Smart Stent Research Articles

Dual-functional carbon nanotube yarn supercapacitor for real-time reactive oxygen species monitoring and sustainable energy supply in implantable device

Smart stents integrate embedded sensors and advanced technology, providing a real-time diagnostic feedback, particularly for detection of thrombotic events. A continuous monitoring reactive oxygen species (ROS) in blood vessels is crucial for cardiovascular disease. The provision of a continuous power supply to sensors integrated within blood vessels is challenging. This study introduces a novel device that combines a sensor and supercapacitor, functioning as a ROS sensor and enabling continuous charging and discharging within blood vessels. This device uses yarn-shaped electrodes integrated with cytochrome c and carbon nanotubes (Cyt.c/CNT). The Cyt.c/CNT electrode exhibits a high specificity to ROS with an sensitivity (49.02 μA μM−1 cm−2), as a real-time biosensor for monitoring of cellular ROS levels in living cells. In addition, it exhibited an energy storage performance of 257.95 mF cm−2 as a supercapacitor and maintained a stable performance during 10,000 repeated cycles in various biofluids. Notably, the integration of the Cyt.c/CNT electrode with an enzymatic biofuel cell enables continuous charging and discharging in a biofluid, making it a promising system for in-vivo applications. This study presents the potential of Cyt.c for ROS sensing as well as its potential as an energy storage system, showing new possibilities for implantable devices for cardiovascular diseases.

Coaxial bioprinting of a stentable and endothelialized human coronary artery-sized in vitro model.

Atherosclerosis accounts for two-thirds of deaths attributed to cardiovascular diseases, which continue to be the leading cause of mortality. Current clinical management strategies for atherosclerosis, such as angioplasty with stenting, face numerous challenges, including restenosis and late thrombosis. Smart stents, integrated with sensors that can monitor cardiovascular health in real-time, are being developed to overcome these limitations. This development necessitates rigorous preclinical trials on either animal models or in vitro models. Despite efforts being made, a suitable human-scale in vitro model compatible with a cardiovascular stent has remained elusive. To address this need, this study utilizes an in-bath bioprinting method to create a human-scale, freestanding in vitro model compatible with cardiovascular stents. Using a coaxial nozzle, a tubular structure of human coronary artery (HCA) size is bioprinted with a collagen-based bioink, ensuring good biocompatibility and suitable rheological properties for printing. We precisely replicated the dimensions of the HCA, including its internal diameter and wall thickness, and simulated the vascular barrier functionality. To simplify post-processing, a pumpless perfusion bioreactor is fabricated to culture a HCA-sized model, eliminating the need for a peristaltic pump and enabling scalability for high-throughput production. This model is expected to accelerate stent development in the future.

The PolyCraft Polymer–Metal Hybrid Smart Stent System: The Future of Cardiovascular Blood Pressure Management

AbstractTo address the complication of in‐stent restenosis that occurs with traditional stent treatments, this study proposes an innovative hybrid smart stent‐based medical system. This approach allows to overcome the limitations of existing bare metal or polymer‐based smart stents, which interfere with radio frequency signals, less deformability, or do not provide adequate radial support, respectively. The proposed hybrid stent, which uses a Co/Cr–polycaprolactone (PCL)–Co/Cr configuration connected by a unique dual inverted Y‐type connector for metal–polymer integration is integrated with a LC wireless pressure sensor fabricated through a semiconductor process. The fabricated hybrid stent made by laser machining and custom‐made 3D printing, offers excellent properties such as radial strength (0.125 N/mm) and flexibility (2 N mm2) and provides intravascular information to the outside through the integrated sensor without signal degradation. After basic experiments using a phantom, animal experiments are conducted by combining the fabricated sensor with artificial blood vessel, and the results measured by the external antenna system are consistent with the results of a commercial reference sensor. The proposed wireless sensor‐based smart stents and artificial blood vessels aim to gather diverse patient health data for integration with artificial intelligence, laying the groundwork for next‐generation medical innovation.

Detection of Blood Clots Using a Whole Stent as an Active Implantable Biosensor.

Many cardiovascular problems stem from blockages that form within the vasculature and often treatment includes fitting a stent through percutaneous coronary intervention. This offers a minimally invasive therapy but re-occlusion through restenosis or thrombosis formation often occurs post-deployment. Research is ongoing into the creation of smart stents that can detect the occurrence of further problems. In this study, it is shown that selectively metalizing a non-conductive stent can create a set of electrodes that are capable of detecting a build-up of material around the stent. The associated increase in electrical impedance across the electrodes is measured, testing the stent with blood clot to mimic thrombosis. It is shown that the device is capable of sensing different amounts of occlusion. The stent can reproducibly sense the presence of clot showing a 16% +/-3% increase in impedance which is sufficient to reliably detect the clot when surrounded by explanted aorta (one sample t-test, p = 0.009, n = 9). It is demonstrated that this approach can be extended beyond the 3D printed prototypes by showing that it can be applied to a commercially available stent and it is believed that it can be further utilized by other types of medical implants.

Continuous monitoring of cardiovascular function with a smart stent incorporating a flexible and stretchable wireless pressure sensor

The development of smart stents, capable of monitoring cardiovascular diseases and communicating vascular abnormalities to medical doctors, has garnered significant attention in the field of biomedical engineering. Various ex-situ fabrication strategies have been proposed to concurrently manufacture the smart stent and pressure sensor, thereby reducing the risk of sensor detachment caused by blood flow. However, the practical utility of these devices is still limited due to the rigidity of the wireless pressure sensor. In this study, we propose a flexible and stretchable smart self-reporting stent that incorporates a wireless pressure sensor. The fabrication process has been optimized to create a serpentine-shaped wireless pressure sensor that matches the shape and flexibility of the polymer stent struts. We thoroughly investigated the structural integrity, resonance frequency, stretchability, flexibility, and radial force of the manufactured smart self-reporting stent under different conditions. The wireless pressure sensor demonstrated a sensitivity of 0.15 MHz mmHg−1, as determined through experimental analysis. To demonstrate the feasibility of the proposed smart stent, we implanted it into the arteries of a three-dimensional phantom system. The obtained results, combined with the flexible and stretchable nature of the proposed smart self-reporting stent, highlight its potential for effective monitoring of the heart’s functional dynamics and detection of in-stent restenosis.

Coronary artery lipid accumulation prevention through vibrating piezo electric nano plates embedded in smart stent.

Considering the lipid concentration and side effects regarding the stents used by surgeons, a new heart stent model is proposed. In the new stent, a few piezo plates are designed and attached to the stents by which release of the lipids can take place due to the applied alternative voltages. Due to the vibrations of small-scale piezoelectric plates, the deposition of low-density-lipoproteins (LDL) floating in the blood flow in the coronary arteries is prevented. Small-scale effects are considered using nonlocal elasticity theory, and the interaction between fluid and solid is modeled using the Navier-Stokes equation. The effect of fluid parameters as well as applied voltage and geometry structure is reported. Developing of smart stents maybe the key for prevention of short time conventional stents failure.

Vascular Health: The Power of Implantable Wireless Electronics

The continuous monitoring of vascular health achievable by implantable electronics can offer improved disease diagnosis and treatments. We developed a wireless nanomembrane system consisting of a smart stent and soft sensors to enable simultaneous monitoring of blood pressure, blood flow, and pulse rate.

Abstract No. 595 Endovascular Recanalization and Reconstruction for the Treatment of Symptomatic Venous Ligation

To report techniques, adverse events, and outcomes of endovascular recanalization and stent reconstruction for symptomatic venous ligation. Nine patients, including six (66.7%) men and three (33.3%) women, with mean age 52.9 ± 11.9 years (range, 35-69 years), underwent endovenous recanalization and stent reconstruction for symptomatic venous ligation over eight years. Five (55.6%), one (11.1%), and three (33.3%) patients presented with CEAP 3, 4, and 5 diseases, respectively. External iliac vein ligation occurred in six (66.7%) patients. Ligations were unilateral left, unilateral right, and bilateral in three (33.3%), four (44.4%), and two (22.2%) patients, respectively. Ligation etiologies included surgical injury in four (44.4%), traumatic injury in two (22.2%), chronic lower extremity venous thrombosis in two (22.2%), and malignant resection in one (11.1%) patient. Technical successes, reconstruction parameters, adverse events, hospital stay lengths, clinical outcomes, stent patencies, follow-up evaluations, and mortalities were recorded. Primary single-session recanalization was achieved in nine (100%) patients. Sharp, extravascular, techniques were required in 6 (66.7%) patients. Reconstructions were created with Wallstents, SMART stents, and cTAG devices. Mean number of stents was 2.9 ± 2.5 stents (range, 1-7 stents). Mean stent diameter was 15.5 ± 3.2-mm (range, 12-26-mm). Adverse events (AEs), according to the Society of Interventional Radiology, included one (10.0%) common iliac vein injury (major AE; class D) and one (7.7%) of neck hematoma (minor AE; class A). Mean hospitalization stay length was 1.6 ± 1.6 days (range, 1-6 days). Clinical improvement was achieved in eight (88.9%) patients with six (66.7%) patients downgraded to CEAP 0 disease. Eight (88.9%) reconstructions remained patent with a mean imaging follow-up of 466.4 ± 500.3 days (range, 17-1,400 days). One (9.1%) reconstruction became occluded within sixty days and was unable to be recanalized. Mean total follow-up was 1,086.2 ± 717.5 days (range, 47-2,707 days). Thirty day and study mortality were both zero. Endovenous recanalization and reconstruction is an effective and safe treatment for symptomatic venous ligation.

Risk factors for in-stent restenosis in maintenance hemodialysis patients with central venous occlusive disease and biomechanical assessment of stents.

To investigate the risk factors and biomechanical mechanisms of in-stent restenosis (ISR) in central venous occlusive disease (CVOD). This retrospective study consecutively included 77 maintenance hemodialysis (MHD) patients with CVOD who received the first percutaneous transluminal angioplasty with stenting (PTS) due to symptomatic CVOD in a tertiary hospital. The mean age was 59.7 ± 14.0 years, and 51.9% of patients were male. The clinical characteristics, occurrence of ISR and patency rates were recorded. Finite element method was applied to assess the biomechanical properties of stents. Among 77 patients with a mean CVS score of 8.0 ± 2.8, 20.8%, 62.3%, and 16.9% of patients had the main vein of CVOD in the subclavian vein, brachiocephalic vein, and superior vena cava, respectively. A total of 72 (93.5%) patients received successful PTS treatment, for which the stents implanted were mainly Fluency covered stent (48.6%) and SMART bare stent (31.9%). During 15 (10-24)-months of follow-up, ISR occurred in 36.1% of the 72 patients. The primary and assisted primary patency rates at 6, 12, and 18 months were 78%, 56%, 42% and 95%, 90%, 87%, respectively. A prolonged dialysis vintage was an independent risk factor for ISR, yet the stent type or the main vein location was not correlated with ISR. Among three laser-engraving stents, the SMART stent was the best in terms of flexibility, stress, and strain on stents but worst in stress or strain on vessels. The Luminexx stent was the best in radial force and worst in stress or strain on stents. The Vici stent was the best in stress and strain on vessels and worst in radial force and flexibility. An unsatisfactory comprehensive biomechanical performance from configurations rooted in existing stents may account for the high incidence of ISR in CVOD.

"The Hunterian approach: Cordis Smart Stent safe and effective, but what about its use in long or severely calcified chronically occluded lesions… Let's get it done the first time".

Key Points The Smart stent has been “battle‐hardened” with years of experience to treat femoropopliteal lesions. Many patients with femoropopliteal lesions require multiple interventions. Are there any therapies that can be performed for long‐term success for longer femoral lesions?

Self-rollable Polymer Stent Integrated with Wireless Pressure Sensor for Real-time Monitoring of Cardiovascular Pressure

In this paper, we propose a self-rollable polymer (SU-8) stent integrated with a passive LC pressure sensor for the uninterrupted monitoring of cardiovascular pressure. The design of the LC pressure sensor and polymer stent was optimized by varying the turns of inductor and the stent thickness. A wireless pressure sensor with 30 turns of coils was selected based on the experimental results of inductance and radial force measurements. The sensor was fabricated simultaneously with a stent structure with a thickness of 40 µm on a two-dimensional plane using conventional micromachining processes. The fabricated smart stent was placed inside a silicon tube, and its performance was evaluated as a function of working distance (0–11 mm), working pressure (0–100 mmHg), and different media (air, DI water, and saline). After the preliminary experiment, the entire stent device was encapsulated with a thin parylene C layer, and improvements in biocompatibility were confirmed using a viability test with human umbilical vein endothelial cells. The proposed smart stent is expected be widely used in medical applications owing to its structural excellence.

Stress induced self-rollable smart-stent-based U-health platform for in-stent restenosis monitoring.

To date, several smart stents have been proposed to continuously detect biological cues, which is essential for tracking patients' critical vital signs and therapy. However, the proposed smart stent fabrication techniques rely on conventional laser micro-cutting or 3D printing technologies. The sensors are then integrated into the stent structure using an adhesive, conductive epoxy, or laser micro-welding process. The sensor packaging method using additional fabrication processes can cause electrical noise, and there is a possibility of sensor detachment from the sent structure after implantation, which may pose a significant risk to patients. Herein, we are demonstrating for the first time a single-step fabrication method to develop a smart stent with an integrated sensor for detecting in-stent restenosis and assessing the functional dynamics of the heart. The smart stent is fabricated using a microelectromechanical system (MEMS)-based micromachining technology. The proposed smart stent can detect biological cues without additional power and wirelessly transmit the signal to the network analyzer. The cytocompatibility of the smart stent is confirmed through a cytotoxicity test by monitoring the cell growth, proliferation, and viability of the cultured cardiomyocytes. The capacitance of the smart stent exhibits an excellent linear relationship with the applied pressure. The exceptional sensitivity of the pressure sensor enabled the proposed smart stent to detect biological cues during in vivo analysis. The preliminary findings confirmed the proposed smart stent's higher level of structural integrity, durability and repeatability. Finally, the practical feasibility of the smart stent is demonstrated by monitoring diastole and systole at various beat rates using a phantom. The results of the phantom study showed a similar pattern to the human model, indicating the potential use of the proposed multifunctional smart stent for real-time applications.

Design and Analysis of Smart Stents Using MEMS Pressure Sensors

In modern day medicine, stents are a commonly used device for patients with cardiovascular diseases.There is however no accurate method of monitoring its working and ensuring that the stent is able to prevent any further blockages. Stents can also cause issues like restenosis and thrombosis, which if not treated immediately can have serious repercussions for the patient. This project aims at understanding,modelling and developing a smart stent which can resolve most of the issues with modern day stents and also work as an early warning system for restenosis and thrombosis. Smart stent can monitor the blood pressure inside the stent and any blockage in the stent can be identified and treated immediately. The motivation for the project is to improve the existing stent technology and provide doctors and patients an accurate system to monitor the working of the stent inside an artery.

Capacitive Sensing for Monitoring Stent Patency in the Central Airway.

Central airway obstruction (CAO) is a respiratory disorder characterized by the blockage of the trachea and/or the main bronchi that can be life-threatening. Airway stenting is a palliative procedure for CAO commonly used given its efficacy. However, mucus impaction, secretion retention, and granulation tissue growth are known complications that can counteract the stent's benefits. To prevent these situations, patients are routinely brought into the hospital to check stent patency, incurring a burden for the patient and the health care system, unnecessarily when no problems are found. In this paper, we introduce a capacitive sensor embedded in a stent that can detect solid and colloidal obstructions in the stent, as such obstructions alter the capacitor's dielectric relative permittivity. In the case of colloidal obstructions (e.g., mucus), volumes as low as 0.1 ml can be detected. Given the small form factor of the sensor, it could be adapted to a variety of stent types without changing the standard bronchoscopy insertion method. The proposed system is a step forward in the development of smart airway stents that overcome the limitations of current stenting technology.Clinical Relevance- This establishes the foundation for smart stent technology to monitor stent patency as an alternative to rutinary bronchoscopies.

A computational study of effects of material properties, strain level, and friction coefficient on smart stent behavior and peripheral artery performance during the interaction process

Peripheral artery stenting (PAS) is an effective alternative for peripheral endarterectomy. Smart stents can be used to minimize the problems of interaction between peripheral arteries and smart stent. To evaluate the biomechanical properties of smart stents and their interactions with the peripheral artery, a 3D nonlinear finite element method (FEM) model that was composed of a peripheral artery and a smart stent was built. The present simulation modeled smart superelasticity material based on thermodynamics of the Helmholtz free energy (Auricchio theory) and Peripheral artery based on hyperelastic models (Mooney-Rivlin and Ogden). Additionally, the present study used FEM to assess the influences of the material properties, strain level, and friction coefficient (with attention to smart stent’s materials properties) of the newly designed smart stent during crimping and its interaction with the peripheral artery. The results showed that the smart stent with high Af: Austenite finish temperature, 90% crimping, and friction coefficient of 0.1 between smart stent and peripheral artery performed better mechanically and clinically, which can be attributed to suitable Chronic Outward Force (COF), high Radial Resistive Force (RRF), whole mechanical hysteresis regarding superelastic performance, the high martensite formation, the low stress on the peripheral artery, and the high strain on the internal curvature of the smart stent and peripheral artery. Moreover, it was found that the Mooney-Rivlin model showed a better mechanical performance that the Ogden model given the distribution of stress and strain level on the peripheral artery. These models were appropriate for the description of the peripheral artery performance and smart stent behavior with considering material properties, strain level, and friction coefficient during the interaction process.

The feasibility of the flower stenting technique for ostial lesions of the common iliac artery.

Background and AimsA balloon‐expandable stent (BES) is generally used for ostial lesions of the common iliac artery (CIA) owing to the positional ease of stent adjustment. However, there are potential risks such as vessel dissection and perforation due to vessel overstretching during. In our hospital, we performed endovascular therapy (EVT) for CIA ostial lesions via a novel method named “the flower stenting method,” using a self‐expandable stent. This study aimed to analyze the efficacy and safety of this method.MethodsThis study was single‐center, retrospective, and observational. We enrolled 83 patients (91 limbs) who underwent EVT with SMART stent (Cordis, Miami, Florida) for CIA ostial lesions from 2007 to 2014. The primary endpoint was the rate of freedom from target lesion revascularization (TLR) in 5 years, and the secondary endpoint was the success rate of stent placement for the CIA ostium.ResultsThe average patient age was 72.3 ± 9.4 years, 71% of the patients were men, 19% were receiving hemodialysis, and 60% had diabetes. Additionally, 38% of the lesions were Trans‐Atlantic Inter‐Society Consensus C/D lesions, while 37% were chronic total occlusion lesions. The average lesion length was 36 ± 23 mm, and the average vessel diameter was 10.7 ± 1.4 mm. The rate of freedom from TLR was 97.3% at 5 years, and the success rate of only stent placement was 90.1%.ConclusionThe flower stenting method leads to acceptable outcomes and is useful for accurate stent deployment.

Abstract No. 504 Update: iliocaval-in-stent restenosis

To examine patient, stent, and angioplasty factors associated with 50% and 75% in-stent restenosis (ISR) of iliocaval stents placed for chronic venous thrombosis with results at 1, 3, 5, and 20 years post-placement. All patients with symptomatic chronic iliocaval venous thrombosis who underwent iliocaval stent placement with either SMART (Cordis, Santa Clara, CA) or Wallstent (Boston Scientific, Natick MA) at an academic medical center from 1996 to 2018 were compiled from a departmental database. In total, 620 iliocaval stents (430 SMART, 190 Wallstent) were placed in 176 patients (52.8% male, median age 51.1 y). Median follow -was 538.1 days (range, 0–6473 days). Rates of ISR at > 50% and > 75% luminal obstruction were calculated using Kaplan-Meier methods. Cox regression analysis of the effects of age, gender, stent brand, stent diameter, stent length, and angioplasty balloon diameter, on ISR was performed. Median and mean time to ISR were 153.5 and 299.2 days, respectively (range, 3–3985 days). In the 20 year follow-up period, ISR occurred in 8.7% of inferior vena cava (IVC) stents, 10.9% of common iliac vein (CIV) stents, and 15.3% of external iliac vein (EIV) stents. Gender did not affect ISR. Increased age was associated with a small but significant increased risk of ISR when all veins were examined as a single cohort at 1, 3, 5, and 20 years and within the EIV at 3, 5, and 20 years. Wallstents were associated with decreased rate of ISR when all veins were examined as a single cohort at 1, 3, 5, and 20 years as well as within EIV and CIV at 1, 3, 5, and 20 years. A small but significant increased risk of ISR was noted with larger stents in the EIV at 1, 3, 5, and 20 years and IVC at 1 year only as well as when all veins are examined as a single cohort at 1, 3, 5, and 20 years. Smaller balloon diameter demonstrated an increased risk of ISR within IVC stents at 1 year only. When the threshold for ISR was raised to > 75% ISR, all of the above significant results were the same. However, in addition, increasing stent length was associated with a small but significant risk of ISR > 75% when all veins were examined as a single cohort at 1, 3, 5, and 20 years. Our study demonstrates clinically acceptable and decreased rates of ISR compared to prior studies for the IVC, CIV, and EIV stents. Age is a small but significant risk factor for ISR, especially within the EIV. Wallstents may decrease ISR in iliac veins but are similar to SMART stents when placed in the IVC. Larger balloon diameters may help with short-term IVC ISR and larger stents may increase the risk of ISR in the EIV.

A novel magneto-mechanical metamaterial cell structure with large, reversible and rapid two-way shape alteration

Smart mechanical metamaterials based on various types of stimuli-sensitive materials break through the limitations of traditional metamaterials and exhibit many attractive properties. The development of multi-functional mechanical metamaterials capable of multi-mode, reversible, large deformations and remote controllability remains a challenge. In this work, we designed and prepared several magneto-mechanical metamaterial unit cells based on magnetoactive soft materials using 3D printing technology. A novel cell structure of cuboctahedron was fabricated and examined deeply which was elongated or contracted along the central magnetic field direction under different external magnetic fields. Experiment and simulation results shown that the special metamaterial structure design enables the magneto-active unit cells to achieve super deformation characteristics that it does not originally possess. The rapid two-way large deformation of the cuboctahedron cell was achieved with a quite remarkable deformation up to 85%, and it could quickly return to the original shape of the cell when the magnetic field was removed. Besides of these capabilities, as an application example, we further demonstrated the multi-modal shape of shrinkage and elongation of the cell structure in a biomimetic blood vessel, to show the effectiveness of the prototype smart stent for particle transport in a remotely controllable manner. The developed magneto-mechanical metamaterial certainly can be extended to various functionalized application, such as soft robots, healthcare and flexible electronics.

A Smart Stent for Monitoring Eventual Restenosis: Computational Fluid Dynamic and Finite Element Analysis in Descending Thoracic Aorta

Even though scientific studies of smart stents are extensive, current smart stents focus on pressure sensors. This paper presents a novel implantable biocompatible smart stent for monitoring eventual restenosis. The device is comprised of a metal mesh structure, a biocompatible and adaptable envelope, and pair-operated ultrasonic sensors for restenosis monitoring through flow velocity. Aside from continuous monitoring of restenosis post-implantation, it is also important to evaluate whether the stent design itself causes complications such as restenosis or thrombosis. Therefore, computational fluid dynamic (CFD) analysis before and after stent implantation were carried out as well as finite element analysis (FEA). The proposed smart stent was put in the descending thoracic section of a virtually reconstructed aorta that comes from a computed tomography (CT) scan. Blood flow velocity showed that after stent implantation, there is not liquid retention or vortex generation. In addition, blood pressures after stent implantation were within the normal blood pressure values. The stress and the factor of safety (FOS) analysis showed that the stress values reached by the stent are very far from the yield strength limit of the materials and that the stent is stiff enough to support the applied loads exported from the CFD results.

Perspectives on smart stents with sensors: From conventional permanent to novel bioabsorbable smart stent technologies

AbstractCardiovascular stent angioplasty represents the pre‐eminent choice for the treatment of coronary artery disease. Despite the widespread developments in this arena such as new‐generation drug‐eluting stents and transient bioabsorbable stents, the stent technologies are still associated with several clinical complications associated with stent thrombosis and in‐stent restenosis. Pertinent ‘smart stent’ systems incorporated with sensors are garnering immense research interest in view of their potential to mitigate/reduce several adverse outcomes associated with stents. In this minireview, we attempt to provide a timely overview on the most recent developments in the field of smart stent systems with embedded sensors. The first two sections of this review discuss about the smart stent technology to detect stent endothelialization and in‐stent restenosis. Next, we briefly summarize the propitious bioabsorbable smart stent systems, and the review concludes by highlighting the future perspectives that can foster this research arena. The latest advancements in this research field by integrating sensors in stents have demonstrated immense potentiality in mitigating the risks associated with cardiovascular clinical complications to ameliorate the problems associated with millions of people worldwide.