Coronary Stent Expansion Research Articles

Impact of Calcium Angle on Coronary Stent Expansion and Eccentricity Index Using Optical Coherence Tomography in Patients Undergoing Intravascular Lithotripsy

Impact of Calcium Angle on Coronary Stent Expansion and Eccentricity Index Using Optical Coherence Tomography in Patients Undergoing Intravascular Lithotripsy

Numerical study to identify the effect of fluid presence on the mechanical behavior of the stents during coronary stent expansion

In this study, structural analysis and one-way fluid-structure interaction (FSI) analysis were performed to identify the effect of fluid presence on the mechanical behavior of the stents during stent expansion. An idealized vessel model with stenosis was used for simulation, and stents made of metal and polymer were assumed, respectively. The bilinear model was applied to the stents, and the Mooney-Rivlin model was applied to the arterial wall and plaque. The blood used in the FSI analysis was assumed to be a non-Newtonian fluid. As a result of all numerical simulations, the von Mises stress, the first principal stress and the displacement were calculated as the mechanical behaviors. Through the comparison of the results of the structural analysis with those of the one-way FSI analysis, our results indicated the fluid had no significant influence on the expansion of the metal stent. However, it was found that the expansion of the polymer stent affected by the presence of fluid. These findings meant the one-way FSI technique was suggested to achieve an accurate analysis when targeting a polymer stent for numerical simulation.

Fast simulation of stent deployment with plastic beam elements.

Coronary stent deployment is a reference cardiology intervention, used to treat atherosclerosis and prevent heart attacks. The outcomes of the intervention highly depend on the accuracy of the stent apposition, which could benefit from per-operative prediction tools. In this paper, we propose a fast and mechanically realistic 3D simulation of a coronary stent expansion. Our simulation relies on the finite element method and involves serially linked beam elements to model the slender geometry of a stent. The elements are implemented with a non-linear elasto-plastic behavior, describing realistically the complex deformation of a balloon-expandable stent. As a proof of concept, we simulated the free expansion of a coronary stent. The simulation output was compared with micro-CT data, acquired experimentally during the device expansion. Results show that the plastic beam model is able to reproduce successfully the final geometry of the stent. In addition, the use of 1D elements allows to achieve a significantly lower computational time than for equivalent literature simulations, based on 3D elements. This preliminary work highlights the compatibility of our method with clinical routine in terms of execution time. Further developments include the application of the method to more advanced simulation scenarios, with the addition of a personalized artery model.

Impact of the Balloon Inflation Time and Pattern on the Coronary Stent Expansion.

Objectives To assess the expansion pattern of coronary stents by using different balloon inflation times and pressures. Background The selection of coronary stent size and its proper deployment is crucial in coronary artery interventions, having an impact on the success of the procedure and further therapy. Methods Ten pairs of different stents were deployed under nominal pressure using sequential (5, 5, 10, and 10 seconds of repeated inflations, thus 30 seconds of summarized time) and continuous (30 seconds) deployment pattern. After each given time-point, intraluminal stent measurements were performed by optical coherence tomography (OCT) and intravascular ultrasound (IVUS). Results Both in-stent diameters and cross-section areas (CSA) of paired stents measured by OCT at all sequential time-points were significantly smaller compared to given manufacturers charts' values (90% to 94% for diameters and 81% to 88% for CSA, p<0.05). Significant increase of in-stent diameter and CSA was observed across the step-by-step deployment pattern. In-stent lumen measurements were significantly larger when sequential deployment pattern was applied compared to continuous deployment. Additional measurements were also done for overlapping segments of stents, showing smaller in-stent measurements of the latter compared to nonoverlapping segments. Validation of OCT and IVUS measurements using a phantom metallic tube showed perfect reproducibility with OCT and overestimation with IVUS (8% for diameters and 16% for CSA). Conclusions Stent diameter after deployment is time-dependent and not only pressure-dependent. Different stent expansion behavior, depending on the applied deployment pattern (sequential and nonsequential), was observed.

100.04 The Effect of Plaque Characteristics on Stent Expansion Assessed by Optical Coherence Tomography Using a Novel Volumetric Method

This study sought to investigate the relationship between plaque characteristics and stent expansion utilizing a novel optical coherence tomography (OCT) volumetric method in patients with stent under-expansion. The analysis of coronary stent expansion evaluated by OCT volumetric method has proven

New Volumetric Analysis Method for Stent Expansion and its Correlation With Final Fractional Flow Reserve and Clinical Outcome: An ILUMIEN I Substudy

ObjectivesThis study sought to compare conventional methodology (CM) with a newly described optical coherence tomography (OCT)-derived volumetric stent expansion analysis in terms of fractional flow reserve (FFR)-derived physiology and device-oriented composite endpoints (DoCE). BackgroundThe analysis of coronary stent expansion with intracoronary imaging has used CM that relies on the analysis of selected single cross-sections for several decades. The introduction of OCT with its ability to perform semiautomated volumetric analysis opens opportunities to redefine optimal stent expansion. MethodsA total of 291 lesions treated with post-stent OCT and FFR were enrolled. The expansion index was calculated by using a novel volumetric algorithm and was defined as: ([actual lumen area / ideal lumen area] × 100) for each frame of the stented segment. The minimum expansion index (MEI) was defined as the minimum value of expansion index along the entire stented segment. MEI and conventional lumen expansion metrics were compared for the ability to predict post-stent low FFR (<0.90) and DoCE at 1 year. ResultsThere was a stronger correlation between MEI and final FFR, compared with CM and final FFR (r = 0.690; p < 0.001) versus (r = 0.165; p = 0.044). MEI was significantly lower in patients with DoCE than those without DoCE (72.18 ± 8.23% vs. 81.48 ± 11.03%; p < 0.001), although stent expansion by CM was similar between patients with and without DoCE (85.05 ± 22.19% and 83.73 ± 17.52%; p = 0.858), respectively. ConclusionsOCT analysis of stent expansion with a newly described volumetric method, but not with CM, yielded data that were predictive of both an acute improvement in FFR-derived physiology and DoCE.

Improved stent expansion with prolonged compared with short balloon inflation: A meta-analysis.

Despite evidence from individual studies suggesting that prolonged inflation improves coronary stent expansion, relatively shorter inflation times are commonly employed in clinical practice. We performed an electronic search of PubMed, Web of Science, Cochrane, and CINAHL databases to retrieve outcome studies comparing prolonged versus short inflation times during stent deployment. Outcomes studied included minimal stent diameter (MSD) and minimal stent area (MSA). Standardized mean difference (SMD) was used to estimate the effect sizes for these continuous variables. Seven studies with a total of 341 patients (415 lesions; mean age 67.6 years; 82% male) were included. Drug-eluting stents were used in 89 ± 15% of coronary lesions. Prolonged stent inflation was associated with increased minimal stent diameter (2.93 ± 0.34 mm vs. 2.72 ± 0.28 mm; SMD = 0.42; 95% CI 0.25-0.59; P < 0.001) and minimal stent area (5.99 ± 1.21 mm2 vs. 5.17 ± 0.87 mm2 ; SMD = 0.46; 95% CI 0.19-0.73; P = 0.001) compared with shorter duration stent inflation. This difference remained significant in sensitivity analyses that excluded studies with very prolonged inflation duration or multiple stent balloon inflations. Despite differences in duration and methodology, prolonged stent inflation is associated with improved expansion compared with shorter duration. The effect of this optimization recommends randomized trials to determine whether long-term outcomes can be improved by this simple technical modification.

PEMODELAN EKSPANSI STENT JANTUNG DENGAN BALON HYPER - ELASTIS

Coronary artery disease (CAD) is a disease that most cause mortality in Indonesia. CAD is caused by cholesterol-containing deposit (plaque) that make the coronary artery become narrow and can cause a heart attack. Stent implantation is the most common treatment to opens or alleviates the narrowing coronary artery. A preliminary study has done to simulate the expansion of coronary stent with negligible balloon method. The negligible balloon is less accurate and far from realistic condition because it neglects the presence of the balloon. This study has proposed another method to simulate the stent expansion. Hyper-elastic balloon method is used to investigate the stress distribution, outer diameter change, and dogboning phenomena of the stent.

Recognition and Management of Incomplete Stent Expansion Facilitated by StentBoost and Guideliner Tools

Suboptimal or incomplete coronary stent expansion is associated with increased restenosis rate and target vessel revascularization. Stent visualisation with plain fluoroscopy has become challenging due to reduction of stent strut thickness. Inability of stent or balloon delivery is a frequent cause of procedural failures in percutaneous coronary interventions. This case report highlights the role of a novel stent enhancing technique, StentBoost, in recognition and management of incomplete stent expansion and of the Guideliner catheter, which is an essential assist device in complex and challenging coronary interventions, especially via the radial access.

StentBoost Visualization for the Evaluation of Coronary Stent Expansion During Percutaneous Coronary Interventions.

IntroductionInadequate stent implantation is associated with stent thrombosis and restenosis. StentBoost can enhance stent visualization and evaluate stent expansion. Currently, there are limited comparison studies between StentBoost and intravascular ultrasound (IVUS). We aimed to test the correlation and agreement between IVUS and StentBoost measurements.MethodsFrom December 2010 to December 2011, 38 patients (54 stents) were analyzed using IVUS and StentBoost. Minimal stent diameter and proximal and distal edge stent diameter were compared between imaging techniques using Pearson correlation and Bland–Altman scatter plot.ResultsThere was good correlation between StentBoost and IVUS measurements regarding minimal stent diameter (p < 0.001 in all stent portions) and an optimal agreement between IVUS and StentBoost, while lesser agreement was found between IVUS and quantitative coronary angiography.ConclusionThe assessment of stent implantation using StentBoost showed an adequate correlation and agreement with IVUS. This easily applicable angiographic technique can be used to guide stent implantation.Electronic supplementary materialThe online version of this article (doi:10.1007/s40119-013-0023-2) contains supplementary material, which is available to authorized users.

Finite Element Analysis of Free Expansion of Coronary Stent Based on ANSYS Workbench

Undertaking the 316L stainless steel as a medical stent material and the coronary stent structure as the research object, ANSYS Workbench12.0 is used to simulate the free expansion process of coronary stent by two expansion methods. Finite element analysis is used to solve such problems as deformation behaviour of the stent, mechanical behaviour as well as nonlinear problems of the stent and balloon interaction during the free expansion process. The simulation results show that the stent and balloon interaction process will appear slip phenomenon, the stent shortening in the axial direction and elongating in the radial direction, and that the arc supporting rod location of the stent is the main area of the maximum stress. These can provide a scientific reference for the next new stent design and optimization.

Effect of Thickness on the Mechanical Properties of Magnesium Alloy Stent

Magnesium stands for a very attractive material for biodegradable stents because of its natural process and its steady disintegration into the human body by a corrosion process. The objective of the present work is to investigate the effect of the thickness on mechanical properties of the magnesium stent design. A nonlinear transient finite element simulation has been performed to analyze the influence of various thicknesses (from 50µm to 110µm with the increment of 30µm) on the behavior of a magnesium coronary stent. The model was constrained symmetrically to ensure that any virtual rigid movement does not occur during the process of coronary stent expansion. The transient load is applied in three steps in the inner surface of the stent. Four mechanical properties are studied by mathematical modeling with determination of: (1) stent deployment pressure; (2) the intrinsic elastic recoil of the material used; (3) the stent longitudinal recoil; (4) and the stress maps. The results indicate the potential application of magnesium stent and the effect of the thickness on the behavior of magnesium stent design and material.

A “real-time” evaluation of a novel coronary stent expansion system using an advanced visibility enhancement tool: initial clinical experience

A “real-time” evaluation of a novel coronary stent expansion system using an advanced visibility enhancement tool: initial clinical experience

Comparison of Complete Versus Incomplete Stent Frame Expansion After Transcatheter Aortic Valve Implantation With Medtronic CoreValve Bioprosthesis

We sought to determine the significance of incomplete stent frame expansion after transcatheter aortic valve implantation with the Medtronic-CoreValve device. Incomplete coronary stent expansion is a well-described phenomenon. Transcatheter valves are mounted on stents; however, the incidence of incomplete stent expansion after transcatheter aortic valve implantation, its sequelae and predictors are poorly elucidated. The 18Fr CoreValve revalving system was used to treat anatomically and clinically suitable patients with severe calcific aortic stenosis. The postdeployment stent dimensions were measured on fluoroscopic images at multiple levels of the stent frame. Incomplete expansion at each was defined as <100% expected and complete expansion as ≥100%. These parameters were correlated to the hemodynamic and clinical end points. A total of 50 consecutive patients underwent transcatheter aortic valve implantation with the Medtronic-CoreValve at a single center from January 2007 to December 2008. For the inflow portion, incomplete expansion was seen in 54% of patients and was unrelated to the aortic valve area, peak or mean aortic valve gradients, or measures of aortic regurgitation, although it was paradoxically associated with a lower incidence of prosthesis-patient mismatch. Incomplete expansion of the constrained portion was seen in 62% of the patients and displayed a trend toward a greater incidence of aortic regurgitation grade 2 or greater, although this was rare. Incomplete expansion of the Medtronic CoreValve stent frame is common. For the most part, valvular hemodynamic function was satisfactory, regardless of the degree of expansion of the stent frame that carries it and a strategy of reluctant postdilation in the context of incomplete stent frame expansion was supported.

Determination of adequate coronary stent expansion using StentBoost, a novel fluoroscopic image processing technique

We tested the hypothesis that the use of motion-corrected fluoroscopic images results in enhanced coronary stent visualization and improved detection of inadequate stent expansion. Intravascular ultrasound (IVUS) more accurately detects inadequate stent expansion when compared with coronary angiography. Stent under-expansion is associated with stent restenosis and thrombosis. Developing a technique to improve fluoroscopic-based assessment of stent expansion is desirable. We analyzed measurements of 48 coronary stents implanted in 30 patients using quantitative coronary angiography (QCA), IVUS, and StentBoost (SB), a novel fluoroscopic image processing technique. Correlations of stent diameter between the modalities were determined. Using established IVUS criteria for adequate stent deployment, we assessed the diagnostic test characteristics of SB to detect inadequate stent expansion. Correlations of minimum stent diameter were highest between IVUS and SB (r=0.75; P<0.0001) when compared with QCA and IVUS (r=0.65; P<0.0001), and QCA and SB (r=0.49; P=0.0004). IVUS and SB demonstrated a small difference in minimum stent diameter, 0.043 mm (95% CI: 0.146-0.061 mm). The correlation between IVUS and SB was lower for vessels with intimal calcification (r=0.57; P=0.002) when compared with vessels with deeper calcification (r=0.84; P<0.0001). A SB minimum diameter of <2.5 mm predicted inadequate stent expansion by IVUS with 88% sensitivity, 70% specificity, and a positive likelihood ratio of 2.9. SB had superior correlations for stent expansion measured by IVUS when compared with QCA. A minimum stent diameter by SB measurement<2.5 mm is associated with inadequate stent expansion using IVUS criteria.

Improved localization of coronary stents using layer decomposition.

Accurate placement and expansion of coronary stents is hindered by the fact that most stents are only slightly radiopaque and hence difficult to see in typical coronary X-ray images. We propose a new technique for improved image guidance of multiple coronary stent deployment using layer decomposition of coronary X-ray image sequences. We hypothesize that layer decomposition can improve the accuracy of localization of the end of a deployed stent. Layer decomposition is used to obtain good quality images of a stent in vitro. The resultant background-subtracted stent images are embedded into other cine X-ray image sequences to form a database of simulated image sequences. For each simulated sequence, the position of the stent edge is estimated from raw and layer-decomposed images using a small region of the original layer image as a template. Layer decomposition reduced median position errors in 33 of 47 image sequences (70%), including 16 of 18 sequences in which the position errors for raw and layer images differed by 5.0 pixels (0.5 mm) or more. Layer decomposition significantly reduces errors in determination of stent edge location in simulated cine X-ray image sequences.

Improved Localization of Coronary Stents Using Layer Decomposition

Accurate placement and expansion of coronary stents is hindered by the fact that most stents are only slightly radiopaque and hence difficult to see in typical coronary X-ray images. We propose a new technique for improved image guidance of multiple coronary stent deployment using layer decomposition of coronary X-ray image sequences. We hypothesize that layer decomposition can improve the accuracy of localization of the end of a deployed stent. Layer decomposition is used to obtain good quality images of a stent in vitro. The resultant background-subtracted stent images are embedded into other cine X-ray image sequences to form a database of simulated image sequences. For each simulated sequence, the position of the stent edge is estimated from raw and layer-decomposed images using a small region of the original layer image as a template. Layer decomposition reduced median position errors in 33 of 47 image sequences (70%), including 16 of 18 sequences in which the position errors for raw and layer images differed by 5.0 pixels (0.5 mm) or more. Layer decomposition significantly reduces errors in determination of stent edge location in simulated cine X-ray image sequences.

Longitudinal plaque redistribution during stent expansion

The purpose of this study was to clarify the 3-dimensional behavior of plaque during coronary stent expansion. Serial intravascular ultrasound (IVUS) studies, preintervention, and poststenting were evaluated in 32 patients treated with a single-balloon expandable tubular stent. External elastic membrane (EEM), lumen, stent, and plaque + media cross-sectional area were measured at 1-mm intervals through the entire stent as well as proximal and distal reference segments 5 mm from the stent edge. Volumetric calculations were based on Simpson’s rule. Overall, the plaque + media volume through the entire lesion did not change during stent expansion (218 ± 51 vs 217 ± 47 mm 3, p = 0.69). However, EEM and lumen volume increased significantly (EEM volume, 391 ± 84 vs 448 ± 87 mm 3 [p <0.0001]; lumen volume, 173 ± 52 vs 231 ± 54 mm 3 [p <0.0001]). The change in lumen volume correlated strongly with the change in EEM volume (r = 0.85, p <0.0001), but poorly with the change in plaque + media volume (r = 0.37, p = 0.03). Plaque + media volume decreased in the midstent zone (59 ± 14 vs 53 ± 11 mm 3, p = 0.0005), and increased in the distal stent zone (40 ± 11 vs 44 ± 9 mm 3, p = 0.003), but did not change in either the proximal stent zone or reference segments. The mechanism of stent expansion is a combination of vessel stretch and plaque redistribution, translating disease accumulation from the midstent zone to the distal stent zone.

Comparison of coronary stent expansion by intravascular ultrasonic imaging in younger versus older patients with diabetes mellitus

The poor long-term outcome in young diabetic patients receiving stents is not well understood. The purpose of this study was to characterize the postprocedural results of stent placement in diabetic patients using intravascular ultrasound to identify factors that might be associated with poor clinical outcome. The acute dimensions from intravascular ultrasound studies after stent deployment at 5 sites were measured from 39 coronary segments from patients with diabetes mellitus (DM) and 161 segments from nondiabetic patients (non-DM). Within these 2 groups, segments were subgrouped into young (y) and old (o) in reference to the mean study age of 64 years, forming 4 groups: yDM (n = 20), y non-DM (n = 65), oDM (n = 19), and o non-DM (n = 96). Results are reported as mean ± 1 SD. Diabetic patients had smaller mean lumen area within the treated segment than o non-DM (8.37 ± 2.59 vs 9.11 ± 3.35 mm 2, p <0.01). These differences were more pronounced at the distal reference vessel lumen of yDM than y non-DM (7.6 ± 2.3 vs 10.3 ± 4.5 mm 2, p <0.003), and were associated with greater percent plaque area in the distal reference vessel (43.4 ± 13% vs 34.1 ± 11.2%, p <0.003). In young diabetic patients undergoing elective stent placement, underexpansion of the stented segment is common, which may contribute to the relatively poor long-term outcome in these patients. We suggest that when stenting is the procedure of choice in this subgroup of high-risk patients, special attention should be given to optimizing lumen dimensions.

Impact of target lesion calcification on coronary stent expansion after rotational atherectomy

Background Calcified lesions carry the risk of suboptimal stent expansion. The purpose of this study was to investigate the impact of target lesion calcification on intracoronary ultrasound (ICUS) guided stent expansion after rotational atherectomy. Methods Stent expansion was assessed by ICUS in 39 patients with the aid of the proximal stent/proximal reference lumen, the minimal stent/mean reference lumen, and the minimal stent/minor reference lumen ratios as well as the symmetry index. Thirty-nine stent implantations in uncalcified lesions served for comparison. Results Relative stent expansion ranged between 76.3% ± 6.7% and 98.4% ± 16.4%. Categorization according to an ICUS-derived arc of superficial lesion calcium of <180 degrees (average 102 ± 74 degrees) or >180 degrees (average 248 ± 71 degrees) revealed decreased stent symmetry in calcified lesions >180 degrees compared with the control group ( P < .05). Despite a trend toward less expansion with increasing calcium load, no significant differences of the lumen area ratios between the study groups was present. Conclusion Rotational atherectomy before ICUS-guided stent implantation enables adequate stent expansion even in significant superficial target lesion calcification. (Am Heart J 1999;137:93-9.)