Stent Fracture in the Coronary and Peripheral Arteries

Left subclavian artery bridging stent fracture after in-situ laser fenestration during emergent thoracic endovascular aortic repair

In-situ laser fenestration (ISLF) has been described as a viable option for urgent thoracic aortic aneurysm cases involving supra-aortic vessels. There are, however, limited data on its durability. Here, we present a case of a 70-year-old man with a symptomatic 13-cm thoracic aortic aneurysm extending proximally to the origin of the left subclavian artery (LSA). Emergent thoracic endovascular aortic repair with chimney stenting of the left common carotid artery and ISLF for the LSA was successfully performed. During the follow-up, a compression of the bridging stent to the LSA progressed to a stent fracture needing realignment. Despite ISLF's reported technical success, this case highlights the risk of bridging stent complications, emphasizing the need for a close follow-up.

Safety and effectiveness of the Phoenix atherectomy device for endovascular treatment of common femoral and popliteal arteries: Results of the EN-MOBILE trial

Background: This study aimed to assess the peri- and postprocedural outcomes of atherectomy-assisted endovascular treatment of the common femoral (CFA) and popliteal arteries. Methods: Phoenix atherectomy was used for the treatment of 73 and 53 de novo CFA and popliteal artery lesions, respectively, in 122 consecutive patients. Safety endpoints encompassed perforation and peripheral embolization. Postprocedural endpoints included freedom from clinically driven target lesion revascularization (CD-TLR) and clinical success (an improvement of ⩾ 2 Rutherford category [RC]). In addition, 531 patients treated for popliteal artery stenosis or occlusion without atherectomy were used as a comparator group. Results: Procedural success (residual stenosis < 30% after treatment) was 99.2%. The need for bail-out stenting was 2 (2.7%) and 3 (5.7%) in CFA and popliteal artery lesions, respectively. Only one (1.4%) embolization occurred in the CFA, which was treated by catheter aspiration. No perforations occurred. After 1.50 (IQR = 1.17-2.20) years, CD-TLR occurred in seven (9.2%) and six (14.6%) patients with CFA and popliteal artery lesions, respectively, whereas clinical success was achieved in 62 (91.2%) and 31 (75.6%), respectively. Patients treated with atherectomy and DCB in the popliteal artery after matching for baseline RC, lesion calcification, length, and the presence of chronic total occlusion, exhibited higher freedom from CD-TLR compared to the nondebulking group (HR = 3.1; 95% CI = 1.1-8.5, p = 0.03). Conclusion: Atherectomy can be used safely and is associated with low rates of bail-out stenting in CFA and popliteal arteries. CD-TLR and clinical success rates are clinically acceptable. In addition, for the popliteal artery, atherectomy combined with DCB demonstrates lower CD-TLR rates compared to a DCB alone strategy. (German Clinical Trials Register: DRKS00016708).

A case of repeated stent fracture

Stent fracture is one of the complications of drug-eluting stent implantation. An 84-year-old man underwent coronary angiography for unstable angina. He had diffuse severe stenosis and calcified plaque in the left anterior descending artery and underwent percutaneous coronary intervention (PCI) in the left anterior descending artery for severe stenosis with chest pain. Thereafter, two subsequent stent fractures occurred, so the patient underwent another PCI to cover them. However, a stent fracture was found again one year later. The patient was asymptomatic and PCI was avoided due to the risk of further stent fracture. When a stent fracture occurs, it is important to provide appropriate treatment according to the anatomical findings of the vessel, symptoms and the presence of ischemia.

Fatigue Test Method to Evaluate the 50 Year Durability of Venous Stents

OBJECTIVE

Iliofemoral venous obstructive disease can result in significant, potentially debilitating symptoms that can negatively affect quality of life. Unlike arterial disease, patients with deep venous disease have a significantly lower median age, therefore the need for long term stent patency becomes a matter of decades rather than years. Furthermore, iliofemoral lesions frequently require stent placement across the inguinal ligament. Such stents are subject to dynamic stress from leg movement and associated concerns for device fatigue, resulting in stent fracture. The aim of this study was to describe an in vitro 50 year stent fatigue test method designed to assess durability against dynamic stress induced device fracture.

METHODS

Through literature review, cadaver studies, and computer modelling, the most challenging loading was confirmed to be hip flexion across the inguinal ligament. This occurs when the patient adjusts between a seated and standing position. Sit to stand hip flexion at the inguinal ligament was effectively simulated on the bench in this in vitro experimental study.

RESULTS

When tested under challenge parameters, hip flexion was reliably found to cause fractures in non-venous nitinol stents. However, a dedicated self expanding nitinol venous stent, engineered for improved durability, underwent up to 50 years of simulated loading on the bench with 15% (3/20) of stents experiencing fractures at 50 years, compared with fractures in 35% (14/40) of non-venous stents tested to 1.4 years; no statistical testing was performed as durations do not match and the objective was to demonstrate the test method.

CONCLUSION

The presented fatigue test method is a suitable approach for evaluating the durability of stents intended for venous use. Venous stents demonstrated superior fatigue resistance compared with non-venous stents via in vitro hip flexion testing.

Objective Evaluation With Noncontrast Computed Tomography Can Reveal Calcified Plaque Solidity in Peripheral Artery Diseases

PURPOSE

The presence of severely calcified plaque remains problematic in endovascular therapy, and no specific endovascular treatment strategy has been established. Estimating plaque solidity before the procedure may help operators penetrate calcified plaque with a guide wire. The aim of this study was to establish a method of measuring plaque solidity with noncontrast computed tomography (CT).

METHODS

This retrospective, single-center study included consecutive patients who, between October 2020 and July 2022, underwent noncontrast 5 mm and 1 mm CTs before endovascular therapy to penetrate calcified plaque with a wire in the common femoral, superficial femoral, and popliteal arteries. Three cross-sectional CT slices were selected. To target a calcified plaque lesion, the operator identified a region of interest, which corresponded to 24×24 pixels, and Hounsfield unit (HU) values of each pixel were displayed on the CT image. The average HU values and the ratio of number of pixels of lower values (130-599 HU) represented plaque solidity. We used the Mann-Whitney-Wilcoxon rank-sum test and the chi-square test to compare the solidity of plaques penetrated and not penetrated by the wire.

RESULTS

We evaluated 108 images of 36 calcified plaque lesions (in 19 patients). The wire penetrated 28 lesions (77.8%) successfully. The average HU value was significantly lower in the lesions that the wire penetrated than in the others, in both the 5 mm CT slices (434.7±86.8 HU vs 554.3±112.7 HU, p=0.0174) and 1 mm slices (497.8±103.1 HU vs 593.5±114.5 HU, p=0.0381). The receiver operating curve revealed that 529.9 and 533.9 HU in the 5 and 1 mm slices, respectively, were the highest values at which wires could penetrate. Moreover, at the lesions that were penetrates successfully, the ratio of number of lower HU value pixels was significantly higher both in 5 mm slice CTs (74.7±13.4 vs 61.7±13.1%, p=0.0347) and 1 mm (68.7±11.8 vs 57.1±11.4%, p=0.0174).

CONCLUSION

The use of noncontrast CT to evaluate plaque solidity was associated with successful wire penetration of calcified lesions in peripheral arteries.

CLINICAL IMPACT

This study revealed an association between the wire penetration inside calcified plaque and plaque solidity estimated using non-contrasted computed tomography. The mean Hounsfield unit values of three cross-sections in calcified plaques were associated with the successful wire penetration. This wire penetration difficulty is associated with extended procedure time, excessive radiation exposure, usage of extra contrast agents, and increased medical costs. Therefore, estimating calcified plaque solidity before procedure enables us to choose effective and lean procedures. In addition, to predict the success of dilating calcified plaque from the inside is also beneficial when the operator wants to avoid extra scaffold implantation for target lesions.

Stretched and fractured Neuroform Atlas® stent during a stent‑assisted coil embolization: A case report

The Neuroform Atlas^® stent is one of the most recently developed stents for coil embolization, with advancements in a lower-profile delivery system, enhanced trackability, smaller cell size, and increased wall conformability. Because of these advantages, the Neuroform Atlas^® stent shows high technical success with few procedure-related complications. However, the present study reported a rare complication of a stretched and partially fractured Neuroform Atlas^® stent due to unexpected partial withdrawal of microcatheter during deployment for coil embolization of an intracranial aneurysm. The measured length of the stent was ~30 mm, which was greater than the normal length (21 mm). An additional stent was inserted into the distal part of the deployed stent to stabilize the damaged stent and remodel the aneurysm neck. This complication was considered to potentially result from the combination of several factors, including: Curved vessel; open-cell stent; unexpected microcatheter withdrawal during stent deployment; and hooking of the aneurysm selecting microcatheter with stent strut. Understanding the stent design and careful manipulation while avoiding unexpected withdrawal of the microcatheter could prevent this complication.

Effects of Tapered-Strut Design on Fatigue Life Enhancement of Peripheral Stents

Peripheral stent could fracture from cyclic loadings as a result of our blood pressures or daily activities. Fatigue performance has therefore become a key issue for peripheral stent design. A simple yet powerful tapered-strut design concept for fatigue life enhancement was investigated. This concept is to move the stress concentration away from the crown and re-distribute the stresses along the strut by narrowing the strut geometry. Finite element analysis was performed to evaluate the stent fatigue performance under various conditions consistent with the current clinical practice. Thirty stent prototypes were manufactured in-house by laser with a series of post-laser treatments, followed by the validation of bench fatigue tests for proof of concept. FEA simulation results show that the fatigue safety factor of the 40% tapered-strut design increased by 4.2 times that of a standard counterpart, which was validated by bench tests with 6.6-times and 5.9-times fatigue enhancement at room temperature and body temperature, respectively. Bench fatigue test results agreed very well with the increasing trend predicted by FEA simulation. The effects of the tapered-strut design were significant and could be considered as an option for fatigue optimization of future stent designs.

Treatment of Difficult, Calcified Lesions: Plaque Modification Strategies

Endovascular management of peripheral arterial disease is continually evolving. Most changes focus on addressing the challenges that hinder optimal patient outcomes; one of the most significant is how to best treat calcified lesions. Hardened plaque results in a variety of technical issues including impaired device delivery, decreased luminal revascularization, poor stent expansion, heightened risk of in-stent stenosis or thrombosis, and increased procedural time and cost. For this reason, plaque modification devices have been developed to mitigate this issue. This paper will describe these strategies and provide the reader with an overview of devices that can be used to treat chronically hardened lesions.

Specialty Balloons for Vessel Preparation During Infrainguinal Endovascular Revascularization Procedures: A Review of Literature

Balloon angioplasty with/without utilizing drug eluting technology or stenting constitutes the treatment of choice for a significant percentage of patients with peripheral artery disease requiring an intervention. However, in cases of diffuse disease and plaque complexity, angioplasty may lead to dissection, recoil, and/or early restenosis, making vessel preparation a key component for successful and durable endovascular revascularization outcome. This review of literature aims to present contemporary data for several commercially available specialty balloons that have been designed to minimize the arterial wall stress of conventional balloon angioplasty and facilitate technical success, as well as long-term patency.

Drug-Eluting Stent Restenosis: Modern Approach to a Classic Challenge

In-stent restenosis (ISR) is a recognized complication following percutaneous coronary intervention in which the luminal diameter is narrowed through neointimal hyperplasia and vessel remodeling. Although rates of ISR have decreased in most recent years owing to newer generation drug-eluting stents, thinner struts, and better intravascular imaging modalities, ISR remains a prevalent dilemma that proves to be challenging to manage. Several factors have been proposed to contribute to ISR formation, including mechanical stent characteristics, technical factors during the coronary intervention, and biological aspects of drug-eluting stents. Presentation of ISR can range from asymptomatic to late myocardial infarction and could be difficult to differentiate from acute thrombus formation. No definite guidelines are present on the management of ISR. In this review, we will discuss the mechanisms underlying ISR and provide insight into patient-related and procedural risk factors contributing to ISR, in addition to highlighting common treatment approaches utilized in the management of ISR.

CRP Albumin Ratio May Predict No Reflow in Patients Undergoing Percutaneous Coronary Intervention for Saphenous Vein Graft Stenosis

Many hypotheses have been proposed to explain no-reflow (NR). Some of these hypotheses, state that NR may be caused by damage to the vascular endothelium and an inflammatory process. In a recent study that did not include patients with coronary artery bypass graft (CABG), the ratio of C-reactive protein (CRP) to albumin (CAR) was found to be associated with NR. Our study aims to evaluate the relationship between CAR and NR in patients who underwent percutaneous coronary intervention (PCI) for saphenous vein graft (SVG). In this retrospective study, among the patients with CABG who underwent primary or elective coronary angiography, 242 patients who underwent PCI to the SVG were selected. The incidence of NR was 19.8% (n = 48). Diabetes mellitus, left ventricular ejection fraction (LVEF), stent length, and CAR were found as independent predictors of NR in multivariate logistic regression analysis (P < .05). Using a cut-off level of .930, the CAR predicted NR with a sensitivity of 75% and a specificity of 73% (AUC: .814, 95% CI: .749-.879, P < .001). The CAR was a better predictor than both stent length and LVEF. CAR was found to be the strongest predictor of NR in our study.

A review on femoropopliteal arterial deformation during daily lives and nickel-titanium stent properties

The increasing number of studies on the behaviour of stent placement in recent decades provides a clear understanding of peripheral artery disease (PAD). The severe mechanical loads (axial tension and compression, bending, radial compression and torsion) deformation of the femoropopliteal artery (FPA) is responsible for the highest failure rate of permanent nickel-titanium (Nitinol) stents. Therefore, the purpose of this article is to review research papers that examined the deformation of the natural load environment of FPA, the properties of Nitinol and mechanical considerations. In conclusion, a better understanding of mechanical behaviour for FPA Nitinol stents contributes to increased mechanical performance and fatigue-life.

Orbital Atherectomy Prior to Drug-Coated Balloon Angioplasty in Calcified Infrapopliteal Lesions: A Randomized, Multicenter Pilot Study

PURPOSE

Optimal balloon angioplasty for infrapopliteal lesions is often limited by severe calcification, which has been associated with decreased procedural success and lower long-term patency.

MATERIALS AND METHODS

This was a prospective, randomized, multicenter pilot trial that included adult subjects with calcified lesions located from the popliteal segment below the knee (BTK) joint to within 5 cm above the ankle with ≥70% diameter stenosis by angiography. Patients were randomized 1:1 to undergo orbital atherectomy (OA) with adjunctive drug-coated balloon (DCB) angioplasty versus plain balloon angioplasty (BA) and DCB angioplasty (control). The periprocedural and 12 month outcomes of both procedures were compared.

RESULTS

Overall, 66 subjects (OA + DCB = 32 vs control = 34) were included in an intention to treat analysis. Baseline demographics and lesion characteristics were well-balanced. The mean lesion length was 101.3 mm (SD = 72.8 mm) and 78.8 (SD = 61.0 mm) in the OA + DCB and control groups, respectively, with almost all lesions having severe calcification per the Peripheral Academic Research Consortium (PARC) criteria. Chronic total occlusions (CTOs) were present in 43.8% and 35.3% of the patients in the OA + DCB and control groups, respectively. The technical success of OA + DCB versus DCB was 81.8% and 89.2%, respectively, with 3 slow flow/no reflow, 1 perforation, 1 severe dissection occurred in OA + DCB group, and one distal embolization occurred in the control group. The target lesion primary patency rate was numerically higher in the OA + DCB versus control group at 6 (88.2% vs 50.0%, p=0.065) and 12 month follow-up (88.2% vs 54.5%, p=0.076). The 12 month freedom from major adverse events, clinically-driven target lesion revascularization, major amputation, and all-cause mortality rates were similar between both groups.

CONCLUSION

The results of the Orbital Vessel PreparaTIon to MaximIZe Dcb Efficacy in Calcified BTK (OPTIMIZE BTK) pilot study indicated that utilization of OA + DCB is safe for infrapopliteal disease. Further prospective adequately powered studies should investigate the potential benefit of combined OA + DCB for BTK lesions.

Stent fractures in the superficial femoral artery: predisposing factors and their implications

Abstract Background Fractures in stents implanted in the superficial femoral artery (SFA) are recognized complications of endovascular management of this arterial territory. Objectives The objective of this study was to determine the prevalence of fractures in stents implanted in the SFA and to identify predisposing factors for these fractures together with their impact on the patency of these devices. Methods The study included 39 patients (65.7±9.0 years) who previously underwent angioplasty for delivery of 56 stents into the SFA. During follow-up, which ranged from 7 to 46 months, variables were collected on the characteristics of the lesions treated and characteristics of the stents implanted. Two examiners independently analyzed digital radiographs for the presence of stent fractures and the patency of the devices. Results We found a 10.7% prevalence of fracture of implanted stents. Implantation of multiple stents was identified as a significant predisposing factor for fractures. We observed a marked tendency for fractures in female patients and in lesions treated with longer stents (> 150 mm). Stenosis exceeding 50% and occlusions were significantly more frequent in fractured stents. Conclusions This study suggests that implants longer than 150 mm and multiple stents are associated with higher device fracture rates. In cases with stent fractures, stenoses exceeding 50% and occlusions were significantly more frequent.

FAK Activation Promotes SMC Dedifferentiation via Increased DNA Methylation in Contractile Genes

Rationale: Vascular smooth muscle cells (SMCs) exhibit remarkable plasticity and can undergo dedifferentiation upon pathological stimuli associated with disease and interventions. Objective: Although epigenetic changes are critical in SMC phenotype switching, a fundamental regulator that governs the epigenetic machineries regulating the fate of SMC phenotype has not been elucidated. Methods and Results: Using SMCs, mouse models, and human atherosclerosis specimens, we found that focal adhesion kinase (FAK) activation elicits SMC dedifferentiation by stabilizing DNA methyltransferase 3A (DNMT3A). FAK in SMCs is activated in the cytoplasm upon serum stimulation in vitro or vessel injury and active FAK prevents DNMT3A from nuclear FAK-mediated degradation. However, pharmacological or genetic FAK catalytic inhibition forced FAK nuclear localization, which reduced DNMT3A protein via enhanced ubiquitination and proteasomal degradation. Reduced DNMT3A protein led to DNA hypomethylation in contractile gene promoters, which increased SMC contractile protein expression. RNA sequencing identified SMC contractile genes as a foremost upregulated group by FAK inhibition from injured femoral artery samples compared to vehicle group. DNMT3A knockdown in injured arteries reduced DNA methylation and enhanced contractile gene expression supports the notion that nuclear FAK-mediated DNMT3A degradation via E3 ligase TRAF6 drives differentiation of SMCs. Furthermore, we observed that SMCs of human atherosclerotic lesions exhibited decreased nuclear FAK, which was associated with increased DNMT3A levels and decreased contractile gene expression. Conclusions: This study reveals that nuclear FAK induced by FAK catalytic inhibition specifically suppresses DNMT3A expression in injured vessels resulting in maintaining SMC differentiation by promoting the contractile gene expression. Thus, FAK inhibitors may provide a new treatment option to block SMC phenotypic switching during vascular remodeling and atherosclerosis.

Computational analysis of the effects of geometric irregularities on the interaction of an additively manufactured 316L stainless steel stent and a coronary artery

Customized additively manufactured (laser powder bed fused (L-PBF)) stents could improve the treatment of complex lesions by enhancing stent-artery conformity. However, geometric irregularities inherent for L-PBF stents are expected to influence not only their mechanical behavior but also their interaction with the artery. In this study, the influence of geometrical irregularities on stent-artery interaction is evaluated within a numerical framework. Thus, computed arterial stresses induced by a reconstructed L-PBF stent model are compared to those induced by the intended stent model (also representing a stent geometry obtained from conventional manufacturing processes) and a modified CAD stent model that accounts for the increased strut thickness inherent for L-PBF stents. It was found that, similar to conventionally manufactured stents, arterial stresses are initially related to the basic stent design/topology, with the highest stresses occurring at the indentations of the stent struts. Compared to the stent CAD model, the L-PBF stent induces distinctly higher and more maximum volume stresses within the plaque and the arterial wall. In return, the modified CAD model overestimates the arterial stresses induced by the L-PBF stent due to its homogeneously increased strut thickness and thus its homogeneously increased geometric stiffness compared with the L-PBF stent. Therefore, the L-PBF-induced geometric irregularities must be explicitly considered when evaluating the L-PBF stent-induced stresses because the intended stent CAD model underestimates the arterial stresses, whereas the modified CAD model overestimates them. The arterial stresses induced by the L-PBF stent were still within the range of values reported for conventional stents in literature, suggesting that the use of L-PBF stents is conceivable in principle. However, because geometric irregularities, such as protruding features from the stent surface, could potentially damage the artery or lead to premature stent failure, further improvement of L-PBF stents is essential.

Viscoelastic Behavior of Drug-Loaded Polyurethane

Drug-eluting stents are desirable platforms for local medicine delivery. However, the incorporation of drugs into polymers can influence the mechanical and physicochemical properties of said matrix, which is a topic that is still poorly understood. In fact, this is more noticeable since the apposition is most often accompanied by mechanical stresses on the polymer coating, which can induce therapeutic failure that can result in death. It is therefore necessary to better understand their behavior by examining their properties in conditions such as those in living beings. We studied polyurethane drug carriers made in-house. Diclofenac epolamine was chosen as a model hydrophilic medicine. We used thermal measurements (DMTA) and tensile tests. The aim was to establish the influence of the loading and release of the drug on the physicochemical properties of this polymer in the presence of a stagnant or circulating fluid medium, phosphate-buffered saline (PBS). For the two PU/drug loadings studied, the effect of the initial drug load was more marked. The free volume fraction and the number of pores in the samples increased with the increasing percent of the drug and with release time. The kinetic profiles were accelerated with the loading ratio and with the presence of flow. Young's modulus and ultimate stress were not significantly influenced by the release time. A relevant relationship between the tensile properties and the viscoelastic behavior of the samples was developed. Our results have implications for optimizing the performance of drug coatings for stents.

Preliminary study on modelling, fabrication by photo-chemical etching and in vivo testing of biodegradable magnesium AZ31 stents

Magnesium metal (Mg) is a promising material for stent applications due to its biocompatibility and ability to be resorbed by the body. Manufacturing of stents by laser cutting has become an industry standard. Our alternative approach uses photo-chemical etching to transfer a pattern of the stent onto a Mg sheet. In this study, we present three stages of creating and validating a stent prototype, which includes design and simulation using finite element analysis (FEA), followed by fabrication based on AZ31 alloy and, finally, in vivo testing in peripheral arteries of domestic pigs. Due to the preliminary character of this study, only six stents were implanted in two domestic farm pigs weighing 25-28 kg and they were evaluated after 28 days, with an interim follow-up on day 14. The left and right superficial femoral, the left iliac, and the right renal artery were selected for this study. The diameters of the stented artery segments were evaluated at the time of implantation, on day 14 and then, finally, on day 28, by quantitative vessel analysis (QVA) using fluoroscopic imaging. Optical Coherence Tomography (OCT) imaging displayed some malposition, breaks, stacking, and protrusion into the lumen at the proximal, distal, and mid-sections of the stented arteries. The stents degraded with time, but simultaneously became embedded in the intima. After 28 days, the animals were euthanized, and explanted vessels were fixed for micro-CT imaging and histology studies. Micro-CT imaging revealed stent morphological and volumetric changes due to the in-body degradation. An in vivo corrosion rate of 0.75 mm/year was obtained by the CT evaluation. The histology suggested no-life threatening effects, although moderate injury, inflammation, and endothelialization scores were observed.

Biodegradable performance of PLA stents affected by geometrical parameters: The risk of fracture and fragment separation

Biodegradable endovascular stents have been claimed to be reliable candidates for implantation devices used in treating cardiovascular diseases since they reduce the long-term side effects on the human biological system. It is aimed in this study to investigate the effect of geometrical parameters on the degradation behavior of poly (lactic acid) stents in term of strut fracture and fragment separation. In this regard, various structural geometry of the PLA stents was simulated in a stenosed artery using finite element method. For predicting the PLA degradation, a computational model was prepared by which the influence of stents design on their radial strength and fracture was investigated. Using a laboratory-scale designed bioreactor, the PLA fibers degradation was evaluated to calibrate the material parameters and verify the simulation method. Simulation results demonstrated that the geometrical parameters, i.e., number of struts, curves radius and stent cells shape, strongly affect the degradation behavior. The results indicated that the smooth design leads to uniform degradation in the whole stent and decreases the danger of stent fragments separation. It was shown that the maximum degradation rate of the stents with rounded curves was one-third of the models with sharp corners.

A systematic review of the quality of cardiovascular surgery studies that extracted data from the MAUDE database

OBJECTIVE

To investigate opportunities and limitations of using the Manufacturer and User Facility Device Experience (MAUDE) database for cardiovascular surgery research, we analyzed the quality of studies having ever used MAUDE, in the field of cardiovascular surgery.

METHODS

We systematically searched the Cochrane Library, PubMed, EMBASE, and Google Scholar for randomized and nonrandomized studies, from inception to July 2019. Two authors evaluated the quality of the retrieved observational studies, according to the National Institutes of Health quality assessment tool for either case series or cross-sectional studies. These tools quantify the quality of case series and cohorts/cross-sectional studies, respectively, with nine and 14 queries.

RESULTS

Fifty-eight studies were included in the final qualitative review. Of 58 identified studies, 32 were case series, 8 were abstracts of case series, and 13 were reviews or case discussion with an included series from MAUDE. Also, five articles were cross-sectional studies. Of the 32 formal case series, 26 (81%) were found to have poor quality. The most common reasons for a poor quality designation included a lack of consecutive participants, undetermined comparability of participants, and undetermined follow-up adequacy. Only one out of five cross-sectional studies had fair quality; four others were evaluated as poor quality studies.

CONCLUSIONS

Cardiovascular surgery studies using the MAUDE database, whether case series or cross-sectional design, are mostly of poor quality. Their low quality is partly caused by poor study design, but mainly by intrinsic limitations to the MAUDE database: cases recruited are not consecutive; patient characteristics are not detailed enough to allow a meaningful comparison of patient characteristics between different patient entries; outcome measures are unclear; there is a limited follow-up; and time-to-event data are lacking. We conclude that the quality of cardiovascular surgery publications that rely on data from MAUDE could be improved if investigators were to extract all relevant data points from MAUDE entries, then apply standard quality assessment tools in compiling and reporting the data. MAUDE might be improved if it used medical case report standards during the process of reporting and indexing adverse events. To calculate the incidence rate of any adverse event, all event-free cases, as well as all adverse events in patients using a device, are required. Neither of these two variables is available in the MAUDE at the time of writing.

Three-Year Outcomes of Orbital Atherectomy for the Endovascular Treatment of Infrainguinal Claudication or Chronic Limb-Threatening Ischemia

Purpose: To investigate the outcomes of orbital atherectomy (OA) for the treatment of patients with peripheral artery disease (PAD) manifesting as claudication or chronic limb-threatening ischemia (CLTI). Materials and Methods: The database from the LIBERTY study (ClinicalTrials.gov identifier NCT01855412) was interrogated to identify 503 PAD patients treated with any commercially available endovascular devices and adjunctive OA for 617 femoropopliteal and/or infrapopliteal lesions. Cox regression analyses were employed to examine the association between baseline Rutherford category (RC) stratified as RC 2-3 (n=214), RC 4-5 (n=233), or RC 6 (n=56) and all-cause mortality, target vessel revascularization (TVR), major amputation, major adverse event (MAE), and major amputation/death at up to 3 years of follow-up. The mean lesion lengths were 78.7±73.7, 131.4±119.0, and 95.2±83.9 mm, respectively, for the 3 groups. Results: After OA, balloon angioplasty was used in >98% of cases, with bailout stenting necessary in 2.0%, 2.8%, and 0% of the RC groups, respectively. A small proportion (10.8%) of patients developed angiographic complications, without differences based on presentation. During the 3-year follow-up, claudicants were at lower risk for MAE, death, and major amputation/death than patients with CLTI. The 3-year Kaplan-Meier survival estimates were 84.6% for the RC 2-3 group, 76.2% for the RC 4-5 group, and 63.7% for the RC 6 group. The 3-year freedom from major amputation was estimated as 100%, 95.3%, and 88.6%, respectively. Among CLTI patients only, the RC at baseline was correlated with the combined outcome of major amputation/death, whereas RC classification did not affect TVR, MAE, major amputation, or death rates. Conclusion: Peripheral artery angioplasty with adjunctive OA in patients with CLTI or claudication is safe and associated with low major amputation rates after 3 years of follow-up. These results demonstrate the utility of OA for patients across the spectrum of PAD.

Stents in the femoropopliteal territory: prevalence of fractures and their consequences

OBJECTIVE

Endovascular treatment for femoropopliteal arterial disease has made revascularization procedures less invasive, but the self-expanding stents used can suffer great wear in arteries with extreme mobility. To evaluate the prevalence of fractures in stents implanted in the femoropopliteal segment, to identify predisposing factors and consequences on arterial patency.

METHOD

between March and June 2019, thirty patients previously operated for femoropopliteal obstruction underwent stent X-rays in anteroposterior and lateral views to detect fractures and Doppler to analyze arterial patency.

RESULTS

we observed 12 cases with fractures (33.3%): 1 type I (2.8%), 3 type II (8.3%), 5 type III (13.9%), 3 type IV (8.3%) and no type V. According to the TASC II we had 1 in group B (8.3%), 6 in group C (50%) and 5 in group D (41.6%) p <0.004. The number of stents per limb was 3.1 (± 1.3) in cases of fracture versus 2.3 (± 1.3) in cases without fracture (p = 0.08). The extension was 274.17mm (± 100.94) in cases of fracture and 230.83mm (± 135.44) in cases without fracture (p = 0.29). On Doppler we had: 17 patients (47.2%) without stenosis, 9 patients (25%) with stenosis> 50% and 10 patients (27.8%) with occlusion (p = 0.37). There was no correlation between fracture and arterial obstruction (p = 0.33).

CONCLUSION

stent fractures are a frequent finding in the femoropopliteal area (33.3%), being more prevalent in cases of more advanced disease (C and D). There was no association between the finding of fracture and arterial obstruction.

Intravascular Lithotripsy for Treatment of Calcified Lesions During Carotid Artery Stenting

Purpose:

To report the use of intravascular lithotripsy (IVL) in the treatment of calcified carotid artery lesions.

Materials and Methods:

The records of 21 high-surgical-risk patients (mean age 75.1±8.1 years; 17 men) who were treated at 8 centers for carotid artery stenosis ≥70% were retrospectively reviewed. Twelve patients had a history of cerebrovascular disease. All patients had heavily calcified carotid artery lesions: 19 de novo and 2 in-stent restenoses (ISR). The mean baseline stenosis was 82.3%±9.7%. IVL was utilized at the discretion of the operator, followed by balloon angioplasty. Embolic protection devices were used in all cases.

Results:

In 19 patients, IVL was followed by stent implantation; the 2 ISR lesions were dilated only. The mean IVL balloon diameter was 4.64±1.13 mm, and the mean number of IVL pulses applied was 67.2±61.4 (range 10–180). All procedures were technically successful (<30% residual stenosis). No patients developed symptomatic bradycardia or hypotension due to IVL, and there were no adverse events associated with IVL delivery. All patients were discharged on dual antiplatelet therapy. Seventeen days after the procedure, 1 patient experienced an ischemic stroke that was deemed due to aortic arch manipulation during transfemoral access. Carotid duplex ultrasound examination identified significant restenosis (>70%) in 1 asymptomatic patient at 12 months after the index procedure. No patients required reintervention during a median follow-up of 6 months (range 1–12).

Conclusion:

This preliminary experience demonstrates that IVL can be a safe and effective approach for the management of severely calcified carotid lesions. Further research is warranted to determine the longer-term safety and efficacy of IVL for dilation of calcified carotid artery lesions as an adjunct to carotid artery stenting.

Intermediate results of the prospective randomized study on the effect of lamina vastoadductoria dissection after superficial femoral artery stenting on the restenosis incidence in TASC-II type C and D lesions

Aim. To compare the effectiveness of superficial femoral artery (SFA) stenting with/without lamina vastoadductoria dissection.

Material and methods. The study included are 70 patients with TASCII type C and D lesions. All patients were divided onto 2 groups: group 1 (n=35) — conventional SFA stenting, group 2 (n=35) — SFA stenting with lamina vastoadductoria dissection. The average lesion length in group 1 was 22,92±5,62 cm, in group 2 — 21,2±5,42 cm. The primary endpoint was the absence of binary restenosis and reocclusion. Secondary composite endpoint was procedural success, limb salvage, secondary patency of the operated segment, intraoperative complications. The groups were comparable in age, sex, risk factors and comorbidities.

Results. The procedural success in both groups was 100%. Primary patency after 24 months was 28,5% in group 1 and 60% in group 2. During the 24-month follow-up period, we recorded 1 death in group 2 due to myocardial infarction. In group 1, 2 deaths due to myocardial infarction and pancreatic cancer metastasis were recorded. Limb salvage was 100% in both groups. There were no intraoperative complications in both groups.

Conclusion. Lamina vastoadductoria dissection is safe and does not lead to limb functional limitations. Biomechanical changes in the distal SFA segment contribute to the improvement of primary patency after stenting of SFA long lesions. Preliminary results of the single-center pilot study demonstrate the safety and efficacy of SFA stenting with lamina vastoadductoria dissection, emphasizing the need for further larger studies to compare it with conventional stenting and to assess the effectiveness during the long-term follow-up.

"Squid-Capture" Modified In Situ Stent-Graft Fenestration Technique for Recurrent Abdominal Aortic Occlusive Disease after Collapse of Balloon-Expandable Stent

We present a case of an 85-year-old woman with bilateral limb-threatening ischemia caused by acute-on-chronic occlusion of the infrarenal aorta. The patient once underwent endovascular recanalization using nitinol and stainless-steel bare-metal stent implantation; however, the stainless-steel stent collapsed 3 months later. In the second endovascular therapy, "Squid-Capture" modified in situ stent-graft fenestration technique followed by stent-in-stent implantation with stent graft and bare-metal stent was successfully applied, and it can be regarded as a promising treatment option for the repair of abdominal aortic occlusive disease in some limited anatomical conditions.

Newly approved devices for endovascular treatment of femoropopliteal disease: a review of clinical evidence

Introduction: Femoropopliteal lesions account for a significant proportion of endovascular interventions for peripheral artery disease. In this manuscript, we review the literature on the application of newly approved devices in the treatment of atherosclerotic lesions at this segment.Areas covered: New drug-coating technologies provide sustained drug-eluting over time and better scaffolds are more resistant to the increased biomechanical stress at the femoropopliteal segment. Thus, the newer drug-eluting stents (i.e. Eluvia®), nitinol interwoven stents (i.e. Supera®), and drug-coated balloons (i.e. Stellarex®) are associated with improved pharmacokinetic profiles and promising primary patency rates. A major predictor of technical failure and restenosis is the calcification of the target vessel. Recently, intravascular lithotripsy of calcified lesions at the femoropopliteal segment with the Shockwave® balloon was introduced as a feasible treatment option for these complex lesions. Finally, we also describe the Tack Endovascular System®, the first-of-its-type, for the repair of post-angioplasty dissections.Expert opinion: The use of innovative stent designs and novel drug-coating, the application of adjunctive intravascular lithotripsy, and the combined use of new devices treating complications might improve the overall outcomes of angioplasty, thereby promising favorable outcomes even for more complex lesions.

Challenges in the use of zinc and its alloys as biodegradable metals: Perspective from biomechanical compatibility

To date, more than fifty articles have been published on the feasibility studies of zinc and its alloys as biodegradable metals. These preliminary in vitro and in vivo studies showed acceptable biodegradability and reasonable biocompatibility in bone and blood microenvironments for the experimental Zn-based biodegradable metals and, for some alloy systems, superior mechanical performance over Mg-based biodegradable metals. For instance, the Zn-Li alloys exhibited higher UTS (UTS), and the Zn-Mn alloys exhibited higher elongation (more than 100%). On the one hand, similar to Mg-based biodegradable metals, insufficient strength and ductility, as well as relatively low fatigue strength, may lead to premature failure of medical devices. On the other hand, owing to the low melting point of the element Zn, several new uncertainties with regard to the mechanical properties of biomedical zinc alloys, including low creep resistance, high susceptibility to natural aging, and static recrystallization (SRX), may lead to device failure during storage at room temperature and usage at body temperature. This paper comprehensively reviews studies on these mechanical aspects of industrial Zn and Zn alloys in the last century and biomedical Zn and Zn alloys in this century. The challenges for the future design of biomedical zinc alloys as biodegradable metals to guarantee 100% mechanical compatibility are pointed out, and this will guide the mechanical property design of Zn-based biodegradable metals. STATEMENT OF SIGNIFICANCE: Previous studies on mechanical properties of industrial Zn and Zn alloys in the last century and biomedical Zn and Zn alloys in this century are comprehensively reviewed herein. The challenges for the future design of zinc-based biodegradable materials considering mechanical compatibility are pointed out. Common considerations such as strength, ductility, and fatigue behaviors are covered together with special attention on several new uncertainties including low creep resistance, high susceptibility to natural aging, and static recrystallization (SRX). These new uncertainties, which are not significantly observed in Mg-based and Fe-based materials, are largely due to the low melting point of the element Zn and may lead to device failure during storage at room temperature and clinical usage at body temperature. Future studies are urgently needed on these topics.

The conundrum of endovascular common femoral artery treatment: a case report of lithoplasty as a viable solution

BACKGROUND

Highly calcific stenosis located in common femoral artery (CFA) represents a difficult target for endovascular treatment due to the possible need for stent implantation in that area.

CASE SUMMARY

A 63-year-old man with history of coronary artery disease and previous multiple percutaneous transluminal angioplasties for peripheral artery disease (PAD) was admitted for recent onset left lower limb pain at rest with severe activity restriction (Leriche-Fontaine Class III and Rutherford Class III-IV). The angio-computed tomography scan showed a highly calcific stenosis of left CFA. The patient underwent lithoplasty balloon angioplasty followed by drug-eluting balloon inflation with excellent angiographic result and complete blood flow restoration. No procedural complications occurred.

DISCUSSION

Highly calcified stenosis in PAD represents a huge challenge for endovascular treatment as not all lower extremity arteries are suitable for stenting because of compressive and torsional forces associated with stent fracture and restenosis. Lithoplasty is a new technology allowing effective blood flow restoration while minimizing vessel injury.

The incidence and risk factors of stent fracture in patients treated for proximal common carotid artery stenosis

OBJECTIVE

Our aim was to identify the incidence of and predictors for common carotid artery (CCA) stent fractures (SFs) and to examine the effect of SFs on the development of in-stent restenosis (ISR).

METHODS

Seventy patients (37 women; median age, 60.9 years) who were stented for significant (≥60%) proximal CCA stenosis from 2006 to 2016 and revisited us to determine SF using fluoroscopy in 2018 were evaluated. Seventy stents were deployed; among them 87.1% were balloon-expandable and 12.9% were self-expandable. SFs were classified as type I (fracture of one strut), type II (fracture of multiple struts without stent deformity), type III (fracture of multiple struts with stent deformity), type IV (complete fracture of the stent without a gap), and type V (complete fracture of the stent with a gap). Duplex ultrasound examination was used for monitoring stent patency. Mann-Whitney U and Fisher's exact tests, Kaplan-Meier and logistic regression analyses, and a log-rank test and a gamma correlation analysis were applied as statistical methods.

RESULTS

The patients were followed for 75.5 months (range, 47-109 months). Significant (≥70%) ISR was observed in eight patients (11.4%). Reintervention was performed in four cases (5.7%). Twenty-seven SFs (38.6%; type I, 8; type II, 10; type III, 4; type IV, 2; and type V, 3) were found. Calcification was shown to be a significant predictor for SF (odds ratio, 13.2; 95% confidence interval, 3.9-45.1; P < .001). There was no significant difference between the fractured and the nonfractured group regarding the number of patients with ISR and reintervention (P = .701 and P = .636, respectively). Neither did the primary patency rates differ significantly (P = .372) in patients with and without SF.

CONCLUSIONS

Fractures frequently occur in a wide variety of stent devices deployed in the proximal CCA, but SFs seem to have no effect on ISR and reintervention.

An Animal Model of Human Peripheral Arterial Bending and Deformation

BACKGROUND

Designing peripheral arterial stents has proved challenging, as implanted devices will repetitively and unpredictably deform and fatigue during movement. Preclinical testing is often inadequate, given the lack of relevant animal models. The purpose of this study was to test the hypothesis that deformation of the human peripheral vasculature could be qualitatively and quantitatively modeled using an experimental animal.

METHODS

Anteroposterior contrast angiography was performed in domestic Landrace-Yorkshire farm pigs. Images were obtained with the hind limbs naturally extended then repeated, (1) flexed approximately 90° at the hip and knee, (2) overflexed in a nonphysiological fashion. Quantitative vascular angiographic analysis was utilized to measure arterial diameter, length, and deformation. Percent axial arterial compression and bending were assessed.

RESULTS

Eight iliofemoral arteries in four animals were imaged. Mean luminal diameters of the iliac and femoral segments in the neutral position were 5.4 ± 0.5 mm and 4.6 ± 0.5 mm. Hind limb physiologic flexion induced profound arterial compression, 17 ± 8% and 29 ± 6% and bending, 36°±10° and 76° ± 13° within the iliac and femoral segments, respectively. With extreme flexion, the femoral artery could be reliably bent >90°. The observed findings exceeded the deformation observed historically within the human superficial femoral (∼5% compression and 10° bending) and popliteal artery (∼10% compression and 70° bending).

CONCLUSIONS

Significant nonradial deformation of the porcine iliofemoral arteries was observed during manual hind limb flexion and exceeded that typically observed in humans. This model constitutes a "worst case" scenario for testing deformation and fatigue of intravascular devices indicated for the human peripheral vasculature.

Systematic Review and Proportional Meta-Analysis of Endarterectomy and Endovascular Therapy with Routine or Selective Stenting for Common Femoral Artery Atherosclerotic Disease

Introduction

Common femoral endarterectomy (CFE) has been the therapy of choice for common femoral artery atherosclerotic disease (CFA-ASD). In the past, there was inhibition to treat CFA-ASD endovascularly with stents due to fear of stent fracture and compromise of future vascular access site. However, recent advances and new evidence suggest that CFA may no longer be a ‘stent-forbidden zone'. In the light of new evidence, we conducted a meta-analysis to determine the use of endovascular treatment for CFA-ASD and compare it with common femoral endarterectomy in the present era.

Methods

Using certain MeSH terms we searched multiple databases for studies done on endovascular and surgical treatment of CFA-ASD in the last two decades. Inclusion criteria were randomized control trials, observational, prospective, or retrospective studies evaluating an endovascular treatment or CFE for CFA-ASD. For comparison, studies were grouped based on the treatment strategy used for CFA-ASD: endovascular treatment with selective stenting (EVT-SS), endovascular treatment with routine stenting (EVT-RS), or common femoral endarterectomy (CFE). Primary patency (PP), target lesion revascularization (TLR), and complications were the outcomes studied. We did proportional meta-analysis using a random-effect model due to heterogeneity among the included studies. If confidence intervals of two results do not overlap, then statistical significance is determined.

Results

Twenty-eight studies met inclusion criteria (7 for EVT-RS, 8 for EVT-SS, and 13 for CFE). Total limbs involved were 2914 (306 in EVT-RS, 678 in EVT-SS, and 1930 in CFE). The pooled PP at 1 year was 84% (95% CI 75-92%) for EVT-RS, 78% (95% CI 69-85%) for EVT-SS, and 93% (95% CI 90-96%) for CFE. PP at maximum follow-up in EVT-RS was 83.7% (95% CI 74-91%) and in CFE group was 88.3% (95% CI 81-94%). The pooled target lesion revascularization (TLR) rate at one year was 8% (95% CI 4-13%) for EVT-RS, 19% (95% CI 14-23%) for EVT-SS, and 4.5% (95% CI 1-9%) for CFE. The pooled rate of local complications for EVT-RS was 5% (95% CI 2-10%), for EVT-SS was 7% (95% CI 3 to 12%), and CFE was 22% (95% CI 14-32%). Mortality at maximum follow-up in CFE group was 23.1% (95% CI 14-33%) and EVT-RS was 5.3% (95% CI 1-11%).

Conclusion

EVT-RS has comparable one-year PP and TLR as CFE. CFE showed an advantage over EVT-SS for one-year PP. The complication rate is lower in EVT RS and EVT SS compared to CFE. At maximum follow-up, CFE and EVT-RS have similar PP but CFE has a higher mortality. These findings support EVT-RS as a management alternative for CFA-ASD.

The presence of long and heavily calcified lesions predisposes for fracture in patients undergoing stenting of the first part of the subclavian artery

OBJECTIVE

To determine the prevalence and risk factors of subclavian artery stent fractures and to investigate their impact on in-stent restenosis development.

METHODS

One hundred eight patients (65 females; median age, 58.3 years [interquartile range, 53.4-65.5 years]) with steno-occlusive disease of the first part of the subclavian artery who underwent stenting (N = 108 stents; balloon-expandable, 83.3%; self-expandable, 16.7%) between 2005 and 2015 and returned for a fluoroscopic examination of the implanted stents in 2017 were included in our study. Fractures were type I (single strut fracture), type II (multiple strut fractures without deformation), type III (multiple strut fractures with deformation), type IV (multiple strut fractures with acquired transection but without gap), or type V (multiple strut fractures with acquired transection with gap in the stent body). Stent patency was monitored by duplex ultrasound imaging. The Mann-Whitney U and Fisher's exact tests; Kaplan-Meier, receiver operating characteristic, and logistic regression analyses; as well as a log-rank test were used as statistical methods.

RESULTS

The median follow-up was 73.8 months (interquartile range, 35.6-104.2 months). Thirty-eight fractures (35.2%) were detected; fractures were type I in 13, type II in 12, type III in 6, type IV in 4, and type V in 3 cases. Multivariable logistic regression analysis revealed the presence of long (≥20 mm) lesions (odds ratio, 3.3; 95% confidence interval, 1.3-8.4; P = .012) and heavy calcification (odds ratio, 4.7; 95% confidence interval, 1.7-12.7; P = .002) to be significant independent predictors of stent fracture. The primary patency rates were significantly worse (P = .035) in patients with stent fracture compared with those without stent fracture.

CONCLUSIONS

Stent fractures frequently occur. Patients with long and/or heavily calcified lesions require closer follow-up.

Pro-resolving lipid mediators in the resolution of neointimal hyperplasia pathogenesis in atherosclerotic diseases

INTRODUCTION

Despite advances in drug eluting technologies, neointimal hyperplasia (NIH) and restenosis still plagues endovascular therapy in atherosclerotic diseases. By appreciating atherosclerosis and NIH as complex inflammatory processes, specialized pro-resolving mediators (SPMs) are a superfamily of endogenous unsaturated fatty-acid derived lipids with the potential for inflammatory resolution. Areas covered: Inquiry into SPMs in this context is a novel approach and is the focus of this review, with emphasis on our understanding with NIH. Prior mechanistic understandings of SPM deficiency with atherosclerosis has offered insight, as well as the complexity and diversity of the SPM superfamily. Therapeutic investigation using SPMs to combat NIH is also evaluated here. Expert commentary: Endogenous deficiency of SPMs synthesis by 12/15-lipoxygenase underlies resolution deficits in atherosclerosis and NIH. Upstream PDGF inhibition by SPMs, most notably RvD1 and LXA4, confers a multifactorial attenuation of NIH that involves interconnected anti-inflammatory efforts, most notably switch pro-resolving smooth muscle cells (vSMCs) and macrophages. The ALX/FPR2 is one receptor system identified on vSMCs that interacts with these SPMs to promote NIH resolution. Therapeutically, while shown to be promising with less stent burden or cytotoxicity, SPMs must be balanced by necessary mechanistic, pharmacokinetic and anatomical considerations.

Endovascular Treatment of Simultaneous Iliac and Superficial Femoral Arterial Pseudoaneurysms After Stenting Procedure Complications

PURPOSE:

To report on the endovascular management of a patient affected by concomitant left common iliac artery and right superficial femoral artery (SFA) pseudoaneurysms after stent positioning.

CASE REPORT:

A 77-year-old man affected by severe lower limb atherosclerosis was previously treated with iliac and femoropopliteal Supera stenting procedures; he presented to our emergency department because of bilateral severe claudication recurrence, back pain, and right groin region swelling. Angio-computed tomography (CT) depicted 2 pseudoaneurysms of the left common iliac artery and right SFA, due to stent fracture and stent intussusception, respectively. A 2-step endovascular treatment was planned using bilaterally covered stent-grafts to exclude vascular lesions from blood flow. The devices were successfully deployed without any complication. At 1 month, angio-CT confirmed patency of the implanted stent-grafts showing complete pseudoaneurysm exclusion without leaks.

CONCLUSION:

Endovascular approach can be a valid option in the treatment of pseudoaneurysms due to stenting procedure complications.

Nanoparticles for Detection and Treatment of Peripheral Arterial Disease

Peripheral arterial disease (PAD) is defined as a slow, progressive disorder of the lower extremity arterial vessels characterized by chronic narrowing that often results in occlusion and is associated with loss of functional capacity. Although the PAD occurrence rate is increasing in the elderly population, outcomes with current treatment strategies are suboptimal. Hence, there is an urgent need to develop new technologies that overcome limitations of traditional modalities for PAD detection and therapy. In this Review, the application of nanotechnology as a tool that bridges the gap in PAD diagnosis and therapy is in focus. Several materials including synthetic, natural, biodegradable, and biocompatible materials are used to develop nanoparticles for PAD diagnostic and/or therapeutic applications. Moreover, various recent research approaches are being explored to diagnose PAD through multimodality imaging with different nanoplatforms. Further efforts include targeted delivery of various therapeutic agents using nanostructures as carriers to treat PAD. Last, but not least, despite being a fairly new field, researchers are exploring the use of nanotheranostics for PAD detection and therapy.

Nitinol Stents in the Femoropopliteal Artery: A Mechanical Perspective on Material, Design, and Performance

Endovascular stenting has matured into a commonly used treatment for peripheral arterial disease (PAD) due to its minimally invasive nature and associated reductions in short-term morbidity and mortality. The mechanical properties of the superelastic Nitinol alloy have played a major role in the explosion of peripheral artery stenting, with modern stents demonstrating reasonable resilience and durability. Yet in the superficial femoral and popliteal arteries, even the newest generation Nitinol stents continue to demonstrate clinical outcomes that leave significant room for improvement. Restenosis and progression of native arterial disease often lead to recurrence of symptoms and reinterventions that increase morbidity and health care expenditures. One of the main factors thought to be associated with stent failure in the femoropopliteal artery (FPA) is the unique and highly dynamic mechanical environment of the lower limb. Clinical and experimental data demonstrate that the FPA undergoes significant deformations with limb flexion. It is hypothesized that the inability of many existing stent designs to conform to these deformations likely plays a role in reconstruction failure, as repetitive movements of the leg and thigh combine with mechanical mismatch between the artery and the stent and result in mechanical damage to both the artery and the stent. In this review we will identify challenges and provide a mechanical perspective of FPA stenting, and then discuss current research directions with promise to provide a better understanding of Nitinol, specific features of stent design, and improved characterization of the biomechanical environment of the FPA to facilitate development of better stents for patients with PAD.

Serial Versus Direct Dilation of Small Diameter Stents Results in a More Predictable and Complete Intentional Transcatheter Stent Fracture: A PICES Bench Testing Study

Balloon-expandable stents, implanted in infants and children with congenital heart disease (CHD), often require redilation to match somatic growth. Small diameter stents may eventually require longitudinal surgical transection to prevent iatrogenic vascular stenosis. Intentional transcatheter stent fracture (TSF) is an emerging alternative approach to stent transection, but little is known about the optimal stent substrate and best protocol to improve the likelihood of successful TSF. Bench testing was performed with a stent dilation protocol. After recording baseline characteristics, stents were serially or directly dilated using ultra-high-pressure balloons (UHPB) until fracture occurred or further stent dilation was not possible. Stent characteristics recorded were as follows: cell design, metallurgy, mechanism, and uniformity of fracture. Stents tested included bare-metal coronary stents, premounted small diameter stents, and ePTFE-covered small diameter premounted stents. Ninety-four stents representing 9 distinct models were maximally dilated, with 80 (85%) demonstrating evidence of fracture. Comprehensive fracture details were recorded in 64 stents: linear and complete in 34/64 stents (53.1%), linear and incomplete in 9/64 stents (14.1%), transverse/complex and complete in 6/64 stents (9.4%), and transverse/complex and incomplete in 15/64 stents (23.4%). Stent fracture was not accomplished in some stent models secondary to significant shortening, i.e., "napkin-ring" formation. Serial dilation resulted in evidence of fracture in 62/67 (92.5%) stents compared with 18/27 (66.7%) stents in the direct dilation group (p = 0.003). Intentional TSF is feasible in an ex vivo model. Serial dilation more reliably expanded the stent and allowed for ultimate stent fracture, whereas direct large diameter dilation of stents was more likely to generate a "napkin-ring" configuration, which may be more resistant to fracture. In vivo animal and human testing is necessary to better understand the response to attempted TSF for newly developed stents as well as those currently in use.

Calcified plaque modification alters local drug delivery in the treatment of peripheral atherosclerosis

BACKGROUND

Calcific atherosclerosis is a major challenge to intraluminal drug delivery in peripheral artery disease (PAD).

OBJECTIVES

We evaluated the effects of orbital atherectomy on intraluminal paclitaxel delivery to human peripheral arteries with substantial calcified plaque.

METHODS

Diagnostic angiography and 3-D rotational imaging of five fresh human lower limbs revealed calcification in all main arteries. The proximal or distal segment of each artery was treated using an orbital atherectomy system (OAS) under simulated blood flow and fluoroscopy. Explanted arterial segments underwent either histomorphometric assessment of effect or tracking of ¹⁴C-labeled or fluorescent-labeled paclitaxel. Radiolabeled drug quantified bulk delivery and fluorescent label established penetration of drug over finer spatial domain in serial microscopic sections. Results were interpreted using a mathematical model of binding-diffusion mediated arterial drug distribution.

RESULTS

Lesion composition affected paclitaxel absorption and distribution in cadaveric human peripheral arteries. Pretreatment imaging calcium scores in control femoropopliteal arterial segments correlated with a log-linear decline in the bulk absorption rate-constant of ¹⁴C-labeled, declining 5.5-fold per calcified quadrant (p=0.05, n=7). Compared to controls, OAS-treated femoropopliteal segments exhibited 180μm thinner intima (p<0.001), 45% less plaque calcification, and 2 log orders higher paclitaxel bulk absorption rate-constants. Correspondingly, fluorescent paclitaxel penetrated deeper in OAS-treated femoropopliteal segments compared to controls, due to a 70% increase in diffusivity (p<0.001).

CONCLUSIONS

These data illustrate that calcified plaque limited intravascular drug delivery, and controlled OAS treatment of calcific plaques resulted in greater drug permeability and improved adjunct drug delivery to diseased arteries.

Effect of Applied Potential on Fatigue Life of Electropolished Nitinol Wires

Nitinol is used as a metallic biomaterial in medical devices due to its shape memory and pseudoelastic properties. The clinical performance of nitinol depends on factors which include the surface finish, the local environment, and the mechanical loads to which the device is subjected. Preclinical evaluations of device durability are performed with fatigue tests while electrochemical characterization methods such as ASTM F2129 are employed to evaluate corrosion susceptibility by determining the rest potential and breakdown potential. However, it is well established that the rest potential of a metal surface can vary with the local environment. Very little is known regarding the influence of voltage on fatigue life of nitinol. In this study, we developed a fatigue testing method in which an electrochemical system was integrated with a rotary bend wire fatigue tester. Samples were fatigued at various strain levels at electropotentials anodic and cathodic to the rest potential to determine if it could influence fatigue life. Wires at potentials negative to the rest potential had a significantly higher number of cycles to fracture than wires held at potentials above the breakdown potential. For wires for which no potential was applied, they had fatigue life similar to wires at negative potentials.

Crush Deformation of a Balloon-Expandable Stent Implanted in an Infrainguinal Bypass Graft

A 59-year-old man with critical claudication underwent left femoro-anterior bypass grafting, which was uneventful. The graft was tunneled medially across the knee, then anterior to the tibia. His symptoms recurred 1 year later and he was found to have critical stenosis of the vein graft just proximal to the anterior tibial arterial anastomosis. This was treated with scaffolded balloon angioplasty and implantation of a coronary, zotarolimus-eluting balloon-expandable stent, which was also uneventful. However, his claudication again recurred 1 year later. Diagnostic angiography revealed crush, deformation and restenosis of the balloon-expandable stent requiring surgical revision of the bypass graft.

Fractured Superior Mesenteric Artery Stent With Stent Displacement Leading to Recurrent Symptoms of Superior Mesenteric Ischemia

We report a case of a patient with recurrent symptoms of superior mesenteric ischemia 7 months after successful percutaneous angioplasty and implantation of a stent in the superior mesenteric artery (SMA). Stent fracture and stent displacement were observed. To the best of our knowledge, this is the first report of SMA stent fracture with stent displacement.

One-year results of primary stenting for TASC II D lesions of the superficial femoral and popliteal arteries

Objective This study aimed to evaluate the safety and the efficacy of primary stenting to treat Trans-Atlantic Inter-Society Consensus II (TASC) D femoropopliteal lesions. Background Advances in wire, balloon and stent design have been reported to improve the durability of stenting of longer femoropopliteal lesions. Methods A total of 57 limbs of 53 patients with Rutherford stage 3 to 6 due to TASC D femoropopliteal lesions were treated with a self-expanding nitinol stent in a prospective, single-centre, observational study. End points of interest included primary and secondary patency, target lesion revascularization, in-stent restenosis, major adverse cardiovascular events, Rutherford class improvement and change in walking capacity at 1 year. Results A total of 53 patients (57 lesions) were treated with a self-expanding nitinol stent and final procedural success was 91.2%. The median length of the treated segment was 330 ± 96 mm. The median stented segment was 366 ± 71 mm and the mean number of the stents was 2.1 ± 0.9. At 1 year, primary and secondary patency rates were 63.9% and 82.1%, respectively. Major adverse cardiovascular events occurred in 11 patients (22.9%), and[[strike_start]] [[strike_end]]significant benefits were observed in Rutherford class and walking distance (both P < 0.001). Conclusions Primary implantation of self-expanding nitinol stents for the treatment of TASC D femoropopliteal lesions appears to be safe and effective, especially in patients who have multiple co-morbidities and a high risk for surgical bypass. The risk of restenosis was higher when long stenting was extended to the popliteal artery.

In Vivo Quantification of the Deformations of the Femoropopliteal Segment: Percutaneous Transluminal Angioplasty vs Nitinol Stent Placement

PURPOSE

To quantify the deformations of the femoropopliteal (FP) segment in patients undergoing endovascular revascularization and to compare the posttreatment deformations caused by primary nitinol stent implantation to those produced by percutaneous transluminal angioplasty (PTA).

METHODS

Thirty-five patients (mean age 69±10 years; 20 men) scheduled for endovascular therapy were recruited for the study. During endovascular interventions, angiographic images were acquired with the legs straight and with a hip/knee flexion of 20°/70°. Image acquisition was performed before PTA for all patients, after PTA in 17 patients receiving this treatment only, and after primary stent implantation in the remaining 18 patients. A semiautomatic approach was used to reconstruct the 3-dimensional patient-specific artery models from 2-dimensional radiographs. Axial shortening and curvature changes in the arteries in vivo were calculated for the calcified, dilated, and stented regions, as well as the regions that were distal and proximal to the diseased and treated segments.

RESULTS

Leg flexion resulted in shortening of the artery in all investigated FP segments. The dilated arteries exhibited greater shortening compared with their stented counterparts (post-PTA 7.6%±4.9%, poststent 3.2%±2.9%; p=0.004). Leg flexion also led to an increase in the curvatures of all the sections of the FP segment. While stented arteries had significantly higher curvature values than PTA within the regions proximal to the treated sections, the choice of the treatment method did not affect the curvature of the other segments. Despite this, 40% of the stented arteries exhibited kinking during leg flexion.

CONCLUSION

The choice of the treatment method affects the postinterventional axial deformations of the FP segment but does not influence the curvature behavior. While PTA results in a more flexible artery, stents restrict the arteries' shortening capabilities. Depending on the anatomical position of the stents, this axial stiffening of the arteries may lead to chronic kinking, which may cause occlusions and, consequently, affect the long-term success of the procedure.

A method to determine the kink resistance of stents and stent delivery systems according to international standards

The kink behavior of vascular stents is of particular interest for clinicians, stent manufacturers and regulatory as a kinked stent generates a lumen loss in the stented vessel and can lead to in-stent restenosis. In this study methods to determine the kink resistance of stents and stent delivery systems according to the ISO 25539-2 and FDA guidance no. 1545 were presented. The methods are applicable for balloon expandable stents as well as for self-expanding stents and determine the lumen loss and residual diameter change dependent on the specific bending radius.