Ideal Stent Research Articles

Optimizing biliary stent patency by coating with hydrophobin alone or hydrophobin and antibiotics or heparin: an in vitro proof of principle study

Although a wide range of biliary plastic and metal stents is on offer nowadays, the ideal cost-effective stent that functions permanently and that is easy to handle regarding its exchange is still not available. Therefore we tested in an in vitro model if the coating of plastic stents with hydrophobin alone or with hydrophobin and antibiotics or heparin in combination leads to an inhibition of the clogging process. We coated commercially available biliary plastic stents with hydrophobin alone, as well as with hydrophobin and antibiotics or heparin in combination. After an incubation period of 28 days in human bile, we examined the stents by scanning electron microscopy to see whether the clogging material on its surface was reduced. Coating of plastic stents with hydrophobin led to a reduction in the amount of adherent material on the surface of the stents. Coupling of ampicillin/sulbactam or levofloxacin did not lead to a further reduction of the clogging material, whereas coupling with highly concentrated heparin did reduce the adherent material. The coating of biliary plastic stents with hydrophobin or with hydrophobin and heparin in combination seems to be a promising option to delay the clogging process.

From implant planning to surgical execution: an integrated approach for surgery in oral implantology

Using oral implantology software and transferring the preoperative planning into a stereolithographic model, prosthodontists can produce the related surgical guide. This procedure has some disadvantages: bone-supported stent invasiveness, lack of references due to scattering and non-negligible stereolithography cost. An alternative solution is presented that provides an ideal surgical stent (not invasive, precise, and cheap) as a result. This work focuses on the third phase of a fully 3D approach to oral implant planning, that starts by CT scanning a patient who wears a markers-equipped radiological stent, continues exploiting built-on-purpose preoperative planning software, and finishes producing the ideal surgical template. A 5-axes bur-equipped robot has been designed able to reproduce the milling vectors planned by the software. Software-robot interfacing has been achieved properly matching the stent reference frame and the software and robot coordinate systems. Invasiveness has been avoided achieving the surgical stent from the mucosa-supported radiological mask wax-up. Scattering is ignored because of the surgical stent independency from the bone structure radiography. Production cost has been strongly reduced by avoiding the stereolithographic model. Finally, software-robot interfacing precision has been validated comparing digitally a multi-marker base and its planning transfer. Average position and orientation errors (respectively 0.283 mm ± 0.073 mm and 1.798° ± 0.496°) were significantly better than those achieved using methods based on stereolithography (respectively, 1.45 mm ± 1.42 mm and 7.25° ± 2.67°, with a general best maximum translation discrepancy of about 1.1 mm). This paper describes the last step of a fully 3D approach in which implant planning can be done in a 3D environment, and the correct position, orientation and depth of the planned implants are easily computed and transferred to the surgical phase.

Prophylactic Pancreatic Stents: Does Size Matter? A Comparison of 4-Fr and 5-Fr Stents in Reference to Post-ERCP Pancreatitis and Migration Rate

The ideal pancreatic stent to prevent post-ERCP pancreatitis (PEP) has yet to be determined. The aim of our study was to assess the relative benefit of 4-Fr versus 5-Fr stents in a population at high risk for post-ERCP pancreatitis, and the relative frequency of spontaneous migration. All patients with prophylactic pancreatic stent (PPS) from 2002 to 2009 were reviewed. Patients were classified into two groups according to stent size and compared based on outcome; spontaneous migration or endoscopic removal. A total of 346 PPS were placed in 308 patients (224 women, 84 men). The average age was 48.9years. The most common indication for PPS was sphincter of Oddi dysfunction. Needle knife papillotomy was the most common procedure performed. Forty-seven patients had PEP, 4Fr (14.6%) and 5Fr (12.9%), with only one case of severe pancreatitis. Factors associated with higher rates PEP were younger age and pancreatic sphincterotomy. Complete follow-up was not available in 37 patients. Spontaneous migration was demonstrated in 115 of the 4Fr (95.8%) and 134 of the 5Fr (68.7%). The remaining 66 (five from the 4Fr and 61 from the 5Fr), were removed by endoscopy. The mean delay to demonstrate spontaneous migration was 34.2days. PPS in high-risk patients reduced the risk of post-ERCP pancreatitis and nearly eliminated severe pancreatitis. No significant difference between the 4Fr and 5Fr in reduction of post-ERCP pancreatitis was observed. However, spontaneous migration was more frequent with the 4-Fr stent.

Geometry parameterization and multidisciplinary constrained optimization of coronary stents

Coronary stents are tubular type scaffolds that are deployed, using an inflatable balloon on a catheter, most commonly to recover the lumen size of narrowed (diseased) arterial segments. A common differentiating factor between the numerous stents used in clinical practice today is their geometric design. An ideal stent should have high radial strength to provide good arterial support post-expansion, have high flexibility for easy manoeuvrability during deployment, cause minimal injury to the artery when being expanded and, for drug eluting stents, should provide adequate drug in the arterial tissue. Often, with any stent design, these objectives are in competition such that improvement in one objective is a result of trade-off in others. This study proposes a technique to parameterize stent geometry, by varying the shape of circumferential rings and the links, and assess performance by modelling the processes of balloon expansion and drug diffusion. Finite element analysis is used to expand each stent (through balloon inflation) into contact with a representative diseased coronary artery model, followed by a drug release simulation. Also, a separate model is constructed to measure stent flexibility. Since the computational simulation time for each design is very high (approximately 24h), a Gaussian process modelling approach is used to analyse the design space corresponding to the proposed parameterization. Four objectives to assess recoil, stress distribution, drug distribution and flexibility are set up to perform optimization studies. In particular, single objective constrained optimization problems are set up to improve the design relative to the baseline geometry-i.e. to improve one objective without compromising the others. Improvements of 8, 6 and 15% are obtained individually for stress, drug and flexibility metrics, respectively. The relative influence of the design features on each objective is quantified in terms of main effects, thereby suggesting the design features which could be altered to improve stent performance. In particular, it is shown that large values of strut width combined with smaller axial lengths of circumferential rings are optimal in terms of minimizing average stresses and maximizing drug delivery. Furthermore, it is shown that a larger amplitude of the links with minimum curved regions is desirable for improved flexibility, average stresses and drug delivery.

İnoperabl Malign Özofagus Darlıklarının Kendiliğinden Genişleyebilen Metalik Stentlerle Palyatif Tedavisi: Tek Merkezli 155 Hastalık Deneyim

Objective: A retrospective study was designed to investigate the success and the complication rates of different types of self-expandable metallic stents in patients with inoperable malignant esophageal strictures. Material and Methods: One hundred fifty five patients with malignant esophageal strictures received self-expandable metallic stents under fluoroscopic guidance in our clinic between the years 1994 and 2008. A total of 137 men and 18 women aged between 26- 83 years (mean age, 58.9 years) were included in the study. Stent types used include Strecker, Wallstent, covered Wallstent, Flamingo Wallstent, Choo Stent and Song Stent. Complications of different stent types and dysphagia scores of the patients were evaluated both prior to the stent placement and afterwards. Results: Stent delivery tecnique was successful in all patients. The average dysphagia score decreased from 3.1 (dysphagia to liquids) to 1.2 (dysphagia to normal solid food) providing a 1.9 improvement in the dysphagia score. In eight cases (5.2%) early complications such as malposition and early migration were detected. In 30 cases (19.4%) late complications such as ingrowth, overgrowth, coexistence of ingrowth and overgrowth, late migration, esophago-bronchial fistula and bleeding were detected. Conclusion: Placement of self-expandable metallic stents in the palliative treatment of malignant esophageal strictures is an easily applied, well-tolerated and effective method which improves the dysphagia score of the patients with low complication rates. Our results are in agreement with the literature. The selection of the ideal stent for each patient is of great importance.

Coronary aorto-ostial stenosis analysed by multislice computed tomography: a new tool for percutaneous coronary intervention?

Conventional quantitative coronary angiography approaches are limited to quantify complex aorto-ostial stenosis. Multislice CT was able to detect and classify coronary plaques, compared with intravascular ultrasound (IVUS). The aim of the present study was to determine the accuracy of multislice computed tomography (CT) in addition to conventional angiography to identify aorto-ostial coronary stenosis characteristics before revascularisation. Patients with coronary ostial stenosis were selected for the study. All patients had selective coronary angiography and retrospectively ECG-gated multislice CT (Siemens AG, Munich, Germany). IVUS was performed in patients with ambiguous ostial stenosis revealed by angiography. Forty significant aorto-ostial lesions (38 patients) were analysed by two independent observers in comparison with an expert consensus blinded or not to the coronary CT data sets. Using CT in addition to angiography permitted observers to obtain a strong agreement for assessment of calcified lesions (kappa value 0.75), a good agreement for aortic plaques location and ideal stent position in aorto-ostial coronary stenosis. This study shows that CT associated with an angiogram allows a better identification of aorto-ostial plaques morphology and ideal stent position in aorto-ostial coronary stenosis before angioplasty.

Biodegradable and Bioabsorbable Stents

Angioplasty of the coronary arteries has made significant headway in the past 20 years as a treatment for atherosclerotic vascular disease. Though drug-eluting stents are effective, they appear to invoke a thrombogenic response. Biodegradable stents are a promising alternative to permanent stents and may eventually be used to solve the lingering problem of in-stent restenosis. Additionally, fully degradable stents have the ability to deliver more drugs to the target site than a thin coating of drug on metallic stents. A variety of degradable materials have been studied for stent design, including polyesters, polycarbonates, bacterial-derived polymers, and corrodible metals. The ideal biodegradable stent would be reliably deployable under fluoroscopic guidance and situate into the target lesion with minimal endovascular trauma. The stent should degrade into nontoxic byproducts and invoke a minimal degree of inflammation at the target site. Finally, the stent itself should disappear within months (to years) without significant displacement from the deployment site. Although initial data from clinical trials have been sufficient to bring biodegradable materials into the realm of feasibility, future research is undoubtedly necessary to resolve the critical issues of inflammation and mechanical stability.

Malignant Gastric Outlet Obstructions: Treatment with Self-Expandable Metallic Stents

Unresectable malignant gastric outlet obstruction (GOO) severely affects the quality of life, with complications that include nausea, vomiting, aspiration, pain, and malnutrition. Although palliative surgical procedures have been traditionally performed, they are associated with high morbidity and mortality rates. Placing self-expandable metallic stents is associated with higher clinical success rates, lower morbidity, shorter time from the procedure to starting oral intake, lower incidence of delayed gastric emptying, and a shorter hospital stay than palliative surgery. Fluoroscopic or endoscopic placement of either bare or covered self-expandable metallic stents is a safe, nonsurgical, palliative treatment option for unresectable malignant GOOs, with a high clinical success rate and a low rate of serious complications. Stent obstruction and migration are the most common complications, but most can be managed by interventional treatments. Although there have been substantial developments in stent design over the past decade, large prospective, randomized studies are required to determine the ideal stent for malignant GOOs.

Closing Holes That Leak: Another Dutch Success Story

The management of nonmalignant esophageal perforations is one of the most challenging situations in esophageal diseases. Traditionally, surgical repair has been the mainstay of therapy. Although endoscopic stenting has traditionally been used for management of malignant stenosis and fistulas, there has been limited information on its role in benign perforations. The study presented in this issue of the American Journal of Gastroenterology provides valuable information on the long-term success rate of esophageal stenting in this situation. In the series of 33 patients, van Heel et al. show that the majority of these perforations can be closed with endoscopic stenting. An important caveat of the study is that stents that are partially covered become increasingly difficult to remove after they have been in place for >6 weeks. Fully covered expandable metal and expandable plastic stents may be easier to remove, although they have a higher risk of migration. An ideal stent, which has low risk of migration and is simple and easy to place and remove, does not yet exist.

Update in airway stents

Malignant central airway obstruction heavily impacts patients' quality of life and its management continues to be a challenge. The current article will review the use of airway stents in this population. Airway stenting is highly effective in palliating symptoms of airway obstruction. There are several types of stents available with different advantages and disadvantages depending mainly on the material they are made from. Clinical outcomes seem to be comparable between silicone and self-expanding metal stents. Self-expanding metal stents have proven to be efficient in recanalizing 'complex' central airway obstructions. Preliminary data show that a new self-expanding 'hybrid' stent appears to be effective and safe for malignant airway obstruction. Airway stent complications vary according to the type of stent and the type of obstruction. Multidetector computed tomography seems to be a valuable adjunct to bronchoscopy in detecting and characterizing stent complications. A clear definition of airway stent-related infection is urgently needed to provide adequate diagnosis and management of this complication. Metal stent fracture is less common in patients with malignant airway obstruction as compared with benign disease, and this could be partially explained by the decreased survival and shorter exposure to stent in the former population. Airway stents are of great help in palliating symptoms of malignant central airway obstruction. Unfortunately, there have been no recent striking advances in stent technology and the ideal stent has yet to be designed.

The evolution of an ideal stent design and its impact on the aortic endothelium during and after percutaneous replacement

Vascular support structures are important devices for treating valve stenosis. A large population of patients is treated for valvular disease and the preferred mode of treatment is percutaneous valve replacement. Stent devices are proving to be an improved technology in minimally invasive cardiac surgery. This new technology provides highly effective results at minimal cost and with a short duration of hospitalisation. Stents as a supporting structure for tissue valves have evolved over the years into remarkably useful and effective devices. During this process, a number of specific designs have come and gone, and a few have remained. Many design changes were successful, and many were not. This article describes the merits and demerits of various stent designs and details the specific reasons why a particular novel design is expected to be the most suitable implant during and after percutaneous aortic valve replacement.

Ureteral stents: new ideas, new designs

Ureteral stents represent a minimally invasive alternative to preserve urinary drainage whenever ureteral patency is deteriorated or is under a significant risk to be occluded due to extrinsic or intrinsic etiologies. The ideal stent that would combine perfect long-term efficacy with no stent-related morbidity is still lacking and stent usage is associated with several adverse effects that limit its value as a tool for long-term urinary drainage. Several new ideas on stent design, composition material and stent coating currently under evaluation, foreseen to eliminate the aforementioned drawbacks of ureteral stent usage. In this article we review the currently applied novel ideas and new designs of ureteral stents. Moreover, we evaluate potential future prospects of ureteral stent development adopted mostly by the pioneering cardiovascular stent industry, focusing, however, on the differences between ureteral and endothelial tissue.

Comment améliorer la tolérance des sondes urétérales autostatiques JJ ?

Placement of a ureteral stent (JJ) is a common practice in urology. Unfortunately, these double pigtails stents are responsible for significant morbidity. Yet there are only few studies, mostly observational, assessing the problem and its management. So, prevention and care are not recommended for high level of evidence. Currently, despite technological advances, there is no ideal stent in terms of shape and/or material. Silicone ureteral stent may be better tolerated but their cost remains high and are reserved for patients who require ureteral stent for long time. The position of the stent and its distal loop appear to be important to improve tolerance. The eradication of urinary infection and minimizing the period of implantation must be systematically searched. Currently, no specific treatment has demonstrated a favorable impact on tolerance. The alphabloquants seem promising preliminary studies, but their role remains to be confirmed.

Choosing the Ideal Length of a Double-Pigtail Ureteral Stent according to Body Height: Study Based on a Chinese Population

Objective: We conducted this study to determine the ideal stent length according to body height, as data are limited. Patients and Methods: A total of 408 patients undergoing ureteroscopic lithotripsy and stent insertion (22, 24 or 26 cm) were enrolled. The appropriateness of the stent length was determined according to the plain films and was further compared among patients with different body heights and stent lengths. Results: In patients <160 cm, the use of a 22-cm stent was significantly more appropriate than a 24- or 26-cm stent (86.5, 51.9 and 46.4%). In patients between 160 and 175 cm, a 22- or 24-cm stent was significantly more appropriate than a 26-cm stent (79.2, 66.7 and 46.3%), while the difference between the use of a 22- and 24-cm stent was not significant. In patients >175 cm, a 24- or 26-cm stent might be more appropriate. Conclusions: Body heights can predict the ideal stent length. Based on a Chinese population, a 22-cm stent length is more appropriate for those <175 cm. A longer, 24- or 26-cm stent may be suitable for those >175 cm.

Performance of Fully Covered Self-Expanding Metallic Stents in Benign Airway Strictures

Background: Airway stenting has become a common technique in inoperable benign strictures. An ideal stent does not yet exist for these conditions. Recently, fully covered self-expandable metallic stents (SEMS) have been commercialized with potential use in benign airway strictures. Objective: We retrospectively reviewed the clinical effectiveness of fully covered SEMS in the management of benign strictures. Methods: A total of 17 patients received 20 stents: 7 Silmet®, 8 Taewoong® and 5 Alveolus® stents. Ten stents were deployed in a structural postintubation tracheal stenosis. Other indications were multinodular goiter, anastomotic stricture, endobronchial posttuberculosis scar, damaged cartilage and relapsing polychondritis. Results: In our series, the short-term (<12 weeks after stent deployment) complication rate was 75%, requiring stent removal in 60%. Overall, stent migration was observed in 65%, stent fracture in 15%, shriveling of the stent in 10% and granulation formation in 10%. Conclusion: The use of fully covered SEMS for the treatment of benign airway strictures is associated with a high short-term complication rate requiring stent removal. We have abandoned in our clinical practice the use of fully covered SEMS for benign airway strictures.

The role of stents in the treatment of congenital heart disease: Current status and future perspectives

Intravascular or intracardiac stenoses occur in many forms of congenital heart disease (CHD). Therefore, the implantation of stents has become an accepted interventional procedure for stenotic lesions in pediatric cardiology. Furthermore, stents are know to be used to exclude vessel aneurysm or to ensure patency of existing or newly created intracardiac communications. With the further refinement of the first generation of devices, a variety of “modern” stents with different design characteristics have evolved. Despite the tremendous technical improvement over the last 20 years, the “ideal stent” has not yet been developed. Therefore, the pediatric interventionalist has to decide which stent is suitable for each lesion. On this basis, currently available stents are discussed in regard to their advantages and disadvantages for common application in CHD. New concepts and designs developed to overcome some of the existing problems, like the failure of adaptation to somatic growth, are presented. Thus, in the future, biodegradable or growth stents might replace the currently used generation of stents. This might truly lead to widening indications for the use of stents in the treatment of CHD.

What Would Be the Ideal Drug-eluting Stent for Managing Patients with Long Lesions?

Drug-eluting stents (DES) substantially reduce the risk of restenosis, particularly in complex coronary disease. Their use is now standard in demanding anatomy, including in long lesions, which represent an increasing proportion of percutaneous coronary intervention (PCI) cases. However, long lesions pose a number of procedural and clinical challenges for DES, specifically stent deliverability, stent overlap and an increased risk of restenosis, peri-procedural myocardial infarction, geographical miss and stent thrombosis. The ideal DES for long lesions would incorporate a number of specific design characteristics to meet these challenges, including low late loss to minimise restenosis risk, thin struts to enhance deliverability and minimise risk of peri-procedural infarction and the availability of long lengths to minimise overlap and avoid geographical miss. It is clear from a knowledge of their properties, and from available data on DES performance in long lesions, that some currently available DES have superior design characteristics and clinical outcomes in the setting of diffuse disease. An awareness of these issues is essential for the practising interventional cardiologist in treating long lesions in routine clinical practice.

Feasibility and safety of placement of a newly designed, fully covered self-expandable metal stent for refractory benign pancreatic ductal strictures: a pilot study (with video)

Painful chronic pancreatitis with main pancreatic ductal strictures is usually managed with endotherapy with a plastic stent. To date, the role of placement of metallic stents, especially uncovered ones in benign pancreatic ductal stricture, has been unsatisfactory as a result of stent dysfunction related to mucosal hyperplasia. We explored the feasibility and safety of temporary placement of a newly designed, fully covered self-expandable metal stent (FCSEMS) in painful chronic pancreatitis and refractory benign pancreatic ductal strictures. A prospective pilot and feasibility study. A tertiary academic center. Thirteen patients with chronic painful pancreatitis of alcoholic (8) or idiopathic (5) etiology. ERCP with temporary FCSEMS placement (2 months). Endoscopic removal of FCSEMSs was performed with a snare or rat-tooth forceps. End points were feasibility, safety, and morbidity. Successful FCSEMS placement was performed in all enrolled patients. After immediate placement of FCSEMS, 2 patients had mild acute pancreatitis related mainly to the stricture dilation procedure (Soehendra stent retriever or balloon dilation). Complications associated with stent placement included 5 migrations (39%, 1 proximal and 4 distal) and 2 incidents of cholestatic liver dysfunction associated with the compression of the bile duct orifice by expansion of FCSEMSs. In 1 patient with proximal migration, the stent was repositioned by an inflated retrieval balloon. Additional endoscopic biliary sphincterotomy with or without biliary stenting was performed in 2 patients with cholestatic liver dysfunction. There was no occurrence of pancreatic sepsis among any patients. FCSEMSs were removed from 9 of 9 patients without stent migration (100% [9/9] as per protocol, and 69% [9/13] as intention to treat, respectively). Improvement or resolution of the pancreatic ductal strictures was confirmed in all 13 patients on follow-up ERCP (2 months after stent placement), regardless of stent migration. Small patient populations without long-term follow-up. Two-month placement of FCSEMSs in patients with refractory benign pancreatic ductal strictures may be feasible and relatively safe. However, stent migration was not uncommon. A further investigation with ideal stent design may therefore be needed before recommending FCSEMSs as a therapeutic option for refractory benign pancreatic ductal strictures.

What is an optimal stent? Biological requirements of drug-eluting stents

Although drug eluting stents (DES) have been successful in preventing neointima formation thereby decreasing the rates of restenosis, several concerns remain about the incidence of stent thrombosis – a rare complication associated to highmortality. For this reason, much effort is being made in searching for new molecules and approaches to develop innovative DES able to inhibit restenosis as well as decreasing the incidence of late stent thrombosis. Second generation DES have recently entered daily clinical practice but definitive data concerning their efficacy are not available yet. Still, the close relationship between agents used on first generation DES and those employed in second generation DES gives us reason to speculate that more efforts are needed in order to make concrete advances. This review article focuses on the existing problems of currently availableDES as well as the innovations needed in order to improve further the outcome of stent implantation. Present time efforts should be directed towards identifying multi-coatings to be applied on inert polymers so as to have targeted approaches for each of the therapeutical requirements of a stented coronary artery. An ideal stent should locally inhibit vascular smooth muscle cells proliferation, enhance endothelial healing through improved endothelial progenitor cells function and ultimately prevent platelets activation. Current technology seems to offer individual alternatives for all these requirements; so the “perfect stent” should be soon available.

External Stenting with a New Polyester Mesh Reduces Neointimal Hyperplasia of Vein Grafts in a Sheep Model

External stents placed around vein grafts have demonstrated effectiveness in reducing neointimal hyperplasia by preventing distension of the thin-walled vein grafts when exposed to arterial pressure. However, the ideal stent material has yet to be defined. The following study investigates the short- and long-term effects of an innovative polyester mesh stent designed with optimized adaptation of circumferential compliance. Following in vitro definition of the ideal macro-porous polyester stent material, a total of 12 sheep underwent implantation of bilateral carotid artery vein graft bypasses. In six sheep, the short term outcome (four weeks of implantation) was investigated by comparing the newly-designed stent to native veins, micro-porous PTFE stent grafts and metallic Biocompound stents (BCGs). Flow volume and graft diameter were measured prior to explantation. Grafts were evaluated histologically with respect to morphometry and immunoassaying. In the long-term group (6-month implantation time), the polyester stent was compared to native veins. All stents effectively prevented dilatation of the graft. Perfused vessel diameters of the polyester veins were 8.3+/-0.6 mm. BCG as well as PTFE veins showed diameter reduction to 7.4+/-0.7 mm (p<0.05) and 7.8+/-0.4 mm (p<0.05), respectively. Both in the short and long terms, the new polyester stent led to significantly higher reduction of neointimal hyperplasia and luminal encroachment compared to the native vessel. It proved superior to PTFE stenting, while the Biocompound material failed to prove efficacy. It was demonstrated that the new macro-porous polyester mesh stent reduced neointimal hyperplasia more effectively than other commercially available stents.