean duration of the intervention was 32 min (range=20-60 min). There were no cardiac complications in either the perioperative or the postoperative period. No patient required reintervention for hemostatic purposes. Three episodes of clot-related acute urinary retention occurred after removal of the bladder catheter, all of which were resolved with replacement of the catheter without needing reintervention.

CONCLUSION

Despite the high number of complications related to cardiac problems that suspension of these drugs causes, this urological intervention, carried out during dual antithrombotic therapy, was feasible and without major complications. Given the high proportion of complications due to clot-related urinary retention, it is advisable to leave the urinary catheter in place for a longer period.

Finite element shape optimization for biodegradable magnesium alloy stents

Biodegradable magnesium alloy stents (MAS) are a promising solution for long-term adverse events caused by interactions between vessels and permanent stent platforms of drug eluting stents. However, the existing MAS showed severe lumen loss after a few months: too short degradation time may be the main reason for this drawback. In this study, a new design concept of MAS was proposed and a shape optimization method with finite element analysis was applied on two-dimensional (2D) stent models considering four different magnesium alloys: AZ80, AZ31, ZM21, and WE43. A morphing procedure was utilized to facilitate the optimization. Two experiments were carried out for a preliminary validation of the 2D models with good results. The optimized designs were compared to an existing MAS by means of three-dimensional finite element analysis. The results showed that the final optimized design with alloy WE43, compared to the existing MAS, has an increased strut width by approximately 48%, improved safety properties (decreased the maximum principal stress after recoil with tissue by 29%, and decreased the maximum principal strain during expansion by 14%) and improved scaffolding ability (increased by 24%). Accordingly, the degradation time can be expected to extend. The used methodology provides a convenient and practical way to develop novel MAS designs.

Development of a novel prohealing stent designed to deliver sirolimus from a biodegradable abluminal matrix

BACKGROUND

We aimed to demonstrate that, by separating endothelial progenitor cell capture from sirolimus delivery through the application of drug to the abluminal surface of the stent, the degree of endothelialization can be enhanced.

METHODS AND RESULTS

Stainless steel R Stents, with biodegradable SynBiosys polymer coating with sirolimus abluminally applied and surface modified with anti-CD34 antibody were prepared at 2 dosages (low-dose sirolimus [LD-Combo, 2.5 microg sirolimus/mm] and full-dose sirolimus [Combo, 5 microg sirolimus/mm). These Combo stents and the Cypher stent (10 microg sirolimus/mm) were deployed in 98 normal porcine arteries and harvested for pharmacokinetic analysis at 0.25, 1, 3, 7, 14, 28, and 35 days. The LD-Combo stents showed faster early release (50%total dose in 72 hours) than the Combo and Cypher. At 30 days, drug release was near complete with both Combo stents, whereas 20% of drug remained on the Cypher stents. To assess efficacy, a total of 50 stents (Xience V=8, Cypher=8, Genous bioengineered R stent=6, LD-Combo=14, and Combo=14) were implanted in 18 pigs for 14 and 28 days. Optical coherence tomography was performed, and stents were harvested for histology. At 28 days, there was less neointimal thickness with Combo (0.173+/-0.088 mm) compared with Cypher (0.358+/-0.225 mm), LD-Combo (0.316+/-0.228 mm), and Xience V (0.305+/-0.252 mm; P<0.00001). Immunohistochemical analysis of endothelialization showed that Genous bioengineered R stent had the highest degree of platelet endothelial cell adhesion molecule expression (87%) followed by the Combo (75%), LD-Combo (65%), and Cypher (58%).

CONCLUSIONS

Both optical coherence tomography and histology demonstrate that anti-CD34 sirolimus-eluting stents promote endothelialization while reducing neointimal formation and inflammation.

In vitro and in vivo performance of a dual drug-eluting stent (DDES)

This study reports on a dual drug-eluting stent (DDES) that has an anti-proliferative and an anti-thrombotic in a biodegradable polymer-coated onto a cobalt-chromium stent. The DDES was prepared by spray coating the bare metal stent with a biodegradable polymer loaded with sirolimus and triflusal, to treat against restenosis and thrombosis, respectively. The 2-layered dual-drug coated stent was characterized in vitro for surface properties before and after expansion, as well as for possible delamination by cross-sectioning the stent in vitro. The in vitro anti-platelet behavior of the triflusal-loaded films was investigated by using dynamic platelet adhesion measurements. Additionally, the in vitro degradation and release study of the films and the stents w/single sirolimus and dual sirolimus-triflusal in different formulations were examined. Finally, in vivo studies (in a porcine carotid artery model) were performed for acute thrombosis, inflammation and restenosis at 30 days. The in vitro results show DDES can sustain release both anti-proliferation drug (sirolimus) and anti-thrombosis drug (triflusal), two drugs were controlled in different rates to effectively reduce thrombosis and proliferation at the same time. In vivo results show a significant reduction in restenosis with dual-drug eluting stent compared with the controls (a bare metal stent, a sirolimus coated and a pure polymer-coated stent). The reduction in restenosis with a dual sirolimus-triflusal eluting stent is associated with an inhibition of inflammation, especially thrombus formation, suggesting that such dual-drug eluting stents have a role to play for the treatment of coronary artery disease.

Next generation drug-eluting stents: focus on bioabsorbable platforms and polymers

The success of drug-eluting stents in preventing restenosis has shifted the focus of new stent development toward enhancing long term safety and efficacy of these devices, while simultaneously eliminating the need for indefinite dual antiplatelet therapy. A technical advance fulfilling these aims would hold tremendous potential to reduce morbidity, mortality and economic costs associated with the percutaneous treatment of coronary artery disease. An attractive approach is the use of bioabsorbable stent designs. These may include stents with different bioabsorbable drugs, bioabsorbable polymers or even bioabsorbable metallic backbones. A device that could achieve excellent acute and long-term results, but disappear completely within months (thereby avoiding the need for prolonged dual antiplatelet therapy), would be a tremendous advance. Too good to be true? We explore here the scientific rationale and prospects for success with this exciting concept.

The short-term effect on restenosis and thrombosis of a cobalt-chromium stent eluting two drugs in a porcine coronary artery model

The aim of this article was to study the effect of dual drug-eluting stent (DES) on both restenosis and thrombosis in a porcine coronary artery model. This study reports on the use of two drugs coated on the stent to simultaneously minimize both restenosis and thrombosis. The DES was prepared by spray coating a bare metal stent with a biodegradable polymer loaded with sirolimus and triflusal, to treat against restenosis and thrombosis, respectively. The two-layered dual drug-coated stent was characterized in vitro for surface properties before and after expansion, as well as for possible delamination by cross-sectioning the stent in vitro. In vivo animal studies (in a pig model) were then performed for acute thrombosis, inflammation, and restenosis. The results show a significant reduction in restenosis with a stent coated with both drugs compared with the controls (a bare metal stent, a sirolimus-coated, and a pure polymer-coated stent). The reduction in restenosis with a sirolimus/triflusal-eluting stent is associated with an inhibition of inflammation and thrombus formation, suggesting that such dual DES have a role to play for the treatment of coronary artery diseases.

Pre-intervention eosinophil cationic protein serum levels predict clinical outcomes following implantation of drug-eluting stents

AIMS

Eosinophils have been identified in post-mortem studies as important players of both restenosis and thrombosis after drug-eluting stent (DES) implantation. We aimed at assessing the association between baseline levels of eosinophil cationic protein (ECP), a marker of eosinophil activation, and recurrence of clinical events in a consecutive series of patients who underwent DES implantation.

METHODS AND RESULTS

Two hundred patients (age 63 +/- 10.4, males 75%) undergoing implantation of first-generation DES (Taxus or Cypher stents) were enrolled. We measured serum levels of ECP and total IgE by enzyme-linked immunosorbent assay and of C-reactive protein by high-sensitivity nephelometry prior to percutaneous coronary intervention. A clinical follow-up was planned 18 months after discharge. Major adverse cardiac events (MACEs), such as cardiac death, recurrent myocardial infarction, or clinically driven target lesion revascularization, were the endpoint of the study. Twenty-two patients (11%) had MACEs and showed higher serum levels of ECP compared with those without MACEs [30.5 (14.4-50) vs. 12.2 (4.4-31) microg/L, P = 0.004]. At simple Cox regression analysis, serum levels of ECP were a significant predictor of MACEs (hazard ratio 1.016, 95% confidence interval 1.003-1.03, P = 0.018).

CONCLUSION

This study shows for the first time an association between baseline ECP levels and the occurrence of MACEs in patients undergoing implantation of DES. Further studies are warranted to establish whether in this setting ECP is a risk marker or plays a contributory pathogenetic role.

[Patients with coronary artery stents: when and how should operations be carried out?]

Nowadays stents are implanted in over 90% of percutaneous coronary interventions. Depending on the type of stent implanted, dual antiplatelet therapy combining a cyclooxygenase inhibitor such as acetylsalicylic acid and an adenosine diphosphate receptor antagonist (thienopyridine) such as clopidogrel is required for 1-12 months. Premature termination of antiplatelet therapy during non-cardiac surgery significantly increases the risk of stent thrombosis and consequently myocardial infarction, whereas continuation of dual antiplatelet therapy during surgery increases the risk of severe bleeding. Accordingly, treatment recommendations have to be based on the individual relative risk. In cases with a high risk for major bleeding during surgery, interruption of antiplatelet therapy may be required, whereas in cases of a high risk of stent thrombosis, both antiplatelet drugs should be continued throughout surgery. Patients on dual antiplatelet therapy should be counseled by a team of anesthesiologists, surgeons and cardiologists, to devise the right point in time for the operation, the best perioperative antiplatelet therapy and the appropriate perioperative monitoring.

The problem of stent thrombosis associated with drug-eluting stents and the optimal duration of dual antiplatelet therapy

Drug-eluting stents have significantly reduced the problem of restenosis, but there is an association between drug-eluting stents and stent thrombosis that can be a significant clinical problem resulting in myocardial infarction or death. The risk for stent thrombosis increases in certain clinical situations and has been reduced through the use of dual antiplatelet therapy for prolonged periods. Until new therapies are developed, it is essential that patients who have had drug-eluting stents implanted continue with dual-antiplatelet therapy for at least 1 year and possibly for an indefinite period.

Long-term clinical benefit of sirolimus-eluting stents in patients with in-stent restenosis results of the RIBS-II (Restenosis Intra-stent: Balloon angioplasty vs. elective sirolimus-eluting Stenting) study

OBJECTIVES

We sought to assess the long-term effectiveness and safety of sirolimus-eluting stents (SES) in patients with in-stent restenosis (ISR).

BACKGROUND

Treatment of patients with ISR remains a challenge. The long-term outcome of patients with ISR treated with SES remains unknown.

METHODS

The RIBS-II (Restenosis Intra-stent: Balloon angioplasty vs. elective sirolimus-eluting Stenting) study was a randomized trial conducted in 150 patients with ISR (76 SES, 74 balloon angioplasty [BA]). The long-term (>1 year) clinical outcome and pre-specified subgroup analyses were pre-defined secondary study end points.

RESULTS

At 1 year, the event-free survival (death, myocardial infarction, target vessel revascularization [TVR]) was better in the SES group (88% vs. 69%, p < 0.005). Additional long-term (>3 years) clinical follow-up was obtained in 97% of patients (median 3.3 years). After the first year, 3 patients died (1 SES, 2 BA), 5 suffered myocardial infarction (4 SES, 1 BA), and 7 required TVR (4 SES, 3 BA). At last follow-up, definitive/probable/possible stent thrombosis was similar in both groups (2/2/1 SES vs. 1/0/3 BA, p = NS). At 4 years, the event-free survival was 76% in the SES arm and 65% in the BA arm (p = 0.019). On multivariate analysis, SES implantation was an independent predictor of event-free survival. Subgroup analyses were consistent with the main outcome measure.

CONCLUSIONS

In patients with ISR, SES implantation remains effective and safe at very long-term clinical follow-up.

Sirolimus-eluting stents versus bare-metal stents in patients with in-stent restenosis: results of a pooled analysis of two randomized studies

BACKGROUND

Treatment of patients with in-stent restenosis (ISR) remains a challenge. We sought to compare results of sirolimus-eluting stents (SES) with those of bare-metal stents (BMS) in patients with ISR.

METHODS

The results obtained in the stent arm of two randomized studies were analyzed. The RIBS I study (450 patients with ISR) allocated 224 patients to BMS; the RIBS II study (150 patients with ISR) allocated 76 patients to SES. Complete 1-year follow-up was obtained in all 300 patients treated with stents.

RESULTS

Although inclusion/exclusion criteria were identical in the two studies, when compared with patients in the BMS group, patients in the SES arm had more adverse baseline characteristics, more diffuse lesions, and smaller vessels. However, late angiographic findings including in-segment recurrent restenosis rate (11 vs. 38%, P < 0.001), minimal lumen diameter (2.52 vs. 1.63 mm, P < 0.001), and late loss (0.13 vs. 1.04 mm, P < 0.001) were significantly better after SES. The 1-year event-free survival was also significantly improved in the SES group (88 vs. 78%, P < 0.05), as the result of a lower requirement for repeated revascularizations (10.5 vs. 19.6%, P < 0.05). Prespecified subgroup analyses were consistent with the main outcome measures. After adjusting for (a) imbalances in baseline characteristics (restenosis OR 0.11 [95% confidence interval (CI) 0.03-0.36]; adverse events hazard ratios (HR) 0.33 [95% CI 0.13-0.84]) and (b) the propensity score (restenosis OR 0.08 [95% CI 0.03-0.28]; adverse events HR 0.24 [95% CI 0.09-0.66]), results of the SES group were superior to those obtained in the BMS group.

CONCLUSIONS

When compared with BMS, SES improved the long-term clinical and angiographic outcome of patients with ISR.

Coronary artery stents: Part I. Evolution of percutaneous coronary intervention

The subspecialty of interventional cardiology has made significant progress in the management of coronary artery disease over the past three decades with the development of percutaneous coronary transluminal angioplasty, atherectomy, and bare-metal and drug-eluting stents (DES). Bare-metal stents (BMS) maintain vessel lumen diameter by acting as a scaffold and prevent collapse incurred by angioplasty. However, these devices cause neointimal hyperplasia leading to in-stent restenosis and requiring reintervention in more than 20% of patients by 6 mo. DES (sirolimus and paclitaxel) prevent restenosis by inhibiting neointimal hyperplasia. However, DESs also delay endothelialization, causing the stents to remain thrombogenic for an extended, yet unknown, period of time. Late stent thrombosis is associated with a 45% mortality rate. Premature discontinuation of antiplatelet therapy, particularly clopidogrel, is the strongest predictor of stent thrombosis. Sixty percent of patients receive stents for off-label (unapproved) indications, which also increases the frequency of stent thrombosis. Clopidogrel and aspirin are the cornerstone of therapy in the prevention of stent thrombosis in both BMS and DES. Recommendations pertaining to the optimal duration of dual-antiplatelet therapy have been debated. Both the Food and Drug Administration and the American Heart Association/American College of Cardiologists, in association with other major societies, have made recommendations to extend the duration of dual-antiplatelet therapy in patients with DES to 1 yr. The 6-wk duration of dual-antiplatelet therapy in patients with BMS remains unchanged. All patients with coronary stents must remain on life-long aspirin monotherapy. Since the introduction of percutaneous transluminal coronary angioplasty for the treatment of coronary atherosclerosis, the practice of percutaneous coronary intervention has undergone a dramatic transformation from simple balloon dilation catheters to sophisticated mechanical endoprostheses. These advancements have impacted the practice of perioperative medicine. In this series of two articles, in Part I we will review the evolution of percutaneous coronary intervention and discuss the issues associated with percutaneous transluminal coronary angioplasty and coronary stenting; in Part II we will discuss perioperative issues and management strategies of coronary stents during noncardiac surgery.

Topology optimization of a novel stent platform with drug reservoirs

The new generation of drug-eluting stents (DES) is required to control drug release kinetics. A novel DES (the Conor stent) with drug reservoirs on struts has been engineered. Topology optimization of one Conor stent strut was based on the commercial finite element analysis code OptiStruct, with the aim of increasing the strut stiffness while retaining its drug holding capacity. Results show that the element density distribution of the strut model was optimized with manufacturing constraints of extrusion constraint and minimum member size control. The optimal result was directly transformed to a clear, manufacturable design concept using the OptiStruct utility OSSmooth. The final manufacturing design increased the strut stiffness and yielded better stress distribution, as compared to the original strut design under the same loading. Topology optimization may help designers devise novel stent platforms for future DES with drug reservoirs and adequate scaffolding.

Safety and efficacy of the drug-eluting stent: a double-edged sword?

Like the introduction of bare metal stents (BMS), that of drug-eluting stents (DES) represented a quantum leap in the interventional cardiology community's ongoing efforts to conquer restenosis. However, recent concerns over late thrombosis (LT) have tempered the initial enthusiasm. Nonetheless, when compared with BMS, the slightly higher DES-LT is counterbalanced by the device's markedly lower incidence of restenosis, resulting in net equivalent rates of death, myocardial infarction, and overall major adverse cardiovascular events. This article summarizes for the noncardiology practitioner the benefits and risks of DES, as well as essentials of postprocedural care of the DES patient. We discuss the pathophysiology of stent thrombosis, pivotal DES trials, and adjunct antiplatelet pharmacology. In December 2006, the Food and Drug Administration convened an expert panel to review these devices. Their recommendations, as well as the joint statement from the American College of Cardiology/American Heart Association/Society of Cardiovascular Angiography and Interventions, are outlined.

Are impaired endothelial progenitor cells involved in the processes of late in-stent thrombosis and re-endothelialization of drug-eluting stents?

Drug-eluting stent (DES) now is the default selection for most of the interventional cardiologists. However, its benefits compromised by the stent-related thrombosis events. Given the catastrophic consequences, it is important to investigate possible mechanisms of stent thrombosis. The cause of stent thrombosis is multifactorial, and several stent-related and patient-related variables have been identified. The stent itself has components that may lead to thrombosis: the metal stent material, the polymer which houses the drug, and the actual cell-cycle inhibiting drugs. Most important the cell-cycle inhibitors (sirolimus and paclitaxel) reduce neointimal formation by impeding smooth muscle cells proliferation and migration, these drugs also impair the normal process of the injured arterial wall and cause delayed re-endothelialization [Tsimikas S. Drug-eluting stents and late adverse clinical outcomes. J Am Coll Cardiol 2006;47:2112-5; Colombo A, Drzewiecki J, Banning A, et al. Randomized study to assess the effectiveness of slow- and moderate-release polymer-based paclitaxel-eluting stent for coronary artery lesions. Circulation 2003;108:788-94; Kedia Gautam, Lee Michael S. Stent thrombosis with drug-eluting stents: a re-examination of the evidence. Catheter Cardiovasc Interv 2007;69:782-9] [1-3]. It has been proposed that bone marrow-derived endothelial progenitor cells may also be involved in re-endothelialization [Urao N, Okigaki M, Yamada H, et al. Erythropoietin-mobilized endothelial progenitors enhance reendothelialization via Akt-endothelial nitric oxide synthase activation and prevent neointimal hyperplasia. Circ Res 2006;98:1405-13; Griese DP, Ehsan A, Melo LG, et al. Isolation and transplantation of autologous circulating endothelial cells into denuded vessels and prosthetic grafts: implications for cell-based vascular therapy. Circulation 2003;108:2710-15] [4-5]. Interestingly, rapamycin inhibits proliferation, migration, and differentiation of human endothelial progenitor cells in vitro [Butzal M, Loges S, Schweizer M, et al. Rapamycin inhibits proliferation and differentiation of human endothelial progenitor cells in vitro. Exp Cell Res 2004;300:65-71; Chen TG, Chen JZ, Wang XX. Effects of rapamycin on number activity and eNOS of endothelial progenitor cells from peripheral blood. Cell Proliferat 2006;39:117-25]. We hypothesis that drugs loaded on DES may affect the number as well as the homing and proliferation of endothelial progenitor cells, thus further preventing proper endothelial healing, increasing platelet aggregation, which could lead to stent thrombosis.

How to prevent perioperative myocardial injury: the conundrum continues

BACKGROUND

Perioperative myocardial injury (PMI) remains a major cause of perioperative morbidity and mortality but clinical strategies to prevent PMI are still uncertain.

METHODS AND RESULTS

We comprehensively searched PubMed for major research articles concerning clinical strategies to prevent PMI. The key findings are as follows: (1) the American College of Cardiology/American Heart Association guideline update for perioperative cardiovascular evaluation for noncardiac surgery is very useful to stratify cardiac risk preoperatively; (2) cardiac troponin has emerged as a biomarker to diagnose postoperative PMI and to predict clinical outcomes; (3) coronary revascularization before noncardiac surgery probably would provide cardiac protection in select patients, especially in patients with high-risk coronary artery disease; (4) elective noncardiac surgery should be postponed in patients who received coronary stenting recently because of high incidence of serious cardiac complications (minimum 6-8 weeks for bare metal stents and 6-12 months for drug-eluting stents); and (5) beta-blockers and statins are very promising drugs and probably would prevent PMI in a select patient population, especially in patients with intermediate risk and stable coronary artery disease.

CONCLUSIONS

Further studies, especially randomized clinical trials and mechanistic investigation are needed to find the best and effective clinical strategies to prevent/reduce PMI.

Outcomes of stent thrombosis and restenosis during extended follow-up of patients treated with bare-metal coronary stents

BACKGROUND

Concern regarding risk of late thrombosis after "off-label" treatment with drug-eluting stents has prompted increased use of bare-metal stents (BMS) in current practice. The sequelae of late BMS failures, however, have been poorly characterized.

METHODS AND RESULTS

We performed a retrospective study of 4503 consecutive patients treated with at least 1 BMS and dual antiplatelet therapy between 1994 and 2000. The cumulative incidence of stent thrombosis was 0.5% at 30 days (95% CI, 0.3% to 0.7%), 0.8% at 1 year (95% CI, 0.6% to 1.1%), and 2.0% at 10 years (95% CI, 1.5% to 2.5%). Risk of late (30 days to 1 year) and very late (>1 year) BMS thrombosis was increased among patients considered off label for drug-eluting stent use (P=0.024). When saphenous vein graft interventions were excluded, however, risk after off-label use was not significantly increased (P=0.23). Other correlates included vein graft intervention, prior myocardial infarction (MI), peripheral vascular disease, and ulcerated lesion (P<0.001). Mortality was markedly increased after late and very late BMS thrombosis, particularly during the first 30 days (hazard ratios, 22 [95% CI, 3.1 to 159] and 40 [95% CI, 15 to 107], respectively). The 10-year incidence of clinical restenosis was 18.1% (95% CI, 16.5% to 19.7%), presenting with MI in 2.1% (95% CI, 1.6% to 2.6%). Restenosis presenting with MI was associated with increased mortality compared with no restenosis (hazard ratio, 2.37; P<0.001) and with restenosis with a non-MI presentation (hazard ratio, 2.42; P<0.001).

CONCLUSIONS

The incidence of BMS thrombosis and of MI caused by restenosis during extended follow-up is significant. Both complications are associated with mortality.

A tale of two stents: perioperative management of patients with drug-eluting coronary stents

Drug-eluting stents were introduced into clinical practice to decrease coronary stent restenosis rates. Though remarkably effective in reducing this complication, recent data reveal that drug-eluting stents pose a significant risk for late stent thrombosis, an event strongly correlated with discontinuation of anti-platelet therapy. Because anti-platelet agents are often discontinued perioperatively, patients with DES are at risk for perioperative stent thrombosis and myocardial infarction. Along with a review of the recent literature, we present two cases of patients with drug-eluting stents scheduled for renal transplantation. Two distinct antithrombotic management strategies illustrate the risk of either approach-bleeding and transfusion versus stent thrombosis and myocardial infarction.

Contemporary use of clopidogrel in patients with coronary artery disease

Antiplatelet agents have long served as the cornerstone of pharmacologic therapy to prevent atherothrombotic events. The thienopyridines have risen to prominence as both an alternative and adjunctive treatment to aspirin monotherapy. These agents prevent platelet aggregation by selectively and irreversibly blocking the platelet ADP P2Y12 receptor. In this article we focus on the use of clopidogrel in the contemporary management of coronary artery disease. We assess the use of clopidogrel following revascularization for coronary artery disease with percutaneous coronary intervention, particularly after deployment of drug-eluting stents. Finally, we address some aspects of clopidogrel resistance.

Late and very late thrombosis of drug-eluting stents: evolving concepts and perspectives

Coronary stents are the mainstay of percutaneous coronary revascularization procedures and have significantly decreased the rates of acute vessel closure and restenosis. Stent thrombosis (ST) after percutaneous coronary intervention is an uncommon and potentially catastrophic event that might manifest as myocardial infarction and sudden death. Optimization of stent implantation and dual antiplatelet therapy have markedly reduced the occurrence of this complication. Bare-metal stent (BMS) thrombosis occurs in <1% of the cases, usually within the first month after implantation. The advent of drug-eluting stents (DES) has raised concerns regarding later occurrence of ST, beyond the traditional 1-month timeframe, especially in complex lesion subsets that were excluded from randomized trials that compared BMS to DES. There is widespread controversy regarding the actual incremental risk associated with DES. Recent studies suggest a 0.5% increased long-term thrombosis risk with DES; however, the clinical significance of these events remains under debate. The degree of protection achieved by dual antiplatelet therapy and optimal duration of treatment are under investigation. Novel stent designs might potentially decrease the incidence of this event. In this review, we will describe the current knowledge of the pathophysiology of late DES thrombosis, although many aspects remain incompletely understood.

The Final 10-Year Follow-Up Results From the BARI Randomized Trial

OBJECTIVES

We sought to compare 10-year clinical outcomes in the BARI (Bypass Angioplasty Revascularization Investigation) trial patients who were randomly assigned to percutaneous transluminal coronary balloon angioplasty (PTCA) versus coronary artery bypass grafting (CABG).

BACKGROUND

Angioplasty and bypass surgery have been compared in numerous studies, but long-term clinical outcomes are limited.

METHODS

Symptomatic patients with multivessel coronary artery disease (n = 1,829) were randomly assigned to initial treatment with PTCA or CABG and followed up for an average of 10.4 years. Analyses were conducted on an intention-to-treat basis.

RESULTS

The 10-year survival was 71.0% for PTCA and 73.5% for CABG (p = 0.18). At 10 years, the PTCA group had substantially higher subsequent revascularization rates than the CABG group (76.8% vs. 20.3%, p < 0.001), but angina rates for the 2 groups were similar. In the subgroup of patients with no treated diabetes, survival rates were nearly identical by randomization (PTCA 77.0% vs. CABG 77.3%, p = 0.59). In the subgroup with treated diabetes, the CABG assigned group had higher survival than the PTCA assigned group (PTCA 45.5% vs. CABG 57.8%, p = 0.025).

CONCLUSIONS

There was no significant long-term disadvantage regarding mortality or myocardial infarction associated with an initial strategy of PTCA compared with CABG. Among patients with treated diabetes, CABG conferred long-term survival benefit, whereas the 2 initial strategies were equivalent regarding survival for patients without diabetes.

Drug-Eluting Stent-Induced Left Anterior Descending Coronary Artery Aneurysm: Repair by Pericardial Patch—Where Are We Headed?

Deployment of drug-eluting stents has been associated with late thrombosis and restenosis on withdrawal of antiplatelet agents. We report a complication of inflammation and localized coronary artery aneurysms immediately adjacent to the stent after 4 years of implantation. Late chronic inflammatory responses may evolve for up to 4 years after sirolimus-eluting stent implantation and can cause weakening, erosion, and aneurysms of the coronary arteries.

Stent thrombosis with drug-eluting stents: A re-examination of the evidence

The excitement of drug-eluting stents and their promise for reduced restenosis rates have been tempered by recent reports of stent thrombosis. The mechanism of stent thrombosis is multifactorial but appears to be related to delayed endothelialization and healing, late stent malapposition, and antiplatelet resistance. The most important risk factor appears to be the discontinuation of dual antiplatelet therapy. The data from clinical trials suggest that drug-eluting stents are associated with increased incidence of death or myocardial infarction compared with bare metal stents at long-term follow-up, suggesting that the window of thrombotic risk with drug-eluting stents may extend far beyond that for bare metal stents. Measures to possibly decrease the incidence of stent thrombosis include improvements in antiplatelet regimens and newer generation of drug-eluting stents which have biodegradable polymers or are polymer-free. In addition, percutaneous coronary intervention with bare metal stents in patients may be helpful in those known to be intolerant or noncompliant to antiplatelet therapy, have planned procedures or surgeries, or have overwhelming risks which may require discontinuation of dual antiplatelet therapy.