Stent Compression Research Articles

Covered Stent Compression in Dialysis Access

Given a recent study which shows that stent grafts provide superior short-term patency compared with angioplasty alone in treatment of venous outflow stenosis in dialysis grafts, these devices are increasingly used for this application.1 Long-term patency data are not yet available and few complications related to these devices have been reported to date.

Stent-Assisted Below-the-Ankle Angioplasty for Limb Salvage

To report the clinical outcome of stent-assisted below-the-ankle angioplasty for limb salvage in the setting of critical limb ischemia (CLI). A retrospective single-center study was conducted of 40 critical ischemic limbs in 31 patients (mean age 67 ± 8 years, range 46-94) undergoing below-the-ankle stent-assisted angioplasty between April 2006 and April 2009. Coronary bare metal stents were implanted in cases of failed balloon angioplasty due to significant recoil, flow-limiting dissection, abrupt closure, or repeat early reocclusion. Technical success was 93% (37 limbs), with 3 failures to cross the occlusive lesions. Acute or subacute occlusion was evident in 9 (23%) limbs. The number of runoff vessels increased significantly (p < 0.001) from 0.6 ± 0.8 to 1.8 ± 0.8. During a clinical follow-up of 19.3 ± 11.4 months (range 1-48), the number of repeat interventions for limb salvage was 2.2 ± 1.6 (range 1-9), and a total of 1.6 ± 0.9 stents (range 1-3) were implanted in 8 dorsalis pedis arteries. Acute or subacute stent thrombosis after stenting was observed in 2 of these, and symptomatic in-stent restenosis was detected in 4, which were all treated by repeat intervention. At 6, 12, and 24 months, the freedom from repeat intervention was 39.6%, 39.6%, and 35.2%, respectively. Amputation-free survival was 80.0%, 69.7%, and 62.7%, and limb salvage was 94.7%, 91.4%, and 82.1% at the same time points. Patient survival rates were 77.4%, 71.0%, and 71.0%, respectively. During a mean follow-up of 13.4 ± 12.7 months (range 1-31 months) in 7 of the 8 stented arteries, all examined stents were deformed: stent compression was evident in 5 and stent fracture in 5. However, 7 limbs undergoing dorsalis pedis artery stenting showed complete wound healing; 1 limb had a resistant wound in the heel. Stent-assisted below-the-ankle angioplasty produced a satisfactory clinical outcome but with the need for repeat intervention. Thus, further refinement in endovascular technology is mandatory to reduce the need for repeat interventions and to resolve stent deformity issues.

Drug-Eluting Stents for the Treatment of Vertebral Artery Origin Stenosis

To present our experience with the use of drug-eluting stents (DES) in patients with symptomatic vertebral artery ostium stenosis (VAOS). Between 2003 and 2008, 28 consecutive patients (17 men; mean age 66 years) with symptomatic extracranial vertebral artery stenosis were treated with a paclitaxel-eluting stent. All patients were prospectively scheduled for serial clinical, duplex, and angiographic follow-up to identify restenosis. After stent implantation, the mean stenosis was reduced from 68% to 9%. There were no periprocedural neurological complications. After a mean follow-up of 16 months (range 5-41), no strokes, worsening of symptoms, or deaths occurred. Angiographic restenosis >50% was seen in 6 (21.4%) patients. Restenosis occurred significantly more often in patients with an ipsilateral subclavian artery stenosis (p = 0.01). Radiography during follow-up angiography revealed stent fracture in 1 patient and stent compression/kinking in 11 (39%) of the patients. Stent compression and recoil, not intimal hyperplasia, were the major contributing factors to restenosis. Compared to the restenosis rate of bare metal stents reported in the literature, DES seems to be superior for the treatment of VAOS. However, stent compression and recoil are relevant problems contributing to restenosis. Further improvement of the materials for the interventional treatment of VAOS seems necessary.

Ten Years of Endovascular Treatment of Traumatic Aortic Transection – A Single Centre Experience

Aim of the study was to present the 10-year results after endovascular repair of acute traumatic rupture of the descending aorta in a single centre. Forty-eight consecutive patients (35 men and 13 women; mean age 39.8 +/- 18 years) with traumatic lesions of the descending aorta were treated between March 1999 and November 2008. All patients were treated within 24 hours of admission. Thirty-one Gore TAG, 13 Medtronic Valiant, 6 Cook Zenith TX2 were used. The technical success rate was 100%, the conversion rate was 0%. Thirty-day mortality rate was 8.3%; overall procedure-related mortality was 2.1% due an acute stent graft compression syndrome. Infolding endografts were observed in 3 patients (6.25%). The left subclavian artery was covered in 35 cases (70%), in one patient revascularisation was necessary. No neurological deficit was reported. Mean follow-up was 51.9 months (4-116 months). No late complications occurred. Endovascular treatment of acute traumatic rupture of the thoracic aorta is a safe method, with a lower morbidity and mortality than open repair.

Prevention of covered enteral stent migration in patients with malignant gastric outlet obstruction: A pilot study of anchoring with endoscopic clips

Objective. Placement of a self-expandable metal stent is a palliative treatment of choice for patients with malignant gastric outlet obstruction (GOO). Although covering an enteral stent with a membrane almost solves the problem of tumor ingrowth, stent migration continues to be a major unresolved problem. Our aim was to evaluate the clinical efficacy of endoscopic clipping for prevention of covered stent migration in the treatment of malignant GOO. Material and methods. A total of 25 consecutive patients with malignant GOO were evaluated prospectively. After deployment of a double-layered combination stent (comprising an outer uncovered stent and an inner covered stent), three endoscopic clips were applied for fixation of the proximal end of the enteral stent to the gastric or duodenal mucosa. Results. Technical and clinical success rates were 100% (25/25) and 88% (22/25), respectively. No stent migration was observed in any of the patients. Five patients (20%) experienced complications such as tumor overgrowth and stent compression. Conclusion. Endoscopic clipping for enteral stent placement seems to be effective for prevention of covered stent migration in patients with malignant GOO.

Next Generation Biodegradable Ureteral Stent in a Yucatan Pig Model

Ureteral stents are commonly used to facilitate kidney drainage but they may produce significant stent symptoms and morbidity, and require a secondary procedure for removal. Previous biodegradable stents showed bio-incompatibility or inconsistent degradation, requiring extra procedures to remove undegraded stent fragments. We previously reported a first generation biodegradable stent composed of suture-like material that required placement through the lumen of a sheath and degraded by 10 weeks. We now report second and third generation biodegradable stents that degrade more rapidly and can be placed directly over a polytetrafluoroethylene guidewire. Two groups of 16 Yucatan pigs each were unilaterally stented endoscopically with a control nondegradable (biostable) stent or a second generation degradable Uriprene stent. Blood studies, renal ultrasound and excretory urography were done throughout the study to determine renal function, hydronephrosis and stent degradation. Genitourinary organs were harvested at necropsy for pathological analysis. A third generation stent designed to improve degradation time was bilaterally implanted endoscopically into 4 Yorkshire Farm pigs (total of 8 stents), followed by excretory urography weekly to assess degradation and kidney function. Biomaterial parameters were tested. Second generation stents began degrading at 2 weeks and were completely degraded by 10 weeks. All third generation stents were degraded by 4 weeks. Hydronephrosis was considerably less in the Uriprene group than in control biostable stented kidneys. Biostable stented ureters showed an average higher degree of inflammation, uropathy and nephropathy. Physical characteristics indicate that Uriprene stents are significantly more resistant to stent compression and have markedly higher tensile strength and coil strength comparable to that of other commercially available plastic stents. Our study confirms that Uriprene stents are biocompatible and provide good renal drainage. They hold promise for decreasing the need for a secondary procedure and stent related morbidity, such as infection and irritative symptoms.

Cryptorchidism with short spermatic vessels: staged orchiopexy preserving spermatic vessels

Editorial Comment This is an important study on the ability of five common urological pathogens (Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa) to adhere and form biofilms on commercially available ureteral stents. Also, it was evaluated the impact of heparin coating on stent compression, tensile and coil strength. This research opens new avenue to a very common and up-to-date problem that is bacterial encrustation and adhesion to stents. It could help modifications in stent design and also in developing drugs to inhibit bacterial adhesion and biofilm formation. I recommend this article as a reference for study design and methodology to all researchers interest in the issue of stent incrustation by bacteria.

Iliac-caval stenting in the obese

Chronic venous insufficiency (CVI) in the obese, often with severe clinical manifestations, is increasingly encountered in clinical practice. The association has drawn special interest as the pathophysiology may be different from that seen in the non-obese. The disease poses special management problems in the obese as traditional conservative measures are seldom effective. Iliac-caval venous stenting has been effective in CVI management but applicability in the obese raises concerns regarding stent compression, morbidity and efficacy. Results of iliac-caval stenting in 101 limbs of 87 patients are presented. Clinical features, venous test results, and outcome after stenting are reported with comparison to select relevant features in the non-obese limbs (n = 1513) that were stented over the same 11 year period. Bilateral clinical manifestations CVI were twice as common in the obese subset compared with the non-obese (28% vs 14% respectively, P = .0007), the incidence increasing with BMI. Resting and exercise femoral vein pressures were similar to the non-obese. Obstructive lesions of primary or postthrombotic origin similar to those seen in non-obese limbs were detected by intravascular ultrasound examination in 89% of limbs. Compression by increased intra-abdominal pressure associated with obesity was likely the mechanism of obstruction in 11% of the limbs. Iliac-caval venous stenting was found to be safe with no mortality (<30 days), low morbidity (deep venous thrombosis in 3%), high patency (86% cumulative at five years), and satisfactory clinical outcome. Sixty-eight percent and 46% of limbs showed cumulative improvement in pain and swelling respectively at 5 1/2 years after stenting, with 65% and 31% limbs achieving complete relief of these respective symptoms. Thirty of 45 limbs (58% cumulative) were free of dermatitis/ulcer at four years. The mechanism of venous obstruction in the obese is substantially similar to those in the non-obese. Primary or post-thrombotic lesions as seen in non-obese CVI cases are present in 89% of cases per IVUS examination. Compression of the venous outflow by adiposity/abdominal pressure may be a factor in 11%. Iliac-caval venous stenting is a satisfactory clinical option in the obese with severe CVI manifestations requiring speedy relief.

In-Vitro Modeling of the Dynamic Forces in the Femoropopliteal Artery

Abstract The use of intravascular stents in the femoropopliteal artery (FPA) continues to be controversial due to the potential fractures in the dynamic environment. The purpose of this study was to (1) develop a representative in-vitro model that simulates physiological motion of the FPA during knee and hip flexion and (2) use the model to characterize the types and ranges of stent distortion produced by extremity movement. This model eliminates inconsistencies often observed in cadaveric models and clinical subjects due to individual anatomical differences, and allows testing with large sample sizes in a controlled environment for variable (tubing length, material, diameter, and thickness) modification. A comparative evaluation of axial mechanical property and elasticity was conducted between the tubing intended to simulate arteries and the ex-vivo porcine carotid arteries, favoring the selection of silicone tubing. The model was assessed for its unstented and stented arterial bending and axial compression under three physiological motions: straight leg, walking (knee/hip flexion 70°/20°), and sitting/stair climbing (knee/hip flexion 90°/90°). Self-expanding nitinol stents implanted in the simulated mid-superficial femoral artery and popliteal artery (PA) of the model exhibit axial compression of 4.5±0.3 % and 7±0.3 % (knee/hip flexion 70°/20°), and 8.4±0.7 % and 8±0.2 % (knee/hip flexion 90°/90°). Stents implanted in the simulated PA exhibit bending of 40° and 74° from knee/hip angle changes to 70°/20° and to 90°/90°, respectively. The model demonstrated stent bending and compression as previously observed in cadaver studies. Additional analysis of stent motion (torsion, localized bending, radial compression) may be evaluated with more advanced imaging techniques and additional model development. The data generated in these analyses could support appropriate modes and parameters for stent fatigue testing, and better understanding of vascular device performance in the dynamic FPA.

Management of pregnancy in women with previous left ilio-caval stenting

Ilio-caval stenting now represents the first line treatment for disabling obstructive ilio-caval lesions. Most patients are young women of child-bearing age. We herein report our experience of pregnancy in women who have a history of ilio-caval stenting. From November 1995 to April 2008, 119 patients had ilio-caval stenting for obstructive venous disease in our department. Of these, 62 women were able to become pregnant. When pregnancy occurred, they received preventive treatment with low molecular weight heparin (LMWH) from the 3rd month of pregnancy to 1 month after delivery and had to wear elastic stockings. Patients also had to sleep on their right side if possible. They were followed during the pregnancy by duplex scanning at 3, 6, and 8 months, and then 1 month after delivery. Eight pregnancies occurred in 6 patients (mean age 26.5 years) who had a patent self-expanding stent (1 patient had 3 pregnancies). They had stenting for May-Thurner disease in 3 patients, for post-deep venous thrombosis (DVT) left common iliac vein occlusion in 1 patient, and during venous thrombectomy in 2 patients. All stents were self-expanding metallic stents located on the left common iliac vein. One patient had unrelated spontaneous abortion after 2 months of pregnancy. No DVT or symptomatic pulmonary embolism occurred during pregnancy, delivery, or during the postpartum period. Four patients needed cesarean delivery and none had hemorrhagic complications. None of the patients had adverse effects from the treatment. Duplex scan showed compression of the stent(s) at 8 months in 4 patients with inflow obstruction in 3 patients. Postpartum duplex-scan showed no remaining stenosis in all patients. No stents had structural damage. Ilio-caval stent compression can occur during pregnancy but does not lead to structural damage to the self-expanding stents. Despite this, no cases of DVT occurred with preventive LMWH treatment.

Uropathogen Interaction With the Surface of Urological Stents Using Different Surface Properties

Ureteral stents commonly become infected or encrusted. Various coatings have been developed to decrease bacterial adherence. To our knowledge there has been no in vitro testing of coating with heparin to date. We determined the effects of heparin coating on bacterial adherence of common uropathogens and physical stent properties. Heparin coated Radiance ureteral stents (Cook) and noncoated Endo-Sof control stents were tested against triclosan eluting Triumph(R) stents and noneluting Polaris control stents for adherence of Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, Staphylococcus aureus and Pseudomonas aeruginosa for 7 days. Adherent bacteria were determined and biofilms were visualized using fluorescent dyes. Radial, tensile and coil strength of the Radiance and Polaris stents was compared to determine the effect of heparin coating on physical stent characteristics. Heparin coating did not decrease bacterial adhesion compared to its control. E. coli adhesion was limited by all stents tested. The Polaris stent showed significantly greater resistance to bacterial adherence for Klebsiella, Pseudomonas and Enterococcus than the Endo-Sof and Radiance stents but was more susceptible to S. aureus adherence. The Triumph stent resisted all bacteria except Pseudomonas and Enterococcus. Mature biofilms were observed on all stents with lower viability on the Triumph stent. Radiance stents showed higher tensile and lower compression strength than its control. Heparin coating does not decrease bacterial adherence to ureteral stents. Drug eluting antimicrobials have an inhibitory effect on bacterial adherence and the Polaris stent showed the least bacterial adherence of the nondrug eluting ureteral stents tested.

A New Design Fully Covered Metal Stent (SX-ELLA Stent Esophageal HV) for the Palliation of Malignant Dysphagia: A Prospective Follow-Up Study

Background: Self-expandable metal stents (SEMS) are frequently used for the palliation of malignant dysphagia. Recurrent dysphagia due to stent migration in covered stents and non-tumoral or tumoral tissue growth in uncovered stents is the main cause of stent failure and occurs in 15-30% and 10-30% of patients, respectively. Aim: We aimed to determine efficacy, recurrent dysphagia, particularly due to migration and tissue growth, and complications of the SX-ELLA stent Esophageal HV (Ella-CS, Hradec Kralove, Czech Republic). This novel design is fully covered to resist tissue ingrowth and has an anti-migration ring to resist migration. Furthermore, it is braided in one piece to improve flexibility and expected to resist hyperplastic tissue reaction. Methods: Between February 2007 and May 2008, 45 patients with malignant dysphagia from inoperable or metastatic esophageal or gastric cardia cancer (n=43) or lung cancer (n=2) underwent placement of an SX-ELLA stent Esophageal HV in two tertiary referral centers. Patients were followed by scheduled telephone calls at 14 days after stent placement, and then monthly until death. Outcome measures were dysphagia score, recurrent dysphagia, complications, endoscopic reinterventions and mortality. Results: At 4 weeks, dysphagia score improved from a median of 3 (liquids only) prior to stent placement to a median of 1 (ability to eat some solid food) (p<0.001). Twelve of 45 (27%) patients developed recurrent dysphagia, in 6 (13%) patients due to stent migration and in 2 (4%) due to tissue overgrowth. Others causes of recurrent dysphagia were food obstruction, stent fracture and partial stent deployment. Major complications (severe pain, hemorrhage, fistula and fever) occurred in 10/45 (22%) patients. Minor complications, i.e., mild pain and gastro-esophageal reflux were observed in 12/45 (27%) patients. In total, 26 endoscopic reinterventions were performed in 18 patients (40%) for recurrent dysphagia or complications. Until November 2008, 39 patients died of whom 5 (11%) due to hemorrhage after a median of 107 days, most likely due to a combination of tumor progression and/or stent compression. Conclusions: The use of the SX-Ella stent Esophageal HV is effective and relatively safe for the palliation of malignant dysphagia. Recurrent dysphagia due to tissue growth and stent migration was reduced compared with other currently available covered stents, although still 40% of patients needed a reintervention for recurrent dysphagia or complications.

Incidence, Anatomical Location, and Clinical Significance of Compressions and Fractures in Infrapopliteal Balloon-Expandable Metal Stents

To investigate the incidence, anatomical location, and clinical impact of fractures and/or compression of infrapopliteal balloon-expandable metal stents implanted for critical limb ischemia (CLI) treatment. This prospective study included 63 CLI patients (45 men; mean age 71.3+/-9.5 years) who had been treated with infrapopliteal angioplasty and stent placement for 191 lesions in 84 limbs. In all, 369 stents (296 stainless steel and 73 cobalt-chromium alloy) were implanted; 239 were placed overlapping in tandem lesions. Mean length of the overall stented segment was 4.4+/-6.3 cm (range 1.6-14.0). Stents were located in the tibioperoneal (n = 34), anterior tibial (n = 195), posterior tibial (n = 63), and peroneal (n = 77) arteries. Follow-up consisted of digital subtraction angiography and infrapopliteal radiography imaging at 2 different angles. Evaluation of stents for the presence of fracture and/or compression was done after digital processing at the highest possible magnification. Stent fractures were defined according to published standards, whereas compression was classified as severe shape alteration and/or collapse of the stent mesh. Angiographic restenosis was based on a 50% threshold. Mean follow-up was 15+/-11 months (range 6-60). Image analysis detected 1 (0.3%) severe stent fracture (complete separation and misalignment of stent struts) and 11 (3.0%) stent compressions. Infrapopliteal stent fracture and compressions were associated with increased artery restenosis [100% (12/12) versus 47.3% (169/357), p<0.001] and an increased rate of clinical deterioration and clinically-driven reinterventions [41.7% (5/12 limbs) versus 19.4% (14/72 limbs), p = 0.04]. The single fracture and most of the compressions were located in the distal third of the anterior tibial artery. Stent fractures and compressions of infrapopliteal balloon-expandable metal stents are infrequent. However, they may be related to increased restenosis.

Analysis of Ureteral Stent Compression Force and its Role in Malignant Obstruction

Extrinsic ureteral obstruction can be a challenging entity for the urologist since half of the ureteral stents placed for malignant obstruction fail. We evaluated the resistance to radial compression of various stents. Silhouette(R) 4.6Fr, 6Fr and 8Fr, Sof-Curl Tecoflex 6Fr, Resonance 6Fr, Polaris Ultra 6Fr and 7Fr, and Percuflex 6Fr and 8Fr stents were tested. The force needed to compress the stent to 50% of its original external diameter was measured at 3 locations along the stent length, including proximal, middle and distal. Statistical analysis was performed. Statistically greater force was required to compress the Resonance and Silhouette stents compared to all others tested. These results were maintained at all 3 locations along the stent. Only the Polaris 6Fr stent differed in resistance to compression along the stent length. The significantly higher forces required to compress the Resonance and Silhouette stents may translate into improved success in patients with malignant ureteral obstruction.

An unexpected complication during stent implantation for coarctation of the aorta: Longitudinal stent compression

We report a 17-year-old adolescent with diagnosis of the coarctation of aorta (CoA) underwent stent implantation in which complicated with non expansion and longitudinal compression of the stent.

Wire-Based Ureteral Stents: Impact on Tensile Strength and Compression

Objectives To evaluate the performance of coil-based ureteral stents in terms of tensile strength and the radial compression force. Methods Three Cook Resonance (RES) metallic coil stents and three coil-reinforced Applied Medical Silhouette (SIL) ureteral stents were tested. An MTS MicroBionix Testing System using Testworks II software, vibration isolation table, and 5-N load cell were used to measure tensile and compressive strength. Stents were placed in hydraulic grips spaced 24 cm apart and stretched at a rate of 5 mm/s for 1 second under uniaxial tension. Extrinsic compression was exerted in 0.2-mm increments to maximum compression. The Young’s modulus, E, was calculated for each trial using the engineering stress. Comparisons were made with the Cook C-flex, which in previous studies was shown to be stiffer and more resistant to compression than other traditional polymer stents. Results The RES and SIL stents demonstrated tensile strengths of 936 ± 485 kPa and 770 ± 82 kPa, respectively ( P = 0.02). The elastic modulus required to cause extrinsic compression was lower for the RES (63,248 ± 3218 Pa) than for the SIL (105,664 ± 11,529 Pa) ( P <0.001). Both stents were more resistant to stent compression than previously tested stents without coil-reinforcement, the strongest of which was the Cook C-Flex (E = 30,355 ± 910 Pa; P <0.001). Conclusions Both the Cook Resonance and Applied Medical Silhouette stents are more resistant to extrinsic stent compression than ureteral stents that are not coil-reinforced. The Cook Resonance has a higher tensile strength, whereas the Applied Medical Silhouette is more resistant to extrinsic compression.

Endovascular Stenting of Obstructed Right Ventricle–to–Pulmonary Artery Conduits

The optimal treatment for dysfunctional right ventricle-to-pulmonary artery (RV-PA) conduits is unknown. Limited follow-up data on stenting of RV-PA conduits have been reported. Between 1990 and 2004, deployment of balloon-expandable bare stents was attempted in 242 obstructed RV-PA conduits in 221 patients (median age, 6.7 years). Acute hemodynamic changes after stenting included significantly decreased RV systolic pressure (89+/-18 to 65+/-20 mm Hg, P<0.001) and peak RV-PA gradient (59+/-19 to 27+/-14 mm Hg, P<0.001). There were no deaths, and, aside from 5 malpositioned stents requiring surgical removal, there were no serious procedural complications. During follow-up of 4.0+/-3.2 years, 9 patients died and 2 underwent heart transplantation, none related to catheterization or stent malfunction. During 155 follow-up catheterizations in 126 patients, the stent was redilated in 83 patients and additional stents were placed in 41. Stent fractures were diagnosed in 56 patients (43%) and associated with stent compression and substernal location but did not cause acute hemodynamic consequences. By Kaplan-Meier analysis, median freedom from conduit surgery after stenting was 2.7 years (3.9 years in patients >5 years), with younger age, homograft conduit, conduit diameter < or =10 mm, diagnosis other than tetralogy of Fallot, Genesis stent, higher prestent RV:aortic pressure ratio, and stent malposition associated with shorter freedom from surgery. Tricuspid regurgitation and RV function did not change between stent implantation and subsequent surgery. Conduit stenting is an effective interim treatment for RV-PA conduit obstruction and prolongs conduit lifespan in most patients. Stent fractures were common but not associated with significant complications or earlier conduit reoperation.

Stent-Graft Treatment of Pseudoaneurysms and Arteriovenous Fistulae in the Carotid Artery

The purpose of this study was to assess the safety and efficacy of stent-graft placement in the management of arteriovenous fistulae (AVF) and pseudoaneurysms (PAs) involving the carotid artery (CA). Twenty-two patients (16 men, 6 women) with a CA AVF (n = 5) or PA (n = 17) owing to a gunshot or stab wound, carotid endarterectomy, blunt trauma, a tumor, spontaneous dissection, or a central venous catheter were treated with percutaneous placement of stent grafts. The patients presented with tumor, bruit, headache, mouth and tracheostomy bleeding, transitory hemiparesis, seizure, or stroke. Diagnoses were made by using computed tomographic angiography (CTA) and digital subtraction angiography. Fourteen lesions were in the common CA; eight were in the internal CA. Homemade devices and stent grafts from a variety of manufacturers were employed. Follow-up evaluations included clinical, CTA, and Doppler ultrasound assessments. All patients had resolution of the PA or AVF. In one patient with a large petrous PA, acute occlusion of the CA developed after placement of three balloon-expandable stent grafts, but there were no neurologic complications because the circle of Willis was functional. During follow-up ranging from 2 months to 13 years, asymptomatic 90% stenosis owing to stent compression was observed on Doppler ultrasound and angiographic examinations in a patient with an autologous vein-covered stent graft in the internal CA. Three other patients died of causes unrelated to stent-graft placement. In all other patients, the stent graft remained patent. Our results indicate that stent grafting is an acceptable alternative to surgery in the treatment of AVF and PAs in the CA.

52: In Vitro Evaluation of Ureteral Stent Compression

You have accessJournal of UrologyModerated Poster, Saturday, May 20, 2006, 1:00 - 3:00 pm1 Apr 200652: In Vitro Evaluation of Ureteral Stent Compression Kari Hendlin, Krishna Vedula, Christina Horn, and Manoj Monga Kari HendlinKari Hendlin More articles by this author , Krishna VedulaKrishna Vedula More articles by this author , Christina HornChristina Horn More articles by this author , and Manoj MongaManoj Monga More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(18)32319-XAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "52: In Vitro Evaluation of Ureteral Stent Compression." The Journal of Urology, 175(4S), p. 18 © 2016 by American Urological AssociationFiguresReferencesRelatedDetails Volume 175Issue 4SApril 2006Page: 18 Advertisement Copyright & Permissions© 2016 by American Urological AssociationMetricsAuthor Information Kari Hendlin More articles by this author Krishna Vedula More articles by this author Christina Horn More articles by this author Manoj Monga More articles by this author Expand All Advertisement PDF downloadLoading ...

In vitro evaluation of ureteral stent compression

Objectives To evaluate the force required to radially compress ureteral stents and the impact of compression on stent performance across a broad range of stent sizes and manufacturers. Methods Fourteen ureteral stents ranging in size from 6F to 10.3F were evaluated for radial compression using an MTS Micro Bionix Testing System using Testworks II software, 5N load cell, vibration isolation table, and socket set screws with rounded caps. Radial compression was exerted in 0.2-mm increments. Cycles of compression and a 100-second hold time were repeated for each stent to maximal compression. Three trials were completed for each stent. The Young’s Modulus, E, was calculated from each trial using the engineering stress. Simultaneous flow data using normal saline were collected for the Amplatz stent. Results The Cook C-Flex (E = 30,355 ± 910 Pa), Microvasive Percuflex Plus 6F (E = 28,973 ± 250 Pa), Cook EndoSof (E = 28,403 ± 471 Pa), and Fossa Open Lumen (E = 28,627 ± 5,338) were the most resistant to compression and the Cook Amplatz 10.2F (E = 11,922 ± 220 Pa) and Microvasive Percuflex Plus 10.3F (E = 8,247 ± 286 Pa) were the least resistant to compression. Stress relaxation occurred similarly in all stents. Flow through the Cook Amplatz stent decreased at a rate of 5 mL/s/mm of compression linearly (R 2 = 0.95). Conclusions Stents resistant to radial compression are critical for function in the face of extrinsic ureteral obstruction. The Cook C-Flex ureteral stent resisted extrinsic compressive forces best. Although large-lumen stents are often used in this clinical situation, they were the most susceptible to compressive forces.