Large Stent Research Articles

Hemodynamic Comparison of Treatment Strategies for Intracranial Vertebral Artery Fusiform Aneurysms.

ObjectiveThis study comparatively analyzed the hemodynamic changes resulting from various simulated stent-assisted embolization treatments to explore an optimal treatment strategy for intracranial vertebral artery fusiform aneurysms. An actual vertebral fusiform aneurysm case treated by large coil post-stenting (PLCS) was used as a control.Materials and MethodsA single case of an intracranial vertebral artery fusiform aneurysm underwent a preoperative and eight postoperative finite element treatment simulations: PLCS [single and dual Low-profile Visualized Intraluminal Support (LVIS)], Jailing technique (single and dual LVIS both simulated twice, Pipeline Embolization Device (PED) with or without large coils (LCs). Qualitative and quantitative assessments were performed to analyze the most common hemodynamic risk factors for recurrence.ResultsJailing technique and PED-only had a high residual flow volume (RFV) and wall shear stress (WSS) on the large curvature of the blood flow impingement region. Quantitative analysis determined that PLSC and PED had a lower RFV compared to preoperative than did the jailing technique [PED+LC 2.46% < PLCS 1.2 (dual LVIS) 4.75% < PLCS 1.1 (single LVIS) 6.34% < PED 6.58% < Jailing 2.2 12.45% < Jailing 1.2 12.71% < Jailing 1.1 14.28% < Jailing 2.1 16.44%]. The sac-averaged flow velocity treated by PLCS, PED and PED+LC compared to preoperatively was significantly lower than the jailing technique [PED+LC = PLCS 1.2 (dual LVIS) 17.5% < PLCS 1.1 (single LVIS) = PED 27.5% < Jailing 1.2 = Jailing 2.2 32.5% < Jailing 1.1 37.5% < Jailing 2.1 40%]. The sac-averaged WSS for the PLCS 1.2 (dual LVIS) model was lower than the PED+LC, while the high WSS area of the Jailing 1 model was larger than for Jailing 2 [PLCS 1.2 38.94% (dual LVIS) < PED+LC 41% < PLCS 1.1 43.36% (single LVIS) < PED 45.23% < Jailing 2.1 47.49% < Jailing 2.2 47.79% < Jailing 1.1 48.97% < Jailing 1.2 49.85%].ConclusionsFor fusiform aneurysms, post large coil stenting can provide a uniform coil configuration potentially reducing the hemodynamic risk factors of recurrence. Flow diverters also may reduce the recurrence risk, with long-term follow-up required, especially to monitor branch blood flow to prevent postoperative ischemia.

Feasibility of Cholangioscopy Using Multibending Ultra-Slim Endoscope Through a Lumen-Apposing Metal Stent for Choledochoduodenostomy.

Endoscopic ultrasound (EUS) guided choledochoduodenostomy using a lumen-apposing metal stent (LAMS) allows access to the biliary system with a sufficiently large diameter stent. However, an appropriate endoscope for this purpose is required. We evaluated the feasibility of per-oral cholangioscopy (POC) using a multibending ultra-slim endoscope through a LAMS for EUS-guided choledochoduodenostomy. Twelve patients who underwent EUS-guided choledochoduodenostomy, followed by POC via a LAMS, were enrolled. POC was performed with an multibending ultra-slim endoscope. The primary outcome was technical success, defined as examination of both hepatic ducts and either the distal common bile duct or stricture site within 10min. The types of intervention and adverse events were also assessed. Technical success was achieved in all cases with the multibending ultra-slim endoscope. Narrow-band imaging endoscopy was performed in five cases (41.7%) and POC-guided targeted biopsy was performed in three cases (25.0%). Stone extraction during POC was performed in two patients (16.7%) and foreign body removal from the intrahepatic duct was performed in one patient. One patient underwent additional metal stent insertion under direct visualization. After POC, no stent migration or severe adverse events were seen in any case. POC using a multibending ultra-slim endoscope for diagnostic or therapeutic purposes can be performed effectively and safely through a LAMS after EUS-guided choledochoduodenostomy.

Impact of a shorter replacement interval of plastic stents on premature stent exchange rate in benign and malignant biliary strictures.

The main disadvantage of plastic stents is the high rate of stent occlusion. The usual replacement interval of biliary plastic stents is 3months. This study aimed to investigate if a shorter interval of 6-8weeks impacts the median premature exchange rate (mPER) in benign and malignant biliary strictures. All cases with endoscopic retrograde cholangiopancreatography (ERCP) and plastic stent placement were retrospectively analyzed since establishing an elective replacement interval of every 6-8weeks at our institution and mPER was determined. A total of 3979 ERCPs (1199 patients) were analyzed, including 1262 (31.7%) malignant and 2717 (68.3%) benign cases, respectively. The median stent patency (mSP) was 41days (range 14-120) for scheduled stent exchanges, whereas it was 17days (1-75) for prematurely exchanged stents. The mPER was significantly higher for malignant (28.1%, 35-50%) compared with benign strictures (15.2%, 10-28%), P<0.0001, respectively. mSP was significantly shorter in cases with only one stent (34days [1-87] vs 41days [1-120]) and in cases with only a 7-Fr stent (28days [2-79]) compared with a larger stent (34days [1-87], P=0.001). Correspondingly, mPER was significantly higher in cases with only one stent (23% vs 16.2%, P<0.0001) and only a 7-Fr stent (31.3% vs 22.4%, P=0.03). A shorter replacement interval does not seem to lead to a clinically meaningful reduction of mPER in benign and malignant strictures. Large stents and multiple stenting should be favored as possible.

Cuffed endotracheal tube as a cardiopulmonary bypass venous return cannula.

Cuffed endotracheal tube as a cardiopulmonary bypass venous return cannula.

Laryngeal silicone stent as a treatment option for laryngeal paralysis in dogs: a preliminary study of 6 cases.

BackgroundLaryngeal paralysis is a common idiopathic degenerative neurological disease in older medium-to-large breed dogs, with surgical correction of the obstruction being the treatment of choice.ObjectivesThis study evaluated the use of laryngeal silicone stents to treat canine laryngeal paralysis in dogs where classic surgical treatment was not accepted by the owners.MethodsDogs diagnosed with laryngeal paralysis, for which the owners refused arytenoid lateralization surgery as a first-line treatment, were treated with laryngeal silicone stents.ResultsSix dogs with bilateral laryngeal paralysis were included in the study. All dogs showed improvement in clinical signs immediately after the procedure. No clinical signs or radiographic changes were noted in four out of six dogs in the follow-up visit performed 1 wk later. One dog was suspected of aspirating water while drinking, but the signs disappeared after repositioning the stent. Another dog had a relapse of stridor due to caudal migration of the stent. This dog underwent arytenoid lateralization surgery because larger stents are not commercially available. At the time of writing, between seven and 13 mon after stent placement, no significant incidents have occurred in four dogs, and all owners report a satisfactory quality of life.ConclusionsLaryngeal silicone stenting is an interesting alternative for treating dogs with acquired laryngeal paralysis when the owners refuse classic arytenoid lateralization surgery. Furthermore, stent placement can be a temporary solution to stabilize these dogs until a permanent surgical treatment can be performed.

Initial Single Centre Experience of SYNERGY MEGATRON BP Stent

Synergy Megatron BP™ is purpose-designed to maximise performance for ostial and large vessel stenting which also allows tapering from 3.5 to 6 mm with improved radial and axial strength and reduced recoil seen on bench-testing. Intravascular-ultrasound (IVUS)-guided can reduce short-long-term major adverse cardiac events compared to angiographically-guided PCI [1,2].

Fully covered metal biliary stents: A review of the literature.

Fully covered self-expandable metal stents (FCSEMS) represent the latest advancement of metal biliary stents used to endoscopically treat a variety of obstructive biliary pathology. A large stent diameter and synthetic covering over the tubular mesh prolong stent patency and reduce risk for tissue hyperplasia and tumor ingrowth. Additionally, FCSEMS can be easily removed. All these features address issues faced by plastic and uncovered metal stents. The purpose of this paper is to comprehensively review the application of FCSEMS in benign and malignant biliary strictures, biliary leak, and post-sphincterotomy bleeding.

Patent ductus arteriosus stenting: ductal dissection and spasm in pulmonary atresia with intact ventricular septum.

Ductal dissection is rarely mentioned but intractable complication of ductal stenting. We demonstrate the dissection image under fluoroscopy and the use of a relatively large stent as an applicable treatment.

Multiple devices inside a large stent

Multiple devices inside a large stent

Comparative study of renal drainage with different ureteral stents subject to extrinsic ureteral obstruction using an in vitro ureter-stent model

BackgroundTo compare the efficacy of different ureteral stents subject to extrinsic ureteral obstruction (EUO), in a controlled in vitro stented ureter experiment.MethodsWe employ an in vitro ureter-stent experimental set-up, with latex tubing simulating flexible ureters attached to vessels simulating renal units and bladders. The flow behavior of five ureteral stents—polymeric 8F, tandem 6F, tandem 7F, endopyelotomy and metal—was tested under a ureteral deformation configuration of 40°, with 2000 g external force over a 3.5 cm length of the ureter. A constant fluid flow was applied through the ureter-stent configurations, and pressure fluctuations in the renal unit were monitored. We considered a renal unit pressure of 10 cmH2O or flow discontinuation in the bladder as stent failure. Urine containing debris was mimicked by use of a colloidal solution.ResultsOf all assessed ureteral stents, under EUO conditions, only the single 8F stents remained patent throughout the length of the experiment. All other stents—tandem 6F and 7F, single 7F, metal and endopyelotomy—displayed limitations.ConclusionsTandem and metal stents show no superiority over large luminal polymeric stents for EUO treatment in this in vitro model. Larger luminal stents offer excellent resistance to external pressure and allow adequate colloidal flow. The need for frequent exchange and bladder irritation should also be considered in the choice of stent configuration for treatment of kidney drainage under EUO.

The addition of flexible endoscopic suturing to stenting for the management of transmural esophageal wall defects: a single tertiary center experience.

Endoscopic stenting is the standard of care for full thickness esophageal wall defects. The aim of this study is to evaluate outcomes of endoscopic closure of esophageal defects using stenting, with or without endoscopic suturing. This is a single-center retrospective study of patients with esophageal wall defects who underwent endoscopic interventions. Outcomes of stenting with or without endoscopic suturing of the defect were assessed. Univariate and multivariate logistic regression models were used to examine factors associated with successful defect closure. One hundred and fourteen patients with esophageal wall defects underwent 254 endoscopies with an overall complete closure rate of 75.8%. Twenty-three (20.2%) patients underwent primary closure using endoscopic suturing and subsequent esophageal stenting, while 91 (79.8%) underwent esophageal stenting only. The dual modality group (versus the stent-only group) had similar defect closure rates (84.2 vs. 73.8%, p = 0.55) and time to stent migration (37 vs. 12.5days, p = 0.07), but was associated with longer procedure times (60 vs. 36min, p < 0.01) and fewer additional endoscopic procedures (13.6 vs. 43.2%, p = 0.01). Stent suturing significantly decreased migration (35.5 vs. 58.5%, p = 0.04), was associated with fewer additional endoscopies (15.4 vs. 50%, p < 0.01) and reduced need for additional stents (7.7 vs. 34.3%, p < 0.01). On multivariate analysis, chronic defects (> four weeks old) were 81% less likely to close compared to acute (≤ 4weeks) defects (OR 0.19, CI 0.04-0.77, p = 0.02), and large diameter stents (23mm) were associated with higher odds of defect closure (OR 3.36, CI 1.02-11.4, p = 0.04). Endoscopic treatment of esophageal wall defects is safe, effective, and more likely to be successful in acute defects using larger caliber stents. Stent suturing reduces migration, need for additional endoscopic procedures, and stent exchanges. Further comparative studies with larger cohorts are needed to validate our results.

ID: 3523829 CLINICAL AND TECHNICAL OUTCOMES OF PATIENTS UNDERGOING EUS-GUIDED GASTROENTEROSTOMY USING 15 MM VS 20 MM LAMS

EUS-guided gastroenterostomy (EUS-GE) has become an established technique for the palliation of malignant gastric outlet obstruction (GOO). The majority of studies on EUS-GE utilized a 15mm lumen apposing metal stent (LAMS). More recently, a 20 mm LAMS has become available. Although the larger stent provides an increase of 77% of luminal area, it is unknown how both stents compare in terms of efficacy and safety.

Abstract No. 504 Update: iliocaval-in-stent restenosis

To examine patient, stent, and angioplasty factors associated with 50% and 75% in-stent restenosis (ISR) of iliocaval stents placed for chronic venous thrombosis with results at 1, 3, 5, and 20 years post-placement. All patients with symptomatic chronic iliocaval venous thrombosis who underwent iliocaval stent placement with either SMART (Cordis, Santa Clara, CA) or Wallstent (Boston Scientific, Natick MA) at an academic medical center from 1996 to 2018 were compiled from a departmental database. In total, 620 iliocaval stents (430 SMART, 190 Wallstent) were placed in 176 patients (52.8% male, median age 51.1 y). Median follow -was 538.1 days (range, 0–6473 days). Rates of ISR at > 50% and > 75% luminal obstruction were calculated using Kaplan-Meier methods. Cox regression analysis of the effects of age, gender, stent brand, stent diameter, stent length, and angioplasty balloon diameter, on ISR was performed. Median and mean time to ISR were 153.5 and 299.2 days, respectively (range, 3–3985 days). In the 20 year follow-up period, ISR occurred in 8.7% of inferior vena cava (IVC) stents, 10.9% of common iliac vein (CIV) stents, and 15.3% of external iliac vein (EIV) stents. Gender did not affect ISR. Increased age was associated with a small but significant increased risk of ISR when all veins were examined as a single cohort at 1, 3, 5, and 20 years and within the EIV at 3, 5, and 20 years. Wallstents were associated with decreased rate of ISR when all veins were examined as a single cohort at 1, 3, 5, and 20 years as well as within EIV and CIV at 1, 3, 5, and 20 years. A small but significant increased risk of ISR was noted with larger stents in the EIV at 1, 3, 5, and 20 years and IVC at 1 year only as well as when all veins are examined as a single cohort at 1, 3, 5, and 20 years. Smaller balloon diameter demonstrated an increased risk of ISR within IVC stents at 1 year only. When the threshold for ISR was raised to > 75% ISR, all of the above significant results were the same. However, in addition, increasing stent length was associated with a small but significant risk of ISR > 75% when all veins were examined as a single cohort at 1, 3, 5, and 20 years. Our study demonstrates clinically acceptable and decreased rates of ISR compared to prior studies for the IVC, CIV, and EIV stents. Age is a small but significant risk factor for ISR, especially within the EIV. Wallstents may decrease ISR in iliac veins but are similar to SMART stents when placed in the IVC. Larger balloon diameters may help with short-term IVC ISR and larger stents may increase the risk of ISR in the EIV.

The Mathematical Revolution in Economics: Factor Flows in the Production of Academics

The main theme of this essay is that the mathematical revolution in economics precipitated factor flows in the production of academics, wherein able, if not creative, mathematicians moved into economics to earn large rents. This “technical migration” set in motion a counterproductive path dependency from which the discipline may find it difficult to extricate itself. A secondary theme explores the disparate views of Keynes and Schumpeter on economics as an “exact science” and the role that mathematics should play. The seminal question is not whether mathematics is an important tool for economic analysis, because this is not a debatable proposition, but whether the deification of mathematics has come at too high a cost. This cost includes elevating elegance over substance, discounting the importance of other disciplines, and dissuading gifted undergraduates from pursuing advanced study in economics because they do not aspire to be “mathematicians.” JEL Classifications: A22, A23, B31, B41

Predictors of stent dysfunction in patients with bilateral metal stents for malignant hilar obstruction.

For unresectable hilar obstruction, restoring and maintaining biliary ductal patency are crucial for improved survival and quality of life. The endoscopic placement of stents is now a mainstay of its treatment, and bilateral stenting is effective for biliary decompression. This study aimed to determine the clinical outcomes of bilateral metal stent placement using large cell-type stents and the clinical predictors of stent dysfunction in patients with malignant hilar obstruction. We performed a retrospective analysis of patients who underwent bilateral metal stent placement using two large cell-type stents at two academic teaching hospitals between September 2017 and February 2019. The primary outcome was stent dysfunction. Secondary outcomes included predictors related to stent dysfunction and overall survival. The study included 87 patients who underwent bilateral metal stent placement for malignant hilar obstruction. Technical success and clinical success were achieved in 80 patients (92.0%) and 83 patients (95.4%), respectively. During the follow-up period (median: 201, range: 18-671 days), stent dysfunction occurred in 42 patients (48.3%), and the median stent patency was 199 days (95% confidence interval [CI]: 181-262). In univariate analysis, age, cholangitis before stent insertion, and subsequent chemotherapy were found to be associated with the cumulative risk of stent dysfunction. In multivariate analysis, cholangitis before stent insertion (hazards ratio [HR]: 2.26, 95% CI: 1.216-4.209, P = 0.010) and subsequent chemotherapy (HR: 0.250, 95% CI: 0.130-0.482, P<0.001) remained as statically significant factors associated with the cumulative risk of stent dysfunction. The median overall survival was 288 days (95% CI: 230-327). The bilateral placement of large cell-type stents for malignant hilar obstruction was effective with high technical and clinical success rates and acceptable patency. Cholangitis before stent insertion was associated with shorter patency, and subsequent chemotherapy was associated with longer stent patency.

Controlled underdilation using novel VIATORR® controlled expansion stents improves survival after transjugular intrahepatic portosystemic shunt implantation

Background & AimsSmaller 8-mm diameter transjugular intrahepatic portosystemic shunts (TIPS) appear to be more beneficial than larger 10-mm TIPS stent-grafts, but lack the ability for secondary dilation in cases of clinical ineffectiveness. Underdilated VIATORR® TIPS stent grafts (VTS) expand passively, whereas novel VIATORR Controlled Expansion (VCX) stent grafts do not. This study evaluated the impact on survival of underdilated VCX compared with VTS in patients with decompensated cirrhosis.MethodsThis was a prospective case-control study including patients with cirrhosis receiving TIPS using 10-mm VCX underdilated to 8 mm. Patients with cirrhosis receiving 10-mm VTS underdilated to 8 mm were matched for age, sex, indication for TIPS, and liver function.ResultsA total of 114 patients (47 VCX, 47 VTS, and 20 fully dilated VCX/VTS) were included. After TIPS implantation, underdilated VCX diameter was 8.0 (7.8–9.2) mm at a median time of 359 (87–450) days, compared with VTS at 9.9 (9.7–10.0) mm (p <0.001). The portosystemic pressure gradient immediately after TIPS procedure and after 7 days did not change significantly in VCX [mean 9.4 (± 0.8) vs. 10.4 (± 0.7) mmHg, p = 0.115). Hospital readmission rates for hepatic encephalopathy were 23% (n = 11) vs 51% (n = 24) for VCX and VTS (p <0.001), respectively. Patients with VCX had significantly lower rates of large-volume paracentesis (n = 5 [11%] vs. n = 10 [21%], p = 0.017) and heart failure (n = 1 [2%] vs. n = 7 [15%], p = 0.015). One-year mortality for underdilated VCX and VTS was 15% (n = 7) and 30% (n = 14) and, for fully dilated VCX/VTS, was 45% (n = 9) (log-rank p = 0.008), respectively.ConclusionsThis study demonstrated that VCX stent grafts underdilated to 8 mm do not passively expand to nominal diameter and suggests reduced hospital readmissions because of hepatic encephalopathy, uncontrolled ascites, and heart failure, and improved 1-year survival compared with underdilated VTS.Lay summaryTransjugular intrahepatic portosystemic shunt (TIPS) improves survival in selected patients with liver cirrhosis and acute variceal bleeding or refractory ascites. Smaller 8-mm diameter TIPS stent grafts appear to improve patient outcome compared with larger 10-mm diameter stent grafts. Novel VIATORR® Controlled Expansion (VCX) stent grafts facilitate safe and stable underdilation to 8 mm of large 10-mm diameter stent grafts with improved patient outcome (survival, hepatic encephalopathy, ascites and heart failure) compared with legacy VIATORR TIPS stent graft (VTS). Thus, the use of underdilated VCX could preserve heart function.Clinical Trials RegistrationThe study is registered at Clinicaltrials.govNCT03628807.

Evasive entrepreneurship: Circumventing and exploiting institutional impediments for new profit opportunity in an emerging market.

Evasive entrepreneurship (circumvention and exploitation of institutions by entrepreneurs) is a prevalent practice in many developing economies. Extant literature on the topic falls short of providing adequate theories to explain its triggers, mechanisms, and consequences. Leveraging extensive survey data from the World Bank, we used structural equation modeling to examine the relationship between evasive entrepreneurial behavior—tax evasion and bribery—and the relative payoff of such practices. Of the 2599 Nigerian entrepreneurs in our sample, the majority admitted to engaging in evasive entrepreneurship. The data suggest that institutional factors thought to constrain entrepreneurship in emerging markets are counter-intuitively perceived by founders as opportunities to earn large rents and improve firm performance. Our results emphasize the urgent need to eliminate institutional constraints that paradoxically enable the growth of evasive entrepreneurship in emerging economies. Our results also suggest that prevailing local conventions involving evasive behavior may motivate nascent entrepreneurs to imitate bribery and tax evasion, normalizing malfeasance as ‘best practice.’

Impact of disconnected pancreatic duct on recurrence of fluid collections and new-onset diabetes: do we finally have an answer?

Disconnected pancreatic duct (DPD) is a frequent occurrence in cases with walled-off necrosis (WON). The impact of DPD on recurrence of collection after removal of metal stents is not clear....

The Risks and Side Effects of Heart Stents

A stent is a small-scale tube, the doctor can insert into a blocked passageway to keep it widely open. The stent can replace the blood flow rate or other fluids passage levels, depending on where it is placed in the body parts. Stents are made of the metal or plastic material. Stent springs are larger stents, they are used for larger arteries purposes. These types of stents are made up of a specialized fabric. Some types of stents are also coated with medication to help keep a blocked artery from closing.

Numerical study on the mechanical coupling of external vascular stent and vein graft in coronary artery bypass surgery

External support stent is a potential means for restricting the deformation and reducing wall stress of the vein graft, thereby improving the long-term patency of the graft in coronary artery bypass surgery. However, there still lacks a theoretical reference for choosing the size of stent based on the diameter of graft. Taking the VEST (venous external support) stent currently used in the clinical practice as the object of study, we constructed three models of VEST stents with different diameters and coupled them respectively to a model of the great saphenous vein graft, and numerically simulated the expansion-contraction process of the vein graft under the constraint of the stents to quantitatively evaluate the influence of stent size on the radial deformation and wall stress of the vein graft. The results showed that while the stent with a small diameter had a high restrictive effect in comparison with larger stents, it led to more severe concentration of wall stress and sharper changes in radial deformation along the axis of the graft, which may have adverse influence on the graft. In order to solve the aforementioned problems, we ameliorated the design of the stent by means of changing the cross-sectional shape of the thick and thin alloy wires from circle into rectangle and square, respectively, while keeping the cross-sectional areas of alloy wires and stent topology unchanged. Further numerical simulations demonstrated that the ameliorated stent evidently reduced the degrees of wall stress concentration and abrupt changes in radial deformation, which may help improve the biomechanical environment of the graft while maintaining the restrictive role of the stent.