Polyester Stent Research Articles

Hybrid interpenetrating network of polyester coronary stent with tunable biodegradation and mechanical properties

Poly(l-lactide) (PLLA) is an important candidate raw material of the next-generation biodegradable stent for percutaneous coronary intervention, yet how to make a polyester stent with sufficient mechanical strength and relatively fast biodegradation gets to be a dilemma. Herein, we put forward a hybrid interpenetrating network (H-IPN) strategy to resolve this dilemma. As such, we synthesize a multi-functional biodegradable macromer of star-like poly(d,l-lactide-co-ɛ-caprolactone) with six acrylate end groups, and photoinitiate it, after mixing with linear PLLA homopolymer, to trigger the free radical polymerization. The resultant crosslinked polymer blend is different from the classic semi-interpenetrating network, and partial chemical crosslinking occurs between the linear polymer and the macromer network. Combined with the tube blow molding and the postprocessing laser cutting, we fabricate a semi-crosslinked-polyester biodegradable coronary stent composed of H-IPN, which includes a physical network of polyester spherulites and a chemical crosslinking network of copolyester macromers and a part of homopolymers. Compared with the currently main-stream PLLA stent in research, this H-IPN stent realizes a higher and more appropriate biodegradation rate while maintaining sufficient radial strength. A series of polymer chemistry, polymer physics, polymer processing, and in vitro and in vivo biological assessments of medical devices have been made to examine the H-IPN material. The interventional implanting of the H-IPN stent into aorta abdominalis of rabbits and the follow-ups to 12 months have confirmed the safety and effectiveness.

Post-Implantation Syndrome Incidence is Higher After Complex Endovascular Aortic Procedures Than After Standard Infrarenal Repair

Post-implantation syndrome (PIS), characterised by malaise, fever, and increased inflammatory markers, is a common occurrence after endovascular aneurysm repair (EVAR), causing prolonged hospitalisation and increased cost. This study aimed to determine the incidence and short-term outcomes of PIS after fenestrated or branched procedures in aorto-iliac aneurysms compared with standard EVAR. A retrospective, comparative study from a tertiary academic institution was undertaken. All patients who underwent elective EVAR with polyester stent grafts from January 2015 to June 2021 were considered. Two groups were defined: standard EVAR (sEVAR) and complex EVAR (cEVAR). The latter included visceral fenestrated and branched or iliac branch and chimney stent grafts. The primary outcome was the incidence of PIS within three days of the index procedure. Secondary outcomes were short-term complications and risk factors for PIS. A multivariable model was constructed to correct for confounders. Overall, 253 patients were included: 165 (65.2%) sEVAR and 88 (34.8%) cEVAR. Complex EVAR patients were younger, with larger aneurysms, had longer procedures, and were more likely to have intra-operative complications. The PIS incidence was 23.7% (n= 60), significantly higher in cEVAR (34.1% vs. 18.2%; p= .005) and increased with the complexity of the procedure (EVAR: 18.2% vs. EVAR+iliac branch device: 25.0% vs. fenestrated and branched EVAR: 36.2%; p= .030). On multivariable analysis, cEVAR (OR 2.833, 95% CI 1.295 - 6.198; p= .009) was associated with a significantly increased risk of PIS. No differences in short term outcomes according to PIS status were noted. Group sub-analysis for cEVAR patients did not reveal any statistically significantly different outcomes according to PIS occurrence. In this cohort, cEVAR procedures were associated with a significantly increased risk of developing PIS compared with standard infrarenal repair. Post-implantation syndrome also appears to have a benign course with no major impact on peri-operative outcomes after cEVAR. Further research to confirm these findings is required.

O068 EVAR Gore salvage fabric technique (ARAFAT) to salvage evar fabric fatigue and graft failure

Abstract Introduction EVAR GORE SalvAge Fabric Technique (ARAFAT) is an innovative management protocol to seal material graft failure due to type IIIb endoleak (EL) in patients who are mainly at high risk for open conversion. We aim to discuss ARAFAT, an innovative management protocol to seal material graft failure due to type IIIb endoleak (EL). Methods We employed ARAFAT in patients following type IIIb EL to salvage previous EVAR with a polyester-based stent graft. The ARAFAT principle relies on the use of polytetrafluoroethylene (PTFE) and the realignment of the polyester stent graft for sealing the microleaks and aortic sac hygroma, resulted due to polyester filtration. First, an oversized EXCLUDER® aortic cuff (GORE®, Flagstaff, Arizona, USA) is deployed into the previously implanted polyester-based stent graft. This is followed by simultaneous deployment of an EXCLUDER® iliac extension, as necessary, in double barrel configuration from the main cuff. A minimum of 2 cm of a distal seal zone is provided to promote stability. Results ARAFAT was employed in 18 patients (mean age 80 ± 6.86 years; 77% male). The average size of the aortic sac that underwent re-intervention was 6.68 ± 2.13 cm. All the patients had primary technical success. There was no peri-operative mortality. The average follow-up was 35.6 ± 6.24 months. Conclusion We successfully employed the ARAFAT technique as a fully functioning protocol to overcome apparent challenges in managing material fatigue graft failure EL in high-risk patients. Take-home message EVAR GORE Salvage Fabric Technique (ARAFAT) technique could be successfully employed as a fully functioning protocol to overcome apparent challenges in managing material fatigue graft failure EL in high-risk patients.

Polyester Stent Graft Devices and Higher Risk of Post-Implantation Syndrome after EVAR: Single-Center Analysis of 367 Patients

The post-implantation syndrome may occur shortly after endovascular aneurysm repair in patients treated for abdominal aortic aneurysm. Different types of biomaterials may provoke varying inflammatory responses in patients receiving different endografts. The purpose of this article is to evaluate the PIS after EVAR and the influence of different types of device fabric. All patients submitted to elective AAA endovascular repair at our institution from January 2014 to December 2019 were enrolled. The PIS was defined by a body temperature of >38°C and WBC >12'000/μl without any evidence of an infection during (48h) the observation period. Three hundred and sixty-seven patients (89% males) were enrolled in this study and post-implantation syndrome occurred in 41 cases (11.2%). The incidence of PIS was significantly higher (P< 0.001) in patients treated with polyester stent grafts (39/201, 19,4%) compared to patients with PTFE stent grafts (2/166, 1,2%). CRP was related to the presence of PIS with a cut-off values of 109.31 mg/dL (P = 0.0052). The median in-hospital stay considering the polyester group was 6,2 days, while in the PTFE group it was 5,6 days (P = 0.04). The postoperative inflammatory response after EVAR seems significantly higher by using polyester stent graft compared to PTFE devices. CRP could be a useful biomarker in defining PIS. Multi-center studies are necessary to confirm these data.

Aging Effect on Functionalized Silver-Based Nanocoating Braided Coronary Stents

A previously developed fiber-based polyester (PES) stent, with mechanical properties comparable to commercial nitinol stents, was coated with metallic silver (Ag0) and silver oxides (AgxO) thin films through direct current (DC) magnetron sputtering. Ag0 and AgxO coatings provide antimicrobial properties to the stents to minimize the occurrence of coronary stent infections. Nevertheless, the stent interacts with the atmosphere and then with the biological fluids and may lead to the generation of silver species with diminished antimicrobial efficiency and/or prone to induce cytotoxicity. Therefore, stent coating nanostructures aged 3 months were thoroughly analyzed by X-ray photoelectron spectroscopy (XPS) and their antimicrobial and cytotoxicity properties were assessed. Aging led to the presence of silver carbonate and bicarbonate as well as chemisorbed oxygen species in Ag0 and AgxO coatings. Bactericidal efficacy was tested against an important nosocomial bacterium, particularly associated to indwelling devices: Staphylococcus epidermidis. Aged Ag0 and AgxO coating presented a Log reduction of 1 and 2 at their surface; respectively. However, aged stents were able to induce a Log reduction of 2 (Ag0) and 4 (AgxO) on the surrounding medium. Only aged AgxO stent was able to provide a mild reduction of the bacterium at its surface and a clear antimicrobial effect (Log reduction &gt;3) within its vicinity. More importantly, both aged Ag0 and AgxO stents were shown to be compatible with fibroblasts cells indicating that they can be safely used as indwelling devices, despite the aging effect.

Type IIIb Endoleak Is Not Extremely Rare and May Be Underdiagnosed after Endovascular Aneurysm Repair.

To investigate the real incidence of type IIIb endoleaks associated with the Zenith stent graft, currently the most widely used third-generation polyester stent graft, in a Japanese multicenter database. Retrospective analysis was conducted of 433 patients who underwent endovascular aneurysm repair (EVAR) of aortoiliac aneurysms with the use of Zenith stent grafts from 2007 to 2016. The mean age of patients was 75.6 y ± 7.8, and 85.2% of patients were men. Mean transverse diameters of abdominal aortic aneurysms and common iliac artery aneurysms were 50.8 mm ± 9.9 and 42.2 mm ± 10.3, respectively. During a mean follow-up period of 41.9 mo, 7 type IIIb endoleaks (1.6%) were identified. Four patients were definitively diagnosed during repeat intervention, and 3 were diagnosed based on postoperative CT images. Three patients were treated surgically, 2 were treated by relining with an additional stent graft, and 2 were conservatively followed with CT imaging. Only 1 of 5 patients who underwent repeat intervention had a preoperative diagnosis of type IIIb endoleak, reflecting the difficulty in its diagnosis. The incidence of type IIIb endoleak in Zenith stent grafts was 1.6% in this study, suggesting that type IIIb endoleaks are not extremely rare. In addition, type IIIb endoleak may be underdiagnosed or misdiagnosed as a different type of endoleak. Type IIIb endoleaks should always be considered in patients with sac expansion after EVAR.

Post-implantation syndrome – retrospective analysis of 52 patients

IntroductionA systemic inflamatory response is common after EVAR. Its clinical impact is unknown, and although is it usually well tolerated, there is concern it might be associated with increased morbidity and mortality in high risk patients. This study aims to evaluate the occurrence of the post-implantation syndrome (PIS) in patients undergoing EVAR, its characteristics and clinical significance. MethodsThis study is a retrospective observational analysis of patients undergoing elective EVAR between November 2012 and November 2014. PIS was defined by fever (>38°C) and leukocytosis (>12,000μL−1), excluding infectious complications. We evaluated the epidemiological characteristics of the patient, aneurysm and procedure characteristics and their relationship with development of PIS. ResultsFifty-two patients were included, and 21.2% were diagnosed with PIS. The ePTFE grafts were not associated with the occurrence of the syndrome, in contrast with polyester stent grafts (0% vs. 28.2%, p=0.031). The age and gender of patients, the diameter of the aneurysm, duration and radiation dose and the configuration of the stent graft (aorto-bi-iliac, aorto-uni-iliac or fenestrated) were not associated with PIS. There was no statistically significant difference in the occurrence of major cardiovascular events during hospitalization in both groups. ConclusionThe inflammatory syndrome after EVAR occurs in a significant percentage of patients (21%). Stent grafts constructed by polyester are a significant risk factor. Despite the exuberant inflammatory response, it was not associated with increased occurrence of cardiovascular events, and it is usually benign, well tolerated and self-limiting.

Effects of Pulsatile Fatigue on In Situ Antegrade Fenestrated Polyester Stent Grafts Deployed in a Patient-Specific Phantom Model of Juxtarenal Aortic Aneurysm

PurposeTo evaluate the effects of in situ fenestration on the fabric of stent grafts deployed in a patient-specific phantom of a juxtarenal abdominal aortic aneurysm. Materials and MethodsFour patient-specific juxtarenal abdominal aortic aneurysm polyurethane models were created, and bifurcated Zenith (Cook, Inc, Bloomington, Indiana) and Endurant (Medtronic, Minneapolis, Minneapolis) endografts were deployed into the models, covering the renal arteries. Antegrade in situ fenestration was carried out with radiofrequency puncture followed by balloon dilation with either conventional or cutting balloons. Renal covered stents were deployed and flared. Specimens were mounted onto an accelerated fatigue tester for 40M cycles (1 patient life-year), and evaluated with microscopy, caliper measurements, and fabric counts. ResultsCutting balloons resulted in more fabric fraying. None of the fenestrations grew beyond the targeted 6-mm diameter despite accelerated fatigue. Fluoroscopic images demonstrated a very prominent waist of the renal fenestration in the Cook device when a conventional balloon was used compared with a cutting balloon. The average fenestration diameter for the Cook device was only 3.1 mm with the conventional balloon compared with 4.8 mm with the cutting balloon. The average fenestration diameter for the Medtronic device was 3.8 mm with the conventional balloon compared with 5.1 mm with the cutting balloon. The fabric counts suggested crowding of yarns around the fenestrations with conventional balloons but less with cutting balloons. ConclusionsThis experimental work suggests that the size of in situ renal fenestrations does not expand beyond the target diameter despite cyclic fatigue. Although the small number of devices tested and selected aortorenal anatomy in this study may limit conclusions, textile analysis suggests that cutting balloons should be used for the Cook Zenith device, whereas conventional balloons should be used for the Medtronic Endurant device when performing in situ fenestration.

Influence of design parameters on the mechanical behavior and porosity of braided fibrous stents

Abstract In spite of all innovations in stent design, commonly used metallic stents present several problems such as corrosion, infection and restenosis, leading to health complications or even death of patients. In this context, the present paper reports a systematic investigation on designing and development of 100% fiber based stents, which can eliminate or minimize the problems with existing metallic stents. For this purpose, braided stents were produced by varying different materials, structural and process parameters such as mono-filament type and diameter, braiding angle and mandrel diameter. The influence of these design parameters on mechanical behavior as well as stent's porosity was thoroughly investigated, and suitable parameters were selected for developing a stent with mechanical characteristics and porosity matching with the commercial stents. According to the experimental results, the best performance was achieved with a polyester stent designed with 0.27 mm monofilament diameter, braiding angle of 35° and mandrel diameter of 6 mm, providing similar properties to commercial Nitinol stents.

Stent graft composition plays a material role in the postimplantation syndrome

In patients undergoing endovascular aneurysm repair (EVAR), the postimplantation syndrome (PIS), comprising fever and inflammation, occurs frequently. The cause of PIS is unclear, but graft composition and acute thrombus formation may play a role. The objective of this study was to evaluate these possible causes of the inflammatory response after EVAR. One hundred forty-nine patients undergoing elective EVAR were included. Implanted stent grafts differed mainly in the type of fabric used: either woven polyester (n=82) or expanded polytetrafluorethylene (ePTFE; n=67). Tympanic temperature and C-reactive protein (CRP) were assessed daily during hospitalization. PIS was defined as the composite of a body temperature of ≥38°C coinciding with CRP>10 mg/L. Besides graft composition, the size of the grafts and the volume of new-onset thrombus were calculated using dedicated software, and results were correlated to PIS. Implantation of grafts made of polyester was associated with higher postoperative temperature (P<.001), CRP levels (P<.001), and incidence of PIS (56.1% vs 17.9%; P<.001) compared to ePFTE. After multivariate analysis, woven polyester stent grafts were independently associated with an increased risk of PIS (hazard ratio, 5.6; 95% confidence interval, 1.6-19.4; P=.007). Demographics, amount of graft material implanted, or new-onset thrombus had no association with PIS. The composition of stent grafts may play a material role in the incidence of postimplantation syndrome in patients undergoing EVAR. Implantation of stent grafts based on woven polyester was independently associated with a stronger inflammatory response.

Techniques for colorectal anastomosis

Colorectal anastomotic leak remains one of the most feared post-operative complications, particularly after anterior resection of the rectum with, the shift from abdomino-peritoneal resections to total mesorectal excision and primary anastomosis. The literature fails to demonstrate superiority of stapled over hand-sewn techniques in colorectal anastomosis, regardless of the level of anastomosis, although a high stricture rate was noted in the former technique. Thus, improvements in safety aspects of anastomosis and alternatives to hand-sewn and stapled techniques are being sought. Here, we review alternative anastomotic techniques used to fashion bowel anastomosis. Compression anastomosis using compression anastomotic clips, endoluminal compression anastomotic rings, AKA-2, biofragmental anastomotic rings, or Magnamosis all involve the concept of creating a sutureless end-to-end anastomosis by compressing two bowel ends together, leading to a simultaneous necrosis and healing process that joins the two lumens. Staple line reinforcement is a new approach that reduce the drawbacks of staplers used in colorectal practice, i.e. leakage, bleeding, misfiring, and inadequate tissue approximation. Various non-absorbable, semi or fully absorbable materials are now available. Two other techniques can provide alternative anastomotic support to the suture line: a colorectal drain and a polyester stent, which can be utilized in ultra-low rectal excision and can negate the formation of a defunctioning stoma. Doxycycline coated sutures have been used to overcome the post-operative weakness in anastomosis secondary to rapid matrix degradation mediated by matrix metalloproteinase. Another novel technique, the electric welding system, showed promising results in construction of a safe, neat, smooth sutureless bowel anastomosis. Various anastomotic techniques have been shown to be comparable to the standard techniques of suturing and stapling. However, most of these alternatives need to be accepted and optimized for future use.

Gene transduction into aortic wall using plasmid-loaded cationized gelatin hydrogel-coated polyester stent graft

Stent grafts are increasingly recognized as useful devices for endovascular repair of aortic aneurysms and other vascular diseases. Stent graft-mediated gene delivery into the vascular wall is expected to improve their therapeutic effects. This study evaluated the efficacy of genetically engineered cationized gelatin (CG) hydrogel-coated partially-covered polyester stent grafts that facilitate delivery of an expression plasmid DNA in rabbit aortic wall. Partially covered polyester stent grafts coated with CG hydrogel impregnated with 10.0 mg/mL of beta-galactosidase (LacZ)-expression plasmid vector (pCAGGS-LacZ) or empty vector (pCAGGS) solutions were implanted via the femoral artery in rabbit balloon-injured aortas. The aortic segments were removed at 1, 3, or 7 days (4 rabbits/each group) after implantation and evaluated for the transgene (LacZ) delivery and expression by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactoside) staining. Partially-covered polyester stent grafts coated with CG hydrogel impregnated with various amounts (0.1 mg/mL, 1.0 mg/mL, and 10.0 mg/mL) of pCAGGS-LacZ or pCAGGS were also implanted in rabbits' balloon-injured aortas (4 rabbits/each group) to evaluate transgene delivery and expression in the aortic wall 3 days after implantation. The difference of transgene efficiency among each group was compared using one-way analysis of variance (ANOVA) and Newman-Keuls' test according to the result of quantitative RT-PCR. In all animals, LacZ gene transduction into the aortic wall was detected at the implantation site of pCAGGS-LacZ-loaded, but not pCAGGS-loaded, stent grafts. LacZ expression was not detected in aortic segments immediately proximal or distal to the implanted pCAGGS-LacZ-loaded stent graft or remote organs including the brain, heart, liver, and kidney by either RT-PCR or X-gal staining. The X-gal staining-positive cells were observed at or near the luminal surface in the aortic segments only in contact with the stent graft and the ingrowth tissues within stent grafts. Immunohistochemical studies suggested that the LacZ-positive cells were mainly the neointimal alpha-smooth-muscle actin-positive cells and macrophages. The extent of the transgene expression was dependent on the quantity of the plasmid DNA loaded onto the stent graft (10.0 mg/mL plasmid vs 1.0 mg/mL plasmid, P < .01 and 10.0 mg/mL plasmid vs 0.1 mg/mL plasmid, P < .05). LacZ mRNA expression was maximal at day 1 and declined at day 7 (P < .05) but was still detectable. Plasmid-loaded CG hydrogel-coated stent graft is a promising vehicle for local transgene delivery to the aortic wall and offers the possibility of transduction of therapeutic genes into the vascular wall.

Management of anastomotic leaks after Roux-en- Y bypass using self-expanding polyester stents

Background To analyze the outcomes of a series of endoscopically placed polyester self-expanding polyflex stents (SEPSs) for the management of anastomotic leaks after Roux-en- Y bypass. Anastomotic leaks after gastric bypass cause significant morbidity and mortality. Covered polyester SEPSs might have a role in the treatment of these leaks. Methods A retrospective chart review was performed from January 2006 to November 2006 that included all acute and chronic leaks treated with SEPSs. Results A total of 6 patients were treated with stents, with a mean procedure time of 22 minutes. Of these 6 patients, 5 had acute postoperative leaks and 1 had a chronic fistula. Five patients started oral intake 1–6 days after their procedure. All acute leaks had complete healing at a median of 44 days. The patient with a chronic gastrocutaneous fistula required revisional surgery for fistula closure. In addition, 5 patients had stent migration, and 3 required stent replacement. Conclusion An endoscopically placed SEPS provides a less-invasive alternative to treat acute anastomotic leaks after Roux-en- Y bypass while simultaneously allowing oral intake. The results of this case series have demonstrated this treatment to be safe and effective.

Placement of a covered polyester stent prevents complications from a colorectal anastomotic leak and supports healing: Randomized controlled trial in a large animal model

Anastomotic leaks after colorectal operation continue to be a significant cause of morbidity. A covered endoluminal stent could seal a leak and eliminate the need for diversion. The aim of this study was to test the efficacy of a temporary covered stent to prevent leak related complications. Sixteen adult pigs (80-120 lbs) underwent open transection of the rectosigmoid followed by anastomosis with a circular stapler. Eight animals (study group) underwent endoscopic placement of a 21-mm covered polyester stent. Eight control group animals were left without stents. In all animals, a 2-cm leak was created along the anterior portion of the anastomosis. The animals were killed after 2 weeks and evaluated for abdominal infection, fistulae, and adhesions. The anastomosis was excised and the following parameters were assessed by a pathologist blinded to treatment: mucosal interruption (mm), inflammatory response, collagen type I and III, granulation, and fibrosis (grade 0-4). Stents were spontaneously expelled between postoperative days 6 and 9. At necropsy, none of the animals in the study group had leak related complications, whereas in the control group, 5 (63%) developed intraabdominal infection (4 abscesses, 1 fistula) at the anastomosis (P = .002). Dense adhesions to the anastomosis were found in 7 (88%) control animals. On histology, anastomotic sites in the study group had significantly less mucosal interruption and granulation. Two pigs in the study group died on postoperative day 7, one due to evisceration and one from bladder necrosis. The mortality result is not different from controls (P = .47), both events seem to be unrelated to stent placement. Temporary placement of a covered polyester stent across a colorectal anastomosis prevents leak-related complications and supports the healing of anastomotic leaks.

Stent placement for benign colonic stenosis: case report, review of the literature, and animal pilot data

Permanent metal stent placement for malignant intestinal obstruction has been proven to be efficient. Temporary stents for benign conditions of the colon and rectum are less studied. This is a case study, review of the literature, and observation from an animal model on placement of stents in the colorectum for benign disease. A 55-year-old man presented with recurrent obstructions from a benign stricture of the distal sigmoid colon. After failed balloon dilations, a polyester coated stent was placed. The purpose of the stent was to improve symptoms and avoid surgery. The stent was expelled after 5 days. We conducted a literature review of stents placed for benign colorectal strictures and an animal study to evaluate stent migration. In the literature, there were 53 reports of uncovered metal stents, four covered metal stents, and six polyester stents. Patency rates were 71%, and migration rate was 43%. Migration occurred earlier with polyester stents (mean=8 days) versus covered (32 days) or uncovered metal stents (112 days). Severe complications were seen in 23% of patients. Four 45-kg pigs underwent rectosigmoid transection with a 21-mm anastomosis and endoscopic placement of a Polyflex stent. Two stents were secured with suture. Stents without fixation were expelled within 24 h of surgery. Stents with fixation were expelled between postoperative days 2 and 14. Stents for the treatment of benign colorectal strictures are safe, with comparable patency rates between stent types. Metal stents can cause severe complications. In a pig model, covered polyester stents tend to migrate early even with fixation. Further investigation needs to focus on new stent designs and/or better fixation.

SU-GG-T-381: Attenuation Due to Bronchial Stents in Photodynamic Therapy

Purpose: Bronchial stents are devices to keep an airway open when it has been obstruct by extrinsic or intrinsic tumor compression. Such device may be in use in a patient undergoing photodynamic therapy(PDT). The magnitude of the light attenuation by commercially available stents is unknown. To study the attenuation properties of four different kinds of commercially available bronchial stents that may be used in PDT.Method and Materials: The stents were a Nitinol mesh, a polyester mesh, a solid silicone and an opaque solid silicone, all manufactured by Boston Scientific. These stents were cut longitudinally so that each could be sandwiched in a 10 × 10 PMMA holder. For each measurement, the holder with and without the stent was positioned between a PDTlaser beams (630 nm, 100 mW) and a laser power/energy monitor. The attenuation was obtained by the ratio of the light intensity that reaches the detector after traverse the PMMA with and without stent, respectively. Results: The Nitinol stent attenuated the light beam by 30.7%, the polyester stent by 51.1%, the transparent silicone stent by 7.83% and the opaque silicone stent by 80.8%. Conclusion: Bronchial stents can great attenuate the light in PDT, so that attenuation of a particular kind of stent should be evaluated, taking into account also treatment time and light intensity, before its use in a patient undergoing PDT.

Use of Temporary Esophageal Stent in Management of Perforations After Benign Esophageal Surgery

Successful conservative management in 3 patients with catastrophic postoperative esophageal leak after nonresection surgery is presented. In each case, the placement of removable stent played a significant role. First patient had persistent leak after primary repair of intrathoracic esophageal perforation. The second patient underwent a transthoracic redo Collis-Nissen repair and was subsequently found to have a perforation in the midesophagus. The last patient had a history of recurrent hiatal hernia repair with mesh reinforcement of the hiatus. A perforation resulted from mesh eroding into the esophagus. All the patients had endoscopic placement of removable silicone-covered polyester stent under fluoroscopic guidance. Stent placement was successful in all patients allowing immediate resumption of diet. After stent removal, contrast study showed no leak or stricture. Endoscopic stent therapy is an effective option in the management of postoperative esophageal perforation.

Silicone-Covered Self-Expanding Polyester Stents for the Closure of Thoracic Anastomotic Leaks After Esophagectomy

Background: Anastomotic leaks are a major source of morbidity and mortality after esophagectomy, with an incidence of 4-17%, and associated mortality of up to 45%. Conservative therapy of prolonged leaks (>2 weeks) has a success rate of 60%, requiring an average of 13 weeks for closure (Bueno JT et al, GIE 2003). Prior studies on the use of a silicone-covered self-expanding polyester stent (Polyflex, Boston Scientific, Natick, MA) for leak closure illustrated a 90-100% success rate, with a low rate of stent migration.

The Fate of Homograft Tracheal Transplants in Sheep

An established method of tracheal substitution is not yet available, but homograft tracheal transplantation might provide a realistic tracheal replacement. With the objective of sequentially examining the healing of tracheal homografts, we have established a suitable large-animal model. Five sheep received orthotopic tracheal transplantation of a 4-cm cervical tracheal homograft. The trachea was supported for 6 weeks with a self-expanding polyester stent. The plan was to euthanize the animals after 2, 4, 8, 12 and 16 weeks, or whenever complications occurred. The implantation itself was performed without complications. After 2 weeks the homograft was firmly encapsulated by connective tissue, without signs of necrosis or abscess. The original mucous membrane no longer existed; the cartilage rings were exposed. In all animals that were euthanized at the later dates, the homografts were completely absorbed and replaced by inflammatory scar tissue. This, in turn, was covered with a shiny cellular surface layer. The results from this animal experiment reveal-contrary to data published to date-that tracheal homografts are not incorporated but absorbed. They are replaced by scar/granulation tissue that cannot secure the stability of the trachea. Therefore, further experiments with respect to the biocompatability of homografts appear to be necessary.

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.