Small-diameter Stents Research Articles

Small Diameter Stents In Cardiovascular Applications.

Small diameter stents play a crucial role in treating congenital heart diseases and variety of vascular conditionsthat has application from pediatrics to geriatric conditions ,acomprehensive review in this direction is lacking. This review explores historical development, design innovations, material compositions, and mechanistic insights into functionsof small diameter stents, with a specific emphasis on biodegradable options. The necessity for stents that can adapt to growth of pediatric patients is discussed, highlighting the transition from durable polymers to bioresorbable materials such as polylactic acid (PLLA) and magnesium alloys. While acknowledging the advancements made in reducing complications like restenosis and thrombosis, the review addresses the challenges that persist, including need for improved biocompatibility , minimization of late adverse cardiac events associated with certain stent technologies. A detailed examination of various stent generations emphasizes importance of drug release kinetics, structural integrity, and potential for personalized interventions based on patient-specific factors. The exploration of novel therapeutic compounds, including nanoparticles and interfering RNA, illustrates the ongoing research aimed at enhancing stent efficacy. Ultimately, the review seeks to provide a comprehensive understanding of current landscape while identifying the gaps that future research must address to develop the ideal stent for diverse patient populations.

Prediction of in-stent restenosis based on systematic and retrospective analyses

Coronary restenosis is a pressing challenge in cardiovascular diseases with an annual incidence of 3 – 4%. The aim of the study was to assess the influence of known risk factors in predicting coronary restenosis in a systematic analysis and an original retrospective survey. In the first stage, we performed a systematic review of restenosis risk factors using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. In the second stage, we searched for the restenosis risk factors in 15,000 patients who had undergone coronary angiography, considering risk factors identified during the first stage. From the second stage, we identified 516 patients with restenosis versus 282 patients without restenosis. Coronary risk factors included male sex (hazard ratio [HR] = 2.194; confidence interval [CI]: 1.5 – 3.22) and history of myocardial infarction (HR = 1.098; CI: 1.05 – 1.15). Moderate-diameter stenosis (2.75 – 3.5 mm) exhibited a protective effect on restenosis (HR = 0.713; CI: 0.58 – 0.87), whereas small-diameter stenosis did not. Drug-eluting stents reduced the risk of restenosis (HR = 0.554; CI: 0.41 – 0.75). The risk factors for coronary restenosis included male sex, history of myocardial infarction, small-diameter stent, and the use of bare-metal stents.

Prognosis and Management of Recurrent Stenosis After Pulmonary Vein Stenting: A Prospective Study.

Pulmonary vein stenting is effective for severe pulmonary vein stenosis, which is limited by restenosis. The assessment and management of in-stent restenosis (ISR) are inadequate, and follow-up outcomes after reintervention remain unknown. This study aimed to assess the prognosis and management of pulmonary vein ISR and determine whether the modified stent-in-stent strategy is superior to balloon angioplasty (BA) in treating ISR. The authors conducted a prospective observational study on patients with severe pulmonary vein stenosis post radiofrequency ablation for atrial fibrillation. A total of 107 patients with 174 severely stenosed veins underwent successful stenting. Forty-three veins among 36 patients experienced ISR (24.7%, 43 of 174). Veins developing ISR had smaller diameter stents (7.8 ± 0.8mm vs 9.2 ± 0.7mm; P=0.008). Restenosis veins were assigned to BA group or stent-in-stent group. Success rate was 95.7% for BA and 90.0% for stent-in-stent. Twelve veins experienced recurrent ISR, including 2 in stent-in-stent group (11.1%, 2 of 18) and 10 in BA group (45.5%, 10 of 22). The risk of recurrent stenosis was significantly lower in veins treated with the stent-in-stent method than with BA (HR: 0.21; 95%CI: 0.07-0.64; P=0.02). Patients in the stent-in-stent group had greater exercise endurance and better World Health Organization cardiac functional class compared with BA group (F=7.2; P< 0.05; and F=4.4; P< 0.05, respectively) at 6- and 12-month follow-ups. Our modified stent-in-stent implantation approach is superior to BA for treating pulmonary vein ISR, byreducing recurrent restenosis rate and improving exercise endurance.

Effects of Fe addition on the mechanical and corrosive properties of biomedical Co-Cr-W-Ni alloys for balloon-expandable stents

Co-20Cr-15W-10Ni (mass%, CCWN) alloy is extensively used as a platform material for balloon-expandable stents. In this study, the mechanical properties of CCWN alloy are improved following the addition of Fe, and the effects of Fe addition on the mechanical and corrosive properties of the alloy are investigated. As-cast specimens were fabricated by adding pure Fe to a commercially available CCWN alloy (base alloy) such that the resulting alloys contained 4, 6, and 8 mass% Fe. The as-cast specimens were subjected to homogenization heat treatment at 1523 K for 7.2 ks and then hot-forged at 1473 K (as-forged specimens). The as-forged specimens were cold-rolled at a reduction rate of 30% and heat-treated at 1473 K for 300 s (recrystallized specimens). The matrix of the recrystallized base- and Fe-containing alloys consisted of a single γ (face-centered cubic)-phase. The Fe-added alloys revealed precipitates composed of the η-phase (M6X-M12X-type phase, M: metallic element, X: C and/or N). The average grain size of the recrystallized base and Fe-added alloy specimens was approximately 34 μm and the amount of added Fe had no significant effect on the static recrystallization behavior of the resulting alloys. Alloys containing 6 mass% or more Fe showed improvements in strength and ductility compared with the base alloy. When the Fe-added alloys were compared, their strength decreased whereas their ductility increased when the added Fe increased. Because Fe acts as a γ-phase-stabilizing element for Co, Fe addition increases the stacking fault energy of the base alloy, resulting in the formation of the ε (hexagonal close-packed)-phase owing to the suppression of strain-induced martensitic transformation (SIMT), and improvements in ductility. No deterioration in corrosion resistance was observed following the addition of up to 8 mass% Fe to the base alloy. Based on these results, the addition of Fe to CCWN alloy may be considered an effective method to improve its mechanical properties, especially ductility, without impairing its corrosion resistance. The results of this study will be useful for the future development of Ni-free Co-Cr alloys for next-generation, small-diameter stents.

Replacement of pulmonary venous stent during Fontan operation.

Post-operative pulmonary venous stenosis is a poor prognostic factor in single-ventricle haemodynamics. Implantation of a drug-eluting stent is a therapeutic option. However, due to their small size, they inevitably become inadequate as the patient grows. We present the first case, to the best of our knowledge, of the replacement of a small-diameter stent with a large-diameter stent during Fontan surgery.

Coronary computed tomography angiographic detection of in-stent restenosis via deep learning reconstruction: a feasibility study.

Evaluation of in-stent restenosis (ISR), especially for small stents, remains challenging during computed tomography (CT) angiography. We used deep learning reconstruction to quantify stent strut thickness and lumen vessel diameter at the stent and compared it with values obtained using conventional reconstruction strategies. We examined 166 stents in 85 consecutive patients who underwent CT and invasive coronary angiography (ICA) within 3months of each other from 2019-2021 after percutaneous coronary intervention with coronary stent placement. The presence of ISR was defined as percent diameter stenosis ≥ 50% on ICA. We compared a super-resolution deep learning reconstruction, Precise IQ Engine (PIQE), and a model-based iterative reconstruction, Forward projected model-based Iterative Reconstruction SoluTion (FIRST). All images were reconstructed using PIQE and FIRST and assessed by two blinded cardiovascular radiographers. PIQE had a larger full width at half maximum of the lumen and smaller strut than FIRST. The image quality score in PIQE was higher than that in FIRST (4.2 ± 1.1 versus 2.7 ± 1.2, p < 0.05). In addition, the specificity and accuracy of ISR detection were better in PIQE than in FIRST (p < 0.05 for both), with particularly pronounced differences for stent diameters < 3.0mm. PIQE provides superior image quality and diagnostic accuracy for ISR, even with stents measuring < 3.0mm in diameter. With improvements in the diagnostic accuracy of in-stent stenosis, CT angiography could become a gatekeeper for ICA in post-stenting cases, obviating ICA in many patients after recent stenting with infrequent ISR and allowing non-invasive ISR detection in the late phase. • Despite CT technology advancements, evaluating in-stent stenosis severity, especially in small-diameter stents, remains challenging. • Compared with conventional methods, the Precise IQ Engine uses deep learning to improve spatial resolution. • Improved diagnostic accuracy of CT angiography helps avoid invasive coronary angiography after coronary artery stenting.

Coronary Stent Evaluation by CTA: Image Quality Comparison Between Super-Resolution Deep-Learning Reconstruction and Other Reconstruction Algorithms.

Background: A super-resolution deep-learning based reconstruction (SR-DLR) algorithm may provide better image sharpness than earlier reconstruction algorithms and thereby improve coronary stent assessment on coronary CTA. Objective: To compare SR-DLR and other reconstruction algorithms in terms of image quality measures related to coronary stent evaluation in patients undergoing coronary CTA. Methods: This retrospective study included patients with at least one coronary artery stent who underwent coronary CTA between January 2020 and December 2020. Examinations were performed using a 320-row normal-resolution scanner and reconstructed with hybrid iterative reconstruction (HIR), model-based iterative reconstruction (MBIR), normal-resolution deep-learning reconstruction (NR-DLR), and SR-DLR algorithms. Quantitative image quality measures were determined. Two radiologists independently reviewed images to rank the four reconstructions (1=worst reconstruction, 4=best reconstruction) for qualitative measures, and to score diagnostic confidence (5-point scale; score≥3 indicating an assessable stent). Assessability rate was calculated for stents with diameter ≤3.0 mm. Results: The sample included 24 patients (18 men, 6 women; mean age, 72.8±9.8 years), with 51 stents. SR-DLR, in comparison with the other reconstructions, yielded lower stent-related blooming artifacts (median, 40.3 vs 53.4-58.2), stent-induced attenuation increase ratio (0.17 vs 0.27-0.31), and quantitative image noise (18.1 vs 20.9-30.4 HU), and higher in-stent lumen diameter (2.41 vs. 1.74-1.94 mm), stent strut sharpness (327 vs 147-210 ΔHU/mm), and CNR (30.0 vs 16.0-25.6), (all p<.001). For both observers, all ranked measures (image sharpness; image noise; noise texture; delineation of stent strut, in-stent lumen, coronary artery wall, and calcified plaque surrounding the stent) and diagnostic confidence showed a higher score for SR-DLR (median, 4.0 for all features) than for the other reconstructions (range, 1.0-3.0) (all p<.001). Assessability rate for stents with diameter ≤3.0 mm (n=37) was higher for SR-DLR (observer 1: 86.5%; observer 2: 89.2%) than for HIR (35.1%, 43.2%), MBIR (59.5%, 62.2%), or NR-DLR (62.2%, 64.9%) (all p<.05). Conclusion: SR-DLR yielded improved delineation of the stent strut and in-stent lumen, with better image sharpness and less image noise and blooming artifacts, in comparison with HIR, MBIR, and NR-DLR. Clinical Impact: SR-DLR may facilitate coronary stent assessment on a 320-row normal-resolution scanner, particularly for small-diameter stents.

Improvement of mechanical properties of Co–Cr–W–Ni alloy tube suitable for balloon-expandable stent applications through heat treatment

This study focuses on the changes in the microstructure and mechanical properties of the Co–20Cr–15W–10Ni (CCWN, mass%) alloy tube, which, with heat treatment, is used as a balloon-expandable stent. To the best of our knowledge, this is the first report on the improvement of mechanical properties by microstructure control in CCWN alloy tubes. In addition, optimized heat treatment conditions are proposed for the development of next-generation small-diameter stents. The cold-worked CCWN alloy tube for stents was statically recrystallized by heat treatment at temperatures of 1373–1473 K for holding times of 60–900 s. The recrystallized alloy tubes exhibited a microstructure with a γ(fcc)-phase matrix and an average grain size of 5.8–34.1 μm. The strength and plastic elongation increased with decreasing grain size. In the coarse-grained structure, a large plate-like ε-phase formed along the twin boundary and stacking fault. The ε-phase grew to the grain boundaries, such that large cracks could form, resulting in early fracture. In the fine-grained structure, a small ε-phase formed by strain-induced martensitic transformation was uniformly dispersed, and the formation of large cracks was suppressed, leading to high ductility. The effect of low-temperature heat treatment (LTHT) at 873 K after recrystallization depended on the grain size of the alloy tube. In the alloy tube with a grain size of >15 μm, ε(hcp)-phase formation during plastic deformation was suppressed through the decrease in stacking fault density during LTHT, which resulted in improved ductility. In contrast, in the alloy tube with a grain size of <15 μm, the amount of precipitates increased during LTHT, resulting in reduced ductility.

Why can primary angioplastics be ineffective despite the precocity of the intervention?

Early coronary revascularization is a first choice therapeutic strategy in the case of acute myocardial infarction (MI). Despite an early coronary angioplasty, however, in some cases, there is a lower efficacy of revascularization, with less favourable clinical outcome in the short and long terms. Various elements participate in the distant prognosis after primary coronary angioplasty (PCI). Among the clinical risk factors that predispose to a recurrence of ischaemic cardiovascular events are advanced age, diabetes mellitus, chronic renal failure, peripheral vascular disease, atrial fibrillation and the multiplicity of cardiovascular risk factors, which identify a higher baseline risk profile. The risk factors associated with the percutaneous interventional procedure include the presence of diffuse or complex coronary lesions, the use of small diameter stents or a suboptimal post procedural thrombolysis in MI flow. The occurrence of procedural complications, such as no-reflow, is in fact associated with an increase in the infarct area and a worse prognosis, as it favours negative ventricular remodelling. The presence of concomitant right ventricular dysfunction, the high ventricular arrhythmic burden in the acute phase, the presence of risk factors for thrombosis or intra-stent restenosis also affect the outcome after primary PCI.

Endovascular Therapy for Isolated Brachiocephalic Pseudoaneurysm.

In this study, we present a successful endovascular therapy using a small-diameter stent graft for a 73-year-old man who developed asymptomatic pseudoaneurysm of the brachiocephalic artery. An 8F sheath was placed in the brachial artery, and a stiff guidewire was advanced to the descending aorta. The stent graft was delivered to the brachiocephalic artery via the brachial approach. After the initial dilatation, the stent graft was post-dilated to maximum diameter. Final digital subtraction angiography confirmed no endoleak. We believed that endovascular for a brachiocephalic pseudoaneurysm using a small-diameter stent graft might be a minimally invasive and simple method useful in clinical practice.

Do ureteral stent diameter and length or patient demographics play a role in stent encrustation?

Retained ureteral stents may constitute a technical challenge. The purpose of this study was to analyze the patient population with retained ureteral stents with regards to stent sizes to better understand if these factors could play a pivotal role in their encrustation. After institutional review board approval, we retrospectively analyzed the data of patients who underwent multimodal surgical procedures for the removal of retained ureteral stents from 2010-2018. The primary outcomes analyzed were ureteral stent length and diameter, location of stent placement, and patients' demographics as potential etiologies for encrustation. We included 30 patients with 32 encrusted ureteral stents and 37 patients with 46 forgotten non-retained ureteral stents. Indications for stenting included urolithiasis, malignancy, pregnancy, ureteral stricture, and ureteropelvic junction obstruction. Stent diameters ranged from 6-8.5 Fr. Stent lengths ranged from 22-30 cm, and multilength stents were used too. Smaller diameter stents were less likely to be retained when compared to larger diameter stents (>6 Fr) (p=0.002). Overall stent length was not found to be significant (p=0.251); however, the difference in stent surface area differed by over 1 cm (p<0.001). Patients who were uninsured were more likely to have retained stents (p=0.003). Patients who reside with longer commuting distance to the main academic medical center were more likely to have retained stents (p=0.010). Retained ureteral stents could be avoided. Taking into consideration ureteral anatomical variation among patients, smaller diameter stents and smaller surface area may prevent encrustation. Uninsured patients with farther distance to seek medical care and females are the most at risk.

Comparison of double-layer large-diameter and conventional small-diameter plastic stents for preoperative biliary drainage in resectable distal malignant biliary obstruction

The use of a plastic stent (PS) in resectable patients with distal malignant biliary obstruction (DMBO) is uncommon due to the high failure rate of this method. This study evaluated the efficacy and safety of a double-layer, large-diameter PS as a bridge to surgery compared with a conventional PS. This was a single-center retrospective cohort study. In total, 129 consecutive patients with DMBO underwent pancreaticoduodenectomy between January 2011 and March 2018. Fifty-five patients who preoperatively underwent plastic biliary drainage were enrolled. The patients were divided into two groups based on stent diameter: a large-diameter plastic stent (LPS) group and a small-diameter plastic stent (SPS) group. The primary endpoint was the stent patency period, and the secondary endpoint was the medical cost. Thirty-six patients received SPSs; 19 patients received LPSs. The patency rate until surgery was significantly higher in the LPS group than in the SPS group (89.5% vs. 41.7%, P = 0.0006). Multivariate analysis revealed that LPS use was significantly associated with sufficient stent patency. The total cost of LPS use was significantly lower than that of SPS use. LPSs had longer patency and reduced medical costs than SPSs. LPSs may be suitable for patients with DMBO who are scheduled to undergo surgery.

Numerical Analysis of Urine Flow with Multiple Sizes of Double-J Stents

This study investigated which sizes of double-J stents are more effective in achieving an acceptable urine flow through stenotic and stented ureters. Sixty four computational fluid dynamics models of the combinations of two different gauge ureters (4.57 mm and 5.39 mm in diameter) with four different levels of ureteral and four different sizes of double-J stents were developed for the numerical analysis of urine flow in the ureter. Luminal, extraluminal, and total flow rates along the ureter were measured, and the flow patterns around the ports and side holes were investigated. For the 4.57-mm ureter, the total flow rate for each gauge of stent was 23–63 mL/h (5 Fr), 20–47 mL/h (6 Fr), 17–35 mL/h (7 Fr), and 16–26 mL/h (8 Fr) and for the 5.39-mm ureter, the total flow rate for each gauge of stent was 43–147 mL/h (5 Fr), 36–116 mL/h (6 Fr), 29–92 mL/h (7 Fr), and 26–71 mL/h (8 Fr). With a 74% stenosis, all stents allowed a low flow rate, and the differences in flow rates between the stents were small. At the other levels of stenosis, 5 Fr stents allowed greater flow rates than the 8 Fr stents. The luminal flow rate increased just before the area of stenosis and decreased after the stenosis because of the increase and decrease in the luminal flow through the side holes before and after the stenosis. Therefore, a larger double-J stent is not favorable in achieving an acceptable urine flow through the stenotic and stented ureters. The results in this study could not be necessarily correlated with clinical situation because peristalsis, viscosity of the urine and real format of the ureter were not considered in our model. In vivo experiments are necessary for confirmation of our findings. Double J stents are commonly used in the ureteral stenosis or occlusion, especially due to ureter stones which obstruct the flow of urine. Clinicians choose the size of double J stent on the basis of their clinical experience. Here, we tried to know which sizes of double J stents are better for sufficient urine flow. According to various documents that try to determine the optimal shape of double J stents to increase the urine flow through the ureter, mostly bigger stent is recommended to occur maximum urine flow. However, in case of ureter with stenosis or occlusion, the right size of the double J stent may vary depending on the degree of stenosis in the ureter. To find appropriate stent size for the ureter with stenosis, computational fluid dynamics was conducted. This study shows that smaller diameter stents are more appropriate than larger diameter stents depending on the situation.

Pro-inflammatory cytokines, oxidative stress and diffuse coronary reocclusions in elderly patients after coronary stenting

BackgroundThe inflammation responses and oxidative stress were closely associated with coronary heart disease. We tried to evaluate the effects of multiple stents, long stents and small-diameter stents on inflammation responses and oxidative stress in the elderly patients with long diffuse reocclusions. MethodsThe blood samples were obtained after an overnight fast and we evaluated the expression levels of soluble ST2 (sST2), acrolein (ACR), aldosterone (ALD), angiotensin II (Ang II), toll-like receptor 4 (TLR4), tumour necrosis factor-α (TNF-α), malondialdehyde (MDA) and high sensitivity C-reactive protein (hs-CRP) in the elderly patients with long diffuse reocclusions after multiple stents, long stents, small-diameter stents implanted. Results: Levels of sST2, ACR, ALD, Ang II, TLR4, TNF-α, MDA and hs-CRP were remarkably increased (P < 0.001) in the elderly patients with long diffuse reocclusions after multiple stents, long stents, small-diameter stents implanted. The multiple stents, long stents and small-diameter stents may promote inflammatory response and oxidative stress, and led to long diffuse reocclusions in the elderly patients. The multiple stents, long stents and small-diameter stents may play the key roles in long diffuse reocclusions of the elderly patients. ConclusionsThe inflammatory and oxidative stress biomarkers could be considered as potential non-invasive diagnostic, predictive, prognostic and therapeutic molecular biomarkers for long diffuse reocclusions in the elderly patients after implantations of multiple stents, long stents and small-diameter stents.

Relationship Between Stent Diameter, Platelet Reactivity, and Thrombotic Events After Percutaneous Coronary Artery Revascularization

Small vessel diameter and residual platelet reactivity are independent predictors of thrombotic events after percutaneous coronary intervention (PCI). We sought to determine whether an interaction exists between residual platelet reactivity and stent diameter regarding the occurrence of stent thrombosis and other adverse events after PCI. We stratified patients in the prospective ADAPT-DES registry who underwent single-lesion PCI according to if they received a small diameter stent (SDS, defined as a stent with a diameter of 2.25 mm). Patients receiving an SDS were compared with patients receiving a stent ≥2.5 mm using Kaplan-Meier rates and multivariable Cox proportional hazards regression. We defined major adverse cardiac events (MACE) as the composite of cardiac death, myocardial infarction, and stent thrombosis (ST). Among 5,608 patients who underwent single-lesion PCI in ADAPT-DES, 222 (4.0%) patients received an SDS. Patients with an SDS were more likely than patients without an SDS to have 3-vessel disease but received, on average, fewer stents and were less likely to present with a thrombotic lesion. Receiving versus not receiving an SDS was associated with increased risk of ST (adjusted hazard ratio 4.35, 95% confidence interval 1.95 to 9.73, p <0.001) as well as MACE (adjusted hazard ratio 1.75, 95% confidence interval 1.11 to 2.75, p = 0.02). There was no statistical interaction between platelet reactivity and SDS regarding ST (p = 0.12) or MACE (p = 0.51). In conclusion, PCI with small drug-eluting stents is associated with a high risk of thrombotic events, including ST. Further studies should explore whether alternative treatment strategies are appropriate in small vessels.

Experimental Direct Measurement of Clot-Capturing Ability of Stent Retrievers

Stent retrievers (SRs) can be used to perform mechanical thrombectomy for the treatment of acute major arterial occlusion. Recanalization is faster, and outcomes are better with treatment involving these devices than with internal treatment. Although several SRs are available, their clot-capturing abilities are unclear. Therefore in the present study, we numerically evaluated the clot-capturing abilities of SRs in an experimental vascular model. A sham clot (urethane foam) was fixed with sutures at the middle of a vascular model (polyvinyl chloride tube). One end of the tube was connected to a measuring instrument. From the other end, an SR was inserted and deployed over the sham clot. The delivery wire of the stent was then withdrawn at a constant velocity using an automatic withdrawal machine. The maximum frictional force before the stent left the clot was measured. Five stents (Trevo ProVue [2 sizes], Revive, and Solitaire [2 sizes]) and three stent-deployment techniques (standard, push-and-fluff, and wire-push techniques) were evaluated. The clot-capturing ability (maximum withdrawing force [N: newton]) was greater for large-diameter stents than for small-diameter stents (mean 0.39 ± 0.11 vs. 0.56 ± 0.18). For Trevo and Revive, the clot-capturing ability was highest with the push and fluff technique (mean 0.43 ± 0.05). For Solitaire, the ability was the highest with the simple wire-push technique (mean 0.705 ± 0.16). We successfully numerically evaluated the clot-capturing abilities of SRs. The clot-capturing ability differed among SRs and among stent-deployment techniques.

Consequences of an early catheter-based intervention on pulmonary artery growth and right ventricular myocardial function in a pig model of pulmonary artery stenosis.

To determine the consequences of an early catheter-based intervention on pulmonary artery (PA) growth and right ventricular (RV) myocardial function in an animal model of branch PA stenosis. Acute results and safety profiles of deliberate stent fracture within the pulmonary vasculature have been demonstrated. The long-term impact of early stent intervention and deliberate stent fracture on PA growth and myocardial function is not understood. Implantation of small diameter stents was performed in a pig model of left PA stenosis at 6 weeks (10 kg) followed by dilations at 10 (35 kg) and 18 weeks (65 kg) with intent to fracture and implant large diameter stents. Hemodynamics, RV contractility, and 2D/3D angiography were performed with each intervention. The heart and pulmonary vasculature were histologically assessed. Stent fracture occurred in 9/12 and implantation of large diameter stents was successful in 10/12 animals with no PA aneurysms or dissections. The final stented PA segment and distal left PA branch origins equaled the corresponding PA diameters of sham controls. Growth of left PA immediately beyond the stent was limited and there was diffuse fibro-intimal proliferation within the distal left and right PA. RV contractility was diminished in the intervention group and the response to dobutamine occurred uniquely via increases in heart rate. Early stent intervention in this surgically created PA stenosis model was associated with improved growth of the distal PA vasculature but additional investigation of PA vessel physiology and impact on the developing heart are needed.

Intentional longitudinal and side-cell stent fractures: Intermediate term follow up.

Use of small diameter stents in young children and jailing of side branches pose significant challenges to future re-interventions. We sought to assess the capacity to induce longitudinal fractures in undersized stents to increase vessel diameter, and side cell fractures to enlarge stenotic jailed branches. Retrospective review of patients who underwent attempted intentional stent fractures (ISF) from 01/06-02/17. Twenty-two patients, median age 4.4 (1.1-47.8) years, weighing 14.3 (6.9-102) kg underwent attempted ISF in 32 vessels. Initial stent implant occurred at a median age of 1.0 (0.1-34.1) years, at the following sites: pulmonary arteries (11), pulmonary veins (14), systemic veins (6), and aorta (1). Initial diameters of the stents were 3.5-12 mm. Thirteen vessels had overlapping stents. Using high-pressure balloons, longitudinal ISF was achieved in 23 and side cell ISF in eight vessels. One longitudinal ISF attempt was unsuccessful. Three lesions were immediately re-stented after longitudinal ISF, and three lesions treated with angioplasty (1) or stenting (2) after side cell ISF. Only one complication occurred (pseudoaneurysm in a pulmonary artery after longitudinal ISF requiring placement of a covered stent). At a median follow up of 2.0 years (2 days - 10.8 years), eight patients had 16 additional interventions for restenosis at site of ISF. ISF can be induced safely in a variety of vascular beds using high-pressure balloons both longitudinally or through side cells. Longitudinal ISF only rarely requires immediate placement of a new stent; however, late restenosis may occur, requiring re-stenting.

Characterization of biofilms in biliary stents and potential factors involved in occlusion.

AIMTo quantify the components in biofilms and analyze the predisposing factors involved in occlusion of biliary stents.METHODSIn a prospective study conducted from April 2011 to March 2014 at a tertiary care hospital, all consecutive patients who required endoscopic biliary stent exchange/removal were included. Etiology of the biliary disease was diagnosed by imaging, cytology and on follow-up. Clinical details of patients with biliary stent retrieval were noted. All extracted stents were collected in sterile containers and immediately processed for quantification of biofilm proteins and polysaccharides. Molecular identification of commonly known and unknown bacteria was performed by polymerase chain reaction and density gradient gel electrophoresis methods.RESULTSEighty one patients (41 males) with age range of 20-86 years were studied. The underlying causes for stent insertion were bile duct stones (n = 46; 56.8%) benign stricture (n = 29; 35.8%) and malignancy (n = 6; 7.4%) with cholangitis in 50 (61.7%) patients. The retrieved stent sizes were 7 Fr (n = 62; 76.5%) and 10 Fr (n = 19; 23.5%) with 65 days median insertion duration. Polybacterial consortia were detected in 90.1% of the stents. The most common bacteria identified by polymerase chain reaction alone and/or sequencing were Pseudomonas (n = 38), Citrobacter (n = 23), Klebsiella (n = 22), Staphylococcus (n = 20), Serratia (n = 16), Escherichia coli (n = 14), Streptococcus (n = 13), Enterococcus (n = 13), Aeromonas (n = 12), Proteus (n = 10) and Enterobacter (n = 9). Protein concentration according to gender (0.547 ± 0.242 mg/mL vs 0.458 ± 0.259 mg/mL; P = 0.115) as well as age > 60 years and < 60 years (0.468 ± 0.295 mg/mL vs 0.386 ± 0.238 mg/mL; P = 0.205) was non-significant. However, polysaccharide concentration was significant both according to gender (0.052 ± 0.021 mg/mL vs 0.049 ± 0.016 mg/mL; P < 0.0001) and age (0.051 ± 0.026 mg/mL vs 0.038 ± 0.016 mg/mL; P < 0.011). Protein concentration in the biofilm was significantly higher (0.555 ± 0.225 mg/mL vs 0.419 ± 0.276 mg/mL; P = 0.018) in patients with cholangitis, lower (0.356 ± 0.252 mg/mL vs 0.541 ± 0.238 mg/mL; P = 0.005) in the 10 Fr group than the 7 Fr group, and significantly higher (0.609 ± 0.240 mg/mL vs 0.476 ± 0.251 mg/mL; P = 0.060) in stents of ≥ 6 mo of indwelling time. However presence/absence of cholangitis, size of stent, indication of stent insertion and indwelling time did not affect the quantity of polysaccharide concentration.CONCLUSIONPlastic stents retrieved from patients with biliary tract disease showed polymicrobial organisms with higher protein content among patients with cholangitis and those with smaller diameter stents. Longer indwelling duration had more biofilm formation.

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.