Stent Failure Research Articles

Incidence, Clinical Relevance and Treatment Options for Outflow Graft Stenosis after LVAD Implantation

LVAD outflow graft stenosis (OGS) is increasingly recognized after left ventricular assist device implantation. We analyzed our institutional experience with (OGS) in order to better understand the clinical significance and treatment options for this new form of pump pathology. We retrospectively reviewed our institutional experience with OGS in patients with contemporary centrifugal LVAD. Study endpoint were incidence and outcomes of LVAD OGS. From March 2006 to October 2019, 284 consecutive patients (183 (64.4%) HVAD and 101 (35.6%) HeartMate3) underwent primary LVAD implantation. Median follow up was 456 (range 1-2921) days. OGS was identified in 17 patients (total incidence 5.0%, 95% CI 3.5%-9.4%; HVAD: 5.5%, 95% CI 2.7%-9.8% vs. HeartMate3 6.9%, 95% CI 2.8%-13.8%, p=0.611). Median time to OGS development was 911 (range 281-2811) days. In all cases, OGS was located within covered segments of the outflow graft (bend relief (Heartmate 3 only) or protective Gore-Tex cover). In 13 patients (76.5%) OGS impaired LVAD flow and necessitated interventions (surgical revision n=2, endovascular stent placement n=9, surgery after failed stent placement n=1, death before intervention n=1). Two patients (11.8%) died following intervention and outflow graft stenosis recurred in two patients (11.8%) after initially successful treatment. Kaplan-Meier estimate of survival free from outflow graft stenosis is depicted on Figure 1. Outflow graft stenosis is a potentially lethal late complication of LVAD implantation. Surgical or interventional treatment is indicated when LVAD flows are impaired. Modification of pump design may be warranted as outflow graft stenosis preferentially occur in covered portions of outflow grafts.

An Anomalous Mechanism Causing Failure of Expanded Polytetrafluoroethylene-Covered Nitinol Stents, Evaluated Using Multiple Intravascular Imaging Modalities

A 73-year-old man with peripheral artery disease, diabetes mellitus, hypertension, and end-stage kidney disease on hemodialysis was admitted to the hospital with right lower limb pain. He had previously undergone stent implantations in the right superficial femoral artery (SFA) on 2 separate

The multiple roles of chemokines in the mechanisms of stent biocompatibility.

While the advent of drug-eluting stents has been clinically effective in substantially reducing the rates of major stent-related adverse events compared with bare metal stents, vascular biological problems such as neointimal hyperplasia, delayed re-endothelialization, late stent thrombosis are not eliminated and, increasingly, neoatherosclerosis is the underlying mechanism for very late stent failure. Further understanding regarding the mechanisms underlying the biological responses to stent deployment is therefore required so that new and improved therapies can be developed. This review will discuss the accumulating evidence that the chemokines, small inflammatory proteins, play a role in each key biological process of stent biocompatibility. It will address the chemokine system in its specialized roles in regulating the multiple facets of vascular biocompatibility including neointimal hyperplasia, endothelial progenitor cell (EPC) mobilization and re-endothelialization after vascular injury, platelet activation and thrombosis, as well as neoatherosclerosis. The evidence in this review suggests that chemokine-targeting strategies may be effective in controlling the pathobiological processes that lead to stent failure. Preclinical studies provide evidence that inhibition of specific chemokines and/or broad-spectrum inhibition of the CC-chemokine class prevents neointimal hyperplasia, reduces thrombosis and suppresses the development of neoatherosclerosis. In contrast, however, to these apparent deleterious effects of chemokines on stent biocompatibility, the CXC chemokine, CXCL12, is essential for the mobilization and recruitment of EPCs that make important contributions to re-endothelialization post-stent deployment. This suggests that future chemokine inhibition strategies would need to be correctly targeted so that all key stent biocompatibility areas could be addressed, without compromising important adaptive biological responses.

Stent coating by electrospinning with chitosan/poly-cyclodextrin based nanofibers loaded with simvastatin for restenosis prevention

The main cause of failure of angioplasty stenting is restenosis due to neointimal hyperplasia, a too high proliferation of smooth muscle cells (SMC). The local and sustained delivery of selective pleiotropic drugs to limit SMC proliferation seems to be the hopeful solution to minimize this post surgery complication. The aim of this study is to develop a stent covered by nanofibers (NFs) produced by electrospinning, loaded with simvastatin (SV), a drug commonly used for restenosis prevention. NFs were prepared from the electrospinning of a solution containing SV and a mixture of chitosan (cationic) and β-cyclodextrin (CD) polymer (anionic) which form together a polyelectrolyte complex that makes up the NFs matrix. First, the SV/CD interactions were studied by phase solubility diagram, DRX and DSC. The electrospinning process was then optimized to cover a self-expandable NiTiNOL stent and the mechanical resistance of the NFs sheath upon its introduction inside the delivery catheter was considered, using a crimper apparatus. The morphology, coating thicknesses and diameters of nanofibers were studied by scanning electron microscopy. The SV loading rates on the stents were controlled by the electrospinning time, and the presence of SV in the NFs was confirmed by FTIR. NFs stability in PBS pH 7.4 buffer could be improved after thermal post-treatment of NFs and in vitro release of SV in dynamic conditions demonstrated that the release profiles were influenced by the presence of CD polymer in NFs and by the thickness of the NFs sheath. Finally, a covered stent delivering 3 µg/mm2 of SV within 6 h was obtained, whose efficiency will be investigated in a further in vivo study.

Chimney Stenting for Coronary Occlusion During TAVR: Insights From the Chimney Registry

ObjectivesThe aim of this study was to determine the safety and efficacy of chimney stenting, a bailout technique to treat coronary artery occlusion (CAO). BackgroundCAO during transcatheter aortic valve replacement (TAVR) is a rare but often fatal complication. MethodsIn the international Chimney Registry, patient and procedural characteristics and data on outcomes are retrospectively collected from patients who underwent chimney stenting during TAVR. ResultsTo date, 16 centers have contributed 60 cases among 12,800 TAVR procedures (0.5%). Chimney stenting was performed for 2 reasons: 1) due to the development of an established CAO (n = 25 [41.6%]); or 2) due to an impending CAO (n = 35 [58.3%]). The majority of cases (92.9%) had 1 or more classical risk factors for CAO. Upfront coronary protection was performed in 44 patients (73.3%). Procedural and in-hospital mortality occurred in 1 and 2 patients, respectively. Myocardial infarction (52.0% vs. 0.0%; p < 0.01), cardiogenic shock (52.0% vs. 2.9%; p < 0.01), and resuscitation (44.0% vs. 2.9%; p < 0.01) all occurred more frequently in patients with established CAO compared with those with impending CAO. The absence of upfront coronary protection was the sole independent risk factor for the combined endpoint of death, cardiogenic shock, or myocardial infarction. During a median follow-up time of 612 days (interquartile range: 405 to 842 days), 2 cases of stent failure were reported (1 in-stent restenosis, 1 possible late stent thrombosis) after 157 and 374 days. ConclusionsChimney stenting appears to be an acceptable bailout technique for CAO, with higher event rates among those with established CAO and among those without upfront coronary protection.

Technique of Xen Implant Revision Surgery and the Surgical Outcomes: A Retrospective Interventional Case Series.

PurposeThe Xen® Gel Stent (Allergan, Irvine, CA, USA) is a minimally invasive glaucoma surgery device implanted to reduce intra-ocular pressure (IOP) in glaucoma. The stents can fail to drain post-operatively due to scarring of the conjunctiva around the stent opening. Data on the success rates of revision surgery in patients with Xen stent failure are scarce. We present the first detailed report of the steps, outcomes and complications of Xen revision surgery with 12 months of follow-up data.MethodsWe share our experiences on the circumstances in which to perform Xen revision surgery, the steps of the surgery and the results of a retrospective interventional case series of all Xen revisions performed at a single centre from 2013 to 2018.ResultsA total of 151 Xen implants were inserted into eyes at our tertiary centre during the study period, of which 21 eyes (patients) underwent revision surgery. Mean pre-operative IOP was 26.1 (standard deviation 8.3) mmHg with the patient on two drops of anti-glaucoma medication. Four patients were excluded from the analysis due to incomplete data (medical records were unavailable for 2 patients; 1 patient died shortly after surgery; and 1 patient moved to another area). A non-functioning Xen implant was identified in another patient during revision surgery, and the procedure was converted to a trabeculectomy. The remaining 16 patients were included in the analysis, all of whom had a minimum follow-up of 12 months, with the longest follow-up being 4 years following revision surgery. Of these 16 patients, four required needling and 5-fluorouracil injection in the first 12 months following revision surgery, three required further glaucoma drainage surgery due to the failure of the revision surgery to control IOP in the first year and one suffered bleb-related endophthalmitis at the site of previous trabeculectomy surgery. Mean IOP at 12 months following revision surgery was 16.3 (standard deviation 3.7) mmHg on 0.7 drops of anti-glaucoma medication, which equates to a 37.5% reduction in IOP and a 65% reduction in the amount of IOP-lowering drops required.ConclusionOur study shares experience on when to perform Xen revision surgery and the steps required. The results of our small cohort are the first in the literature and show that revisions can achieve promising IOP and medication reductions. Some patients still require needling in the post-operative period to optimise outcomes.

Pathology and Multimodality Imaging of Acute and Chronic Femoral Stenting in Humans

ObjectivesThe objective of this study was to comprehensively evaluate the pathology of acute and chronic femoral stenting in symptomatic atherosclerotic patients and to understand the causes of stent failure (SF) using multimodality imaging including micro–computed tomography. BackgroundAlthough the pathology of coronary stenting has been well studied, the pathology of lower extremity femoral stenting remains poorly understood. MethodsTwelve stented femoral lesions removed at surgery (n = 10) and at autopsy (n = 2) were obtained from 10 patients (median age 74 years; interquartile range [IQR]: 66 to 82 years) with histories of peripheral artery disease (critical limb ischemia in 7) (7 men and 3 women). All specimens underwent radiography, micro–computed tomography, and histological assessment. ResultsThe median duration of implantation was 150 days (IQR: 30 to 365 days), the median stent diameter was 5.90 mm (IQR: 5.44 to 7.16 mm), and the median stent length was 39.5 mm (IQR: 27 to 107.5 mm). Of the 12 stented lesions, 2 had drug-eluting stents, and 10 had bare-metal stents. SF was observed in 8 of 12 lesions. The major cause of SF was acute thrombosis (6 of 8), but causes varied (delayed healing, stent underexpansion, false lumen stenting, and fracture), and 2 had restenosis. Stent fractures were observed in 3 cases by micro–computed tomography. Both drug-eluting stents, implanted for >1 year, showed delayed healing with circumferential peristrut fibrin deposition and SF. ConclusionsThis histological study is the first to examine the pathological cause of SF. Stent thrombosis was the major cause of SF. Delayed healing was a common feature of bare-metal stents implanted for <90 days, while all drug-eluting stents, despite implantation duration >1 year, showed delayed healing.

Comparative Computational Study of Mechanical Behavior in Self-Expanding Femoropopliteal Stents

The use of the stent to treat peripheral artery disease (PAD) is increased and the proportion of failures also increases. The femoropopliteal artery (FPA) experiences a high deformation ratio compared to the cardiovascular artery due to limp flexion and daily activities that could lead to stent failure, as well as increasing the number of observed mortality and morbidity. In the present work, two of the common PAD stent design models represented as STENT I and STENT II were analyzed by using of finite element method (FEM) to simulate the most mechanical loading modes that could occur in FPA, such as axial tension and compression, torsion, three-point bending and radial compression to give a good understanding of deformation that affected stent inside the in-vivo. The gradual force load was used to simulate all modes, the force values are 0.25 N, 0.5 N, 1.5 N, 2.5 N, 3.5 N and 5.5 N until the stent models obtain the yield-point. The comparison of stent models (STENT I, STENT II) was performed in terms of graphs of total deformation, force-stress and stress-strain for all test modes. The similarity ratio of the total deformation in axial tension and the compression mode for STENT I and STENT II was 17% and that may indicate that STENT I obtained a high deformation value instead of STENT II, while, the torsion similarity ratio was 86% which could show a good agreement in this mode, as well as the similarity ratio, was 78% of the total three-point bending deformation and the value of the similarity ratio in the radial compression mode was 23%. Still unclear what is the clinical mode of mechanical deformation that is more important than others with changing the length of the lesion and stent diameter, and the fatigue life test provides a better understanding of the mechanical tests that must be sought.

Case Report: The Role of Intravascular Ultrasonography in Patients Underwent Percutaneous Coronary Intervention

Intravascular ultrasonography (IVUS) has an important role as a complimentary diagnostic tool in percutaneous coronary intervention procedure. IVUS provides valuable information regarding coronary vessel lumen and dimension and also plaque burden and its characteristic. The main use of IVUS in PCI is to guide the choose of interventional strategies to optimize stent deployment. Since drug eluting stent (DES) has promised to decrease the incidence in stent restenosis and stent thrombosis than bare metal stent, but neither the suboptimal results nor the complication after stenting with DES is still high. Thus, optimization of stent deployment under IVUS guidance is important in cases to decrease stent failure after PCI procedure, as well as to decrease complication rate after stenting in order to decrease mortality rate caused by coronary artery disease. We present here the use of IVUS guidance in a 43 and 46 year-old man underwent PCI.

Post-dilatation improves stent apposition in patients with ST-segment elevation myocardial infarction receiving primary percutaneous intervention: A multicenter, randomized controlled trial using optical coherence tomography.

Stent failure is more likely in the lipid rich and thrombus laden culprit lesions underlying ST-segment elevation myocardial infarction (STEMI). This study assessed the effectiveness of post-dilatation in primary percutaneous coronary intervention (pPCI) for acute STEMI. The multi-center POST-STEMI trial enrolled 41 consecutive STEMI patients with symptom onset <12 hours undergoing manual thrombus aspiration and Promus Element stent implantation. Patients were randomly assigned to control group (n=20) or post-dilatation group (n=21) in which a non-compliant balloon was inflated to >16 atm pressure. Strut apposition and coverage were evaluated by optical coherence tomography (OCT) after intracoronary verapamil administration via thrombus aspiration catheter, post pPCI and at 7-month follow-up. The primary endpoint was rate of incomplete strut apposition (ISA) at 7 months after pPCI. There were similar baseline characteristics except for stent length (21.9 [SD 6.5] mm vs. 26.0 [SD 5.8] mm, respectively, P=0.03). In post-dilatation vs. control group, ISA rate was lower (2.5% vs. 4.5%, P=0.04) immediately after pPCI without affecting final TIMI flow 3 rate (95.2% vs. 95.0%, P>0.05) or corrected TIMI frame counts (22.6±9.4 vs. 22.0±9.7, P>0.05); and at 7-month follow-up (0.7% vs. 1.8%, P<0.0001), the primary study endpoint, with similar strut coverage (98.5% vs. 98.4%, P=0.63) and 1-year rate of major adverse cardiovascular events (MACE). In STEMI patients, post-dilatation after stent implantation and thrombus aspiration improved strut apposition up to 7 months without affecting coronary blood flow or 1-year MACE rate. Larger and longer term studies are warranted to further assess safety (ClinicalTrials.gov identifier: NCT02121223).

Ultrathin (60 μm), ultralong (≥40 mm) sirolimus-eluting stent: study of clinical and safety profiles among real-world patients.

Although thin-strut drug-eluting stents (DES) with a more flexible design are easily obtainable, data regarding using ultralong DES (≥40 mm) for long coronary lesions are limited in the literature. Therefore, the current study assessed the safety and efficacy of an ultralong (≥40 mm) and ultrathin (60 μm) biodegradable polymer-coated sirolimus-eluting stent (SES), Supralimus Grace, with a unique Long Dual Z-link (LDZ-link) design (Sahajanand Medical Technologies Pvt. Ltd., Surat, India) in real-world patients with long coronary lesions. The assigned stents were implanted in 684 patients. The primary endpoint was target lesion failure (TLF), which is a composite of cardiovascular death, target vessel myocardial infarction (MI), and target lesion revascularization (TLR), whereas periprocedural secondary endpoints included device failure (failure of stent delivery, change of stent, and stent fracture) and patient-oriented composite endpoint (POCE), which is a composite of all deaths, any MI, and any revascularization, and stent thrombosis (ST). These outcomes were analyzed at one-year follow-up and during the procedure. The patients' mean age was 52.7±15.9 years; 537 (78.5%) were males. 626 (91.5%) patients suffered from acute coronary syndrome and 58 (8.5%) patients from chronic coronary syndrome (CSS). 989 lesions were removed. The mean numbers of lesions and stents implanted per patient were 1.3±0.2 mm and 1.4±0.3 mm, respectively. TLF occurred in 42 (6.1%) as a result of cardiac death, target vessel MI, and TLR in 9 (1.3%), 20 (2.9%), and 13 (1.9%) patients, respectively. POCE was observed in 131 patients (19.1%) at one-year follow-up, mainly in 63 (9.2%) patients because of any revascularization. Stent failure was seen in 21 patients (3.1%) as a result of delivery failure (2.2%), edge dissection (0.8%), and fracture (0.1%). Definite and probable ST were observed in 8 (1.1%) and 9 (1.3%) patients, respectively. Ultralong (≥40 mm), ultrathin (60 μm) Supralimus Grace stent can be safely implanted in vessels having long and multiple lesions.

Structural analysis of bulk metallic glass cardio-vascular stent under dynamic and failure criteria

Failure of Cardio-vascular stents is a predominant and persistent problem in cardiology to which the structural analysis of the stent is the primary and necessary solution. In this research, the structural analysis of Bare Metallic Stent designed for Cu-Zr-Al Bulk Metallic Glass (BMG) material is performed. BMGs have outstanding properties like high yield and UTS, toughness, and good fatigue life. Due to characteristics like zero inherent defects, grain boundaries, non-toxicity and non-corrosiveness makes them feasible materials for coronary stents. The structural analysis of the coronary stent is carried out based on Dynamic and Failure modes, involving bending, torsion, and fatigue (US-FDA standards). The presiding factors are analysed in FEM using ANSYS-Static-Structural and the fatigue analysis involving CFD in ANSYS-Fluent. In the dynamic mode under Von-Mises criterion, using the bending force of 0.17 N the total deformation of BMG coronary stent is 0.02 mm while under the torque of the same magnitude the total deformation is 0.002 mm in the longitudinal direction. Fatigue test carried out at 400 million cycles using Goodman criterion yielded a total deformation of 1.1 × 10−5 mm, the stress of 0.42 MPa with a factor of safety 15 and fatigue life of 4.0 × 1019. The failure mode under Von-Mises criterion has yielded a total deformation of 2.28 mm within a pressure of 4500 MPa wherein a force of 32.5KN acts on the BMG stent in the transverse direction. Fatigue under failure mode yielded a total deformation of 7.39 mm for the stress of 7704 MPa with a factor of safety 1 for a unicycle test. The CFD analysis of the blood within the BMG stent has indicated a maximum velocity of 5.06 × 10−1 m/s and a minimum of 1.31 × 10−1 m/s. The results indicate that the BMG cardio-vascular stent is better suited to perform to the existing standards of coronary stents and can even surpass them in failure criterion.

Salvage coronary artery bypass after failed stent insertion in adult Kawasaki disease

Salvage coronary artery bypass after failed stent insertion in adult Kawasaki disease

A New Customized Ureteral Stent with Nonrefluxing Silicone End-piece to Alleviate Stent-related Symptoms in Malignant Diseases

To evaluate the stent-related symptoms using a new customized ureteral stent with a nonrefluxing silicone end-piece. By decreasing the amount of material within the bladder, it should be possible to attenuate the stent-related symptoms. To minimize the amount of material, 17 consecutive patients already fitted with a double-pigtail stent for malignant ureteral obstruction agreed to be fitted with a customized stent where the bladder loop was replaced by a nonrefluxing silicone end-piece. The ureteral stent symptom questionnaire was prospectively administered to patients at baseline with double-pigtail stent and Day 15 after customized stent placement. No difficulty in the placement of the customized stent was encountered. No stent failure, no dislodgment and no calcification were observed 6 months after stenting. The scores for the main domain "Urinary symptoms" (34.4 ± 3.6 vs 23.0 ± 7.0; P=.0004) and the question "Global quality of life" (4.4 ± 2.0 vs 2.4 ± 2.1; P=.01) were significantly decreased by the replacement of the double-pigtail stent by the customized stent. The customized ureteral stent may constitute an improvement in the field of stent-related symptoms and seems fit for use in its current shape. Studies exploring and exploiting new concepts are greatly required to reduce stent-related symptoms in all patients including those with cancer.

Primary Patency of Long-Segment Femoropopliteal Artery Lesions in Patients with Peripheral Arterial Occlusive Disease Treated with Paclitaxel-Eluting Technology

The aim of this study is to evaluate the performance and predictors of failure of paclitaxel drug-eluting stents and paclitaxel-coated balloons in the treatment of long-segment femoropopliteal disease. We report a retrospective cohort analysis of patients treated with paclitaxel-eluting stents and paclitaxel-coated balloons in lesions >100mm, which were not included in any of the pivotal trials. Ninety-seven patients with peripheral vascular disease (Rutherford III-VI) underwent long-segment (≥100mm) femoropopliteal drug-eluting stent (DES) implantation or angioplasty with drug-coated balloons (DCB). Patients were followed after their initial procedure for target lesion restenosis, defined as a reduction in lumen diameter by greater than 50% as measured by duplex ultrasonography (ratio >2). The median length of the affected arterial segments was 110mm (interquartile range [IQR] 100-150, absolute range 100-260) using up to 4 overlapping stents. During the median 13-month follow-up (IQR 7-16), no early thrombotic occlusions occurred within 30days, but 28 (29%) patients developed a target lesion restenosis after 1year. Cumulative primary patency at 6 and 12months was 87% and 71% overall, respectively. The cumulative patency during the same follow-up periods varied between patients treated with different paclitaxel modalities with 88% and 80% primary patency in patients treated with DES (n=63) versus 81% and 49% in patients treated with DCB (n=21) (adjusted hazard ratio 2.46, P=0.03). Lesion length, concurrent tibial intervention, and recurrent target lesions were not associated with restenosis. Short-term outcomes in patients treated with paclitaxel-eluting stents and paclitaxel-coated balloons in long lesions, mirror results from the clinical trials. The primary patency observed in patients treated with DES was significantly higher than in patients treated with DCB.

Carotid Stent Failure as a Predictor for Periprocedural Stroke or Death After Carotid Artery Stenting: A Substudy of the International Carotid Stenting Study (ICSS)

Introduction - Compared to carotid endarterectomy (CEA), carotid artery stenting (CAS) has been associated with a higher 30-day stroke rate and increased rate of new postprocedural ischemic brain lesions on magnetic resonance-diffusion weighted imaging (MR-DWI). We assessed whether this periprocedural risk after CAS was related to stent failure within the randomised International Carotid Stenting Study (ICSS). Methods - Patients with recently symptomatic carotid artery stenosis enrolled in ICSS were randomly assigned in a 1:1 ratio to receive CAS or CEA. CAS patients were eligible for the present analysis if a postprocedural computed tomography angiography (CTA) of the treated carotid was available. Two observers independently scored stent failure, defined as presence of any of the following parameters: in-stent lesions (hypo- or hyperattenuating), residual stenosis (>30%, according to NASCET criteria) and stent fracture (by visual assessment). In addition, residual stenosis was scored on completion angiography. The primary outcome measure was the occurrence of any stroke or death within 30 days of treatment. The secondary outcome was the presence of any new ischemic brain lesion on postprocedural MR-DWI. This is a substudy of a registered trial, ISRCTN 25337470. Results - [PRELIMINARY] A total of 92 CAS patients were included. Postprocedural CTA was performed after median 33 (interquartile range 29-35) days. The primary outcome measure occurred in eight patients. No stent fractures occurred. Stent failure was scored as in-stent lesion in 19 [21%] patients, with an occlusion in two. Stent failure was noted in 3 [38%] patients with a stroke, and in 16 [19%] of patients without a stroke (odds ratio [OR] 2.55, 95% confidence interval [CI] 0.55-11.79). One of the stent occlusions resulted in a stroke, the other remained asymptomatic. In-stent lesions were found in two of 11 [18%] patients with a new postprocedural MR-DWI lesion and in six of 37 [16%] patients without a new lesion (OR 1.15, 95% CI 0.20-6.70). Data on residual stenosis on completion angiography will be ready at the time of the ESVS conference. Conclusion - These preliminary data show that stent failure occurred in about one of every five CAS patients. In-stent lesions occurred twice as often in patients who had experienced a 30-day stroke compared to stroke-free patients, although no significance was shown. To allow for definite conclusions, these findings need to be validated in a larger cohort.

Why do Human Femoral Stents Fail? First In-man Pathology and Multimodality Imaging of Acute and Chronic Femoral Stenting in Human

Introduction: Lower extremity peripheral arterial disease (PAD) is a major cause of morbidity. Endovascular therapy remains the gold standard to treat PAD1. While pathology of coronary stenting has been well studied2, pathology of lower extremity femoral stenting remains poorly understood. The objective was to comprehensively evaluate the pathology of acute and chronic femoral stenting in symptomatic atherosclerotic patients and to understand the causes of stent failures (SF) using multi-modality imaging including micro-computed tomography (microCT). Methods: Twelve stents were obtained from 10 patients with history of PAD (mean age 74 ± 9.3; 7 male and three female); all the stented arteries underwent radiography, microCT and histologic assessment. Dissected arteries were embedded in Spurr and sawed at 3-5 mm intervals and Exact slides were prepared at 60 to 100 mm and a total of 78 sections examined following co-registration with microCT. Results are reported as median and interquartile (25 to 75th percentile, IQR). Results: Duration was 150 days (30 - 365, IQR), diameter was 5.90 mm (5.44 - 7.16, IQR) and stented length was 39.5 mm (27 - 107.5, IQR). Two of 12 stents were drug-eluting stents, 10 of 12 were bare-metal stents. Half of them were overlapping stents. Indications for stenting were intermittent claudication (40%), chronic limb ischemia (50%), and acute limb ischemia (10%). Morphometric analysis of the histologic sections showed stent success [(defined as < 75% cross sectional area narrowing and absence a thrombus (>30% narrowing from thrombus)] in 4 of 12 stents with 31.0% stenosis (22.16 - 35.0, IQR). The causes of SF in the remaining 8 were: stent-thrombosis (Figure 1), 3; in-stent restenosis, 2; and chronic total occlusions, 3, with 91.5% stenosis (78.3 - 100, IQR). Histologic malapposition3 occurred in 8 of the 12 stented lesions. Underlying nodular calcification (NC) was observed in half of the lesions, medial calcifications observed in 67% of cases with the median arch of calcification of 63° (0-283, IQR). Intimal calcification was observed in 11/12 cases, degree of calcification was 126° (38 - 248, IQR). The duration of implantation was divided into short-term (≤90 days) and long-term (>90 days) stenting. The extent of medial calcification was significantly different in short-term vs. long-term stenting [126° (18.0 - 195.8) vs 0 (0 - 2.25) respectively, p=0.003]. Malapposition (Figure 2) was observed more frequently in the short-term vs. long-term groups [50.0% (25.0 - 87.5) vs 0% (0-11.9) respectively, p=0.02]. Stent fractures were observed in 3 stents (3/11, 27.7%) and all of them were associated with SF. Also, SF had a higher medial injury score4: 2 (1 - 3, IQR) vs 1 (1 - 2, IQR), p=0.04. Conclusion: This descriptive histologic study is the first series of explanted human femoral stents, removed at surgery (n=10) and autopsy (n=2). Medial calcification and malapposition play an important role in long-term stent patency. Excessive injury and stent fracture also contributes to SF. Use of microCT in this study illustrates the advantages of high-resolution CT to detect SF, especially stent fractures. This study also enlightens the necessity to evaluate any explanted material in the future5.Figure 2Multi-modality imaging showing stent malapposition.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Disclosure: Sho Torii receives research grants from SUNRISE lab. Renu Virmani and Aloke V. Finn have received institutional research support from Abbott Vascular, Boston Scientific, Cook Medical, Cardiovascular Systems, Inc., Medtronic, and Terumo Corporation; Renu Virmani is a consultant for 480 Biomedical, Abbott Vascular, Medtronic, and W.L. Gore. Other authors report no conflicts of interest.

Endovascular Treatment of Superficial Femoral and Proximal Popliteal Arteries Lesions

Abstract Mechanical stress due to flexion-extension in the femoropopliteal space may cause stent failure via stent fracture and thrombosis. Wire-Interwoven self-expanding Nitinol Stents design partially mimics the reticular structure of native vessels, emphasizing radial strength, flexibility and kink resistance; these stent features can offer more chances for short and long term patency. We have evaluated 5 patients with peripheral artery disease with significant superficial femoral artery or proximal popliteal artery lesions. All patients underwent endovascular therapy with Wire-Interwoven self-expanding Nitinol Stents, with primary focus on stent patency at follow-up visits (1, 6, 12 months). The endovascular initial success was achieved in all 5 patients. Stent patency at 1-year follow-up was achieved in 3 patients (60%). 2 patients (40%) had stent thrombosis within 30 days after procedure secondary to arterial dissection at distal stent extremity and self-withdrawal dual antiplatelet therapy; subsequently target lesion revascularization with endovascular therapy and ilio-femoral bypass was performed.

The Current Literature on Bioabsorbable Stents: a Review.

The purpose of this review is to explore the evolution of the coronary stent, from the advent of bare-metal stents, to the newest adopted technology of bioresorbable vascular scaffolds (BVS) used in bioresorbable stents. To date, there have been conflicting data regarding the safety and efficacy of BVS stents, especially when compared to current-generation drug-eluting stents (DES). This review will cover the data that exist regarding current BVS stents, as well as the active clinical trials for future iterations of BVS. The ABSORB BVS, the most widely circulated stent of its class, was promised to decrease rates of stent thrombosis and target vessel revascularization. Several randomized control trials, however, found the opposite to be true, with the ABSORB BVS demonstrating higher rates of thrombosis, target vessel revascularization, and even target lesion myocardial infarctions when compared to current-generation DES. These data caused the product to be pulled from all markets, leaving the field with uncertainty as to the role of BVS in coronary interventions. Coronary stents have evolved significantly from 1977, when they were first introduced. The original bare-metal stent was later fitted with a drug-eluting polymer, to prevent restenosis and thrombosis over time. Subsequent iterations of the stent attempted to further mitigate that risk by replacing the durable polymer to one that is bioresorbable. The final step in this progression was to create a stent that was fully bioresorbable, which Abbott did with the creation of their ABSORB BVS stent. The product, however, was found to perform poorly when compared to current-generation drug-eluting stents, with several trials showing high rates of stent thrombosis (ST), late stent thrombosis (LST), target-lesion myocardial infarction, and target vessel revascularization. Observational studies of BVS stents have proposed several mechanisms for their thrombogenicity, including higher stent-strut profiles leading to turbulent flow, low radial strength leading to strut disruption, and a higher propensity for neoatherosclerosis. Given the failure of the first-generation BVS stent, but the lingering desire for fully bioresorbable scaffolds, various manufacturers have proposed their solutions with new stents. Until data from their clinical trials emerge, it remains unclear whether fully bioresorbable stents will play any role in coronary interventions.

Very Late Stent Thrombosis in Drug-Eluting Stents New Observations and Clinical Implications.

Despite the reduction in stent failure with newer-generation drug-eluting stents, very late stent thrombosis (VLST) remains an unpredictable and potentially catastrophic complication of coronary revascularization procedures and is associated with high morbidity and mortality. Here, we present an updated overview of the latest advances in understanding the causes of VLST. Clinical studies that revealed potential risk factors and pathophysiologic studies on the mechanisms of VLST are discussed. Importantly, novel insights from recent advances in intravascular imaging are included. To date, there is no clinical guideline for VLST treatment. We propose an evidence-based recommendation that an intravascular-imaging-informed percutaneous coronary intervention strategy combined with optimized antiplatelet therapy is the foundation for successful VLST clinical management. Moreover, the future of VLST prevention, such as improved patient risk stratification and advances in addressing late stent failure, are also discussed.