Intravascular Stents Research Articles

Topology optimization of coronary artery stent considering structural and hemodynamic parameters

In the present study, the impact of geometric variables and structural features of stents on hemodynamic parameters is investigated. Intravascular stent implantation is a treatment method whose success largely depends on the geometric structure of the stent and its effect on hemodynamic parameters. Medical devices called stents are inserted into arteries to restore blood flow when an artery is blocked. In this research, an optimal stent was designed and its effect compared to the common commercial stent used for coronary arteries was investigated and compared. It has been found that the geometry of the stent has an effective impact on the wall shear stress in the stented artery. Therefore, in this article, the importance of stent structures in the treatment of the coronary artery disease is discussed. For this purpose, first, an optimal stent is created with the topology optimization technique to find the best structure in the stent design. Finally, the optimized stent is numerically verified with ANSYS software and compared with existing commercial stents, and then the prototype is fabricated using additive manufacturing techniques. Commercial software ABAQUS, SolidWorks, and ANSYS are used in this research. The results showed that in optimizing a square plate, a sample with a minimum residual volume limit equal to 10 and 7 % can be selected as the optimal state. The results indicate that the new design can improve the distribution of wall shear stresses to reduce the adverse hemodynamic changes. Therefore, the proposed stent geometric structure can help improve the treatment. Finally, the optimized stent along with a commercial stent was made with the 3D printing method.

Modified Intravascular Stent for Microvascular Suture in a Rat Superficial Femoral Artery.

Intravascular stent (IVaS) is sometimes used for suturing small vessels, but removing the stent after suturing is difficult. To overcome this problem, we developed an IVaS that integrates a stent and a manipulating string. This study aimed to investigate the usefulness of the modified IVaS (M-IVaS) by comparing it with conventional sutures (CS) and conventional IVaS (C-IVaS). Forty-five superficial femoral arteries from rats were resected and sutured. The rats were randomly divided into the following 3 groups: CS, M-IVaS, and C-IVaS, with 15 rats per group. Patency rate, operating time, and ultrasonographic blood flow dynamics were examined immediately after suturing. Patency tests, ultrasonographic evaluations, and histological investigations were performed 1 week (n = 5), 2 weeks (n = 5), and 6 weeks (n = 5) after surgery. The 3 groups showed vessel patency in all cases immediately after suturing and at 1 week, 2 weeks, and 6 weeks after surgery. The mean operative time was 22.6 minutes for the CS group, 21.5 minutes for the M-IVaS group, and 25.9 minutes for the C-IVaS group. There were no significant differences in peak flow velocity and stenosis rate among the 3 groups as evaluated by ultrasonography. Histopathological evaluation revealed a similar recovery process of endothelial cells and no damage to the vascular wall. The surgical time using M-IVaS was significantly shorter compared to that using C-IVaS. The M-IVaS reduced the inconvenience of C-IVaS removal. M-IVaS showed the same effectiveness as did the CS in terms of patency rate, operating time, ultrasonographic blood flow dynamics, and histological evaluation. M-IVaS can be used in the field of microsurgery.

Constructing sodium alginate/carboxymethyl chitosan coating capable of catalytically releasing NO or CO for improving the hemocompatibility and endothelialization of magnesium alloys

Although significant progress in developing biodegradable magnesium alloy materials in cardiovascular stents has been achieved recently, they still face challenges such as rapid in vivo corrosion degradation, inferior blood compatibility, and limited re-endothelialization after the implantation. Hydrogel coating that can catalyze the liberation of gas signal molecules offers a good solution to alleviate the corrosion rate and enhance the biocompatibility of magnesium and its alloys. In this study, based on alkaline heat treatment and construction of polydopamine coating on the surface of magnesium alloy, sodium alginate/carboxymethyl chitosan (SA/CMCS) gel was simultaneously covalently grafted onto the surface to build a natural polymer hydrogel coating, and selenocystamine (SeCA) and CO release molecules (CORM-401) were respectively immobilized on the surface of the hydrogel coating to ameliorate the anticoagulant performance and accelerate endothelial cells (ECs) growth by catalyzing the release of endogenous gas signal molecules (NO or CO). The findings verified that the as-prepared hydrogel coating can catalyze the liberation of CO or NO and significantly improve the corrosion resistance of magnesium alloy. At the same time, owing to the excellent hydrophilicity of the hydrogel coating, the good anticoagulant property of sodium alginate, and the ability of CMCS to promote the ECs growth, the modified magnesium alloy could significantly improve the albumin adsorption while preventing the adsorption of fibrinogen, hence significantly augmenting the anticoagulant properties and promoting the ECs growth. Under the catalytic release of NO or CO, the released gas molecules further enhanced hemocompatibility and promoted endothelial cell (EC) growth and the expression of vascular endothelial growth factor (VEGF) and NO of ECs. Therefore, the bioactive coatings that can catalyze the release of NO or CO have potential applications in constructing surface bioactive coatings for magnesium alloy materials used for intravascular stents.

Exploring the biodegradability of candidate metallic intravascular stent materials using X-ray microfocus computed tomography: An in vitro study.

In vitro testing for evaluating degradation mode and rate of candidate biodegradable metals to be used as intravascular stents is crucial before going to in vivo animal models. In this study, we show that X-ray microfocus computed tomography (microCT) presents a key added value to visualize degradation mode and to evaluate degradation rate and material surface properties in 3D and at high resolution of large regions of interest. The in vitro degradation behavior of three candidate biodegradable stent materials was evaluated: pure iron (Fe), pure zinc (Zn), and a quinary Zn alloy (ZnAgCuMnZr). These metals were compared to a reference biostable cobaltchromium (CoCr) alloy. To compare the degradation mode and degradation rate evaluated with microCT, scanning electron microscopy (SEM) and inductively-coupled plasma (ICP) were included. We confirmed that Fe degrades very slowly but with desirable uniform surface corrosion. Zn degrades faster but exhibits localized deep pitting corrosion. The Zn alloy degrades at a similar rate as the pure Zn, but more homogeneously. However, the formation of deep internal dendrites was observed. Our study provides a detailed microCT-based comparison of essential surface and corrosion properties, with a structural characterization of the corrosion behavior, of different candidate stent materials in 3D in a non-destructive way.

"Double Intravascular Stenting (dIVaS): Optimizing Watertight Anastomosis for Ectatic-Type Lymphatics During Lymphaticovenous Anastomosis".

"Double Intravascular Stenting (dIVaS): Optimizing Watertight Anastomosis for Ectatic-Type Lymphatics During Lymphaticovenous Anastomosis".

Research on the heat treatment process of intravascular nitinol stents

With the aging of China’s population and changes in dietary structure, the incidence of peripheral arterial disease (PAD) is increasing year by year, and the number of PADs requiring intervention is increasing. Atherosclerosis, inflammation, trauma or injury, structural abnormalities of ligaments or muscles, or exposure to radiation are common causes of PAD. Minimally invasive treatment is an effective method to treat PAD, and nitinol alloy vascular stent has become an effective and safe minimally invasive interventional treatment method because of its shape memory effect, super elasticity, and excellent biocompatibility. This topic mainly studies the preparation of nitinol stents through finite element analysis simulation and heat treatment shaping. The stents are analyzed by optical microscope, DSC, Tensile Testing Machine, and Radial Force Tester. The specific research results are as follows: through finite element analysis, the shaping process parameters of the stent are determined. When the diameter of the stent is expanded to 5 mm in three steps, as the heating temperature increases from 500°C to 540°C, the color of the stent surface changes from blue to yellow, the temperature of the stent Af decreases, the radial support force and the stress of the upper and lower yield plateaus of the stent increase.

Electrolytic polishing process of intravascular nitinol stents

Electrolytic polishing process of intravascular nitinol stents

Intravascular Ultrasound-guided Carotid Artery Stenting in Carotid Web Suspicion: Its Role on Diagnosis and Treatment of this Infrequent Condition

Intravascular Ultrasound-guided Carotid Artery Stenting in Carotid Web Suspicion: Its Role on Diagnosis and Treatment of this Infrequent Condition

Optimization of the electrolytic polishing parameters of intravascular stent based on the orthogonal test method

Cardiovascular diseases are the most important global health threat because of their prevalence. Intravascular stent interventional surgery is regarded as the primary treatment method of cardiovascular diseases, so high-performance stents are in great demand. In this study, the influence of key process parameters on the surface properties of the stent was investigated to improve the serviceability of laser cut intravascular stent. Using the test method, the influence of each process parameter on the surface integrity of the support was determined, and then the optimal combination of electrolytic polishing parameters was obtained. On this basis, the quantitative statistics of material removal and the wettability of electrolytic polishing were studied. The results show that the surface quality of the scaffold is the best when the volume ratio of concentrated sulfuric acid and glacial acetic acid electrolyte is 1:11, the polishing temperature is 34 ℃, the polishing voltage is 22 V, the polishing time is 80 s, and the electrode distance is 22 mm. The wall thickness and bridge width of the stent were reduced by 26.99 and 29.34 μm, respectively, and the mean hydrostatic contact angle was increased by 24.35°, which improved the biocompatibility of the stent.

Effects of a step-by-step inpatient rehabilitation program on self-care ability and quality of life in patients with acute cerebral infarction following intravascular stent implantation: a prospective cohort study

Effects of a step-by-step inpatient rehabilitation program on self-care ability and quality of life in patients with acute cerebral infarction following intravascular stent implantation: a prospective cohort study

Mathematical and numerical analysis for PDE systems modeling intravascular drug release from arterial stents and transport in arterial tissue.

This paper is concerned with the PDE (partial differential equation) and numerical analysis of a modified one-dimensional intravascular stent model. It is proved that the modified model has a unique weak solution by using the Galerkin method combined with a compactness argument. A semi-discrete finite-element method and a fully discrete scheme using the Euler time-stepping have been formulated for the PDE model. Optimal order error estimates in the energy norm are proved for both schemes. Numerical results are presented, along with comparisons between different decoupling strategies and time-stepping schemes. Lastly, extensions of the model and its PDE and numerical analysis results to the two-dimensional case are also briefly discussed.

Abstract P186: Does Lipoprotein (a) Level Have a Predictive Value in Reintervention After Iliofemoral Vein Stenting?

Background: Lipoprotein (a), Lp(a), is associated with cardiovascular complications and atherothrombosis in arteries. However, the effects of Lp(a) in venous disease are unknown and uninvestigated. Hypothesis: Utilizing a patient population with iliofemoral stenosis from external compression (May-Thurner Syndrome) of which 30% had a prior deep vein thrombosis (DVT), we hypothesize that elevated Lp(a) levels may be associated with an increased risk of major reoperations after intravascular vein stenting (IVS) when compared to patients with non-elevated Lp(a) levels. Methods: In this study, 584 patients who underwent IVS for chronic iliofemoral stenosis between 2011 and 2019 were retrospectively studied. Patients with acute DVT, any prior IVS, or no Lp(a) results were excluded. Patients were stratified into two groups according to Lp(a) levels: non-elevated Lp(a) <50 mg/dL (N=472 patients), and elevated Lp(a) ≥50 mg/dL (N=112). Statistical analysis of demographics, clinical outcomes, and venous clinical severity score (VCSS) included paired t-tests and chi-squared tests. Kaplan-Meier curves and Cox proportional hazard models assessed the relationship of Lp(a) with time to major reoperation requiring venography and/or intravascular ultrasound (IVUS). Results: Patients with elevated Lp(a) levels were more likely to be Black (14% vs. 2.3%; p <0.001), hypertensive (56% vs. 44%; p = 0.025), higher preop VCSS pain (2.0 vs. 1.6; P<0.01), and greater number of reoperations (2.1 vs. 1.7; p = 0.037), specifically major reoperations (54% vs. 21%; p = 0.012) than those with non-elevated Lp(a) levels. Both non-elevated and elevated Lp(a) demonstrated comparable changes in composite VCSS scores during post-op, 1, 2, and 3-year follow-up (p = 0.12, 0.3, 0.4, and 0.5, respectively). However, multivariate analysis, controlling for demographic variables and comorbidities, showed no significant association between elevated Lp(a) and major reoperation (HR: 1.3; 95% CI: 0.84-2.00; p = 0.2). A statistically significant interaction was found between Lp(a) and hypertension status (p = 0.003). Compared with the reference group (Lp(a)) <50 mg/dL and no hypertension), those with Lp(a) ≥50 mg/dL and hypertension demonstrated a statistically significant increase in risk for reoperation (p = 0.01). Conclusion: This study found that elevated Lp(a) levels were not associated with major reoperations in patients undergoing IVS for chronic iliofemoral stenosis. While Lp(a) levels have a significant impact in arterial disease, this study suggested that Lp(a) may have a lesser influence in venous disease. As such, the utility of Lp(a) as a predictive biomarker in venous disease may be limited.

Long-term outcomes of intravascular ultrasound-guided drug-eluting stents implantation in patients with acute coronary syndrome: ULTIMATE ACS subgroup

Objective: To explore the long-term effects of intravascular ultrasound (IVUS) guidance on patients with acute coronary syndrome (ACS) undergoing drug-eluting stents (DES) implantation. Methods: Data used in this study derived from ULTIMATE trial, which was a prospective, multicenter, randomized study. A total of 1 448 all-comer patients were enrolled between 2014 August and 2017 May. Primary endpoint of this study was target vessel failure (TVF) at 3 years, including cardiac death, target-vessel-related myocardial infarction, and clinically-driven target vessel revascularization. Results: ACS was present in 1 136 (78.5%) patients, and 3-year clinical follow-up was available in 1 423 patients (98.3%). TVF in the ACS group was 9.6% (109/1 136), which was significantly higher than 4.5% (14/312) in the non-ACS group (log-rank P=0.005). There were 109 TVFs in the ACS patients, with 7.6% (43/569) TVFs in the IVUS group and 11.6% (66/567) TVFs in the angiography group (log-rank P=0.019). Moreover, patients with optimal IVUS guidance were associated with a lower risk of 3-year TVF compared to those with suboptimal IVUS results (5.4% (16/296) vs. 9.9% (27/273),log-rank P=0.041). Conclusions: This ULTIMATE-ACS subgroup analysis showed that ACS patients undergoing DES implantation were associated with a higher risk of 3-year TVF. More importantly, the risk of TVF could be significantly decreased through IVUS guidance in patients with ACS, especially in those who had an IVUS-defined optimal procedure.

Comparison of intravascular lithotripsy and rotational atherectomy for the treatment of heavily calcified coronary lesions: the STIFF ( S tenoses with calcificaTIon treated with angioplasty e FF ected with dedicated interventional tools) study.

Percutaneous coronary interventions in heavily calcified coronary lesions are associated with technical difficulties and the worse prognosis. Lesion preparation is important to reduce complications and improve outcomes. The aim of this study is to compare the results of rotational atherectomy (RA) and intravascular lithotripsy (IVL) at achieving optimal stent implantation using intravascular ultrasound criteria. Retrospective, single-center study comparing patients with heavily calcified coronary lesions that underwent percutaneous coronary interventions using RA or IVL. 25 patients (13 in the RA group and 12 in the IVL group) were included. Reference vessel diameter was similar between the groups [2.59 (2.51-3.63) mm in the RA group vs. 2.79 (2.59-3.16) mm in the IVL group; P = 0.89], as were minimal lumen area [1.02 (0.80-1.23) mm vs. 1.40 (1.01-1.40) mm; P = 0.43] and diameter stenosis [60.4% (52.3-72.3) vs. 56.1% (47.8-61.3); P = 0.56). The final minimal lumen area was significantly larger in the IVL group [7.6 mm 2 (5.8-8.6) vs. 5.4 mm 2 (4.5-6.2); P = 0.01] as were lumen area gain [4.1 mm 2 (2.6-5.9) vs. 2.3 mm 2 (1.4-3.6); P = 0.01] and final stent volume [491.2 mm 3 (372.2-729.8) vs. 326.2 mm 3 (257.1-435.4); P = 0.03]. In the RA group, 69.2% of the patients achieved the preestablished intravascular ultrasound-based criteria for successful stent implantation, vs. 100% of the patients in the IVL group ( P = 0.04). Patients in the IVL group achieved the Intravascular Ultrasound Versus Angiography-Guided Drug-Eluting Stent Implantation trial criteria of successful stent implantation more frequently than those treated with RA.

Revolutionary auxetic intravascular medical stents for angioplasty applications

Due to the significant mortality rate associated with atherosclerosis-induced cardiovascular disease, the utilization of advanced intravascular stents with superior mechanical performance is imperative for the restoration of obstructed arteries. This study proposes novel auxetic medical stents that aim to enhance critical parameters of biomedical stents. This includes load-bearing capacity, expanded opening percentage, and reduced recoil percentage. On this matter, the missing rib auxetic unit cell has been considered and geometrically modified to achieve these objectives. Two-dimensional (2D) metamaterials were fabricated through additive manufacturing technique and subjected to experimental testing. Then, finite element analysis (FEA) was employed to gain comprehensive insights into the mechanical behaviour of the proposed medical stents. Remarkably, an excellent correlation was observed between the FEA and experimental results, validating the high precision of the analysis. The findings reveal that the stents classified as “E-category” exhibit the highest final opening percentage while concurrently demonstrating the lowest recoil percentage. The base stent exhibited a relatively high recoil percentage of 15.56%, indicating a significant amount of recoil or spring-back after deformation. In contrast, the modified “E-category” stent displayed a substantially lower recoil percentage of 1.62%. This notable reduction in recoil percentage indicates that the modifications made to the rib-unit cells had a significant and beneficial effect on the stent's recoil behaviour and minimizing potential damage to arterial tissue during stent deployment (angioplasty) and balloon pressure. The modified design likely enhances the stent's ability to maintain its shape and resist recoil, making it more effective and reliable in its intended application. Additionally, more aspects of biomedical stents such as foreshortening, and dog-boning of the modified missing rib stents were meticulously examined through FEA.

Modified Preparatory Intravascular Stenting Technique in Super-microsurgical Lymphaticovenular Anastomosis for the Treatment of Lymphedema.

Clinical studies have reported that lymphaticovenular anastomosis (LVA) is more effective for early-stage lymphedema. However, the diameter of lymphatic vessels in early-stage lymphedema is thin (only about 0.3 mm). In this article, we report a modified preparatory intravascular stenting technique (PIST) for LVA with smaller lymphatic vessels and present the results of its application for the treatment of secondary lymphedema. In this technique, a 9-0 nylon thread is inserted into the target lymphatic vessel. Then, the thread is pulled until its tip has entered the lymphatic vessel. After that, the thread is allowed to proceed into the lumen by pushing it. Finally, with the nylon in place, the lymphatic vessel is transected and the lumen is secured. In this report, we investigated the surgical time for LVA between 10 patients who underwent LVA with modified PIST (group A) and another group of 10 patients who underwent LVA without the technique (group B). Lymphatic lumen was secured at all sites where indocyanine green lymphangiography confirmed lymphatic flow. The average outer diameter of lymphatic vessels in group A and B were 0.36 mm and 0.53 mm, respectively. The average surgical time for LVA in group A was 136 minutes, which was significantly shorter than the 187 minutes in group B. Our results indicated that modified PIST can help secure the lymphatic lumen even when the lymphatic vessels are thin. As a result, this technique can significantly reduce the surgical time for this procedure.

On-Site Intravascular Ultrasound-Guided Stenting for Bifurcation Lesions With Angiographically Difficulty in Separation.

On-Site Intravascular Ultrasound-Guided Stenting for Bifurcation Lesions With Angiographically Difficulty in Separation.

Computational fluid dynamics of coronary arteries with implanted stents: Effects of Newtonian and non‐Newtonian blood flows

AbstractThis study introduces and compares computational fluid dynamics of Newtonian and non‐Newtonian blood flows in coronary arteries, with and without considering stents. Three blood flow models, including Newtonian, Carreau, and non‐Newtonian power‐law models, were simulated to investigate their effect, and the solution algorithm includes drawing the geometry, creating the desired mesh, and then simulating Newtonian and non‐Newtonian blood flow different models and comparing them with each other, is presented in the article. A Newtonian fluid model has been commonly used in the simulation of blood flow, whereas blood has non‐Newtonian properties due to the nature of a solution containing suspended particles. The goal of this research is to investigate the differences between the models built with Newtonian and non‐Newtonian fluid assumptions. In addition, a stent was designed and the effect of the stent on blood flow parameters was investigated for all three flow models, including Newtonian, Carreau, and non‐Newtonian power‐law models. Stents are medical devices that can be placed in arteries to open up blood flow in a blocked vessel. Stents can affect the wall shear stress. Knowing the slight deformation of the shear stress makes the importance of stent implantation and also helps to optimize the design of the intravascular stent, which can affect the occlusion of the vessels. The distribution of the velocity, pressure, and wall shear stress in all blood flow models with and without considering the effect of stents have been investigated and finally compared. Therefore, in general, the innovation of this article is to find the effect of implanted stents on blood flow parameters with different blood flow models, both Newtonian and non‐Newtonian. A comparison of Newtonian and non‐Newtonian flows showed that in the case of the Carreau non‐Newtonian model, the wall shear stress was higher. In addition, in the results of the geometric model with a stent effect compared to the geometric model without a stent effect, it is evident that there was a higher velocity and wall shear stress.

Analysis of Serum Markers of Perioperative Brain Injury and Inflammation Associated with Endovascular Treatment of Intracranial Aneurysms: A Preliminary Study.

Embolization is the preferred method for treating intracranial aneurysms due to its less invasive nature. However, recent findings suggest that even uncomplicated embolization may cause structural damage to the brain through ischemic or inflammatory mechanisms. This study aimed to find possible biomarkers of brain injury and inflammation in patients suffering from intracranial aneurysms who underwent endovascular treatment by measuring serological markers indicating brain damage. The study involved 26 patients who underwent uncomplicated intravascular stenting for unruptured intracranial aneurysms between January 2020 and December 2021. Blood samples were collected before the procedure, at 6-12 h, and at 24 h after the procedure. The following protein biomarkers levels were tested with ELISA: S100B, hNSE, TNF, hsCRP, FABP7, NFL, and GP39. Statistical analysis of the results revealed significant increases in serum levels for the four biomarkers: FABP7-before 0.25 (ng/mL) vs. 6-12 h 0.26 (p = 0.012) and vs. 24 h 0.27 (p < 0.001); GP39-before 0.03 (pg/mL) vs. 6-12 h 0.64 (p = 0.011) and vs. 24 h 0.57 (p = 0.001); hsCRP-before 1.65 (μg/mL) vs. 24 h 4.17 (p = 0.037); NFL-before 0.01 (pg/mL) vs. 6-12 h 3.99 (p = 0.004) and vs. 24 h 1.86 (p = 0.033). These biomarkers are recognized as potential indicators of neurovascular damage and should be monitored in clinical settings. Consequently, serum levels of NFL, GP39, hsCRP, and FABP7 measured before and 24 h after endovascular procedures can serve as important markers for assessing brain damage and indicate avenues for further research on biomarkers of neurovascular injury.

Dual intravascular stent flipping technique for microvascular anastomosis

The anastomosis of vessels <0.5mm in diameter is challenging. We developed a supermicrosurgical anastomosis technique, the dual intravascular stent flipping technique with a double or single clip (dual flipping technique, double-clip technique, and single-clip technique). In the dual flipping technique, we used a 7-0 nylon intravascular stent and clipped the vessel along with the nylon. The double-clip technique was performed in 10 rats with 20 saphenous and 15 superficial inferior epigastric arteries. Immediate and 1-week patency rates were assessed. Subsequently, we examined ten epigastric arteries in five rats with the single-clip technique. The clinical application was performed in six cases involving finger/fingertip amputations, two cases involving radial artery superficial palmar branch flap, and one case involving superficial circumflex iliac artery perforator flap. Using the double-clip technique, the immediate patency rate was 90% and 93% in the saphenous and superficial epigastric arteries, respectively, whereas the 1-week patency rate was 81%. With the single-clip technique, the immediate patency rate was 100%. The replantation and flaps were successful. The advantages of the dual flipping technique included easy insertion, rare slipping-out possibility, and spontaneous vessel dilation by the flipped nylon. Additionally, the posterior vessel wall could be sutured more easily than could the anterior wall. By using the elasticity of the thread to invert the blood vessel, the posterior wall can be sutured without the double clip. When forceps tip insertion into the lumen is difficult, the dual flipping technique enables a relatively easy anastomosis if the 7-0 nylon is inserted into the vessel lumen.