Mechanical Evaluation of Polyvinyl Alcohol Cryogels for Covered Stents

2010 ◽  
Vol 4 (3) ◽  
Author(s):  
Jason D. Weaver ◽  
David N. Ku

Covered stents could reduce restenosis rates by preventing cellular migration with a physical barrier and may have reduced thrombotic complications if an appropriate material is selected. Previous Dacron™ or poly(tetrafluoroethylene) (PTFE) covered stents have had mixed clinical results in part because they are too thick and too thrombogenic at small diameters. Ideally, the covering should be as thin as a stent strut, mechanically able to expand as much as a stent, and durable enough to withstand deployment. As an alternative to PTFE, thin polyvinyl alcohol (PVA) cryogel membranes were tested for their ability to stretch with uniaxial tension tests and for puncture strength with a modified ASTM method. Additionally, PVA cryogel covered stents were made by coating expanded bare metal stents. These covered stents were then hand-crimped onto a balloon catheter and expanded. PVA cryogel membranes were made as thin as 100 μm—thinner than some stent struts—and stretched to approximately 3.0 times their original diameter (similar to a stent during deployment). PVA cryogel membranes resisted puncture well with an average push-through displacement of 4.77 mm—allowing for safe deployment in vessels of up to 9 mm in diameter. Push-through displacement did not depend on membrane thickness in the range tested—a trait that could reduce stent profile without increased risk of puncture. All the PVA cryogel covered stents tolerated the crimping and expansion process well and there was little to no visible membrane damage. In conclusion, based on the results of these mechanical tests, PVA cryogels are mechanically suitable for covered stent membranes. This work represents a first step toward the creation of a new class of covered stent, which could prevent complications from both restenosis and thrombosis.

2021 ◽  
pp. 153857442110103
Author(s):  
Austin Mallory ◽  
Stefanos Giannopoulos ◽  
Paul Lee ◽  
Damianos G. Kokkinidis ◽  
Ehrin J. Armstrong

Purpose: The treatment of aortoiliac occlusive disease (AIOD) has largely shifted to endovascular techniques, with primary stenting constituting the preferred treatment approach. The goal of the current study was to summarize available literature and to determine whether covered stents are superior to bare metal stents for the treatment of AIOD, in terms of both periprocedural and long-term outcomes. Methods: A meta-analysis of 47 studies was conducted with the use of random effects modeling. The incidence of adverse events during follow up among the individual included studies was synthesized. Results: Most of the lesions were located at the common iliac arteries and were chronic total occlusions. The procedure was technically successful in almost all cases in both groups, with a low rate of periprocedural complications observed in both groups. The reported primary patency rates for the non-covered and covered stent group during an average follow up of 24.3 months among the individual studies, were 84% and 92% respectively, while surgical or endovascular re-intervention was required in 10% of non-covered stent cases and in 6% of covered stent cases. Eight studies comparing covered vs non-covered stents in terms of patency demonstrated superiority of covered stents (OR: 2.47; 95% CI: 1.01-6.01; p = 0.047 Combining TASC C/D lesions together 12 studies reported 92% (95%CI:89%-95%) primary patency in the covered stent group, while 7 studies reported 75% (95%CI: 60%-88%) primary patency for cases treated with non-covered stents. Conclusion: This study demonstrated that covered stents are safe and effective when utilized for the treatment of AIOD. Covered stents were associated with a statistically significant higher odds of primary patency in both the overall cohort and in more complex TASC C/D lesions. However, additional high-quality comparative analyses between covered vs bare metal stents and between several types of covered stents are needed to determine the most optimal treatment modality for AIOD.


2021 ◽  
Author(s):  
Ciara G. McKenna ◽  
Ted J Vaughan

Polymer covered stents have demonstrated promising clinical outcomes with improved patency rates compared to traditional bare-metal stents, however little is known on the mechanical implication of stent covering. In the present work, a combined experimental-computational investigation was carried out to determine the role of a polymeric cover on the biomechanical performance of self-expanding laser-cut stents. Experimental bench top tests were conducted on bare and covered versions of a commercial stent to evaluate the radial, axial and bending response. In parallel, a computational framework with a novel covering strategy was developed that accurately predicts stent mechanical performance, and provides further insight into covered stent mechanics by considering different stent geometries and polymer materials. Results show that stent covering causes increased initial axial stiffness and substantial radial stiffening at small crimp diameters as the cover folds and self-contacts. It was also shown that use of a stiffer polymeric covering material caused significant alterations to the radial and axial response, highlighting the importance of considering the mechanical properties of the combined cover and stent.


2012 ◽  
Vol 7 (1) ◽  
pp. 37
Author(s):  
Donald E Cutlip ◽  

Coronary artery disease in patients with diabetes is frequently a diffuse process with multivessel involvement and is associated with increased risk for myocardial infarction and death. The role of percutaneous coronary intervention (PCI) versus coronary artery bypass grafting (CABG) in patients with diabetes and multivessel disease who require revascularisation has been debated and remains uncertain. The debate has been continued mainly because of the question to what degree an increased risk for in-stent restenosis among patients with diabetes contributes to other late adverse outcomes. This article reviews outcomes from early trials of balloon angioplasty versus CABG through later trials of bare-metal stents versus CABG and more recent data with drug-eluting stents as the comparator. Although not all studies have been powered to show statistical significance, the results have been generally consistent with a mortality benefit for CABG versus PCI, despite differential risks for restenosis with the various PCI approaches. The review also considers the impact of mammary artery grafting of the left anterior descending artery and individual case selection on these results, and proposes an algorithm for selection of patients in whom PCI remains a reasonable strategy.


Vascular ◽  
2021 ◽  
pp. 170853812110232
Author(s):  
Peixian Gao ◽  
Changliang Li ◽  
Xuejun Wu ◽  
Gang Li ◽  
Dianning Dong ◽  
...  

Purpose To evaluate the safety and efficacy of transbrachial and transfemoral approaches combined with visceral protection for the endovascular treatment of juxtarenal aortoiliac occlusive disease (AIOD) over an average 19-month follow-up period. Methods In this retrospective analysis, all patients with juxtarenal AIOD at a single institution were reviewed from June 2015 to January 2020. Patient characteristics, angiographic results, and follow-up outcomes were retrospectively recorded. The indications for treatment were critical limb threatening ischemia in 12 patients and bilateral claudication in five patients. Percutaneous access via the left brachial artery was first obtained to recanalize the infrarenal occluded lesions. After that, femoral accesses were achieved. A 4-Fr catheter, a 4 mm balloon, or a 6-Fr 90-cm-long sheath was used to complete visceral artery protection. Results A total of 17 juxtarenal AIOD patients (14 males; mean age, 63.4 ± 8.1 years) underwent endovascular treatment. The technical success rate was 100%. Complete reconstruction was achieved in 15 (88.2%) patients. The infrarenal aorta was reconstructed with kissing covered stent grafts ( n = 7), kissing bare-metal stents ( n = 2), covered stent grafts ( n = 2), bare-metal stents ( n = 1), or the off-label use of iliac limb stent grafts ( n = 5). Renal embolization was found in 3 (17.6%) patients during intraoperative angiography. There was 1 (5.9%) case of distal runoff embolization after CDT and 1 (5.9%) case of left iliac artery rupture. One (5.9%) death occurred due to acute myocardial infarction 20 days after the operation. The average follow-up period was 19.3 ± 16.7 months (range, 1–54 months) in the remaining 16 cases. The renal artery patency rate was 100%. The estimated cumulative primary patency rates were 92.3% at 12 months and 59.3% at 36 months according to the Kaplan–Meier method. Conclusions Transbrachial and transfemoral approaches combined with visceral protection offer a safe and effective alternative to open revascularization for the endovascular treatment of juxtarenal AIOD.


2010 ◽  
Vol 57 (2) ◽  
pp. 61-64 ◽  
Author(s):  
A. Mladenovic ◽  
K. Davidovic ◽  
B. Markovic ◽  
P. Anojcic ◽  
M. Stojadinovic ◽  
...  

Introduction: Application of the metallic stents in the interventional uroradioligy is the result of continuous development of the new generation methods percutaneous nephrostomy (PCN), ballon catheter dilatation (BCD), methal and covered stent application. Application of metal stents in the renal canal system was attempted in order to eliminate BCD and PCN - related limitations as well as poor therapeutic results of these methods in a number of etiopathogenic groups of urinary stasis. Years - long application of interventional uroradiology methods, until the development of metallic stengts had shown the following therapeutics facts: PCN is incapable to resolve the cause of urinary obstruction. Permanent good therapeutic BCD results mostly depend on pathohistological aspect of the stricture, metallic stents are most frequently the last choice in therapeutics approch to urinary tract obstructions and their application is directly dependent on previous therapeutics results accomplished by PCN and BCD. In therapeutical sequences new generation of covered stents have important place as method of selection in patients of irreversible uroopstruction of distal ureter. Objective: The main goal of this study was to analyze therapeutics results, advanteges and shortages of insercion plastics and opened metallic endoprothesis, and to analyze results of covered methal applications on the contrary of using older interventional uroradiology methods. Method: Sixthytwo patients with distal urether strictures threated in the Deparment of interventional uroradiology Institute of Radiology Clinical centre of Serbia in Belgrade, participated in the study. Results were analyzed with Person's 2- test, Fisher test and Student T-test. Results: In our study we had highly significant differences in comparison with number of patients and type of stents during the time after recanalization was reached. Also it was highly significant differences according the type of used interventional uroradiology method that treated proliferation and the success of recanalization. Conclusion: Application of covered temporary uretheral stents have number advantages against using generation older permanent methal endoprothesis.


2020 ◽  
Vol 9 (7) ◽  
pp. 2221
Author(s):  
Aleksander Falkowski ◽  
Hubert Bogacki ◽  
Marcin Szemitko

The use of drug-coated devices in intravascular therapy is aimed at preventing neointimal hyperplasia caused by excessive proliferation of vascular smooth muscle and thereby restenosis. Although its use seemed initially promising, a recent publication has shown an increased risk of mortality with paclitaxel-coated devices, and there is an urgent need to reaffirm assessments of drug-eluting stents (DES). Objective: The aim of the study was to compare mortality and effectiveness of paclitaxel-coated stents and bare-metal stents (BMS) in the treatment of peripheral arterial disease (PAD) with long-term follow-up. Materials and methods: In a single center randomized study, 256 patients with PAD were treated intravascularly with stent implantation. Patients were randomized into two groups: the first (n = 126) were treated with DES, and the second (n = 130) were treated with BMS. The study included evaluation after the procedure, after about 6 months and 36 months. Co-morbidities, with risks for atherosclerosis, were analyzed in all patients. Patients were evaluated for clinical outcome, restenosis frequency, and safety (complications and total mortality). Results: Clinical benefit at the end of the investigation was statistically significantly better in the DES group compared with the BMS group: 85.7% versus 66.2% (p = 0.0003), respectively. Restenosis occurred significantly less frequently in patients with DES: 16.0% versus BMS: 35.0%, p = 0.012. There was no significant effect of comorbidities on the frequency of restenoses. There were no differences in all-cause mortality over the three years with paclitaxel and no-paclitaxel stents cohorts (8.7% versus 7.1%; long-rank p = 0.575). No association was found with mortality and treatment with DES or BMS. Conclusions: The use of paclitaxel-coated stents gave good clinical benefit and caused a significantly lower frequency of restenosis compared to bare-metal stents. The use of paclitaxel-coated stents did not increase mortality.


2020 ◽  
Vol 43 (12) ◽  
pp. 1881-1888 ◽  
Author(s):  
Louise C. D. Konijn ◽  
Thijs Wakkie ◽  
Marlon I. Spreen ◽  
Pim A. de Jong ◽  
Lukas C. van Dijk ◽  
...  

Abstract Purpose Recently, two meta-analyses concluded that there appears to be an increased risk of long-term mortality of paclitaxel-coated balloons and stents in the superficial femoral and popliteal artery, and paclitaxel-coated balloons below the knee. In this post hoc study of the PADI Trial, we investigated the long-term safety of first-generation paclitaxel-coated drug-eluting stents (DES) below the knee and the dose–mortality relationships of paclitaxel in patients with chronic limb-threatening ischemia (CLI). Materials and Methods The PADI Trial compared paclitaxel-coated DES with percutaneous transluminal angioplasty with bail-out bare-metal stents (PTA ± BMS) in patients with CLI treated below the knee. Follow-up was extended to 10 years after the first inclusion, and survival analyses were performed. In addition, dose-related mortality and dose per patient weight-related mortality relations were examined. Results A total of 140 limbs in 137 patients were included in the PADI Trial. Ten years after the first inclusion, 109/137 (79.6%) patients had died. There was no significant difference between mortality in the DES group compared with the PTA ± BMS group (Log-rank p value = 0.12). No specific dose-related mortality (HR 1.00, 95% CI 0.99–1.00, p = 0.99) or dose per weight mortality (HR 1.05, 95% CI 0.93–1.18, p = 0.46) relationships were identified in the Cox-proportional Hazard models or by Kaplan–Meier survival analyses. Conclusions There is a poor 10-year survival in both paclitaxel-coated DES and PTA ± BMS in patients with CLI treated below the knee. No dose-related adverse effects of paclitaxel-coated DES were observed in our study of patients with CLI treated below the knee. Level of Evidence The PADI Trial: level 1, randomized clinical trial


2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Ryan James Ocsan ◽  
Ata Doost ◽  
Paul Marley ◽  
Ahmad Farshid

Objectives. The aim of this study was to evaluate the outcomes of acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) via transradial artery access (TRA) or transfemoral artery access (TFA). Background. Over the last decade, evidence for the benefit of TRA for PCI has grown, leading to a steady uptake of TRA around the world. Despite this, the topic remains controversial with contrary evidence to suggest no significant benefit over TFA. Methods. A retrospective study of consecutive ACS patients from 2011 to 2017 who underwent PCI via TRA or TFA. The primary outcome was Major Adverse Cardiovascular Events (MACE), a composite of death, myocardial infarction (MI), target lesion revascularisation (TLR), or coronary artery bypass graft surgery (CABG) at 12 months. Secondary outcomes included Bleeding Academic Research Consortium (BARC) bleeding events scored 2 or higher, haematoma formation, and stent thrombosis, in addition to all individual components of MACE. Results. We treated 3624 patients (77% male), with PCI via TFA (n = 2391) or TRA (n = 1233). Transradial artery access was associated with a reduction in mortality (3% vs 6.3%; p < 0.0001 ), MI (1.8% vs 3.9%; p = 0.0004 ), CABG (0.6% vs 1.5%; p = 0.0205 ), TLR (1% vs 2.9%; p < 0.0001 ), large haematoma (0.4% vs 1.8%; p = 0.0003 ), BARC 2 (0.2% vs 1.1%; p = 0.0029 ), and BARC 3 events (0.4% vs 1.0%; p = 0.0426 ). On multivariate Cox regression analysis, TFA, age ≥ 75, prior PCI, use of bare metal stents, cardiogenic shock, cardiac arrest, and multivessel coronary artery disease were associated with an increased risk of MACE. Conclusion. Despite the limitations secondary to the observational nature of our study and multiple confounders, our results are in line with results of major trials and, as such, we feel that our results support the use of TRA as the preferred access site in patients undergoing PCI for ACS to improve patient outcomes.


Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1741
Author(s):  
Konstantin A. Kuznetsov ◽  
Ivan S. Murashov ◽  
Vera S. Chernonosova ◽  
Boris P. Chelobanov ◽  
Alena O. Stepanova ◽  
...  

A stenting procedure aimed at blood flow restoration in stenosed arteries significantly improves the efficiency of vascular surgery. However, the current challenge is to prevent neointimal growth, which reduces the vessel lumen, in the stented segments in the long run. We tested in vivo drug-eluting coating applied by electrospinning to metal vascular stents to inhibit the overgrowth of neointimal cells via both the drug release and mechanical support of the vascular wall. The blend of polycaprolactone with human serum albumin and paclitaxel was used for stent coating by electrospinning. The drug-eluting stents (DESs) were placed using a balloon catheter to the rabbit common iliac artery for 1, 3, and 6 months. The blood flow rate was ultrasonically determined in vivo. After explantation, the stented arterial segment was visually and histologically examined. Any undesirable biological responses (rejection or hemodynamically significant stenosis) were unobservable in the experimental groups. DESs were less traumatic and induced weaker neointimal growth; over six months, the blood flow increased by 37% versus bare-metal stents, where it increased by at least double the rate. Thus, electrospun-coated DESs demonstrate considerable advantages over the bare-metal variants.


Sign in / Sign up

Export Citation Format

Share Document