Stent Deformation Research Articles

Interventional Applications for an Ostial Protection Guidewire-The WALPO Technique.

Coronary atherosclerotic lesions at the ostium and proximal coronary arteries pose significant challenges in percutaneous coronary interventions (PCI), especially in the left main coronary artery (LMCA). Guide catheter-induced damage can lead to severe complications such as vessel dissection or myocardial infarction. Ostial stent placement with drug-eluting stents offers mechanical support and reduces restenosis but is technically challenging due to the anatomical complexity of the ostium. Complications like longitudinal stent deformation and hydraulic dissection from contrast media are specific concerns. The aortic free-floating wire technique, expanded in this article to Wire in Aorta for Localization and Protection of the Ostium (WALPO), provides a method for safely locating and protecting the ostium during PCI, aiming to improve the safety and efficacy of PCI at this location.

Fatigue Analysis of Nitinol Peripheral Artery Stents Under Complex Loads

Abstract The complex deformation of a peripheral arterial stent during limb movements is the main reason for its fatigue fracture. The aim of this study is to explore the impact of complex loads on the fatigue behavior and life of lower limb arterial stents. Specifically, the finite element simulation was adopted to compare and analyze the fatigue performance of three stents under five superimposed loads. Besides, the life and the fatigue crack growth life of these stents were predicted. It demonstrated that the bending load superimposed on other loads exerted a significant impact on the fatigue performance of these stents. The “spiral” structure design of the stent helped to improve the fatigue durability under complex deformations. Moreover, the prediction method for fatigue crack growth life is relatively conservative, which accounted for approximately 65–97% of the full life. The work provides important references for the fracture assessment and the optimization design of structure of stents.

Calcified nodules in the stented segment concomitant with stent deformation at the hinge point.

Calcified nodules in the stented segment concomitant with stent deformation at the hinge point.

Double Kissing Mini-Culotte Stenting in Unprotected Distal Left Main Bifurcation Under Optical Coherence Tomography Guidance: Immediate and Short-Term Outcomes

IntroductionCulotte stenting is an effective strategy for left main coronary bifurcation lesions. Increased side branch ostial restenosis is the main drawback of Culotte stenting. This is due to a napkin ring or potential gap produced at the ostium of the side branch. A bench study by Toth et al. has shown that additional sequential kissing balloon dilation before main vessel stenting can prevent this deformity. AimWe report immediate and short-term results of Double Kissing (DK) mini-Culotte stenting with a one-year angiographic follow-up. MethodsForty-five patients of distal left main (LM) disease underwent DK mini-Culotte stenting at our center between March 2020 and December 2022 under Optical Coherence Tomography (OCT) guidance. ResultsOut of 45 patients [male:35(77.77%); mean age:63.67±4.94years], chronic coronary syndrome was present in 26(57.8%) and unstable angina in rest. All lesions were Medina (1,1,1), (0,1,1), or (1,0,1) with a median Syntax score of 28 (IQR=23-29). All procedures were technically successful with no adverse clinical events (death, myocardial infarction, or stent thrombosis). Under OCT guidance, adequate minimal stent area (MSA) of 13.28 ± 0.77mm2, 8.25 ± 0.29 mm2, and 7.54 ± 0.45mm2 was achieved in LM, left anterior descending (LAD) and left circumflex (LCx) respectively. Adequate stent expansion of >80% was achieved in all cases. At the end of 1 year, the incidence of major adverse cardiovascular events (MACE) was 2.2%. Further, one (2.2%) patient developed restenosis of the side branch which was managed conservatively. ConclusionDK mini-Culotte stenting in the distal left main bifurcation has shown promising results and is effective in preventing side branch stent deformation and its sequelae of in-stent restenosis.

Characterization and In-vitro Study of Polyethylene Glycol as Coating Material used as Drug Carriers on Coronary Stent for Treatment of Cardiac Diseases

Background: The way coronary artery disease is treated has changed dramatically with the use of coronary angioplasty and stenting. Nowadays, acute coronary syndromes brought on by coronary artery disease are frequently treated using drug-eluting stents. A review of the literature reveals that the polymer coating’s thickness affects the stent’s safety; moreover, current computational studies suggest that larger coatings increase the risk of stent deformity. Polyethylene glycol is the preferred polymer coating material for coronary artery stents.Objectives: Characterization of polyethylene glycol as a medication carrier coating for coronary stents used in cardiac disease therapyMethods: Using UV-visible spectrophotometer, differential scanning calorimetry (DSC), fourier-transform infrared (FTIR), X-ray diffraction, thermogravimetric analysis, and surface morphology, polyethylene glycol was characterized.Results: The calibration curves’ linear regression results, as revealed by the UV-visible spectrophotometer investigation, showed a significant linear association between the concentration range of 10 to 60 μg/mL for polyethylene glycol Y = 0.0354X + 0.0212 (r2 = 0.999), was found. Polyethylene glycol’s molecular miscibility, recrystallization, and phase separation were investigated using a DSC analysis. It was found that the material was physically stable because no recrystallization peaks were visible. According to the results of the thermogravimetric study, a ceramic sample cup with 4 to 6 mg of sample was heated to 400°C at a rate of 5°C every minute. Nitrogen gas was continuously supplied at a rate of 20 mL/min into the sample chamber during the analysis. The results of each batch were measured, and an average was determined. The study of surface coatings to examine the microstructure of the coatings produced both before and after the use of polymers is known as surface morphology. Within analytical imaging is the subset of surface morphology. Pure polyethylene glycol’s morphology showed broad plate-shaped structures. Additionally, a strong band is detected between 1362 and 1287 cm-1, which is comparable to the C-O stretching vibration seen in primary alcohol.Conclusion: On base of the characterization results above shows that polymers were stable and included functional groups and structures throughout a range of conditions. It is possible to use polyethylene glycol as a coating material for coronary stents.

Modeling of valve-in-valve transcatheter aortic valve implantation after aortic root replacement using a 3-dimensional artificial intelligence algorithm

ObjectiveAortic root replacement requires construction of a composite valve-graft and reimplantation of coronary arteries. This study assessed the feasibility of valve-in-valve transcatheter aortic valve implantation after aortic root replacement. MethodsA retrospective review was conducted on 74 consecutive patients who received a composite valve-graft at a single institution from 2019 to 2021. Forty patients had bioprosthetic valves with adequate postoperative gated computed tomographic angiography scans. Computational simulations of balloon and self-expanding transcatheter valve deployments were performed. The modeled coronary distances were compared with traditional, manually measured valve-to-coronary distances. ResultsThere was a statistically significant difference in the modeled versus manual measurements of valve to coronary distances for all patients regardless of valve type or coronary artery analyzed (P < .05). Most patients are low risk for coronary obstruction per 3-dimensional modeling, including those with a valve-to-coronary distance <4 mm. Only 1 patient (2.5%) was at risk for coronary obstruction for the left coronary artery using a balloon valve. No other valve combination was considered high risk of coronary obstruction. Five patients (12.5%) were at risk for possible valve stent deformation at the outflow, due to angulation at the graft anastomosis. ConclusionsFollowing aortic root replacement, all patients were candidates for valve-in-valve procedure using 1 or both types of transcatheter heart valves. Self-expanding valves may be at higher risk for stent frame deformation at graft anastomotic lines and balloon-expandable valves may be at higher risk of coronary obstruction.

Analysis of the effect and safety of lumen reshaping after endovascular repair of Stanford B type aortic dissection at different intervention times

Objective: To Compare the effects and safety of lumen reshaping after thoracic endovascular aortic repair (TEVAR) for Stanford B type aortic dissection (AD) at different intervention times. Methods: A retrospective analysis was conducted on the clinical data of 189 patients with Stanford type B aortic dissection treated with TEVAR at the Affiliated Hospital of Chengde Medical College from January 2016 to December 2020.Based on the time from onset to surgery, patients were divided into an early intervention group (≤14 days, n=127) and a delayed intervention group (>14 days, n=62).The diameters of the total aorta, true lumen and false lumen at different times and planes (S1 plane: at the bifurcation of the pulmonary artery; S2 plane: at the lower edge of the left atrium; S3 plane: at the upper edge of the celiac trunk) post-surgery were compared between the two groups, and the rate of change in diameters of true and false lumens across these planes was calculated. The patients were followed until December 1st, 2023, and the median follow-up time was 45(40, 49) months. The postoperative complications and survival of the two groups were compared. Results: The early intervention group comprised 86 men and 41 women, with an average age of (58.3±10.7) years. The delayed intervention group included 41 men and 21 women, with an average age of (58.5±9.2) years. Both groups had an operation success rate of 100%. Six months post-surgery, the early intervention group had an expansion rate of the true lumen diameter at planes S2 and S3 of 40.1%(25.5%, 56.1%) and 5.3%(-2.5%, 15.8%), respectively, which was superior to the delayed intervention group's 18.5%(10.6%, 39.8%) and 1.0%(-8.2%, 9.6%) (both P<0.05).The early intervention group had a reduction rate of the false lumen diameter at planes S1, S2, and S3 of -56.2%(-61.3%, -48.8%), -70.4%(-81.8%, -56.6%), and -5.4%(-17.4%, 0.1%), respectively, better than the delayed intervention group's -44.2%(-53.7%, -38.3%), -49.0%(-57.6%, -35.8%), and -3.1%(-6.7%, 1.8%) (all P<0.05).At plane S1, the true lumen diameter of patients in both groups showed an increasing trend over 36 months post-surgery, while the false lumen diameter showed a decreasing trend (both P<0.05).At plane S2, the true lumen diameter of patients in the early intervention group exhibited an increasing trend over 36 months post-surgery, and the false lumen diameter exhibited a decreasing trend (both P<0.05).At plane S3, the total aortic diameter of patients in the delayed intervention group showed a slight increasing trend over 36 months post-surgery (P<0.05).The overall survival time were 45.0 months (95%CI: 42.9-47.1) for patients in the early intervention group and 46.0 months (95%CI: 43.5-48.5) for those in the delayed intervention group, with no statistically significant difference observed (P>0.05).The incidence rates of complications such as aortic rupture, retrograde Type A dissection, new distal endograft dissection, endoleak, paraplegia, and others showed no statistically significant difference between the two groups (all P>0.05), with no cases of stent migration or deformation observed. Conclusion: Early intervention for Stanford type B aortic dissection provides a better aortic remodeling outcome than delayed intervention, with similar safety.

Longitudinal Stent Deformation at the Proximal Segment of the Left Main Coronary Artery Caused by a Stuck OCT Catheter: Case Report and Review of Literature.

It has been rarely reported that a stuck optical coherence tomography (OCT) catheter can lead to longitudinal stent deformation (LSD). This complication can result in incomplete stent apposition and dissection after stent implantation. In this study, we present a case where a bailout stent was implanted in the distal segment of the left anterior descending artery (LAD) after longitudinal stent deformation caused by a stuck OCT catheter. This approach was taken to prevent acute stent thrombosis, subacute stent thrombosis, in-stent restenosis (ISR), and death. The patients were followed up for one year, and no adverse events were observed.

Commentary: Coronary stent deformation induced by guide catheter extension.

Commentary: Coronary stent deformation induced by guide catheter extension.

Evaluation of post-dilatation on longitudinal stent deformation and postprocedural stent malapposition in the left main artery by optical coherence tomography (OCT): an in vitro study

BackgroundThe diameter of the ostial and proximal left main coronary artery can be greater than 5.0 mm. However, the diameters of the mostly available coronary drug-eluting stents (DESs) are ≤ 4.0 mm. Whether high-pressure dilatation can increase the diameter of stents from 4.0 to 5.0 mm and whether post-dilatation leads to longitudinal stent deformation (LSD) of 4.0-mm-diameter stents have rarely been studied. Therefore, this study aims to evaluate LSD and stent malapposition of six types of commercially available 4.0-mm-diameter stents in China in a 5.0-mm-diameter artificial blood vessel model by optical coherence tomography (OCT) in vitro.MethodsThe left main coronary artery was simulated by a truncated cone-shaped silicone tube. The internal diameters were 4.0 mm at one end of the silicone tube and 5.0 mm at the other end. Six different types of coronary stents widely used in China were selected for this study. Each stent was respectively implanted into the simulated blood vessel and dilated to a diameter of 4.2 mm according to the stent-balloon pressure compliance table. The stents were subjected to post-dilatation with a 5.0 × 15-mm noncompliant balloon. The LSD ratio of the longitudinal axis of each stent and stent malapposition were measured through OCT, and any fractures of the stents were determined.ResultsNone of the six types of stents fractured following post-dilatation. The longitudinal axes of the BuMA and Excrossal stents were slightly shortened, while the other stents were elongated after high-pressure post-dilatation. All stents expanded to a diameter of 5.0 mm without incomplete stent apposition, except for the Nano Plus stent, which remained malapposed after high-pressure post-dilatation.ConclusionAll 4.0-mm-diameter stents can be expanded to a diameter of 5.0 mm by noncompliant balloon post-dilatation without stent strut fracture. Most stents were found to be well apposed after high-pressure post-dilatation. However, LSD was observed after post-balloon dilatation. Stent malapposition might be positively correlated with the percentage change in stent length.

Impact of stent strut link location in proximal balloon edge dilation technique for bifurcation percutaneous coronary intervention.

The single-stent strategy has generally been accepted as the default approach to bifurcation percutaneous coronary intervention. We have proposed the proximal balloon edge dilation (PBED) technique to prevent stent deformation during side branch (SB) dilation. This bench study aimed to evaluate the impact of stent link location and stent design on stent deformation, obstruction by stent struts at a jailed SB ostium, and incomplete stent apposition in the proximal optimization technique (POT)-PBED procedure. A coronary bifurcation model was used. We intentionally set the absence or presence of stent link on the carina (link-free or link-connect) under videoscope observation and compared stent parameters between 3- and 2-link stents (n = 5 each, n = 20 total). In the link-free group, the SB jailing rate of 3-link stents was significantly higher than that of 2-link stents (15.5 ± 5.1% vs. 6.6 ± 1.2%, p = 0.009). In the link-connect group, the SB jailing rate of 3-link stents was significantly lower than that of 2-link stents (30.0 ± 4.5% vs. 39.0 ± 2.6%, p = 0.009). In the bifurcation segment, the rate of incomplete stent apposition was significantly lower for 3-link stents of the link-connect group than for 2-link stents of the link-connect group (3.3 ± 4.2% vs. 19.0 ± 7.8%, p = 0.009). For both stent designs, ellipticity ratio was higher for link-connect group than link-free group. Link location as well as stent cell design greatly impacted stent deformation during the POT-PBED procedure.

Multi-modality findings of immediate stent deformation after everolimus-eluting stent placement.

Multi-modality findings of immediate stent deformation after everolimus-eluting stent placement.

Longitudinal Stent Elongation: A Rare Complication of Third-Generation Drug-eluting Stent Platform

Abstract Longitudinal stent deformation (LSD) is an infrequent complication of percutaneous coronary intervention. While the occurrence of gross LSD is a rare phenomenon, minor changes in length are common and have been recognized as accepted behavior of stents during implantation. Due to the proximity of the guide catheter, ostial or ostio-proximal lesions are prone to stent deformation either by the guide or other devices during navigation. Moreover, to satisfy the fractal geometry of coronary bifurcation, the proximal optimization technique is commonly performed during different bifurcation procedures, which can subject the stent to extreme overexpansion resulting in structural deformation. We describe two cases of longitudinal stent elongation during ostial deployment and try to analyze the factors behind this rare, yet complicated behavior of the latest-generation drug-eluting stent.

The Horrible Scenario in Cath Lab: Percutaneous Management of Guide Wire Entrapment During Coronary Intervention

The Horrible Scenario in Cath Lab: Percutaneous Management of Guide Wire Entrapment During Coronary Intervention

Transcatheter aortic valve replacement using the two-step inflation technique and the kissing-balloon technique for a patient with a protruding stent in the left main coronary artery: a case report

Abstract Background When performing transcatheter aortic valve replacement (TAVR) for a patient with a protruding stent in the coronary arteries, there is a risk of stent deformation and coronary occlusion. However, safe and optimal methods have not been established. Case summary An 87-year-old woman with a protruding stent in the left main coronary artery (LMCA) underwent TAVR. The two-step inflation and kissing-balloon techniques were performed to optimize the transcatheter heart valve (THV) and to avoid LMCA stent deformation. The THV was implemented with minimal aortic regurgitation and no deformation of the stent in the LMCA. Discussion This was the first case report of TAVR, performed in a patient with a protruding stent in the coronary arteries, using the kissing-balloon technique and the two-step inflation technique. The combination of these two techniques was the optimal method for THV implantation without stent deformation in coronary arteries.

Reduced Order Modeling for Real-Time Stent Deformation Simulations of Transcatheter Aortic Valve Prostheses.

Computational modeling can be a critical tool to predict deployment behavior for transcatheter aortic valve replacement (TAVR) in patients with aortic stenosis. However, due to the mechanical complexity of the aortic valve and the multiphysics nature of the problem, described by partial differential equations (PDEs), traditional finite element (FE) modeling of TAVR deployment is computationally expensive. In this preliminary study, a PDEs-based reduced order modeling (ROM) framework is introduced for rapidly simulating structural deformation of the Medtronic Evolut R valve stent frame. Using fifteen probing points from an Evolut model with parametrized loads enforced, 105 FE simulations were performed in the so-called offline phase, creating a snapshot library. The library was used in the online phase of the ROM for a new set of applied loads via the proper orthogonal decomposition-Galerkin (POD-Galerkin) approach. Simulations of small radial deformations of the Evolut stent frame were performed and compared to full order model (FOM) solutions. Linear elastic and hyperelastic constitutive models in steady and unsteady regimes were implemented within the ROM. Since the original POD-Galerkin method is formulated for linear problems, specific methods for the nonlinear terms in the hyperelastic case were employed, namely, the Discrete Empirical Interpolation Method. The ROM solutions were in strong agreement with the FOM in all numerical experiments, with a speed-up of at least 92% in CPU Time. This framework serves as a first step toward real-time predictive models for TAVR deployment simulations.

In silico fatigue optimization of TAVR stent designs with physiological motion in a beating heart model

Background and ObjectiveThe rapid expansion of TAVR to younger, low-risk patients raises concerns regarding device durability. Necessarily, extended stent lifetime will become more critical for new generation devices. In vitro methods commonly used for TAVR stent fatigue testing exclude the effects of the beating heart. We present a more realistic in silico stent fatigue analysis utilizing a beating heart model in which TAVR stents experience complex, nonuniform dynamic loading. MethodsVirtual TAVR deployments were simulated in the SIMULIA Living Heart Human Model of a beating heart using stent models of the self-expandable nitinol 26-mm CoreValve and Evolut R devices, and a 27-mm PolyV-2. Stent deformation was monitored over three cardiac cycles, and fatigue resistance was evaluated for the nitinol stents using finite element analysis via ABAQUS/Explicit. The average strain and strain amplitude of each stent element were tracked, and established thresholds were applied to determine potential fatigue failure. Fatigue performance of control stents was compared to parametrically modified models with a 20% increase or decrease in strut width. ResultsStents with reduced strut width applied lower radial force against the contracting myocardium of the beating heart, resulting in larger displacements and higher strain values. Formulas relating in vivo strain to stent design do not account for this. In all models, there were elements in which strains exceeded fatigue failure. The PolyV-2 stent had far fewer failing elements since its struts were optimized to reduce the strain in stent joints, achieving better fatigue resistance in the stent crown and waist elements. Different stent sections showed markedly different fatigue resistance due to the varying loading conditions. ConclusionsOur analysis indicates that previous studies underestimate strain amplitudes that may cause stent failure. This study demonstrates the utility of advanced in silico analysis of devices deployed within a beating heart that mimics in vivo loading, offering a cost-effective alternative to human or animal trials and establishing a platform to assess the impact of device design on device durability. The limited fatigue life of TAVR stents indicated here highlights a clinical complication that may eventually develop as younger, lower-risk TAVR patients, age.

Deformation of cardiovascular stents due to manipulation in the adjacent anatomy

Deformation of cardiovascular stents due to manipulation in the adjacent anatomy

TCT-466 Unintended Deformation of Stents During Bifurcation PCI: An OCTOBER Trial Substudy

TCT-466 Unintended Deformation of Stents During Bifurcation PCI: An OCTOBER Trial Substudy

Mechanisms and treatment outcomes of ostial right coronary artery in-stent restenosis.

Despite a high rate of in-stent restenosis (ISR) after stenting the right coronary artery (RCA) ostium, the mechanism of ostial RCA ISR is not well understood. We aimed to clarify the cause of ostial RCA ISR using intravascular ultrasound (IVUS). Overall, 139 ostial RCA ISR lesions were identified with IVUS, pre-revascularisation. Primary ISR mechanisms were classified as follows: 1) neointimal hyperplasia (NIH); 2) neoatherosclerosis; 3) ostium not covered by the stent; 4) stent fracture or deformation; 5) stent underexpansion (old minimum stent area <4.0 mm2 or stent expansion <50%); or 6) a protruding calcified nodule. The median duration from prior stenting was 1.2 (first quartile 0.6, third quartile 3.1) years. The primary mechanisms of ISR were NIH in 25% (n=35) of lesions, neoatherosclerosis in 22% (n=30), uncovered ostium in 6% (n=9) (biological cause 53%, n=74), stent fracture or deformation in 25% (n=35), underexpansion in 11% (n=15), and protruding calcified nodules in 11% (n=15) (mechanical cause 47%, n=65). Including secondary mechanisms, 51% (n=71) of ostial RCA ISRs had stent fractures that were associated with greater hinge motion of the ostial-aorta angle during the cardiac cycle. The Kaplan-Meier rate of target lesion failure at 1 year was 11.5%. When the mechanically caused ISRs were treated without new stents, they suffered a higher subsequent event rate (41.4%) compared with non-mechanical causes or mechanical causes treated without restenting (7.8%, unadjusted hazard ratio 6.44, 95% confidence interval: 2.33-17.78; p<0.0001). Half of the ostial RCA ISRs were due to mechanical causes. Subsequent event rates were high, especially in mechanically caused ISRs treated without the implantation of a new stent.