Stent-based antirestenotic coatings (sirolimus/paclitaxel)

Different drugs in drug-eluting stents for peripheral artery disease: a systematic evaluation and Bayesian meta-analysis

Drug-eluting stents (DESs) have become the first-line treatment for symptomatic peripheral arterial disease (PAD). Currently, there are many types of DESs on the market. The same type of DESs has different concentrations, and various drugs in them show uneven efficacy. The selection of DESs remains controversial. This study was aimed at comparing the long-term real-world outcomes of different DESs in the treatment of peripheral arterial occlusive disease (PAOD). The databases including Cochrane Library, Embase, and PubMed were searched with a time frame until March 25, 2023. The primary patency (PP) and target lesion revascularization (TLR) at 6 months were used as the primary endpoints. A total of 32 studies (5467 patients) were eligible. At the six-month follow-up, DES-Evero 1 ug/mm2 ranked first in terms of PP, with a significant difference from BMSs (RR [95% CI] = 1.6). DES-Siro 0.9 ug/mm2, DES-Siro 1.4 ug/mm2, DES-Siro 1.95 ug/mm2, DES-PTX 0.167 ug/mm2, DES-PTX 1 ug/mm2 and covered stents (CSs) showed significantly better PPs than BMSs. In terms of TLR, DES-Siro 0.9 ug/mm2 (0.31) ranked first, and DES-Evero 1 ug/mm2 ranked last. Among the treatment modalities for PAD, different DESs showed overall encouraging results in improving PP and TLR compared with BMSs. DES-Evero 1 ug/mm2 showed the best PP, but it had the highest reintervention rate at 6 months. Sirolimus-eluting stents were not always more effective with higher concentrations of sirolimus. Among various DESs, sirolimus-eluting stents and everolimus-eluting stents were superior to paclitaxel-eluting stents.

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

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

Modeling Dual Drug Delivery from Eluting Stents: The Influence of Non-Linear Binding Competition and Non-Uniform Drug Loading

OBJECTIVE

There is increasing interest in simultaneous endovascular delivery of more than one drug from a drug-loaded stent into a diseased artery. There may be an opportunity to obtain a therapeutically desirable uptake profile of the two drugs over time by appropriate design of the initial drug distribution in the stent. Due to the non-linear, coupled nature of diffusion and reversible specific/non-specific binding of both drugs as well as competition between the drugs for a fixed binding site density, a comprehensive numerical investigation of this problem is critically needed.

METHODS

This paper presents numerical computation of dual drug delivery in a stent-artery system, accounting for diffusion as well as specific and non-specific reversible binding. The governing differential equations are discretized in space, followed by integration over time using a stiff numerical solver. Three different cases of initial dual drug distribution are considered.

RESULTS

For the particular case of sirolimus and paclitaxel, results show that competition for a limited non-specific binding site density and the significant difference in the forward/backward reaction coefficients play a key role in determining the nature of drug uptake. The nature of initial distribution of the two drugs in the stent is also found to influence the binding process, which can potentially be used to engineer a desirable dual drug uptake profile.

CONCLUSIONS

These results help improve the fundamental understanding of endovascular dual drug delivery. In addition, the numerical technique and results presented here may be helpful for designing and optimizing other drug delivery problems as well.

Do we really understand how drug eluted from stents modulates arterial healing?

The advent of drug-eluting stents (DES) has revolutionised the treatment of coronary artery disease. These devices, coated with anti-proliferative drugs, are deployed into stenosed or occluded vessels, compressing the plaque to restore natural blood flow, whilst simultaneously combating the evolution of restenotic tissue. Since the development of the first stent, extensive research has investigated how further advancements in stent technology can improve patient outcome. Mathematical and computational modelling has featured heavily, with models focussing on structural mechanics, computational fluid dynamics, drug elution kinetics and subsequent binding within the arterial wall; often considered separately. Smooth Muscle Cell (SMC) proliferation and neointimal growth are key features of the healing process following stent deployment. However, models which depict the action of drug on these processes are lacking. In this article, we start by reviewing current models of cell growth, which predominantly emanate from cancer research, and available published data on SMC proliferation, before presenting a series of mathematical models of varying complexity to detail the action of drug on SMC growth in vitro. Our results highlight that, at least for Sodium Salicylate and Paclitaxel, the current state-of-the-art nonlinear saturable binding model is incapable of capturing the proliferative response of SMCs across a range of drug doses and exposure times. Our findings potentially have important implications on the interpretation of current computational models and their future use to optimise and control drug release from DES and drug-coated balloons.

In vitro and in vivo Assessment of Keratose as a Novel Excipient of Paclitaxel Coated Balloons

Purpose: Drug coated balloons (DCB) are continually improving due to advances in coating techniques and more effective excipients. Paclitaxel, the current drug choice of DCB, is a microtubule-stabilizing chemotherapeutic agent that inhibits smooth muscle cell proliferation. Excipients work to promote coating stability and facilitate paclitaxel transfer and retention at the target lesion, although current excipients lack sustained, long-term paclitaxel retention. Keratose, a naturally derived protein, has exhibited unique properties allowing for tuned release of various therapeutic agents. However, little is known regarding its ability to support delivery of anti-proliferative agents such as paclitaxel. The goal of this project was to thus demonstrate the feasibility of keratose as a DCB-coating excipient to promote the release and delivery of paclitaxel. Methods: Keratose was combined with paclitaxel in vitro and the release kinetics of paclitaxel and keratose were evaluated through high performance liquid chromatograph-mass spectroscopy (HPLC-MS) and spectrophotometry, respectively. A custom coating method was developed to deposit keratose and paclitaxel on commercially available angioplasty balloons via an air spraying method. Coatings were then visualized under scanning electron microscopy and drug load quantified by HPLC-MS. Acute arterial transfer of paclitaxel at 1 h was assessed using a novel ex vivo model and further evaluated in vivo in a porcine ilio-femoral injury model. Results: Keratose demonstrated tunable release of paclitaxel as a function of keratose concentration in vitro. DCB coated via air spraying yielded consistent drug loading of 4.0 ± 0.70 μg/mm2. Under scanning electron microscopy, the keratose-paclitaxel DCB showed uniform coverage with a consistent, textured appearance. The acute drug transfer of the keratose-paclitaxel DCB was 43.60 ± 14.8 ng/mg at 1 h ex vivo. These measurements were further confirmed in vivo as the acute 1 h arterial paclitaxel levels were 56.60 ± 66.4 ng/mg. Conclusion: The keratose-paclitaxel coated DCB exhibited paclitaxel uptake and achieved acute therapeutic arterial tissue levels, confirming the feasibility of keratose as a novel excipient for DCB.

Crystalline paclitaxel coated DES with bioactive protective layer development

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

HPLC-MS/MS method for quantification of paclitaxel from keratin containing samples

Local drug delivery of paclitaxel is becoming ever more prevalent. As complex drug/excipient combinations are being developed and tested, new high performance liquid chromatography-mass spectrometry (HPLC-MS) techniques capable of quantifying paclitaxel from such formulations are needed. Here a method for quantifying paclitaxel from aqueous, protein and oil containing samples was developed and validated. Keratin, derived from human hair, is the protein component/paclitaxel excipient in the development and validation of said method. The novelty of this method is described by its ability to overcome water solubility issues and address clean-up of residual solvents in clinical grade paclitaxel injection composition. The method evaluates tert-butyl methyl ether and ethanol as extraction solvents with an extraction efficiency of 31.9±2.3% and 86.4±4.5% respectively. Upon evaporation and rehydration, samples were evaluated by HPLC-MS and a method was developed for paclitaxel quantification. The method developed had an inter-day precision of 9.1% relative standard deviation and an intra-day precision of 4.3% relative standard deviation normalized to a docetaxel internal standard. The described method is applicable to any aqueous paclitaxel sample containing protein and/or oils.

A chemical stability study of trimethylsilane plasma nanocoatings for coronary stents

Trimethylsilane (TMS) plasma nanocoatings were deposited onto stainless steel coupons in direct current (DC) and radio frequency (RF) glow discharges and additional NH₃/O₂ plasma treatment to tailor the coating surface properties. The chemical stability of the nanocoatings were evaluated after 12 week storage under dry condition (25 °C) and immersion in simulated body fluid (SBF) at 37 °C. It was found that nanocoatings did not impact surface roughness of underlying stainless steel substrates. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to characterize surface chemistry and compositions. Both DC and RF nanocoatings had Si- and C-rich composition; and the O- and N-contents on the surfaces were substantially increased after NH₃/O₂ plasma treatment. Contact angle measurements showed that DC-TMS nanocoating with NH₃/O₂ treatment generated very hydrophilic surfaces. DC-TMS nanocoatings with NH₃/O₂ treatment showed minimal surface chemistry change after 12 week immersion in SBF. However, nitrogen functionalities on RF-TMS coating with NH₃/O₂ post treatment were not as stable as in DC case. Cell culture studies revealed that the surfaces with DC coating and NH₃/O₂ post treatment demonstrated substantially improved proliferation of endothelial cells over the 12 week storage period at both dry and wet conditions, as compared to other coated surfaces. Therefore, DC nanocoatings with NH₃/O₂ post treatment may be chemically stable for long-term properties, including shelf-life storage and exposure to the bloodstream for coronary stent applications.

Elevated high sensitive C-reactive protein and apelin levels after percutaneous coronary intervention and drug-eluting stent implantation

OBJECTIVE

Percutaneous coronary intervention (PCI) triggers an acute inflammatory response, while sirolimus is known to have anti-inflammatory properties; the inflammatory system response to PCI after sirolimus-eluting stent placement remains unclear. The purpose of this study is to determine the changes in high sensitive C-reactive protein (hs-CRP) and apelin after PCI procedure and drug-eluting stent implantation in patients with and without reduced left ventricular systolic function.

METHODS

Forty-eight consecutive patients undergoing PCI at the Beijing Anzhen Hospital between July and September 2006 were recruited. Sirolimus-eluting stents were employed in all patients. Blood samples were drawn immediately before and 24 h after the procedure. Plasma hs-CRP and apelin levels were determined by enzyme immunoassay.

RESULTS

Paired t-test revealed a significant increase in both hs-CRP and apelin post-procedure (P=0.006 and P<0.0001, respectively). Patients with reduced left ventricular ejection fraction (LVEF) had significantly lower baseline apelin levels compared to those with normal ventricular function [(46.8+/-10.8) vs. (72.0+/-8.4) pg/ml, P<0.001]. However, apelin increased to a level similar to the level of those with normal left ventricular systolic function 24 h after the PCI procedure [(86.7+/-11.6) vs. (85.1+/-6.1) pg/ml, P=0.72].

CONCLUSIONS

hs-CRP and apelin levels increased after PCI and sirolimus-eluting stent implantation. Patients with impaired left ventricular systolic function had significantly lower baseline apelin levels, which increased significantly after PCI.

Serum Inflammatory and Immune Marker Response After Bare-Metal or Drug-Eluting Stent Implantation Following Percutaneous Coronary Intervention

We assessed the changes in serum antiheat shock protein (HSP)-27 antibody and high-sensitivity C-reactive protein (hsCRP) levels, following the placement of a drug-eluting stent (DES) or bare-metal stent (BMS) in patients with stable coronary artery disease. Either a BMS or DES was implanted in 137 patients (82 BMS; 55 DES). Anti-HSP27 and hsCRP levels were measured 24 hours before and 24 hours after stenting. Median hsCRP serum levels increased significantly to 60.78 (10.13-84.87) and 77.80 (50.00-84.84) mg/L for BMS and DES groups (P = .006 and P = .000, respectively); this increase did not differ significantly between the 2 groups. Median anti-HSP27 antibody levels decreased to 0.26 (0.17-0.49) and 0.21 (0.16-0.29) absorbency units in BMS and DES groups (P = .045 and P = < 0.001, respectively). The changes in anti-HSP27 antibody titers were significant between the 2 groups (P = .015). Bare-metal stent and DES differ in stimulation of immune rather than inflammatory responses. Less stent restenosis after DES compared with BMS implantation could, in part, be attributed to differences in immune responses.

Adjustable paclitaxel release kinetics and its efficacy to inhibit smooth muscle cells proliferation

Despite the success of drug-eluting stents in the field of interventional cardiology, very little work has been reported on the role of drug (paclitaxel) release kinetics on smooth muscle cell proliferation. This paper demonstrates how paclitaxel release from degradable polymers was successfully tailored from fast release rate to moderate and slow by changing the matrix composition. Cell counting and proliferation assays were employed to investigate the efficacy of each type of release kinetics in preventing human coronary artery smooth muscle cells proliferation. The fast release kinetics presented excellent inhibition immediately but may affect the re-endothelialization process. In this study, the moderate release kinetics appeared to be the best choice to prevent cell proliferation with consequently less effect on re-endothelialization. The slow release kinetics showed little inhibition in the early days but may be beneficial in the long term as a result of its sustained release.

Reduced systemic inflammatory response to implantation of sirolimus-eluting stents in patients with stable coronary artery disease

Stent implantation causes significant injury to the vascular wall, resulting in inflammatory activation. Although sirolimus-eluting stents (SES) have anti-inflammatory properties, their effect on periprocedural systemic inflammatory response has not been sufficiently investigated. Eighty-one patients with stable coronary artery disease involving severe stenosis of one major epicardial coronary artery underwent coronary angioplasty with stent implantation and randomly received either SES or bare metal stents (BMS). Blood samples were taken 24h before, at 24h, 48 h and 1 month after the angioplasty and levels of high sensitive C-reactive protein (hsCRP), interleukin-6 (IL-6), interleukin-1 beta (IL-1 beta), and monocyte chemoattractant protein-1 (MCP-1) were determined. HsCRP after BMS implantation increased over 24h (p<0.001) and then remained steady, as did IL-6 and IL-1 beta similarly. In contrast, their levels in SES patients decreased to below baseline by the end of the month. MCP-1 levels increased by the end of 1 month (p<0.001) in the BMS group, whereas in SES they steadily decreased, becoming significantly lower than baseline from 48 h (p=0.015). In conclusion, patients with SES exhibit an attenuation of the postprocedural systemic inflammatory activation during a 1-month follow-up after stent implantation. This might partially explain the reduced restenosis rate associated with SES.

Amorphous oxide--a platform for drug delivery

Usually, a drug is loaded onto the metallic surface of a medical device by applying a polymer layer containing the drug. Unfortunately, polymer coatings on the metallic surface may exhibit numerous problems after implantation, such as late thrombosis, inflammation, and restenosis. Current research was conducted to investigate whether a suitable oxide layer can be used as a polymer-free platform for drug loading, especially for cardiovascular stents. The loading of heparin onto, as well as eluting of heparin from, the amorphous oxide film on the 316LVM stainless steel wire was confirmed by experimental studies using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), electron spectroscopy for chemical analysis (ESCA), high-performance liquid chromatography (HPLC), and activated clotting time (ACT). Evidence shows that amorphous oxide can be an ideal substitute for the polymer coating of drug-loaded stents to minimize metallic corrosion, inflammation, late-thrombosis, and restenosis.

Tissue Hyperplasia: Influence of a Paclitaxel-eluting Covered Stent—Preliminary Study in a Canine Urethral Model

PURPOSE

To evaluate a paclitaxel-eluting covered stent in reduction of tissue hyperplasia after stent placement in a canine urethral model.

MATERIALS AND METHODS

Procedures were performed in accordance with the National Institutes of Health guidelines for humane handling of animals; approval of the committee of animal research was obtained. Twenty paclitaxel-eluting polyurethane-covered stents (drug stents) and 20 polyurethane-covered stents (control stents) were placed alternately between the proximal and distal urethra in 20 male dogs. The dose of paclitaxel was approximately 1800 mug in each drug stent but absent in each control stent. Dogs were sacrificed either 4 (n = 10) or 8 (n = 10) weeks after stent placement. The percentage diameter of stenosis was assessed with follow-up retrograde urethrography and histologic findings obtained after sacrifice and compared between drug stents and control stents and between the proximal and the distal urethra.

RESULTS

Two drug stents partially migrated during retrograde urethrography immediately after stent placement; they were removed and replaced with a second stent during the same procedure. There was a strong tendency toward a lower percentage diameter of stenosis and numeric mean values of the four histologic findings, which indicates less formation of tissue hyperplasia in the proximal urethra than in the distal urethra. In particular, thickness of the papillary projection denoting the entire thickness of hyperplastic reaction was significantly less in drug stents than in control stents in the proximal urethra in the 8-week group (P = .016, Mann-Whitney U test).

CONCLUSION

Local delivery of paclitaxel via covered stents has the potential to reduce tissue hyperplasia secondary to stent placement in a canine urethral model. With stent placement, there are distinct differences of tissue hyperplasia between the proximal and distal urethra.

Drug-eluting stents: a mechanical and pharmacologic approach to coronary artery disease

Coronary artery disease is the largest killer of men and women in the United States and costs the health care system billions of dollars annually. Several advances in both mechanical and pharmacologic treatment of coronary artery disease have occurred in recent decades. Mechanically, percutaneous coronary intervention is commonly used to treat coronary atherosclerosis. This approach has dramatically reduced both morbidity and mortality for patients with different levels of severity of coronary artery disease. However, percutaneous coronary intervention is limited by restenosis, which is an increase in growth of the intimal layer of the vessel wall. Despite the introduction of intracoronary stents and the addition of systemic pharmacotherapy, restenosis still affects a significant number of patients. The new technology of drug-eluting stents combines mechanical and pharmacologic approaches to prevent restenosis. Various types of these stents exist in different stages of development; several have been shown to prevent or reduce intimal growth after stent deployment. An understanding of how this combined mechanical and pharmacologic approach reduces restenosis requires consideration of complex issues in pathophysiology and pharmacology.

In vitro hemocompatibility studies of drug-loaded poly-(L-lactic acid) fibers

Our objective was to evaluate the hemocompatibility of biodegradable stent fibers, employing a closed-loop circulation system filled with human blood. We also investigated the effects of the anti-inflammatory and anti-proliferative drugs curcumin and paclitaxel, incorporated into stent fibers. Fresh whole blood was circulated in four parallel closed-loop systems: the empty tube circuit (control) and tubes containing either a PLLA fiber coil (PLLA), a curcumin-loaded PLLA coil (C-PLLA) or a paclitaxel-loaded PLLA coil (P-PLLA). The influence of PLLA fiber, alone or loaded with drug incorporated during melt-extrusion, on leukocyte and platelet adhesion and activation was determined by flow cytometry. The effects of blood flow and fiber properties on cell deposition were assessed by scanning electron microscopy (SEM). The flow cytometry results clearly demonstrated that PLLA triggers blood cell activation at the site of deployment, as shown by increases in CD11b, CD62P and leukocyte-platelet aggregates, compared to controls. Curcumin and paclitaxel treatments both significantly reduced leukocyte and platelet activation and adhesion to PLLA fibers, as shown by flow cytometry and SEM. Activated leukocytes and platelets revealed significantly lower CD11b and CD62P receptor binding for C-PLLA compared with PLLA alone, and slightly lower for P-PLLA. Reductions in platelet-leukocyte aggregates were observed as well. In addition, there was less leukocyte and platelet adhesion to C-PLLA, compared with PLLA fiber controls, as shown by SEM. A continuous linear thrombus, composed of platelets, leukocytes, red blood cells and fibrin was occasionally detected along the line of tangency between the coil and the tube wall. Flow separation and eddying, proximal and distal to the line of tangency of coil and tube, is thought to contribute to this deposit. Curcumin was more effective than paclitaxel in reducing leukocyte and platelet activation and adhesion to PLLA stent fibers in this setting. However there was evidence of paclitaxel degeneration during melt extrusion that may have inhibited its effectiveness. Incorporation of the anti-inflammatory and anti-proliferative drug curcumin into bioresorbable stent fibers is proposed to prevent thrombosis and in-stent restenosis.

In vitro study of release mechanisms of paclitaxel and rapamycin from drug-incorporated biodegradable stent matrices

We have studied the in vitro release kinetics of two important antirestenosis drugs from biodegradable stent matrices. A helical stent incorporating drugs was exposed to buffer, and both degradation-controlled and diffusion-controlled drug releases were observed. New methods for in vitro drug release for both paclitaxel and rapamycin have been developed. The release profile shows a slow diffusion-controlled phase, followed by a more rapid degradation-controlled region. In the early part of the drug release, no burst effect is observed for either drug. This might be significant for paclitaxel administration, where cardiotoxicity has been sometimes of concern. By suitable polymer/drug formulations, it is possible to develop controlled release stent matrices that can exhibit a variety of release profiles. These release profiles may have relevance to antirestenotic effects and to local or systemic toxic effects.

Sirolimus-Eluting Coronary Stents: Novel Devices for the Management of Coronary Artery Disease

Despite major technological advances in the practice of percutaneous coronary intervention, restenosis of the treated arteries remains a challenge for many interventional cardiologists. Sirolimus is a macrolide antibiotic with potent antifungal, immunosuppressive, and antimitotic activities. Sirolimus inhibits in-stent restenosis via 2 major mechanisms of action: by blocking the process of neointimal hyperplasia by inhibiting smooth muscle cell proliferation and by inhibiting inflammatory cell activity. In pivotal clinical trials, the sirolimus-eluting stent has demonstrated significant improvements in angiographic and clinical outcomes compared with bare metal stents in patients with de novo lesions in native coronary arteries. Since the systemic exposure of sirolimus in patients who received the drug-eluting stent is minimal, adverse effects resulting from systemic exposure of sirolimus are unlikely to occur. Further studies are needed to determine the safety and effectiveness of sirolimus-eluting stents in patients with more complex coronary artery lesions. In addition, the long-term safety, efficacy, and cost-effectiveness of this novel drug-eluting device will need to be established in ongoing clinical trials. This review article focuses on the pharmacology as well as clinical studies of the sirolimus-eluting stent.

Molecular responses of vascular smooth muscle cells to paclitaxel-eluting bioresorbable stent materials

We studied the influence of paclitaxel, eluted from poly(L-lactic acid) (PLLA), on cultured vascular smooth muscle cell (VSMC) proliferation as a model of bioresorbable stent-induced restenosis. We blended paclitaxel in cast PLLA films (P-PLLA), demonstrating controlled release of the drug, then studied VSMC adhesion, proliferation, and gene expression profiles. No difference in cell adhesion was found between P-PLLA and PLLA controls (105 +/- 12% of PLLA controls). However, P-PLLA significantly reduced VSMC proliferation (40 +/- 15% of PLLA controls, p < 0.05). Using cDNA microarray technology, we identified major effects of P-PLLA, including: upregulation of genes related to apoptosis, anti-proliferation and antioxidation; and suppression of cell cycle regulators and cell survival markers. The expression patterns indicate that P-PLLA regulates gene expression and cell functions via new pathways, including receptor tyrosine kinase (RTKs), mitogen-activated protein kinase (MAPKs), and protein kinase (PKs, e.g., PKA) pathways, in addition to the stabilization of polymerized-microtubules.

Current status of intravascular stents as delivery devices to prevent restenosis

The acute technical success of percutaneous transluminal angioplasty (PTA) has been improved with the use of intravascular stents. However, stent placement has led to the development of an increased myointimal hyperplastic response leading to late reduction in vessel lumen. Restenosis (> or =50% reduction in reference lumen diameter) rates for coronary angioplasty and stenting are reported between 20% and 50% at 1 year. Several studies are currently evaluating novel delivery of antiproliferative agents to prevent neointimal hyperplasia. The authors review the mechanism of neointimal hyperplasia as it relates to stent placement and discuss recent and ongoing trials evaluating intravascular brachytherapy and drug-eluting stent technology in the inhibition of restenotic lesions.

Inflammation and restenosis in the stent era

The pathophysiology of restenosis involves early elements of direct injury to smooth muscle cells, deendothelialization, and thrombus deposition. Over time, this leads to smooth muscle cell proliferation/migration and extracellular matrix deposition. There is an increasing body of evidence to suggest that inflammation plays a pivotal role linking early vascular injury to the eventual consequence of neointimal growth and lumen compromise. The widespread use of coronary stents has fundamentally altered the vascular response to injury by causing a more intense and prolonged inflammatory state. Many of the cellular and molecular elements responsible for leukocyte recruitment have been elucidated, providing potential therapeutic targets for restenosis. This review seeks to provide an integrated view of the pathophysiology of restenosis that explains the central role of inflammation.