Stent Struts Research Articles

Super-resolution deep learning reconstruction at coronary computed tomography angiography to evaluate the coronary arteries and in-stent lumen: an initial experience

A super-resolution deep learning reconstruction (SR-DLR) algorithm trained using data acquired on the ultrahigh spatial resolution computed tomography (UHRCT) has the potential to provide better image quality of coronary arteries on the whole-heart, single-rotation cardiac coverage on a 320-detector row CT scanner. However, the advantages of SR-DLR at coronary computed tomography angiography (CCTA) have not been fully investigated. The present study aimed to compare the image quality of the coronary arteries and in-stent lumen between SR-DLR and model-based iterative reconstruction (MBIR). We prospectively enrolled 70 patients (median age, 69 years; interquartile range [IQR], 59–75 years; 50 men) who underwent CCTA using a 320-detector row CT scanner between January and August 2022. The image noise in the ascending aorta, left atrium, and septal wall of the ventricle was measured, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in the proximal coronary arteries were calculated. Of the twenty stents, stent strut thickness and luminal diameter were quantitatively evaluated. The image noise on SR-DLR was significantly lower than that on MBIR (median 22.1 HU; IQR, 19.3–24.9 HU vs. 27.4 HU; IQR, 24.2–31.2 HU, p < 0.01), whereas the SNR (median 16.3; IQR, 11.8–21.8 vs. 13.7; IQR, 9.9–18.4, p = 0.01) and CNR (median 24.4; IQR, 15.5–30.2 vs. 19.2; IQR, 14.1–23.2, p < 0.01) on SR-DLR were significantly higher than that on MBIR. Stent struts were significantly thinner (median, 0.68 mm; IQR, 0.61–0.78 mm vs. 0.81 mm; IQR, 0.72–0.96 mm, p < 0.01) and in-stent lumens were significantly larger (median, 1.84 mm; IQR, 1.65–2.26 mm vs. 1.52 mm; IQR, 1.28–2.25 mm, p < 0.01) on SR-DLR than on MBIR. Although further large-scale studies using invasive coronary angiography as the reference standard, comparative studies with UHRCT, and studies in more challenging population for CCTA are needed, this study’s initial experience with SR-DLR would improve the utility of CCTA in daily clinical practice due to the better image quality of the coronary arteries and in-stent lumen at CCTA compared with conventional MBIR.

TCT-52 Coronary Bifurcation Bench to Assess the Impact of Stent Strut Link Location in Proximal Balloon Edge Dilation Technique

TCT-52 Coronary Bifurcation Bench to Assess the Impact of Stent Strut Link Location in Proximal Balloon Edge Dilation Technique

Computational modeling of low-density lipoprotein accumulation at the carotid artery bifurcation after stenting.

Restenosis typically occurs in regions of low and oscillating wall shear stress, which also favor the accumulation of atherogenic macromolecules such as low-density lipoprotein (LDL). This study aims to evaluate LDL transport and accumulation at the carotid artery bifurcation following carotid artery stenting (CAS) by means of computational simulation. The computational model consists of coupled blood flow and LDL transport, with the latter being modeled as a dilute substance dissolved in the blood and transported by the flow through a convection-diffusion transport equation. The endothelial layer was assumed to be permeable to LDL, and the hydraulic conductivity of LDL was shear-dependent. Anatomically realistic geometric models of the carotid bifurcation were built based on pre- and post-stent computed tomography (CT) scans. The influence of stent design was investigated by virtually deploying two different types of stents (open- and closed-cell stents) into the same carotid bifurcation model. Predicted LDL concentrations were compared between the post-stent carotid models and the relatively normal contralateral model reconstructed from patient-specific CT images. Our results show elevated LDL concentration in the distal section of the stent in all post-stent models, where LDL concentration is 20 times higher than that in the contralateral carotid. Compared with the open-cell stents, the closed-cell stents have larger areas exposed to high LDL concentration, suggesting an increased risk of stent restenosis. This computational approach is readily applicable to multiple patient studies and, once fully validated against follow-up data, it can help elucidate the role of stent strut design in the development of in-stent restenosis after CAS.

Geometric optimization of vascular stents modeled as networks of 1D rods

We develop a novel mathematical and computational framework for geometric optimization of mesh-like devices such as stents, based on modeling mesh-like structures as networks of one-dimensional curved rods. To simplify calculations, the curved rods are approximated by piecewise straight rods. Constrained optimization problems for different cost functionals are stated and mathematically analyzed. The cost functionals considered include: (1) stents' compliance, (2) L2 norm of displacement, (3) L2 norm of contact moment (which is related to fatigue), and (4) multicriteria optimization in which stents are optimized to achieve maximal radial stiffness and minimal bending rigidity. The optimization parameters are stent's vertices, namely, the location of points where the stent struts meet. Existence of solutions to the mathematically posed optimization problems is obtained, and a numerical method based on the gradient descent algorithm is proposed to find the solutions. Three representative stents' geometries are numerically analyzed to show that the optimization algorithms provide tangible solutions. The stent geometries considered are those of Palmaz type stents, single zig-zag stent rings, and Express type stents. Interesting findings are obtained, including several new stent designs. Several optimized stents are presented, including an optimized Palmaz stent with a reduction in contact moment of 30%, and optimized Express and Palmaz stents with a reduction in compliance by more than 70%.

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.

Comparison of Supraflex Cruz 60 μm Versus Ultimaster Tansei 80 μm Stent Struts in High Bleeding Risk PCI Patients: Study design and Rational of Compare 60/80 HBR trial

Up to 45% of patients who underwent percutaneous coronary intervention (PCI) may have a high bleeding risk (HBR), depending on the bleeding risk definition.1 This condition is often associated with an enhanced risk of thrombotic events with a negative impact on short- and long-term outcomes,2-8 making the choice of an appropriate antithrombotic regimen after PCI particularly challenging. Advances in stent technologies, in which the introduction of newer generations of thinner strut drug-eluting stents (DES), have significantly reduced the rate of thrombotic complications and may justify a shorter dual antiplatelet therapy (DAPT) duration. Both in vitro and in vivo studies have shown that local hemodynamic factors may critically affect the natural history of atherosclerosis. Strut thickness correlates with flow disturbances and endothelial shear stress. Flow separation within struts determines areas of recirculation with low endothelial shear stress which promotes local concentration of activated platelets.9 By mitigating inflammation, vessel injury, and neointimal proliferation, thin and streamlined struts have been associated with faster vascular healing and re-endothelization and have resulted in lower rates of thrombotic events after PCI.10,11 The use of thin strut and ultra-thin strut stents may lead to a favorable trade-off in bleeding and ischemic events in patients with HBR. However, dedicated studies evaluating the performance of thin strut versus ultrathin strut stents in patients with HBR are lacking.

The Usefulness of Intracoronary Imaging in Patients with ST-Segment Elevation Myocardial Infarction.

Intracoronary imaging (ICI) modalities, namely intravascular ultrasound (IVUS) and optical coherence tomography (OCT), have shown to be able to reduce major adverse cardiovascular events in patients undergoing percutaneous coronary intervention (PCI). Nevertheless, patients with ST-segment elevation myocardial infarction (STEMI) have been practically excluded from contemporary large randomized controlled trials. The available data are limited and derive mostly from observational studies. Nevertheless, contemporary studies are in favor of ICI utilization in patients who undergo primary PCI. Regarding technical aspects of PCI, ICI has been associated with the implantation of larger stent diameters, higher balloon inflations and lower residual in-stent stenosis post-PCI. OCT, although used significantly less often than IVUS, is a useful tool in the context of myocardial infarction without obstructive coronary artery disease since, due to its high spatial resolution, it can identify the underlying mechanism of STEMI, and, thus, guide therapy. Stent thrombosis (ST) is a rare, albeit a potential lethal, complication that is expressed clinically as STEMI in the vast majority of cases. Use of ICI is encouraged with current guidelines in order to discriminate the mechanism of ST among stent malapposition, underexpansion, uncovered stent struts, edge dissections, ruptured neoatherosclerotic lesions and coronary evaginations. Finally, ICI has been proposed as a tool to facilitate stent deferring during primary PCI based on culprit lesion characteristics.

Dipyridamole and vascular healing following stent implantation.

Patients undergoing coronary stent implantation incur a 2% annual rate of adverse events, largely driven by in-stent restenosis (ISR) due to neointimal (NI) tissue proliferation, a process in which smooth muscle cell (SMC) biology may play a central role. Dipyridamole (DP) is an approved therapeutic agent with data supporting improved vascular patency rates. Pre-clinical data supports that DP may enact its vasculoprotective effects via adenosine receptor-A2B (ADOR-A2B). We sought to evaluate the efficacy of DP to mitigate ISR in a pre-clinical rabbit stent model. 24 New Zealand White Rabbits were divided into two cohorts-non-atherosclerosis and atherosclerosis (n = 12/cohort, 6 male and 6 female). Following stent implantation, rabbits were randomized 1:1 to control or oral dipyridamole therapy for 6 weeks followed by optical coherence tomography (OCT) and histology assessment of NI burden and stent strut healing. Compared to control, DP demonstrated a 16.6% relative reduction in NI volume (14.7 ± 0.8% vs. 12.5 ± 0.4%, p = 0.03) and a 36.2% relative increase in optimally healed stent struts (37.8 ± 2.8% vs. 54.6 ± 2.5%, p < 0.0001). Atherosclerosis demonstrated attenuated effect with no difference in NI burden (15.2 ± 1.0% vs. 16.9 ± 0.8%, p = 0.22) and only a 14.2% relative increase in strut healing (68.3 ± 4.1% vs. 78.7 ± 2.5%, p = 0.02). DP treated rabbits had a 44.6% (p = 0.045) relative reduction in NI SMC content. In vitro assessment of DP and coronary artery SMCs yielded dose-dependent reduction in SMC migration and proliferation. Selective small molecule antagonism of ADOR-A2B abrogated the effects of DP on SMC proliferation. DP modulated SMC phenotypic switching with ADOR-A2B siRNA knockdown supporting its role in the observed effects. Dipyridamole reduces NI proliferation and improves stent healing in a preclinical model of stent implantation with conventional antiplatelets. Atherosclerosis attenuates the observed effect. Clinical trials of DP as an adjunctive agent may be warranted to evaluate for clinical efficacy in stent outcomes.

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.

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.

Control of diabetes mellitus and the risk of neointimal hyperplasia after percutaneous coronary intervention: Post-hoc analysis from the BLADE-PCI trial

Background and aimsDiabetes-mellitus (DM) is associated with increased risk of neointimal hyperplasia (NIH) and restenosis after percutaneous coronary intervention (PCI). We examined a possible association of DM severity at the time of PCI with the development of NIH. MethodsThis post-hoc analysis from the BLADE-PCI randomized, multi-center trial included only patients with DM and baseline data of HbA1c within 14 days prior to the index PCI. All patients were treated with zotarolimus-eluting stents. The primary endpoint was percent of NIH volume at 9 months as evaluated by optical coherence tomography. This endpoint was compared between patients with uncontrolled DM (HbA1c ≥ 7.5%) and controlled DM (HbA1c <7.5%) at the index PCI. ResultsThe mean percentages of NIH volume were 16.5% ± 9.9 and 12.75% ± 7.9 among patients with baseline HbA1c ≥ 7.5% (n = 74) and <7.5% (n = 102), respectively (p < 0.05). In multivariable analysis, HbA1c ≥ 7.5% was not associated with higher risk of NIH development [95% CI; 2.2 (−0.8, 5.3; p = 0.15)]. Higher HbA1c was not associated with increased risk of NIH at the minimum lumen area site [95% CI; 0.9 (−5.0, 6.7); p = 0.77) or percent stent strut coverage [95% CI; −0.3 (−1.3, 0.6); p = 0.45]. Secondary clinical endpoints including major adverse cardiac and cerebrovascular events, target lesion failure and death were similar between patients with worse and better DM control. ConclusionsUncontrolled DM at the time of PCI performed with contemporary drug-eluting stents was not associated with an increased risk of NIH development.

Ultra-high-resolution spectral silicon-based photon-counting detector CT for coronary CT angiography: Initial results in a dynamic phantom

BackgroundRecent improvements in CT detector technology have led to smaller detector pixels resolving frequencies beyond 20 lp/cm and enabled ultra-high-resolution CT. Silicon-based photon-counting detector (PCD) CT is one such technology that promises improved spatial and spectral resolution. However, when the detector pixel sizes are reduced, the impact of cardiac motion on CT images becomes more pronounced. Here, we investigated the effects cardiac motion on the image quality of a clinical prototype Si-PCD scanner in a dynamic heart phantom. MethodsA series of 3D-printed vessels were created to simulate coronary arteries with diameter in the 1–3.5 ​mm range. Four coronary stents were set inside the d ​= ​3.5 ​mm vessels and all vessels were filled with contrast agents and were placed inside a dynamic cardiac phantom. The phantom was scanned in motion (60 bpm) and at rest on a prototype clinical Si-PCD CT scanner in 8-bin spectral UHR mode. Virtual monoenergetic images (VMI) were generated at 70 ​keV and CT number accuracy and effective spatial resolution (blooming) of rest and motion VMIs were compared. ResultsLinear regression analysis of CT numbers showed excellent agreement (r ​> ​0.99) between rest and motion. We did not observe a significant difference (p ​> ​0.48) in estimating free lumen diameters. Differences in in-stent lumen diameter and stent strut thickness were non-significant with maximum mean difference of approximately 70 ​μm. ConclusionWe found no significant degradation in CT number accuracy or spatial resolution due to cardiac motion. The results demonstrate the potential of spectral UHR coronary CT angiography enabled by Si-PCD.

Three-dimensional reconstruction imaging by C-arm computed tomography accurately visualizes in-stent neointimal formation in patients with stent-assisted coil embolization.

Stent apposition to the vessel wall and in-stent neointimal formation after stent-assisted coil embolization for intracranial aneurysm are important factors associated with postoperative thromboembolic complications. No assessment methods have been established to depict 3-dimensional (3D) all-round in-stent neointimal formation. To demonstrate the superiority of Dyna-3D imaging assessment as a modality for all-round ISNF in comparison with conventional two-dimensional digital subtraction angiography (2D-DSA). Consecutive patients who underwent braided stent-assisted coil embolization for unruptured aneurysm between November 2016 and September 2021 were enrolled. Radiological assessments for stent apposition to the parent vessel after stent deployment and in-stent neointimal formation after 3 months were obtained. Dyna-3D was reconstructed by overlapping a plain image showing stent struts with a rotational DSA image showing the vessel lumen. Reconstructed Dyna-3D images can be rotated to any angle on the screen to evaluate to stent apposition around the vessel and in-stent neointimal formation in 3D, for comparison with 2D-DSA evaluations. Among the 73 patients enrolled, 70 patients (96%) showed complete stent wall apposition on Dyna-3D. Higher intra-rater agreement was confirmed on assessment of in-stent neointimal formation with Dyna-3D (Cohen's κ = 0.811) than with conventional 2D-DSA (Cohen's κ = 0.517). in-stent neointimal formation could not be confirmed on conventional imaging in 9 cases (16%) and on Dyna-3D in 2 cases (3%). The number of in-stent neointimal formations rated as stent wire completely outside the endothelial line was significantly higher with Dyna-3D than with 2D-DSA (p = 0.0001). All-round 3D evaluation by Dyna-3D imaging appears useful for confirming in-stent neointimal formation after braided stent deployment in patients after stent-assisted coil embolization.

In-vivo assessment of vascular injury for the prediction of in-stent restenosis

BackgroundDespite optimizations of coronary stenting technology, a residual risk of in-stent restenosis (ISR) remains. Vessel wall injury has important impact on the development of ISR. While injury can be assessed in histology, there is no injury score available to be used in clinical practice. MethodsSeven rats underwent abdominal aorta stent implantation. At 4 weeks after implantation, animals were euthanized, and strut indentation, defined as the impression of the strut into the vessel wall, as well as neointimal growth were assessed. Established histological injury scores were assessed to confirm associations between indentation and vessel wall injury. In addition, stent strut indentation was assessed by optical coherence tomography (OCT) in an exemplary clinical case. ResultsStent strut indentation was associated with vessel wall injury in histology. Furthermore, indentation was positively correlated with neointimal thickness, both in the per-strut analysis (r = 0.5579) and in the per-section analysis (r = 0.8620; both p ≤ 0.001). In a clinical case, indentation quantification in OCT was feasible, enabling assessment of injury in vivo. ConclusionAssessing stent strut indentation enables periprocedural assessment of stent-induced damage in vivo and therefore allows for optimization of stent implantation. The assessment of stent strut indentation might become a valuable tool in clinical practice.

Contrast Venography Versus Intravenous Ultrasound in Hemodialysis Arteriovenous Access Dysfunction

Contrast Venography Versus Intravenous Ultrasound in Hemodialysis Arteriovenous Access Dysfunction

A Two-Species Finite Volume Scalar Model for Modeling the Diffusion of Poly(lactic-co-glycolic acid) into a Coronary Arterial Wall from a Single Half-Embedded Drug Eluting Stent Strut

This paper outlines the methodology and results for a two-species finite volume scalar computational drug transport model developed for simulating the mass transport of Poly(lactic-co-glycolic acid (PLGA)) from a half-embedded single strut implanted in a coronary arterial vessel wall. The mathematical drug transport model incorporates the convection-diffusion equation in scalar form (dimensionless) with a two-species (free-drug and bound-drug) mass transport setup, including reversible equilibrium reaction source terms for the free and bound-drug states to account for the pharmaco-kinetic reactions in the arterial wall. The relative reaction rates of the added source terms control the interconversion of the drug between the free and bound-drug states. The model is solved by a 2D finite-volume method for discretizing and solving the free and bound drug transport equations with anisotropic vascular drug diffusivities. This model is an improvement over previously developed models using the finite-difference and finite element method. A dimensionless characteristic scaling pre-analysis was conducted a priori to evaluate the significance of implementing the reaction source terms in the transport equations. This paper reports the findings of an investigation of the interstitial flow profile into the arterial wall and the free and bound drug diffusion profiles with a parametric study of varying the polymer drug concentration (low and high), tortuosity, porosity, and Peclet and DamKöhler numbers over the course of 400 h (16.67 days). The results also reveal how a single species drug delivery model that neglects both a reversible binding reaction source term and the porosity and tortuosity of the arterial wall cannot accurately predict the distribution of both the free and bound drug.

Stenting of native right ventricular outflow tract obstructions in symptomatic infants: histological work-up of explanted specimen.

Stenting of stenotic right ventricular outflow tract is a palliative measure for severely impaired small babies with Tetralogy of Fallot or similar pathologies. Little is known about the histopathological fate of the stents in the right ventricular outflow tract. Eight samples of surgically removed right ventricular outflow tract stents were histologically analysed according to a predefined protocol. The most frequent diagnosis was Tetralogy of Fallot in four patients, pulmonary atresia with ventricular septal defect in two patients, double outlet right ventricle with pulmonary obstruction in one patient, and muscular obstruction of the right ventricular outflow tract in one patient with a syndromic disease with hypertrophic cardiomyopathy. Stents mean implantation duration was 444 days ranging from 105 to 1117 days (median 305.5 days). Histology revealed a variable degree of pseudointima formation consisting of fibromuscular cells surrounded by extracellular matrix. Four of the specimen contained adjacent myocardial tissue fragments, which showed regressive changes. Neither myocardium nor pseudointima tissue or tissue parts locally related to stent struts were infiltrated by inflammatory cells. Histological analysis after explantation of early-in-life implanted right ventricular outflow tract stents revealed predominantly pronounced neo-intimal proliferation with a visible endothelial layer, no signs of inflammation, and no prolapse of muscular tissue through the stent struts. Thus, implantation of stents in early life seems to interfere little with the hosts' immune system and might help to open up the right ventricular outflow tract by mechanical forces and regressive changes in adjacent muscular tissue.

P42 ACUTE STENT THROMBOSIS IN CATH LAB DURING OPTIMIZED PCI: HOW TO RECOGNIZE IT AND POSSIBLE TREATMENT

Abstract Angiographic Acute Stent Thrombosis occur in 0.5%–2% of procedures.OCT–PCI or Optimized PCI represents a new approach particularly indicated in complex high thrombotic risk lesions, in patients at high bleeding risk with need for short DAPT and in the treatment of vulnerable plaques. Post–stent OCT thrombus finding was defined in previous studies as mass with diameter ≥250μm attached to the stent struts, was present until 40% of cases and is associated with definite angiographic thrombosis. Outcome of OCT thrombus is generally favorable although in about 25% there may be a progression. Case 1: 75–y smoker female with hypertension and atrial fibrillation on NOAC therapy presented in ICU with NSTEMI. At angiography: 75% stenosis focal plaque at proximal circumflex (Fig1A). At OCT vulnerable plaque: ulcerated with intimal flap &amp;lt; 90°, thin fibrous cap 20 µm, MLA 2.17mm² and AS 63%, intimal micro–calcifications and cholesterol crystals (Fig1C). We implanted DES with post–dilatation. Treatment was Cangrelor, heparin 100 IU/kg and ASA 250 mg ev. OCT showed acute 660 µm thrombosis of the stent body although there was perfect angiographic result (Fig1D+B). Further multiple balloon dilatation of the stent was carried out with thrombosis persistence on OCT control (Fig1E) and new appearance of multiple thromboses adhering to the intravascular side stent struts (Fig1F–G). Switch from Cangrelor to Tirofiban was done. Patient‘s clinical course was uneventful with discharge after six days on triple antithrombotic therapy with low–dose NOAC, ASA and clopidogrel.Case 2: 63–y smoker man arrived in cath lab for anterior STEMI. He had already taken ASA 300 mg ev and Ticagrelor 180 mg oral bolus about 60 minutes earlier in the ambulance. In Cath Lab was done heparin 100 IU/kg. P–PCI was performed for acute sub–occlusion (Fig2A) of the ostial DA treated by pre–dilation, DES implantation on Left Main–DA and multiple post–dilations according to the POT technique. OCT control showing extensive stent malapposition (860 µm) with evidence of multiple thromboses adhering to the stent struts on Left Main (diameter 410 µm) although there was perfect angiographic result (Fig2B–E). Procedure was optimized by adequate post–dilatation of the LM and administration of Abciximab. Patient‘s clinical course was uneventful with discharge after five days on ASA and Ticagrelor. Conclusions Post–stent OCT thrombus may guide the choice of use of Glicoprotein IIb/IIIA Inhibitors in Cath Lab.

Tissue Growth Model for Maintaining Tensional Homeostasis With Applications to Hypertension and Stented Artery

Abstract In this work, a theoretical growth model for maintaining a homeostatic mechanical environment was developed to capture the growth behavior of the artery and its association with its mechanical environment. The multiplicative decomposition approach was adopted to decompose the deformation matrix into an elastic term and a growth term. A growth factor relating to homeostatic stress was used to regulate the progressive changes in the arterial morphology. In addition, a growth coefficient was adopted to avoid unlimited growth. The arterial growth model was implemented in a commercial finite element software and tested in the cases of hypertension and stenting. Results have demonstrated that the arterial growth induced by hypertension can mitigate abnormal arterial stresses and restore the stress level in the artery back to its homeostasis. Following stenting, the arterial growth pattern was consistent with the distribution of the von Mises stresses in the artery. The arterial growth homogenized the stress distribution in the artery, except for the regions under the stent struts. The heterogeneous growth of the artery disrupted the alignment of the maximum principal stresses in the artery, elongated the stent, reduced the lumen area, and aggregated the tissue prolapse. It is expected that the growth model developed in this work could help to understand and regulate the chronic response of the tissue. Appropriate modeling of arterial growth in connection with tensional homeostasis provided insights for predicting alterations to the arterial mechanical environment, identifying biomechanical factors leading to restenosis, and designing therapeutic strategies to regulate the tissue adaptations.

Computer Simulation of the Coupling Between Recirculation Flows and Drug Release from a Coronary Drug-Eluting Stent

This study examines the effect of recirculation zones and flow pulsatility on the transfer of the active ingredient from drug-eluting stents to the arterial wall, which can be hindered by recirculation zones located upstream and downstream of stent struts, leading to restenosis and thrombosis. Numerical simulations were conducted using a left coronary artery model with steady or pulsatile flows, and mass transfer analysis was performed on a single-stent strut with a square cross section. The findings offer valuable insights into optimizing the geometric design of drug-eluting stents by controlling the size and dynamics of induced recirculation cells, thereby enhancing the efficacy of stent treatments.