Comparison of the heparin coated vs the uncoated Jostent--no influence on restenosis or clinical outcome

Experimental study of a heparin-coated venous stent fabricated by atomic layer deposition

OBJECTIVE

To evaluate the safety and efficacy of heparin-coated venous stents in animals.

METHODS

We used atomic layer deposition technology to obtain a heparin coating with good stability and then prepared a heparin-coated venous stent based on this technology. The experimental stents were prepared according to the diameter of the rabbit inferior vena cava and were divided into Ni-Ti alloy stent group, Ni-Ti-Al₂O₃ stent group and Ni-Ti-Al₂O₃-Heparin stent group. 3 days, 7 days and 14 days after stent implantation, the materials were collected, and the three groups of stents were observed by hard tissue section pathology, immunohistochemistry and scanning electron microscope to observe the differences in vascular wall inflammation, thrombosis, lumen stenosis and vascular intima regeneration.

RESULT AND CONCLUSION

The experiment confirmed the safety of the heparin-coated stent in vivo. Compared with the control group, the experimental group showed a high degree of vascular endothelialization and an intact neointimal structure 14 days after implantation. The long-term safety and biological effects of heparin-coated venous stents in animals require further study.

Thrombogenic and Inflammatory Reactions to Biomaterials in Medical Devices

Blood-contacting medical devices of different biomaterials are often used to treat various cardiovascular diseases. Thrombus formation is a common cause of failure of cardiovascular devices. Currently, there are no clinically available biomaterials that can totally inhibit thrombosis under the more challenging environments (e.g., low flow in the venous system). Although some biomaterials reduce protein adsorption or cell adhesion, the issue of biomaterial associated with thrombosis and inflammation still exists. To better understand how to develop more thrombosis-resistant medical devices, it is essential to understand the biology and mechano-transduction of thrombus nucleation and progression. In this review, we will compare the mechanisms of thrombus development and progression in the arterial and venous systems. We will address various aspects of thrombosis, starting with biology of thrombosis, mathematical modeling to integrate the mechanism of thrombosis, and thrombus formation on medical devices. Prevention of these problems requires a multifaceted approach that involves more effective and safer thrombolytic agents but more importantly the development of novel thrombosis-resistant biomaterials mimicking the biological characteristics of the endothelium and extracellular matrix tissues that also ameliorate the development and the progression of chronic inflammation as part of the processes associated with the detrimental generation of late thrombosis and neo-atherosclerosis. Until such developments occur, engineers and clinicians must work together to develop devices that require minimal anticoagulants and thrombolytics to mitigate thrombosis and inflammation without causing serious bleeding side effects.

Vascular smooth muscle cell proliferation as a therapeutic target. Part 2: Natural products inhibiting proliferation

Many natural products have been so far tested regarding their potency to inhibit vascular smooth muscle cell proliferation, a process involved in atherosclerosis, pulmonary hypertension and restenosis. Compounds studied in vitro and in vivo as VSMC proliferation inhibitors include, for example indirubin-3'-monoxime, resveratrol, hyperoside, plumericin, pelargonidin, zerumbone and apamin. Moreover, taxol and rapamycin, the most prominent compounds applied in drug-eluting stents to counteract restenosis, are natural products. Numerous studies show that natural products have proven to yield effective inhibitors of vascular smooth muscle cell proliferation and ongoing research effort might result in the discovery of further clinically relevant compounds.

Anti-fouling strategies for central venous catheters

Central venous catheters (CVCs) are ubiquitous in the healthcare industry and carry two common complications, catheter related infections and occlusion, particularly by thrombus. Catheter-related bloodstream infections (CRBSI) are an important cause of nosocomial infections that increase patient morbidity, mortality, and hospital cost. Innovative design strategies for intravenous catheters can help reduce these preventable infections. Antimicrobial coatings can play a major role in preventing disease. These coatings can be divided into two major categories: drug eluting and non-drug eluting. Much of these catheter designs are targeted at preventing the formation of microbial biofilms that make treatment of CRBSI nearly impossible without removal of the intravenous device. Exciting developments in catheter impregnation with antibiotics as well as nanoscale surface design promise innovative changes in the way that physicians manage intravenous catheters. Occlusion of a catheter renders the catheter unusable and is often treated by tissue plasminogen activator administration or replacement of the line. Prevention of this complication requires a thorough understanding of the mechanisms of platelet aggregation, signaling and cross-linking. This article will look at the advances in biomaterial design specifically drug eluting, non-drug eluting, lubricious coatings and micropatterning as well as some of the characteristics of each as they relate to CVCs.

Stent Polymers: Do They Make a Difference?

The necessity of polymers on drug-eluting stent (DES) platforms is dictated by the need of an adequate amount and optimal release kinetic of the antiproliferative drugs for achieving ideal DES performance. However, the chronic vessel wall inflammation related to permanent polymer persistence after the drug has been eluted might trigger late restenosis and stent thrombosis. Biodegradable polymers have the potential to avoid these adverse events. A variety of biodegradable polymer DES platforms have been clinically tested, showing equal outcomes with the standard-bearer permanent polymer DES within the first year of implantation. At longer-term follow-up, promising lower rates of stent thrombosis have been observed with the early generation biodegradable polymer DES platforms compared to first-generation DES. Whether this safety benefit still persists with newer biodegradable polymer DES generations against second-generation permanent polymer DES needs to be explored.

Biodegradable polymer-based, argatroban-eluting, cobalt-chromium stent (JF-04) for treatment of native coronary lesions: final results of the first-in-man study and lessons learned

AIMS

The aim of the study was to investigate the six-month angiographic and nine-month clinical follow-up outcomes in a first-in-man study using the biodegradable polymer-based cobalt-chromium argatroban-eluting stent (JF-04) for treatment of native coronary atherosclerotic lesions.

METHODS AND RESULTS

A total of 31 patients with either stable or unstable angina, or silent myocardial ischaemia, exhibiting de novo coronary lesions were enrolled at seven Japanese sites. The lesions were treated with the JF-04 stent after predilatation. The primary endpoint was angiographic in-stent late loss six months after implantation. The secondary endpoints included angiographic restenosis and in-stent volume obstruction by intravascular ultrasound at six months and target vessel failure (TVF) at nine months. Procedural success was achieved in 100% of cases. At six months, angiographic in-stent late loss was 1.01±0.48 mm and binary restenosis was observed in nine cases (29.0%). Among these restenotic cases, most (n=8) demonstrated advanced angiographic restenosis patterns, including diffuse/proliferative restenosis and total occlusion. At nine months, TVF was observed in four cases (12.9%), exclusively attributed to target vessel revascularisation.

CONCLUSIONS

This argatroban-eluting stent failed to inhibit neointimal hyperplasia sufficiently, despite the theoretical benefits and promising clinical experience with local drug delivery.

Heparin coatings for improving blood compatibility of medical devices

Blood contact with biomaterials triggers activation of multiple reactive mechanisms that can impair the performance of implantable medical devices and potentially cause serious adverse clinical events. This includes thrombosis and thromboembolic complications due to activation of platelets and the coagulation cascade, activation of the complement system, and inflammation. Numerous surface coatings have been developed to improve blood compatibility of biomaterials. For more than thirty years, the anticoagulant drug heparin has been employed as a covalently immobilized surface coating on a variety of medical devices. This review describes the fundamental principles of non-eluting heparin coatings, mechanisms of action, and clinical applications with focus on those technologies which have been commercialized. Because of its extensive publication history, there is emphasis on the CARMEDA^® BioActive Surface (CBAS^® Heparin Surface), a widely used commercialized technology for the covalent bonding of heparin.

Pharmacology of Heparin and Related Drugs

Heparin has been recognized as a valuable anticoagulant and antithrombotic for several decades and is still widely used in clinical practice for a variety of indications. The anticoagulant activity of heparin is mainly attributable to the action of a specific pentasaccharide sequence that acts in concert with antithrombin, a plasma coagulation factor inhibitor. This observation has led to the development of synthetic heparin mimetics for clinical use. However, it is increasingly recognized that heparin has many other pharmacological properties, including but not limited to antiviral, anti-inflammatory, and antimetastatic actions. Many of these activities are independent of its anticoagulant activity, although the mechanisms of these other activities are currently less well defined. Nonetheless, heparin is being exploited for clinical uses beyond anticoagulation and developed for a wide range of clinical disorders. This article provides a "state of the art" review of our current understanding of the pharmacology of heparin and related drugs and an overview of the status of development of such drugs.

Drug-eluting stents: the past, present, and future

Since the advent of percutaneous coronary intervention, enormous advances have been made in the treatment of coronary artery disease. Angioplasty and bare metal stents were plagued by high rates of restenosis leading to repeat revascularization procedures. Examination of the underlying pathophysiology of restenosis led to the development of drug-eluting stents to reduce neointimal hyperplasia. However, as restenosis rates declined, length of dual antiplatelet therapy use and risk of long-term stent thrombosis associated with drug-eluting stents increased. Subsequent generations have improved each facet of stent design. Novel alloys maintain durability and reduce strut thickness to increase deliverability, biocompatible polymers decrease the inflammatory response and improve drug elution kinetics, and new generations of drugs predictably inhibit restenosis. Developments on the horizon include stents with bioabsorbable polymers and platforms. The purpose of this review is to assess the evolution of stent design and the evidence behind each generation and to peer into the future of stent technology.

Medical device-induced thrombosis: what causes it and how can we prevent it?

Blood-contacting medical devices, such as vascular grafts, stents, heart valves, and catheters, are often used to treat cardiovascular diseases. Thrombus formation is a common cause of failure of these devices. This study (i) examines the interface between devices and blood, (ii) reviews the pathogenesis of clotting on blood-contacting medical devices, (iii) describes contemporary methods to prevent thrombosis on blood-contacting medical devices, (iv) explains why some anticoagulants are better than others for prevention of thrombosis on medical devices, and (v) identifies future directions in biomaterial research for prevention of thrombosis on blood-contacting medical devices.

Biocompatibility of Coronary Stents

Cardiovascular disease is the dominant cause of mortality in developed countries, with coronary artery disease (CAD) a predominant contributor. The development of stents to treat CAD was a significant innovation, facilitating effective percutaneous coronary revascularization. Coronary stents have evolved from bare metal compositions, to incorporate advances in pharmacological therapy in what are now known as drug eluting stents (DES). Deployment of a stent overcomes some limitations of balloon angioplasty alone, but provides an acute stimulus for thrombus formation and promotes neointimal hyperplasia. First generation DES effectively reduced in-stent restenosis, but profoundly delay healing and are susceptible to late stent thrombosis, leading to significant clinical complications in the long term. This review characterizes the development of coronary stents, detailing the incremental improvements, which aim to attenuate the major clinical complications of thrombosis and restenosis. Despite these enhancements, coronary stents remain fundamentally incompatible with the vasculature, an issue which has largely gone unaddressed. We highlight the latest modifications and research directions that promise to more holistically design coronary implants that are truly biocompatible.

Saccular aneurysm and stenosis of the left anterior descending artery presenting with acute coronary syndrome. What is the best treatment: CABG or PCI?

Treatment of coronary artery aneurysms (CAAs) can either take the way of a close regular follow up with antiplatelet and anticoagulation therapy, percutaneous coronary intervention with possible stenting, or reach the extent of doing coronary artery bypass grafting. The severity of coexistent coronary artery stenosis, symptomatology, embolization to distal coronary beds, and increasing measurements over time are key players to decide whether to proceed with surgery in patients with CAAs. <Learning objective: (i) Coronary artery aneurysms (CAAs) are defined as luminal dilation 50% larger than that of the adjacent reference segment. They are found in 1.4% of patients and could have multiple shapes and forms. (ii) Up to one-third of CAAs are associated with obstructive coronary artery disease and have been associated with myocardial infarction, arrhythmias, or sudden cardiac death. (iii) Treatment of CAAs can be medical, or invasive by performing percutaneous coronary intervention, or surgical using coronary artery bypass grafting. (iv) The severity of coexistent coronary artery stenosis, symptomatology, and embolization to distal coronary beds are important in the final decision on treatment modality.>.

The immobilization of recombinant human tropoelastin on metals using a plasma-activated coating to improve the biocompatibility of coronary stents

Current endovascular stents have sub-optimal biocompatibility reducing their clinical efficacy. We previously demonstrated a plasma-activated coating (PAC) that covalently bound recombinant human tropoelastin (TE), a major regulator of vascular cells in vivo, to enhance endothelial cell interactions. We sought to develop this coating to enhance its mechanical properties and hemocompatibility for application onto coronary stents. The plasma vapor composition was altered by incorporating argon, nitrogen, hydrogen or oxygen to modulate coating properties. Coatings were characterized for 1) surface properties, 2) mechanical durability, 3) covalent protein binding, 4) endothelial cell interactions and 5) thrombogenicity. The N(2)/Ar PAC had optimal mechanical properties and did not delaminate after stent expansion. The N(2)/Ar PAC was mildly hydrophilic and covalently bound the highest proportion of TE, which enhanced endothelial cell proliferation. Acute thrombogenicity was assessed in a modified Chandler loop using human blood. Strikingly, the N(2)/Ar PAC alone reduced thrombus weight by ten-fold compared to 316L SS, a finding unaltered with immobilized TE. Serum soluble P-selectin was reduced on N(2)/Ar PAC and N(2)/Ar PAC + TE (p < 0.05), consistent with reduced platelet activation. We have demonstrated a coating for metal alloys with multifaceted biocompatibility that resists delamination and is non-thrombogenic, with implications for improving coronary stent efficacy.

c-Jun regulates shear- and injury-inducible Egr-1 expression, vein graft stenosis after autologous end-to-side transplantation in rabbits, and intimal hyperplasia in human saphenous veins

Coronary artery bypass graft failure represents an unsolved problem in interventional cardiology and heart surgery. Late occlusion of autologous saphenous vein bypass grafts is a consequence of neointima formation underpinned by smooth muscle cell (SMC) migration and proliferation. Poor long term patency and the lack of pharmacologic agents that prevent graft failure necessitate effective alternative therapies. Our objective here was to evaluate the effect of targeted inhibition of the bZIP transcription factor c-Jun on intimal hyperplasia in human saphenous veins and vein graft stenosis after autologous end-to-side transplantation. DNAzymes targeting c-Jun attenuated intimal hyperplasia in human saphenous vein explants. Adenovirus-forced c-Jun expression stimulated SMC proliferation, proliferating cell nuclear antigen, and MMP-2 expression. c-Jun DNAzymes abrogated Adeno-c-Jun-inducible SMC growth and wound repair and reduced intimal thickening in jugular veins of New Zealand white rabbits 4 weeks after autologous end-to-side transplantation to carotid arteries. Conversely, in a DNAzyme-free setting, Adeno-c-Jun potentiated neointima formation in the veins compared with Adeno-LacZ. Inducible c-Jun expression is ERK1/2- and JNK-dependent but p38-independent. Injury- and shear-inducible c-Jun controls early growth response-1. These data demonstrate that strategies targeting c-Jun may be useful for the prevention of vein graft stenosis. Control of one important shear-responsive transcription factor by another indicates the existence of transcriptional amplification mechanisms that magnify the vascular response to cell injury or stress through inducible transcriptional networks.

Passive and active polymer coatings for intracoronary stents: novel devices to promote arterial healing

Coronary stent implantation is the second great advance in the treatment of obstructive coronary artery disease since the introduction of balloon catheter angioplasty. However, in-stent restenosis (ISR) caused by neointimal hyperplasia has been a major limitation of stents, occurring in up to 30% of cases. Advances in coronary stent technology both in terms of stent design and function and especially drug-eluting stents (DES) have significantly improved the safety and efficacy of percutaneous coronary intervention (PCI) with stenting, including marked reduction in ISR. This has led to use of DES for increasingly challenging clinical and lesional subsets, with potential for increased risk of stent-associated complications, especially late stent thrombosis (LST). Because restenosis and stent thrombosis are caused by multiple and often interrelated factors, ideal agents for stent coatings should inhibit thrombus formation, inflammatory reaction, and cellular proliferation, while supporting reendothelialization. To avoid undesirable effects of currently applied (durable) polymers, biocompatible, and bioabsorbable polymers as well as DES delivery systems that minimize polymer burden have been produced and tested. Bioabsorbable stents, both polymeric and metallic, have been developed to decrease potential late complications after stent implantation. Novel strategies to address some of these challenges are in various stages of research and development. In this article we outline developments in the field of passive and active stent coatings and evaluate the ongoing role of such coatings in the contemporary era of DES.

Stent‐based percutaneous coronary interventions in small coronary arteries

A third to half of all percutaneous coronary interventions involve small diameter vessels of less than 3 mm. Small vessel size is a predictor of restenosis after balloon angioplasty, as well as after stent placement. Stents deployed in small arteries, have a higher metal-to-artery ratio; this may increase the risk of sub-acute thrombosis or restenosis. Various studies have shown that stent design, stent coating, and stent strut thickness may determine event-free survival. Dedicated stents for small vessels with less amount of metal, appropriate expansion to the vessel size with correct radial force and cells morphology, and less prothrombotic properties, may further improve the results of stenting in this setting (thinner struts, fewer cells, or loops per circumference). This review provides an update on the current status, review the major trials and define the clinical utility of small vessel stenting, particularly in the era of drug-eluting stents.

Delivery of large biopharmaceuticals from cardiovascular stents: a review

This review focuses on new and emerging large-molecule bioactive agents delivered from stent surfaces in drug-eluting stents (DESs) to inhibit vascular restenosis in the context of interventional cardiology. New therapeutic agents representing proteins, nucleic acids (small interfering RNAs and large DNA plasmids), viral delivery vectors, and even engineered cell therapies require specific delivery designs distinct from traditional smaller-molecule approaches on DESs. While small molecules are currently the clinical standard for coronary stenting, extension of the DESs to other lesion types, peripheral vasculature, and nonvasculature therapies will seek to deliver an increasingly sophisticated armada of drug types. This review describes many of the larger-molecule and biopharmaceutical approaches reported recently for stent-based delivery with the challenges associated with formulating and delivering these drug classes compared to the current small-molecule drugs. It also includes perspectives on possible future applications that may improve safety and efficacy and facilitate diversification of the DESs to other clinical applications.

Anti-inflammatory effect of abciximab-coated stent in a porcine coronary restenosis model

The aim of this study was to examine the anti-inflammatory effect of abciximab-coated stent in a porcine coronary overstretch restenosis model. Ten abciximab-coated stents, ten sirolimus-eluting stents (SES), and ten paclitaxel-eluting stents (PES) were deployed with oversizing (stent/artery ratio 1.3:1) in porcine coronary arteries, and histopathologic analysis was done at 28 days after stenting. There were no significant differences in the neointima area normalized to injury score and inflammation score among the three stent groups (1.58 +/- 0.43 mm(2), 1.57 +/-0.39 mm(2) in abciximab-coated stent group vs. 1.69 +/- 0.57 mm(2), 1.72 +/- 0.49 mm(2) in the SES group vs. 1.92 +/- 0.86 mm(2), 1.79 +/- 0.87 mm(2) in the PES group, respectively). In the neointima, most inflammatory cells were lymphohistiocytes. Significant positive correlations were found between the extent of inflammatory reaction and the neointima area (r=0.567, p<0.001) and percent area stenosis (r=0.587, p<0.001). Significant correlations were found between the injury score and neointimal area (r=0.645, p<0.001), between the injury score and the inflammation score (r=0.837, p<0.001), and between the inflammation score and neointimal area (r=0.536, p=0.001). There was no significant difference in the inflammatory cell counts normalized to injury score among the three stent groups (75.5 +/- 23.1/microL in abciximabcoated stent group vs. 78.8 +/- 33.2/microL in the SES group vs. 130.3 +/- 46.9/microL in the PES group). Abciximab-coated stent showed comparable inhibition of inflammatory cell infiltration and neointimal hyperplasia with other drug-eluting stents in a porcine coronary restenosis model.

Novel thromboresistant materials

The development of a clinically durable small-diameter vascular graft as well as permanently implantable biosensors and artificial organ systems that interface with blood, including the artificial heart, kidney, liver, and lung, remain limited by surface-induced thrombotic responses. Recent breakthroughs in materials science, along with a growing understanding of the molecular events that underlay thrombosis, has led to the design and clinical evaluation of a variety of biologically active coatings that inhibit components of the coagulation pathway and platelet responses by surface immobilization or controlled release of bioactive agents. This report reviews recent progress in generating synthetic thromboresistant surfaces that inhibit (1) protein and cell adsorption, (2) thrombin and fibrin formation, and (3) platelet activation and aggregation.

Use of heparin-coated stents in neurovascular interventional procedures: preliminary experience with 10 patients

OBJECTIVE

Currently, there is minimal published data on the use of heparin-coated stents in the neurovasculature; however, these stents have a proven clinical record in the treatment of coronary disease. This article details our experience with the safety and technical aspects of stent deployment in the first 10 patients who had heparin-coated stents placed in the intracranial and cervical vasculature and the preliminary follow-up in most cases.

METHODS

We retrospectively reviewed the clinical history, intra- and periprocedural data, and imaging for the patients who received heparin-coated stents in the cervical and intracranial vasculature for cerebrovascular disease between October 2002 and October 2003.

RESULTS

Thirteen heparin-coated stents were placed in 10 patients. Seven out of the 10 patients had heparin-coated stents placed in the posterior circulation; the remaining three patients had stents placed in the anterior circulation. Four patients had stents placed intracranially. There was no acute or subacute in-stent thrombosis and no procedure-related complications. Follow-up was performed on most patients, with no clinical symptoms attributable to restenosis in any patient.

CONCLUSION

This small series suggests that heparin-coated stents are safe for use in the treatment of cervical and intracranial atherosclerotic disease. Longer-term follow-up is needed to study the heparin coating effect on in-stent restenosis rates and to assess the long-term durability and clinical efficacy of this stent. The use of drug-coated stents in the cerebrovascular circulation is an area that warrants further investigation.

Effects on blood compatibility in vitro by combining a direct P2Y12 receptor inhibitor and heparin coating of stents

The effect of the direct platelet P2Y12 receptor inhibitor, AR-C69931MX, on activation of blood induced by stents with and without heparin coating was investigated using a whole blood Chandler loop model in vitro. Stents were deployed in Chandler loops. Fresh human blood with heparin and AR-C69931MX was rotated for 1 h at 37 degrees C and used for measurements of platelets, microparticles, thrombin-antithrombin complex (TAT), fibrinogen binding to platelets, P-selectin expression by platelets, CD11b, Prothrombin Fragment F1+2, FXIa-AT, FXIIa-AT, C3a, sC5b-9 and stent score. In the first experiment there were four study groups with unmodified stents: 1a, no AR-C69931MX; 1b, 250 nmol/L; 1c, 750 nmol/L; 1d, 2250 nmol/L of AR-C69931MX. In the second experiment the concentration of AR-C69931MX was 500 nmol/L: 2a; tubings without stent; 2b; tubings with heparin-coated stent; 2c; tubings with unmodified stents. Heparin-coated stents were used in the third experiment: 3a; no AR-C69931MX; 3b; 500 nmol/L of AR-C69931MX. In the first experiment there were significant differences in all parameters analysed except for C3a, and stent score when the group with no AR-C69931MX was compared to all the groups with AR-C69931MX. In the second experiment there were significant differences in platelet count, TAT, FXIa-AT, FXIIa-AT and stent score when unmodified stents were compared to loops with no stents and partly to loops with heparin-coated stents. In the third experiment there was a significant reduction in generation of TAT, stent score and better preservation of platelet number by combining the platelet inhibitor and heparin-coated stents as compared to heparin-coated stents alone. The conclusion is that the direct P2Y12 receptor inhibitor AR-C69931MX reduced the different aspects of activation of blood induced by both unmodified and heparin-coated stents.

Role of stent design and coatings on restenosis and thrombosis

More than 15 years have passed since stent technology was introduced by Sigwart et al. [U. Sigwart, J. Puel, V. Mirkovitch, F. Joffe, et al. Intravascular stents to prevent occlusion and restenosis after transluminal angioplasty. N. Engl. J. Med. 316 (1987) 701-706.] among interventional cardiologists. Recently drug eluting stents have assumed dominance in the interventional world as positive trial results revealed their efficacy for preventing restenosis. Stent design, delivery-vehicle materials, and drug properties affect the function of these stents. Stainless steel stents with tubular and multicellular design have proven superior to coil or hybrid stent models. This chapter describes stents which have subtle influences of modular design, metal coverage, strut thickness, strut shape, surface smoothness, and coating materials like an alloy composition.

A novel application of multi-wavelength TIRF spectroscopy for real time monitoring of antithrombin interactions with immobilized heparin

Real time interactions of antithrombin (AT) with Corline Heparin Surfaces (CHS) with one and two layers of heparin conjugate have been examined using a multi-wavelength TIRF spectroscopy technique with continuous flow. Fluorescently labeled AT, adsorbed from citrated human blood plasma, showed significantly higher signals on CHS compared to the cationic surface used to attach the heparin conjugate. The AT binding to CHS was very stable, also after exposure to soluble heparin at a concentration of 1.5 IU/mL. Only a few percent of the bound AT were displaced from the surfaces by AT present in plasma after long-term exposure to plasma. In contrast, larger amounts of the freshly added AT had adsorbed to the surfaces, especially to the surface with two layers of heparin conjugate, indicating the presence of unsaturated AT binding sites. The amount of AT bound to the different surfaces was quantified after elution using an enzyme immunoassay (EIA). Characteristic emission spectra of proteins and fluorophores of labeled proteins, obtained at the surfaces after a long-term exposure to plasma, confirmed their presence at the surfaces. The multi-wavelength TIRF technique proved to be a useful tool when combined with other techniques to study the time course of interactions of fluorescently labeled proteins with biomaterials, even in a complex environment such as plasma.

Drug-eluting stents: results, promises and problems

In-stent restenosis is the major drawback of percutaneous coronary interventions, occurring in 10-40% of the patients. Recently, new stents have emerged which are loaded with anti-inflammatory, anti-migratory, anti-proliferative or pro-healing drugs. These drugs are supposed to inhibit inflammation and neointimal growth and subsequently in-stent restenosis. In this review article the results of human clinical studies investigating drug-eluting stents are discussed from a clinical point of view, focussing on the efficacy in the prevention of restenosis and their potential side effects. Both success and failure in the field of drug-eluting stents have been described. Successful devices are the sirolimus-eluting and the polymer-based paclitaxel-eluting stents. Potentially dangerous side effects of drug-eluting stents are adverse drug interactions, incomplete stent apposition and increased in-stent thrombosis rates. Demonstration of long-term efficacy is mandatory since in some animal studies a delayed healing has been observed. Currently, the successful drug-eluting stents are under investigation in all types of lesions. We conclude that the results with some drug-eluting stents are promising, but further evidence on long-term efficacy and safety, also in high-risk subgroups, is needed.

Early Surgical Outcome After Failed Primary Stenting for Lower Limb Occlusive Disease

PURPOSE

To evaluate the early results of revascularization after failed primary stent placement for lower limb occlusive disease.

METHODS

A retrospective review was conducted of 25 consecutive patients (16 men; mean age 65 years, range 32-89) treated between January 2001 to October 2003 for infrainguinal stent failure at a median 6.6 months (range 3-60) after primary stent implantation (27 femoropopliteal and 20 popliteal-crural) at referring hospitals. All surgical procedures for stent failure were performed at tertiary centers. The results of bypass grafting for failed stenting were compared to a contemporaneous cohort of patients undergoing primary bypass surgery performed by the same surgeons.

RESULTS

At the time of admission, 22 stents were thrombosed, and 3 patent stents presented with >50% in-stent stenosis. Twenty patients had 7 femoropopliteal or 9 femorodistal vein bypasses and 4 reconstructions of the common femoral or profunda femoris artery. Four patients had 3 primary amputations and 1 lumbar sympathectomy. One patient with claudication was treated conservatively. Procedure-related complications were observed in 40%; 30-day mortality was 4% (1/25). Early (30-day) graft thrombosis occurred in 6 (30%) of 20 arterial reconstructions, necessitating 8 secondary amputations (44% [11/ 25] overall amputation rate). A total of 47 surgical procedures were performed in the 24 surviving patients (median 2 operations per patient, range 1-9) over an 11-month period (range 1-57). Primary patency rates at 30 days and at 6 and 12 months were 67%, 44%, and 33%, respectively, in the poststent bypass cohort versus 98%, 96%, and 88%, respectively, in a contemporaneous group of patients treated with primary bypass grafting.

CONCLUSIONS

Failed stents in lower limb arteries often require distal reconstructive bypass surgery, which is associated with high complication rates and poor outcome, including major amputations. There is no scientific evidence to support stenting below the inguinal ligament.

Cardiac rehabilitation reduces the rate of major adverse cardiac events after percutaneous coronary intervention

BACKGROUND

Despite multiple publications on effects of rehabilitation in cardiac patients, rehabilitation is not fully known to be of value in post-percutaneous coronary intervention (PCI) patients.

AIMS

To investigate the influence of cardiac rehabilitation on the incidence of major adverse cardiac events (MACEs) in post-PCI patients.

METHODS

Retrospectively and nonrandomized 140 post-PCI patients (107 males, mean age 62 (7) years) participated in a 3-month rehabilitation program, starting 2 weeks post-PCI, while 83 post-PCI patients (54 males, mean age 68 (8) years) did not and were all followed up for 15 months. Data on cardiac medication prescription and incidence of MACE (including angina pectoris with or without reintervention, restenosis, myocardial infarction, revascularisation with re-PCI or CABG, and death) were collected. The relationship with cardiovascular risk factors including sex, smoking behaviour, obesity, diabetes mellitus, hypertension, familiar predisposition, and hypercholesterolemia was analysed.

RESULTS

The incidence of total MACE in the rehabilitation group is significantly lower than in the control group (24% vs. 42%, respectively; P<0.005). The incidence of documented restenosis, angina pectoris with resulting reintervention, all revascularisations, and death is significantly lower in the rehabilitation group, compared with the control group.

CONCLUSION

The incidence of MACE and restenosis is significantly lower when PCI patients are included in a cardiac rehabilitation program.

Clinical impact of stent construction and design in percutaneous coronary intervention

Convincing end point data demonstrating the anatomic and clinical superiority of stent placement compared with balloon angioplasty together with significant improvement in stenting technique and poststent management have resulted in an explosion in stenting procedures and the emergence of more than 40 stent types with disparate designs and material composition in clinical use. Structural nuances in design, composition, and coating of different stent models, however, have been shown to have a major influence on the risk of stent thrombosis, the degree of vessel wall injury, and subsequent intimal proliferation in the experimental model. There is now substantial amount of evidence to indicate that the same relationship between stent structural characteristics and vessel wall outcome holds true in humans. This article provides an up-to-date overview of the clinical impact of stent construction and design, including the clinical performance of drug-eluting stents.

Silicon carbide-coated stents in patients with acute coronary syndrome

Silicon carbide (aSIC-C) is a stent coating with antithrombogenic as well as anti-inflammatory properties as compared with uncoated stainless steal based on in vitro and in vivo studies. This study investigated the potential of this coating in patients with unstable angina. At 38 study sites, 485 patients were randomized to an aSIC-C (n = 238) or a conventional stainless steal stent (n = 247). Patient were classified according to angina at rest within last 48 hr to Braunwald in class IIB (= 314) and IIIB (n = 171). The primary endpoint was a combination of death, myocardial infarction, or ischemia-driven target vessel revascularization at 6 months. Complications of procedures performed at 0.4 +/- 1.1 days after admission occurred at lower rates than previously reported in this high-risk population, but the primary endpoint was not different between the study groups. Only in Braunwald class IIIB patients did the primary endpoint occur less frequently in patients with an aSIC-C stent as compared to patients with a conventional stent (5.8% vs. 15.3%; P = 0.049). At 9-month follow-up, the level of difference was maintained, but statistical significance was lost. Quantitative angiography revealed no significant difference between the stents in the subgroups. This study suggests that aSIC-C stents exert clinically measurable effects in patients with unstable angina with recent symptoms at rest. This coating deserves further clinical investigation and may serve as platform for antiproliferative drugs.

Comparison of outcomes up to six months of Heparin-Coated with noncoated stents after percutaneous coronary intervention for acute myocardial infarction

We prospectively followed 238 patients who underwent percutaneous coronary intervention for acute ST-elevation myocardial infarction and compared the outcomes of patients who received heparin-coated stents (n = 124) with those of patients who received noncoated stents (n = 114). The clinical characteristics and adjunctive medications of the 2 groups were similar. The use of heparin-coated stents was associated with improved 30-day outcome but had no significant effect on 180-day outcome.

Re-angioplasty of in-stent restenosis versus balloon restenoses—a matched pair comparison

BACKGROUND

Despite different biological mechanisms involved in the restenotic process of in-stent restenosis and restenosis after balloon angioplasty alone, the occurrence of a second restenosis has been reported in the same range. There are no data available comparing the outcome after re-angioplasty of such lesions. We analyzed in a matched pair comparison the clinical outcome and angiographic long-term result of patients with balloon angioplasty of a first in-stent restenosis versus patients with balloon re-angioplasty of a first balloon restenosis.

METHODS

Both groups consisted of 74 lesions matched by treated vessel, lesion location differentiated in proximal and non-proximal, and angiographic appearance of coronary artery disease differentiated in singular stenosis, diffuse or mixed pattern. Clinical follow-up was 100%. Angiographic follow-up was 78.4% after median 174 days.

RESULTS

Angiographic restenosis rate in matched pairs of patients (n=46/74) was significantly higher in the balloon restenosis group (41.3%, n=19/46) compared to the in-stent restenosis group (21.7%, n=10/46, p<0.042). There was no death or myocardial infarction. After clinical follow-up, target lesion revascularization rate was significantly lower in the in-stent restenosis group compared to the balloon restenosis group (12.1%, n=9/74 versus 27.0%, n=20/74; difference between groups 14.9%, 95% confidence interval 2.0-27.3%, p<0.023). Multivariate logistic regression analysis revealed as predictors for a second restenosis unstable angina pectoris, non-proximal lesion, restenosis after balloon angioplasty and the occurrence of the first restenosis within 90 days after initial intervention.

CONCLUSION

Clinical and angiographic outcome after balloon angioplasty of a first in-stent restenosis was significantly better compared with balloon re-angioplasty of a first balloon restenosis.

Biologic Response to Polymer-coated Stents: In Vitro Analysis and Results in an Iliac Artery Sheep Model

PURPOSE

To evaluate biologic response to poly(hydroxymethyl-p-xylylene-co-p-xylylene) (PHPX)-coated stents in vitro and in vivo in sheep.

MATERIALS AND METHODS

Physical stability, hemocompatibility, and cytotoxicity of the coating were first assessed in vitro. Thirty-six self-expanding nitinol (Memotherm), 24 stainless steel balloon-mounted (Palmaz), and 12 self-expanding nitinol (ZA) stents were coated with PHPX by using chemical vapor deposition polymerization. Seventy-two coated and 72 uncoated stents were placed into iliac arteries of 36 sheep. Sheep were classified into three groups of 12 animals each. In each group, six sheep were killed after 1 month; six, after 6 months. In each sheep, two uncoated stents were placed into one limb; two coated stents of the same type, into the opposite limb. In groups 1 and 2, Palmaz and Memotherm stents were used; in group 3, Memotherm and ZA stents were used. In groups 1 and 3, arteries were healthy. In group 2, arteries were pretreated with a Fogarty maneuver. Stent patency was measured with intravascular ultrasonography (US) and histologic analysis. Cellular response to coated and uncoated stents was assessed. Measurements were compared (Wilcoxon test).

RESULTS

In vitro, PHPX coating was stable; hemocompatibility and cytotoxicity were similar to those of stainless steel. In vivo, patency of coated and uncoated Palmaz and ZA stents was not different (P >.05). Patency of coated and uncoated Memotherm stents did not differ in four of six follow-up subgroups, but it was significantly reduced in group 2 after 6 months (intravascular US, P =.03; histologic analysis, P =.01) and in group 3 after 1 month (histologic analysis, P =.01). Histologically, the cellular response to coated and uncoated stents was not different (P >.05).

CONCLUSION

PHPX coating had good physical stability and biocompatibility in vitro and in vivo. Performance of coated and uncoated Palmaz and ZA stents was similar. Patency of Memotherm stents was similar in four of six follow-up subgroups. Materials effects did not result in severely enhanced neointimal hyperplasia.

Clinical and angiographic results of coronary artery stenting using PURA-VARIO (PUVA) stents

BACKGROUND

Many different stent types are available for intracoronary placement. No clinical trial has demonstrated clearly the superiority of any stent design over another.

METHODS

This study was designed to analyze clinical and angiographic results after using intracoronary PURA-VARIO (Devon Medical, Hamburg, Germany) (PUVA) stents. A total of 306 implanted stents were investigated in a series of 217 unselected patients (61.2 +/- 10.7 years, 74.3% male). Stenting was performed electively and during acute coronary syndromes. Stents were manually mounted on angioplasty balloons and expanded in the target lesion. Angiographic measurements were carried out by quantitative coronary angiography.

RESULTS

Stenting was successful in 214/217 patients (98.8%). During hospitalization (median three days) 206 patients (94.9%) were free from adverse cardiac events. Stent thrombosis occurred in five patients (2.3%), Q-wave infarction in one (0.5%) and urgent percutaneous target vessel revascularization in four (1.8%). Follow-up angiography, performed in 170 patients (78.3%) showed a restenosis (>/=50% diameter stenosis) in 44/170 patients (25.9%), requiring angioplasty in 29 (17.2%). A surgical revascularization was recommended in 13 patients (7.6%). One patient died during follow-up from an unknown cause; however, sudden cardiac death was most likely.

CONCLUSIONS

PUVA stents are characterized by a high level of safety and efficacy. Clinical and angiographic results are comparable with those of other approved stents.

Effectiveness of stents in small coronary arteries

This study was prospectively randomized to assess the efficacy and safety of Jo heparin-coated stent deployment in small vessels compared with balloon angioplasty. In 202 patients, restenosis in balloon and stent arms was 49% and 30%, respectively.

Clinical outcome of patients undergoing non-cardiac surgery in the two months following coronary stenting

OBJECTIVES

We sought to determine the frequency and timing of complications at our institution when surgery was performed within two months of coronary stent placement.

BACKGROUND

The optimal delay following coronary stent placement prior to non-cardiac surgery is unknown.

METHODS

We analyzed the Mayo Clinic Percutaneous Coronary Intervention and Surgical databases between 1990 and 2000 and identified 207 patients who underwent surgery in the two months following successful coronary stent placement.

RESULTS

Eight patients (4.0%) died or suffered a myocardial infarction or stent thrombosis. All 8 patients were among the 168 patients (4.8%, 95% confidence interval [CI] 2.1 to 9.2) undergoing surgery six weeks after stent placement; the frequency of these events ranged from 3.8% to 7.1% per week during each of the six weeks. No events occurred in the 39 patients undergoing surgery seven to nine weeks after stent placement (0%, 95% CI 0.0 to 9.0).

CONCLUSIONS

These data suggest that, whenever possible, non-cardiac surgery should be delayed six weeks after stent placement, by which time stents are generally endothelialized, and a course of antiplatelet therapy to prevent stent thrombosis has been completed.

Intracoronary beta-irradiation with a rhenium-188-filled balloon catheter: a randomized trial in patients with de novo and restenotic lesions

BACKGROUND

Restenosis requiring reintervention is the main limitation of coronary angioplasty. Intracoronary irradiation reduces neointimal proliferation. We studied the efficacy of a self-centering liquid rhenium-188-filled balloon catheter for coronary beta-brachytherapy.

METHODS AND RESULTS

After successful coronary angioplasty with or without stenting, 225 patients (71% de novo lesions) were randomly assigned to receive 22.5 Gy intravascular beta-irradiation in 0.5-mm tissue depth (n=113) or to receive no additional intervention (n=112). Clinical and procedural data did not differ between the groups except a higher rate of stenting in the control group (63%) compared with the rhenium-188 group (45%, P<0.02). After 6 months of follow-up, late loss was significantly lower in the irradiated group compared with the control group, both of the target lesion (0.11+/-0.54 versus 0.69+/-0.81 mm, P<0.0001) and of the total segment (0.22+/-0.67 versus 0.70+/-0.82 mm, P<0.0001). This was also evident in the subgroup of patients with de novo lesions and independent from stenting. Binary restenosis rates were significantly lower at the target lesion (6.3% versus 27.5%, P<0.0001) and of the total segment (12.6% versus 28.6%, P<0.007) after rhenium-188 brachytherapy compared with the control group. Target vessel revascularization rate was significantly lower in the rhenium-188 (6.3%) compared with the control group (19.8%, P=0.006).

CONCLUSIONS

Intracoronary beta-brachytherapy with a rhenium-188 liquid-filled balloon is safe and efficiently reduces restenosis and revascularization rates after coronary angioplasty.

Heparin-coated stent placement for the treatment of stenoses in small coronary arteries of symptomatic patients

BACKGROUND

The role of stents, especially of heparin-coated stents for the treatment of stenoses in small coronary arteries, is still unclear. Therefore, we performed this prospective, randomized trial to evaluate the angiographic and clinical outcome after treatment of stenoses in small coronary arteries (2.0 to 2.6 mm) of symptomatic patients.

METHODS AND RESULTS

We randomly assigned 588 patients to angioplasty (n=195), bare stenting (n=196), or heparin-coated stenting (n=197). The primary end point was minimal lumen diameter (MLD) at 6 months. With comparable baseline parameters, the two stent arms showed a larger postinterventional MLD, larger acute gain, and smaller residual percent diameter stenosis, although a residual stenosis of 12+/-16% was achieved in the angioplasty arm, including a 27% crossover rate to stenting. Eighty percent of patients had follow-up angiography, which documented a borderline significantly larger MLD and smaller percent diameter stenosis for the two stent groups (1.34+/-0.48 mm and 42+/-20% after angioplasty, 1.47+/-0.48 mm and 36+/-20% after bare stenting, and 1.45+/-0.54 mm and 38+/-23% after heparin-coated stenting; P=0.049 and P=0.038, respectively), but restenosis rates were not different (32%, 25%, and 30%). Thrombotic events occurred in 1.0% after angioplasty and 0.5% after bare or heparin-coated stenting. Survival without myocardial infarction or target vessel revascularization at 250 days was 84.6% (angioplasty), 88.3% (bare stenting), and 88.3% (heparin-coated stenting; log-rank P=0.39).

CONCLUSION

Compared with angioplasty with provisional stenting, bare and heparin-coated stenting confer superior angiographic results and a nonsignificant 24% reduction in clinical events, with no difference between bare and heparin-coated stenting in the treatment of stenoses in small coronary arteries.