Evaluation of metal allergies in patients with coronary stents

Nickels and tines: the myth of nickel allergy in intracranial stents

BACKGROUND

Most intracranial stents contain nickel alloy, and nickel allergy or hypersensitivity is common. Neurological injury following endovascular treatment with a nickel containing intracranial stent has been reported in patients with purported nickel allergy, but it is unclear whether these reactions represent true nickel hypersensitivity. We quantified nickel release from commonly used intracranial stents to investigate whether such stents should be avoided in patients with nickel allergy.

METHODS

We examined nickel release from seven commonly used intracranial stents: Enterprise, LVIS Jr, Neuroform, Wingspan, Zilver, Pipeline Flex Embolization Device, and Surpass Evolve. We incubated each stent in human plasma-like media for 30 days. Dimethylglyoxime (DMG) spot testing was performed on each stent to detect released nickel at 0 and 30 days. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was then used to quantify the nickel concentration of the media at 30 days. Nickel currency and nickel standard for atomic absorption spectrometry were used as positive controls.

RESULTS

DMG spot tests indicated nickel release only from nickel currency at 0 and 30 days of incubation. No nickel release was detected from any stent at 30 days using ICP-OES.

CONCLUSIONS

Nickel release from commonly used intracranial stents is negligible. These results suggest that previously reported hypersensitivity to these stents may be misattributed to nickel allergy, and that patients with nickel allergy may be safely treated with select nickel-containing stents.

Some Perspectives on Hypersensitivity to Coronary Stents

The development of coronary stents has represented a revolution in the treatment of coronary heart disease. Beyond their many advantages, stents also have their limitations and complications. Allergic reactions to coronary stents are more common than acknowledged. These stented patients are exposed to foreign substances inserted in direct contact with the coronary intima. Hypersensitivity to stent components and drugs prescribed after stent insertion together with any environmental exposure seem to contribute to these adverse reactions. Patients can present to the hospital with a wide range of symptoms and multiple complications, the most important ones being instent restenosis and stent thrombosis. Although not very common (and not always easy to identify), allergic reactions after coronary or peripheral stents should be taken into account. Careful selection of patients (for elective stent implantation) depending on the propensity to allergies, although hard to achieve, represents a key factor in reducing the number of these complications.

Inflammation as a determinant of healing response after coronary stent implantation

Cardiovascular disease remains the leading cause of death and morbidity worldwide. Inflammation plays an important role in the development of atherosclerosis and is associated with adverse clinical outcomes in patients after percutaneous coronary interventions. Data on stent elements that lead to excessive inflammatory response, proper identification of high-risk patients, prevention and treatment targeting residual inflammatory risk are limited. This review aims to present the role of inflammation in the context of evolving stent technologies and appraise the potential imaging modalities in detection of inflammatory response and anti-inflammatory therapies.

Use of Pipeline Endovascular Device in Patients with Nickel Allergies

BACKGROUND

Metal allergies affect a significant portion of the population; intracranial flow diverters contain many of the most commonly allergenic metals. Prior literature has suggested patch testing for all patients with documented or suspected metal allergies before intracranial flow diverter placement; however, there remains a paucity of reports of patients with documented metal allergies undergoing intracranial flow diversion.

CASE DESCRIPTION

We report 2 patients with documented nickel allergies, confirmed via patch testing by a board-certified allergist, and unruptured intracranial aneurysms that underwent treatment with the PED. Both patients developed contact dermatitis when a PED was affixed to their skin during their preoperative workup. Follow-up arteriography at 12 and 36 months post PED placement showed no evidence of in-stent stenosis or intimal hyperplasia, and both patients never developed systemic allergic reactions.

CONCLUSIONS

In 2 patients with known nickel allergies and intracranial aneurysms treated with the PED, there were no clinically or radiographically apparent allergic reactions at greater than 2 years of follow-up.

Impact of nitinol stent surface processing on in-vivo nickel release and biological response

Although nitinol is widely used in percutaneous cardiovascular interventions, a causal relationship between nickel released from implanted cardiovascular devices and adverse systemic or local biological responses has not been established. The objective of this study was to investigate the relationship between nitinol surface processing, in-vivo nickel release, and biocompatibility. Nitinol stents manufactured using select surface treatments were implanted into the iliac arteries of minipigs for 6 months. Clinical chemistry profile, complete blood count, serum and urine nickel analyses were performed periodically during the implantation period. After explant, stented arteries were either digested and analyzed for local nickel concentration or fixed and sectioned for histopathological analysis of stenosis and inflammation within the artery. The results indicated that markers for liver and kidney function were not different than baseline values throughout 180 days of implantation regardless of surface finish. In addition, white blood cell, red blood cell, and platelet counts were similar to baseline values for all surface finishes. Systemic nickel concentrations in serum and urine were not significantly different between processing groups and comparable to baseline values during 180 days of implantation. However, stents with non-optimized surface finishing had significantly greater nickel levels in the surrounding artery compared to polished stents. These stents had increased stenosis with potential for local inflammation compared to polished stents. These findings demonstrate that proper polishing of nitinol surfaces can reduce in-vivo nickel release locally, which may aid in minimizing adverse inflammatory reactions and restenosis.

STATEMENT OF SIGNIFICANCE

Nitinol is a commonly used material in cardiovascular medical devices. However, relationships between nitinol surface finishing, in-vivo metal ion release, and adverse biological responses have yet to be established. We addressed this knowledge gap by implanting single and overlapped nitinol stents with different surface finishes to assess systemic impact on minipigs (i.e. serum and urine nickel levels, liver and kidney function, immune and blood count) over the 6 month implantation period. In addition, nickel levels and histopathology in stented arteries were analyzed on explant to determine relationships between surface processing and local adverse tissue reactions. The findings presented here highlight the importance of surface processing on in-vivo nickel release and subsequent impact on local biological response for nitinol implants.

Coronary stent restenosis and the association with allergy to metal content of 316L stainless steel

Background

Most intra-coronary stents in use are made of 316 L stainless steel, which contains nickel, chromate and molybdenum. Whether inflammatory and allergic reactions to metals contribute to in-stent restenosis is still a matter of debate.

Aim

The aim of this study was to ascertain the relationship between metal allergy and the occurrence of in-stent restenosis.

Methods

Ninety-nine adult patients who underwent two cardiac catheterisations, up to two years apart, were included in the study. Seventy patients had patent stents at the second angiogram (patent stent group) and 29 were found to have in-stent restenosis (restenosis group). All patients underwent patch testing with the relevant metals and the 316L stainless steel plate.

Results

Twenty-eight (28.3%) patients were found to have an allergy to at least one metal. There was no significant difference in the prevalence of metal allergy between the patent stent group and the restenosis group (28.6 and 27.6%, respectively; p = 0.921).

Conclusion

Our data do not support the theory that contact allergy plays a role in the pathogenesis of in-stent restenosis.

The value of peripheral blood eosinophil count in predicting in-stent restenosis in patients with stable angina pectoris undergoing drug eluting stenting

INTRODUCTION

In-stent restenosis (ISR) remains a major limitation of percutaneous coronary intervention (PCI). A role for peripheral blood cells as major regulators of immune and inflammatory systems has been proposed. We aim to evaluate the relationship between eosinophil count and development of restenosis after drug-eluting stent (DES) implantation.

METHODS

In this prospective study, all consecutive patients undergoing elective DES implantation for chronic stable angina (CSA) in a university-affiliated heart center within a 6-month period were enrolled and followed for another 6 months. Complete blood count with differentiation was performed 6 weeks after the index procedure. During the follow-up period, the cohort of patients who developed ISR was compared to the cohort of patients without ISR, descriptively and the total number of eosinophilic white cells was used to predict the occurrence of ISR.

RESULTS

153 men and 48 women with CSA underwent PCI with DES implantation, from which, 26 patients needed repeat coronary angiography for recurrent symptoms. There was an established ISR in 17 (8.5%) patients. The total number of eosinophils in their peripheral blood was 267 ± 132 cells/μL in patients with ISR, significantly higher than the number of eosinophils in those without ISR 174 ± 133 cells/μL (P-value < 0.010). Eosinophil count remained an independent predictor of ISR in multivariate analysis as the eosinophil count value over 242 cells/μL had sensitivity of 66.7% and specificity of 84.5% for the presence of ISR.

CONCLUSION

The total number of eosinophils, counted 6 weeks after DES implantation, prevails as the sole predictor of ISR occurrence in our study. This suggests an association between immune sensitivity reaction to DES material and development of ISR in patients after PCI.

Making Sense of Metal Allergy and Hypersensitivity to Metallic Implants in Relation to Hand Surgery

All metals implanted into a biological system undergo some degree of corrosion depending upon its composition. The electrochemical process of corrosion produces free metal ions, which may activate the host's immune system through a variety of mechanisms. Whereas dermal metal hypersensitivity is common, affecting 10% to 15% of the population, the immune reaction from implanted metals is much less common (< 0.1%), but has been associated with metal allergy and hypersensitivity producing a multitude of patient symptoms. Superficial symptoms may be mild to severe forms of dermatitis, urticaria, pruritus, and vasculitis, whereas deep sequelae include metallosis-related pseudotumor, implant loosening, and joint stiffness. Currently, there are clinical tests to evaluate patients for metal hypersensitivity, but there is little agreement regarding the ideal timing and clinical situation prompting the work-up of a patient for a metal allergy or hypersensitivity. An understanding of the epidemiology, etiology, basic science, diagnostic testing, and treatment of patients with suspected metal allergy, as it pertains to the current literature, will aid orthopedic and plastic surgeons of all subspecialties in the management of patients requiring metallic implants.

Current practices in corrosion, surface characterization, and nickel leach testing of cardiovascular metallic implants

In an effort to better understand current test practices and improve nonclinical testing of cardiovascular metallic implants, the Food and Drug Administration (FDA) held a public workshop on Cardiovascular Metallic Implants: corrosion, surface characterization, and nickel leaching. The following topics were discussed: (1) methods used for corrosion assessments, surface characterization techniques, and nickel leach testing of metallic cardiovascular implant devices, (2) the limitations of each of these in vitro tests in predicting in vivo performance, (3) the need, utility, and circumstances when each test should be considered, and (4) the potential testing paradigms, including acceptance criteria for each test. In addition to the above topics, best practices for these various tests were discussed, and knowledge gaps were identified. Prior to the workshop, discussants had the option to provide feedback and information on issues relating to each of the topics via a voluntary preworkshop assignment. During the workshop, the pooled responses were presented and a panel of experts discussed the results. This article summarizes the proceedings of this workshop and background information provided by workshop participants. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. J Biomed Mater Res Part B: Appl Biomater, 105B: 1330-1341, 2017.

Design and characterization of a novel nickel-free cobalt-base alloy for intravascular stents

Co-Cr-W-Ni alloy (L605) with high tensile strength is used in coronary stents. The thickness of individual strut of the stent is reduced which can decrease the stent restenosis rate. However, about 10% Ni element content in L605 is found to cause allergic reactions and pulmonary embolism, similar to the traditional 316L stainless steel. In this study, a novel nickel-free cobalt-base alloy Co-20Cr-12Fe-18Mn-2Mo-4W-N (wt%) was designed and fabricated in order to efficiently avoid the potential hazards of Ni element. Fe and Mn, essential elements of human body, were added in the alloy to substitute part of Co element. In comparison to L605 alloy, the tensile strength of the new alloy was higher than 1000MPa while elongation was above 55%. The pitting potential of the new alloy was measured close to 1000mV, also higher than that of L605 alloy. CCK-8 test indicated that the cytotoxicity of the new alloy is grade 1, reflecting that Co-20Cr-12Fe-18Mn-2Mo-4W-N alloy has no cytotoxic effects. There was no significant difference in the apoptosis rates between Co-20Cr-12Fe-18Mn-2Mo-4W-N and L605 alloy. The newly developed cobalt-base alloy showed excellent mechanical, corrosion resistance and biological properties, which could make it a desirable material for future clinical investigations.

The effect of REDV/TiO2 coating coronary stents on in-stent restenosis and re-endothelialization

The coronary artery stent has been widely used in clinic. In-stent restenosis was mainly caused by the excessive proliferation of smooth muscle cell and the inflammation due to the metal ion released from stent scaffold of the drug-eluting stent. Thus, to reduce the in-stent restenosis and promote the vascular endothelialization have become a hot research point in this area. In this paper, a nano-TiO₂ ceramic coating was deposited on 316L stainless steel to reduce the metal ion release and to inhibit the inflammation reaction. An endothelia cell selective adhesion peptide Arg-Glu-Asp-Val (REDV) coating was prepared on the ceramic coating by a polydopamine technology to promote the endothelialization. The corrosion test indicated that nano-TiO₂ ceramic film could effectively decrease the nickel ion released from 316L stainless steel. REDV/TiO₂ coating could promote the endothelial cell adhesion and proliferation, meanwhile REDV/TiO₂ coating could also increase the nitric oxide concentration. Bare metal stent, TiO₂-coated stent and REDV/TiO₂-coated stent were implanted in the iliac arteries of rabbit model. In-stent restenosis and re-endothelialization were evaluated at 28 days post-implantation of the stents. The results showed that REDV/TiO₂-coated stents could effectively reduce in-stent restenosis and promote re-endothelialization in comparison with TiO₂-coated drug-eluting stent and bare metal stent. These results suggest that REDV/TiO₂-coated drug-eluting stent maybe a good choice of the application for coronary artery disease.

Biological behaviour of human umbilical artery smooth muscle cell grown on nickel-free and nickel-containing stainless steel for stent implantation

To evaluate the clinical potential of high nitrogen nickel-free austenitic stainless steel (HNNF SS), we have compared the cellular and molecular responses of human umbilical artery smooth muscle cells (HUASMCs) to HNNF SS and 316L SS (nickel-containing austenitic 316L stainless steel). CCK-8 analysis and flow cytometric analysis were used to assess the cellular responses (proliferation, apoptosis, and cell cycle), and quantitative real-time PCR (qRT-PCR) was used to analyze the gene expression profiles of HUASMCs exposed to HNNF SS and 316L SS, respectively. CCK-8 analysis demonstrated that HUASMCs cultured on HNNF SS proliferated more slowly than those on 316L SS. Flow cytometric analysis revealed that HNNF SS could activate more cellular apoptosis. The qRT-PCR results showed that the genes regulating cell apoptosis and autophagy were up-regulated on HNNF SS. Thus, HNNF SS could reduce the HUASMC proliferation in comparison to 316L SS. The findings furnish valuable information for developing new biomedical materials for stent implantation.

Systemic contact dermatitis and allergy to biomedical devices

Systemic contact dermatitis (SCD) refers to a skin condition where an individual who is cutaneously sensitized to an allergen will subsequently react to that same allergen or a cross-reacting allergen via the systemic route. It occurs to allergens including metals, medications, and foods. There has been recent interest in metal allergy as it relates to the implantation of devices such as orthopedic, dental, cardiac, and gynecologic implants. This review will briefly address all causes of systemic contact dermatitis with a special and expanded focus on metal implant allergy. We present literature on SCD to various metal biomedical devices, patch testing for diagnosis of metal allergy pre and post implantation and treatment.

Reduction of in-stent restenosis risk on nickel-free stainless steel by regulating cell apoptosis and cell cycle

High nitrogen nickel-free austenitic stainless steel (HNNF SS) is one of the biomaterials developed recently for circumventing the in-stent restenosis (ISR) in coronary stent applications. To understand the ISR-resistance mechanism, we have conducted a comparative study of cellular and molecular responses of human umbilical vein endothelial cells (HUVECs) to HNNF SS and 316L SS (nickel-containing austenitic 316L stainless steel) which is the stent material used currently. CCK-8 analysis and flow cytometric analysis were used to assess the cellular responses (proliferation, apoptosis, and cell cycle), and quantitative real-time PCR (qRT-PCR) was used to analyze the gene expression profile of HUVECs exposed to HNNF SS and 316L SS, respectively. Flow cytometry analysis revealed that 316L SS could activate the cellular apoptosis more efficiently and initiate an earlier entry into the S-phase of cell cycle than HNNF SS. At the molecular level, qRT-PCR results showed that the genes regulating cell apoptosis and autophagy were overexpressed on 316L SS. Further examination indicated that nickel released from 316L SS triggered the cell apoptosis via Fas-Caspase8-Caspase3 exogenous pathway. These molecular mechanisms of HUVECs present a good model for elucidating the observed cellular responses. The findings in this study furnish valuable information for understanding the mechanism of ISR-resistance on the cellular and molecular basis as well as for developing new biomedical materials for stent applications.

Relation of Nickel Allergy with in-Stent Restenosis in Patients Treated with Cobalt Chromium Stents

Background

In-stent restenosis (ISR) is the major limitation of percutaneous coronary stenting procedure. The elements like nickel, chromate and molybdenum are known to cause contact allergy. Hypersensitivity reaction, against these metal ions, may be one of the reasons of ISR. Cobalt chromium coronary stents, which are increasingly being used in percutaneous coronary interventions, have more nickel amount than the stainless steel stents.

Objective

We aimed to investigate the association between nickel hypersensitivity reaction and ISR in patients treated with cobalt chromium coronary stents.

Methods

Epicutaneous patch tests for nickel were applied to 31 patients who had undergone elective cobalt chromium coronary stent implantation and had ISR in control angiogram. Thirty patients, without ISR, were included as the control group. Patch test results and other clinical variables were compared.

Results

There was no statistically significant difference of the mean age, sex, body mass index, rate of hypercholesterolemia, diabetes, hypertension and smoking between the patients with and without ISR. All other lesion characteristics were similar in the 2 groups. According to the patch test results, 7 patients had nickel contact allergy. All of these patients were in the ISR group, which was statistically significant (p<0.006).

Conclusion

Patients treated with cobalt chromium coronary stents and had ISR were found to have significantly more nickel allergy than the control group. Nickel allergy may play role in restenosis pathophysiology.

Atrial septum defect closure device in a beating heart, from the perspective of a researcher in artificial organs

Transcatheter closure of atrial septum defect (ASD) with a closure device is increasing, but the history of clinical use of this procedure is still short, and the efficacy and long-term safety remain unproved. The total number of closure devices implanted throughout the world has not been counted accurately. Therefore, the probability of complications occurring after implantation is uncertain. Device-related complications that occur suddenly late after implantation are life-threatening, and quite often necessitate emergency surgical intervention. In Japanese medical journals, authors reporting closure devices have mentioned no complications and problems in their facilities. Detailed studies of device-related complications and device removal have not been reported in Japan. In fact, this literature search found an unexpectedly large number of reports of various adverse events from many overseas countries. When follow-up duration is short and the number of patients is small, the incidence of complications cannot be determined. Rare complications may emerge in a large series with a long observation period. Consequently, the actual number of incidents related to ASD closure devices is possibly several times higher than the number reported. Guidelines for long-term patient management for patients with an implanted closure device are necessary and post-marketing surveillance is appropriate. Development of a national database, a worldwide registration system, and continuous information disclosure will improve the quality of treatment. The devices currently available are not ideal in view of reports of late complications requiring urgent surgery and the need for life-long follow-up. An ideal device should be free from complications during life, and reliability is indispensable.

Restenosis after PCI. Part 1: pathophysiology and risk factors

Restenosis is a complex disease for which the pathophysiological mechanisms have not yet been fully elucidated, but are thought to include inflammation, proliferation, and matrix remodeling. Over the years, many predictive clinical, biological, (epi)genetic, lesion-related, and procedural risk factors for restenosis have been identified. These factors are not only useful in risk stratification of patients, they also contribute to our understanding of this condition. Furthermore, these factors provide evidence on which to base treatment tailored to the individual and aid in the development of novel therapeutic modalities. In this Review, we will evaluate the available evidence on the pathophysiological mechanisms of restenosis and provide an overview of the various risk factors, together with the possible clinical application of this knowledge.

Cutaneous and systemic hypersensitivity reactions to metallic implants

Cutaneous reactions to metal implants, orthopedic or otherwise, are well documented in the literature. The first case of a dermatitis reaction over a stainless steel fracture plate was described in 1966. Most skin reactions are eczematous and allergic in nature, although urticarial, bullous, and vasculitic eruptions may occur. Also, more complex immune reactions may develop around the implants, resulting in pain, inflammation, and loosening. Nickel, cobalt, and chromium are the three most common metals that elicit both cutaneous and extracutaneous allergic reactions from chronic internal exposure. However, other metal ions as well as bone cement components can cause such hypersensitivity reactions. To complicate things, patients may also develop delayed-type hypersensitivity reactions to metals (ie, in-stent restenosis, prosthesis loosening, inflammation, pain, or allergic contact dermatitis) following the insertion of intravascular stents, dental implants, cardiac pacemakers, or implanted gynecologic devices. Despite repeated attempts by researchers and clinicians to further understand this difficult area of medicine, the association between metal sensitivity and cutaneous allergic reactions remains to be fully understood. This review provides an update of the current knowledge in this field and should be valuable to health care providers who manage patients with conditions related to this field.

Metal allergy--a review on exposures, penetration, genetics, prevalence, and clinical implications

The prevalence of metal allergy is high in the general population, and it is estimated that up to 17% of women and 3% of men are allergic to nickel and that 1-3% are allergic to cobalt and chromium. Among dermatitis patients, the prevalence of metal allergy is even higher. Metal allergy is mainly an environmental disorder although null mutations in the filaggrin gene complex were recently found to be associated with nickel allergy and dermatitis. Environmental metal exposures include jewelry, buttons, clothing fasteners, dental restorations, mobile phones, and leather. Although consumer exposure is responsible for most cases of metal allergy, the importance of occupational metal exposure remains present and should always be taken into consideration when one interprets allergic patch test reactions to metals. Traditionally, nickel, cobalt, and chromium have been the most important contact allergens. However, recently, gold and palladium have drawn much attention as the prevalence of contact allergy to these metals is high. Palladium allergy is mainly a result of cross-sensitization to nickel, whereas gold allergy is rarely clinically relevant when one takes its high prevalence into account. The epidemiology of metal allergy has recently changed in Europe as nickel allergy among ear-pierced Danish women has decreased following regulatory intervention on nickel release from consumer products. In the United States, the prevalence of nickel allergy is still increasing, which may be explained by the absence of regulation. The prevalence of chromium allergy is increasing in the United States, Singapore, and Denmark among dermatitis patients. This increase is significantly associated with leather exposure in Denmark. Metal allergy may result in allergic contact dermatitis and systemic allergic (contact) dermatitis. Furthermore, metal allergy has been associated with device failure following insertion of intracoronary stents, hip and knee prostheses, as well as other implants. This area is in need of more research.

Coronary artery aneurysm formation after drug-eluting stent implantation

Drug-eluting stents (DES) have had a profound impact on the practice of interventional cardiology. Important safety concerns regarding DES have been widely publicized and acknowledged. The primary emphasis has been placed on late stent thrombosis and the adverse sequela which result. Another emerging adverse effect of DES is coronary aneurysm (CAA) formation. We report on a patient who developed CAA formation after DES implantation but not at the site of previous bare-metal stent (BMS) implantation. We also review the current understanding of DES-associated CAA formation.

High frequency of contact allergy to gold in patients with endovascular coronary stents

BACKGROUND

Stent implantation is an effective method for treatment of atherosclerotic disease. Factors predisposing to in-stent restenosis are still largely unknown. Contact allergy to metal ions eluted from the stent has been suggested to be a risk factor.

OBJECTIVES

To explore whether there is a possible induction of contact allergy to metals used in stents among patients with a stainless steel stent containing nickel (Ni stent) and patients with a gold-plated stent (Au stent).

METHODS

Adults (n = 484) treated with coronary stent implantation participated in the study with patch testing. The study design was retrospective and cross-sectional with no assessment of contact allergy before stenting. Age- and sex-matched patch-tested patients with dermatitis (n = 447) served as controls.

RESULTS

Of Au-stented patients, 54 of 146 (37%) were allergic to gold compared with 85 of 447 (19%) controls (P < 0.001). Within the stented population there were no statistically significant differences in contact allergy to gold or nickel between Ni-stented and Au-stented patients. In multivariate models where other risk factors for contact allergy to gold were considered, the Au stent showed a trend towards statistical significance (odds ratio 1.43, 95% confidence interval 0.95-2.16; P = 0.09).

CONCLUSIONS

As the frequency of contact allergy to gold is higher in stented patients independent of stent type it suggests a previous sensitization. However, several pieces of circumstantial evidence as well as statistical analysis indicate the possibility of sensitization in the coronary vessel by the Au stent. Ni stents and Au stents should not be ruled out as risk factors for induction of contact allergy to these metals.

Coronary Stents, Hypersensitivity Reactions, and the Kounis Syndrome

The use of drug-eluting stents (DES) for the treatment of coronary stenosis has increased sharply and now accounts for more than 75% of all coronary stents utilized. However, concern has been increasing that DES could be associated with stent thrombosis, paradoxical coronary vasoconstriction, and hypersensitivity reactions. Components of currently used DES have been reported to induce, either separately or synergistically, hypersensitivity reactions and possibly lead to cardiac events. DES-activated intracoronary mast cells could release histamine, arachidonic acid metabolites, proteolytic enzymes, as well as a variety of cytokines, chemokines, and platelet-activating factor (PAF) leading to local inflammation and thrombosis. These events may be more common than suspected because it is hard to document them, unless they become systemic, in which case they manifest themselves as the "Kounis syndrome," characterized by the concurrence of acute coronary events with hypersensitivity reactions. Recognition of this problem may lead to better vigilance, as well as new DES with mast cell blocking molecules that may also be disease modifying.

Stability of passivated 316L stainless steel oxide films for cardiovascular stents

Passivated 316L stainless steel is used extensively in cardiovascular stents. The degree of chloride ion attack might increase as the oxide film on the implant degrades from exposure to physiological fluid. Stability of 316L stainless steel stent is a function of the concentration of hydrated and hydrolyated oxide concentration inside the passivated film. A high concentration of hydrated and hydrolyated oxide inside the passivated oxide film is required to maintain the integrity of the passivated oxide film, reduce the chance of chloride ion attack, and prevent any possible leaching of positively charged ions into the surrounding tissue that accelerate the inflammatory process. Leaching of metallic ions from corroded implant surface into surrounding tissue was confirmed by the X-ray mapping technique. The degree of thrombi weight percentage [W(ao): (2.1 +/- 0.9)%; W(ep): (12.5 +/- 4.9)%, p < 0.01] between the amorphous oxide (AO) and the electropolishing (EP) treatment groups was statistically significant in ex-vivo extracorporeal thrombosis experiment of mongrel dog. The thickness of neointima (T(ao): 100 +/- 20 microm; T(ep): 500 +/- 150 microm, p < 0.01) and the area ratio of intimal response at 4 weeks (AR(ao): 0.62 +/- 0.22; AR(ep): 1.15 +/- 0.42, p < 0.001) on the implanted iliac stents of New Zealand rabbit could be a function of the oxide properties.

Corrosion of stainless steel sternal wire after long-term implantation

A variety of metallic components have been used in medical devices where lifelong durability and physical strength are demanded. To investigate the in vivo changes of implanted metallic medical devices in humans, stainless steel sternal wires removed from patients were evaluated. Stainless steel (316L) sternal wires removed from four patients after 10, 13, 22, and 30 years of implantation were evaluated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Macroscopically, the removed specimens maintained their metallic luster and color. Under SEM, small holes were observed sporadically at 10 years and they tended to connect in the drawing direction. The longer the implanted duration, the more numerous and deeper were the crevices observed. By EDS, sulfur, phosphorus, and calcium were identified in all areas at 10 years, in addition to the component elements of stainless steel, comprising iron, chromium, nickel, and manganese. Corrosion products observed at 30 years were identified as calcium phosphate. In conclusion, stainless steel sternal wires develop corroded pores that grow larger and deeper with time after implantation; however, the pores remain shallow even after decades of implantation and they may not be a cause of mechanical failure. An amount of metal ions equivalent to the corroded volume must have been released into the human body, but the effect of these metal ions on the body is not apparent.

Fallopian Tube Occlusion, An Alternative to Tubal Ligation

Diagnosis of fallopian tube pathology has been performed with X-rays, ultrasound, magnetic resonance imaging, and even nuclear medicine exams. However, fallopian tube interventions are almost exclusively the domain of fluoroscopy. Fallopian tube interventions can be divided into two categories: embolization and recanalization. The former has only recently been described using imaging guidance while the latter has been accepted as a safe and effective procedure since the early 1990s. This article will highlight the technique and results associated with fallopian tube embolization.

Corrosion rates of stainless steel under shear stress measured by a novel parallel-plate flow chamber

A unique parallel-plate flow chamber has been engineered to assess the corrosion properties of implant materials in biological environments under shear flow. This parallel-plate flow chamber provides a novel approach to investigate hypotheses regarding cellular-material-mechanical-force interactions that influence the success or failure of implant devices. The results of the current study demonstrated that physiological stresses (0.5-50 dynes/cm2) from laminar flow from cell culture media did not significantly alter corrosion rates of stainless steel, providing baseline information for an extensive study of the cellular-material-mechanical-force interactions. Furthermore, this study demonstrated that this device is electrochemically stable and provides reproducible results within test parameters. In addition, the results were not significantly different from corrosion tests on bulk samples. Therefore, this system will be useful for investigating cell-material interactions under shear stress for implant alloys or other opaque materials. This information is currently lacking. The results of the present study also support further development of this test system to assess cellular responses to these materials under shear stresses.

Hypersensitivity cases associated with drug-eluting coronary stents: a review of available cases from the Research on Adverse Drug Events and Reports (RADAR) project

OBJECTIVES

We undertook the review of all available cases of hypersensitivity reactions after placement of a drug-eluting stent (DES) and classified potential causes.

BACKGROUND

Six months after the approval of the first DES, the Food and Drug Administration (FDA) reported 50 hypersensitivity reactions after stent placement but later concluded these were due to concomitantly prescribed medications such as clopidogrel. Nevertheless, the FDA continued to receive reports of hypersensitivity.

METHODS

Reports available from April 2003 through December 2004 for hypersensitivity-like reactions associated with the sirolimus-eluting stent (CYPHER, Cordis Corp., Miami Lakes, Florida) and paclitaxel-eluting stent (TAXUS, Boston Scientific Corp., Natick, Massachusetts) were reviewed. Sources of reports included the FDA's adverse-device-event database, the published literature, and investigators from the Research on Adverse Drug/Device events And Reports (RADAR) project. Causality was assessed using standardized World Health Organization criteria.

RESULTS

Of 5,783 reports identified for the DES in the FDA database, 262 unique events included hypersensitivity symptoms. Of these reports, 2 were certainly and 39 unlikely caused by clopidogrel and 1 was certainly, 9 probably, and 13 unlikely caused by the DES. From all sources, we identified 17 distinct cases that were probably or certainly caused by the stent, of which 9 had symptoms that lasted longer than four weeks. Four autopsies confirmed intrastent eosinophilic inflammation, thrombosis, and lack of intimal healing.

CONCLUSIONS

The FDA reports and autopsy findings suggest that DES may be a cause of systemic and intrastent hypersensitivity reactions that, in some cases, have been associated with late thrombosis and death.