Stent Recoil Research Articles

A Comparative Reliability and Performance Study of Different Stent Designs in Terms of Mechanical Properties: Foreshortening, Recoil, Radial Force, and Flexibility

This study seeks to improve the mechanical performance of stents by conducting reliability performance testing and finite element method (FEM)-based simulations for coronary stents. Three commercially available stent designs and our own new design were tested to measure the factors affecting performance, specifically foreshortening, recoil, radial force, and flexibility. The stents used in the present experiments were 3 mm in working diameter and 18 mm of working length. The results of the experiments indicate that the foreshortening of stents A, B, C, and our new design, D, was equivalent to 2.25, 0.67, 0.46, and 0.41%, respectively. The recoil of stents A, B, C, and D was 6.00, 4.35, 3.50, and 4.36%, respectively. Parallel plate radial force measurements were A, 3.72 ± 0.28 N; B, 3.81 ± 0.32 N; C, 4.35 ± 0.18 N; and D, 4.02 ± 0.24 N. Radial forces determined by applying uniform pressure in the circumferential direction were A, 28.749 ± 0.81 N; B, 32.231 ± 1.80 N; C, 34.522 ± 3.06 N; and D, 42.183 ± 2.84 N. The maximum force of crimped stent at 2.2-mm deflection was 1.01 ± 0.08 N, 0.82 ± 0.08 N, 0.92 ± 0.12 N, and 0.68 ± 0.07 N for each of stents A, B, C and D. The results of this study enabled us to identify several factors to enhance the performance of stents. In comparing these stents, we found that our design, stent D, which was designed by a collaborative team from seven universities, performed better than the commercial stents across all parameter of foreshortening, recoil, radial force, and flexibility.

Acute Stent Recoil From Aggressive Post-Dilation of a Second-Generation Drug-Eluting Stent

A 43-year-old man presented with crescendo angina. Coronary angiography demonstrated ambiguous stenosis of ostial left main stem (LM) ([Figs. 1][1]A and [1][1]B). After pre-dilation, a 4.0/12 mm Everolimus-eluting stent (Xience Prime, Abbott Vascular, Santa Clara, California) was deployed in the

Letter by Williams et al Regarding Article, “Incidence and Clinical Impact of Stent Fracture After Everolimus-Eluting Stent Implantation”

We read with interest the article, “Incidence and clinical impact of stent fracture after everolimus-eluting stent implantation” by Kuramitsu et al,1 which provides interesting data on the frequency of stent fracture with contemporary drug-eluting stents. However, we believe that some of the terminology used is misleading. Firstly, we believe the term everolimus-eluting stent as used in this article is inappropriate. Mechanical stent complications such as stent recoil, stent fracture, or longitudinal stent deformation (LSD) are not primarily related to the polymer or drug coating but to the underlying stent design. The authors examined the everolimus-eluting Xience V (Abbott …

Comparison of Acute Stent Recoil Between the Everolimus-Eluting Bioresorbable Vascular Scaffold and Two Different Drug-Eluting Metallic Stents

Bioresorbable vascular scaffolds (BVS) have been developed to provide support to the vessel wall during the healing process after percutaneous coronary intervention (PCI), being resorbed afterwards. Because the scaffold is made of polymeric material, there is a concern regarding the acute recoil of the device. We compared the BVS acute recoil with that of two different metal drug-eluting stents. Fifty patients with non-complex lesions were included. Twenty-five of these patients were treated with a BVS who were compared to 25 patients treated with a cobalt-chromium everolimus-eluting stent (EES, n = 12) or a stainless steel biolimus-eluting stent (BES, n = 13). Acute recoil was defined as the difference between the mean diameter of the balloon during its maximum inflation pressure (X) and the mean diameter of the stent immediately after balloon deflation (Y). The percentage of acute recoil was defined as (X-Y)/X. There was no significant difference in the baseline clinical and angiographic characteristics. Acute luminal gain was lower with BVS compared to EES and BES (1.51 ± 0.41 mm vs. 1.76 ± 0.28 mm vs. 1.9 ± 0.42 mm, P = 0.02). Acute recoil was 0.21 ± 0.13 mm vs. 0.15 ± 0.08 mm vs. 0.14 ± 0.08 mm (P = 0.21) and the percentage of acute recoil was 7.0 ± 4.6% vs. 5.0 ± 2.2% vs. 5.7 ± 4.1% (P = 0.16). BVS presented a slightly higher, although not significant, acute recoil than the two second-generation metallic drug-eluting stents. Comparação da Retração Aguda do Stent Entre o Suporte Vascular Bioabsorvível Eluidor de Everolimus e Dois Diferentes Stents Metálicos Farmacológicos Suportes vasculares bioabsorvíveis (SVB) têm sido desenvolvidos como forma de fornecer sustentação à parede do vaso enquanto ocorre o processo de cicatrização, após a intervenção coronária percutânea (ICP), sendo absorvido posteriormente. Pelo fato da plataforma ser de material polimérico, existe preocupação em relação à retração aguda do dispositivo. Avaliamos aqui a retração aguda do SVB com a de dois diferentes stents farmacológicos metálicos. Foram incluídos 50 pacientes com lesões não complexas. Dentre esses pacientes, 25 foram tratados com SVB e comparados a outros 25 pacientes tratados com stent de cromo-cobalto eluidor de everolimus (EES; n = 12) ou stent de aço inoxidável eluidor de biolimus (BES; n = 13). A retração aguda foi definida como a diferença entre o diâmetro médio do balão durante a pressão máxima de inflação (X) e o diâmetro médio do stent após o esvaziamento do balão (Y). A porcentagem de retração aguda foi definida como (X – Y)/X. Não houve diferença significativa em relação às características clínicas e angiográficas basais. O ganho luminal agudo foi menor com o SVB comparado ao EES e ao BES (1,51 ± 0,41 mm vs. 1,76 ± 0,28 mm vs. 1,9 ± 0,42 mm; P = 0,02). A retração aguda foi de 0,21 ± 0,13 mm vs. 0,15 ± 0,08 mm vs. 0,14 ± 0,08 mm (P = 0,21), e o porcentual de retração aguda foi de 7,0 ± 4,6% vs. 5,0 ± 2,2% vs. 5,7 ± 4,1% (P = 0,16). O SVB demonstrou ter retração aguda ligeiramente maior, embora não significativa, que os stents metálicos farmacológicos de segunda geração.

Comparison of Acute Stent Recoil Between the Everolimus-Eluting Bioresorbable Vascular Scaffold and Two Different Drug-Eluting Metallic Stents

Bioresorbable vascular scaffolds (BVS) have been developed to provide support to the vessel wall during the healing process after percutaneous coronary intervention (PCI), being resorbed afterwards. Because the scaffold is made of polymeric material, there is a concern regarding the acute recoil of the device. We compared the BVS acute recoil with that of two different metal drug-eluting stents. Fifty patients with non-complex lesions were included. Twenty-five of these patients were treated with a BVS who were compared to 25 patients treated with a cobalt-chromium everolimus-eluting stent (EES, n = 12) or a stainless steel biolimus-eluting stent (BES, n = 13). Acute recoil was defined as the difference between the mean diameter of the balloon during its maximum inflation pressure (X) and the mean diameter of the stent immediately after balloon deflation (Y). The percentage of acute recoil was defined as (X-Y)/X. There was no significant difference in the baseline clinical and angiographic characteristics. Acute luminal gain was lower with BVS compared to EES and BES (1.51 ± 0.41 mm vs. 1.76 ± 0.28 mm vs. 1.9 ± 0.42 mm, P = 0.02). Acute recoil was 0.21 ± 0.13 mm vs. 0.15 ± 0.08 mm vs. 0.14 ± 0.08 mm (P = 0.21) and the percentage of acute recoil was 7.0 ± 4.6% vs. 5.0 ± 2.2% vs. 5.7 ± 4.1% (P = 0.16). BVS presented a slightly higher, although not significant, acute recoil than the two second-generation metallic drug-eluting stents. Comparação da Retração Aguda do Stent Entre o Suporte Vascular Bioabsorvível Eluidor de Everolimus e Dois Diferentes Stents Metálicos Farmacológicos Suportes vasculares bioabsorvíveis (SVB) têm sido desenvolvidos como forma de fornecer sustentação à parede do vaso enquanto ocorre o processo de cicatrização, após a intervenção coronária percutânea (ICP), sendo absorvido posteriormente. Pelo fato da plataforma ser de material polimérico, existe preocupação em relação à retração aguda do dispositivo. Avaliamos aqui a retração aguda do SVB com a de dois diferentes stents farmacológicos metálicos. Foram incluídos 50 pacientes com lesões não complexas. Dentre esses pacientes, 25 foram tratados com SVB e comparados a outros 25 pacientes tratados com stent de cromo-cobalto eluidor de everolimus (EES; n = 12) ou stent de aço inoxidável eluidor de biolimus (BES; n = 13). A retração aguda foi definida como a diferença entre o diâmetro médio do balão durante a pressão máxima de inflação (X) e o diâmetro médio do stent após o esvaziamento do balão (Y). A porcentagem de retração aguda foi definida como (X – Y)/X. Não houve diferença significativa em relação às características clínicas e angiográficas basais. O ganho luminal agudo foi menor com o SVB comparado ao EES e ao BES (1,51 ± 0,41 mm vs. 1,76 ± 0,28 mm vs. 1,9 ± 0,42 mm; P = 0,02). A retração aguda foi de 0,21 ± 0,13 mm vs. 0,15 ± 0,08 mm vs. 0,14 ± 0,08 mm (P = 0,21), e o porcentual de retração aguda foi de 7,0 ± 4,6% vs. 5,0 ± 2,2% vs. 5,7 ± 4,1% (P = 0,16). O SVB demonstrou ter retração aguda ligeiramente maior, embora não significativa, que os stents metálicos farmacológicos de segunda geração.

Serial Gray Scale Intravascular Ultrasound Findings in Late Drug-Eluting Stent Restenosis

The primary aim of the present study was to assess the gray scale intravascular ultrasound (IVUS) findings that might be associated with late drug-eluting stent restenosis. The study included 47 patients (54 lesions) who had undergone either baseline IVUS-guided stent implantation or IVUS-guided repeat stenting to treat in-stent restenosis and then had IVUS follow-up data for ≥1.5 years afterward without any intervening procedures. The left anterior descending artery was the culprit in 59% of cases, and 50% of the lesions were at bifurcation sites. Quantitative and qualitative IVUS analyses showed a decreased minimum lumen area at follow-up from 6.0 ± 1.8 to 3.8 ± 1.4 mm(2) (p <0.0001) that was mainly due to neointimal hyperplasia with chronic stent recoil (defined as a >15% decrease in minimum stent area) in only 2 lesions and stent fracture in only 5 lesions. Calcified neointima appeared in 12 lesions, mostly in the form of macrocalcification, and was associated with increased calcium both behind the stent and in the reference segment. In conclusion, late drug-eluting stent restenosis showed neointimal calcification in 20% of cases, and chronic stent recoil was rare.

Abstract 18633: Prevalemce and Clinical Outcomes of Stent Fracture and Stent Recoil After Drug-eluting Stent Implantation at the Right Coronary Artery Ostial Site at Mid and Late Term

Background: After stent implantation at the right coronary artery (RCA) ostial site, in-stent restenosis (ISR) often occurs and target lesion revascularization (TLR) is required. But at the RCA ostial site, the impact of stent fracture(SF) or stent recoil(SR) on midterm and especially late term restenosis is unknown. Methods: From March 2004 to June 2010, 129 RCA ostial sites were successfully treated with 3 types of drug-eluting stent: sirolimus-eluting stent (SES), n=74; paclitaxel-eluting stent (PES), 39; everolimus-eluting stent (EES), 16. Mid and late term follow-up coronary angiography(CAG) was performed at 8 months and after 20 months. And SF and SR were assessed. We defined SF as apparent strut separation and SR as axial recoil less than 80% in the stent diameter, both analyzed by coronary angiography. Results: We found 41 SF lesions (31.8%) and 24 SR lesions (18.6%) at the 8months follow up CAG. Out of the 102 patients without ISR at the 8months CAG, we were able to follow up 86 patients until the late term. The data of ISR and TLR at 8month and ISR at late term are shown in the table. Conclusion: At the RCA ostial site, SF and SR have an effect on the ISR and TLR at 8month. Furthermore SF and SR have impact on late term ISR consecutively.

In vivo assessment of stent recoil of biodegradable polymer-coated cobalt–chromium sirolimus-eluting coronary stent system

IntroductionImmediate and acute stent recoil has been observed following balloon deflation in normal and diseased coronary arteries, and the degree varies by stent design. MethodsA total of 19 patients, who underwent elective stent implantation for single de novo native coronary artery lesions, were enrolled: all patients treated with the biodegradable polymer-coated sirolimus-eluting cobalt–chromium coronary stent system (Supralimus-Core®). The immediate, acute and cumulative stent recoil was assessed by quantitative coronary angiography. The cumulative stent recoil was measured at 24 h of stent implantation. ResultsThe absolute late loss due to recoil was found 0.08 ± 0.19 mm for Immediate Stent Recoil (ISR), 0.05 ± 0.21 mm for Acute Stent Recoil (ASR) and 0.11 ± 0.25 mm for Cumulative Stent Recoil (CSR) respectively. ConclusionsIn vivo acute stent recoil of the Supralimus-Core® has higher radial strength compared to other available standard drug-eluting stents.

Long-Term (&gt;10 Years) Clinical Outcomes of First-in-Human Biodegradable Poly- l -Lactic Acid Coronary Stents

Background— The purpose of this study was to evaluate the long-term safety of the Igaki-Tamai stent, the first-in-human fully biodegradable coronary stent made of poly- l -lactic acid. Methods and Results— Between September 1998 and April 2000, 50 patients with 63 lesions were treated electively with 84 Igaki-Tamai stents. Overall clinical follow-up (&gt;10 years) of major adverse cardiac events and rates of scaffold thrombosis was analyzed together with the results of angiography and intravascular ultrasound. Major adverse cardiac events included all-cause death, nonfatal myocardial infarction, and target lesion revascularization/target vessel revascularization. During the overall clinical follow-up period (121±17 months), 2 patients were lost to follow-up. There were 1 cardiac death, 6 noncardiac deaths, and 4 myocardial infarctions. Survival rates free of all-cause death, cardiac death, and major adverse cardiac events at 10 years were 87%, 98%, and 50%, respectively. The cumulative rates of target lesion revascularization (target vessel revascularization) were 16% (16%) at 1 year, 18% (22%) at 5 years, and 28% (38%) at 10 years. Two definite scaffold thromboses (1 subacute, 1 very late) were recorded. The latter case was related to a sirolimus-eluting stent, which was implanted for a lesion proximal to an Igaki-Tamai stent. From the analysis of intravascular ultrasound data, the stent struts mostly disappeared within 3 years. The external elastic membrane area and stent area did not change. Conclusion— Acceptable major adverse cardiac events and scaffold thrombosis rates without stent recoil and vessel remodeling suggested the long-term safety of the Igaki-Tamai stent.

Comparison of Acute Recoil between Bioabsorbable Poly-L-lactic Acid XINSORB Stent and Metallic Stent in Porcine Model

Objective. To investigate acute recoil of bioabsorbable poly-L-lactic acid (PLLA) stent. Background. As newly developed coronary stent, bioabsorbable PLLA stent still encountered concern of acute stent recoil. Methods. Sixteen minipigs were enrolled in our study. Eight PLLA XINSORB stents (Weite Biotechnology Co., Ltd., China) and eight metallic stents (EXCEL, Jiwei Co., Ltd. China) were implanted into coronary arteries. Upon quantitative coronary angiography analysis, acute absolute recoil was defined as the difference between mean diameter of inflated balloon (X) and mean lumen diameter of stent immediately after deployment (Y), while acute percent recoil was defined as (X−Y)/X and expressed as a percentage. Intravascular ultrasound (IVUS) was performed immediately after implantation and 24 hours later to compare cross-sectional area (CSA) between two groups and detect stent malapposition or collapse. Results. Acute absolute recoil in XINSORB and EXCEL was 0.02 ± 0.13 mm and −0.08 ± 0.08 mm respectively (P = 0.19). Acute percent recoil in XINSORB and EXCEL was 0.66 ± 4.32% and −1.40 ± 3.83%, respectively (P = 0.45). CSA of XINSORB was similar to that of EXCEL immediately after implantation, so was CSA of XINSORB at 24-hours followup. Within XINSORB group, no difference existed between CSA after implantation and CSA at 24-hours followup. No sign of acute stent malapposition was detected by IVUS. Conclusions. The acute stent recoil of XINSORB is similar to that of EXCEL. No acute stent malapposition or collapse appeared in both kinds of stent. This preclinical study was designed to provide preliminary data for future studies of long-term efficacy and safety of XINSORB stent.

Third in‐stent restenosis in sirolimus eluting stents

We evaluated the predictive factors for recurrent restenosis lesions treated on two previous occasions with sirolimus-eluting stents (SES). Angiography data related to recurrent SES restenosis have not been reported. Binary restenosis was observed in 66 patients with 78 lesions from a total of 1,393 patients with 1,965 lesions who received follow-up angiography after SES implantation. We enrolled 55 patients with 67 lesions who underwent revascularization using another SES with a second follow-up coronary angiography. These restenotic lesions were divided into two groups based on the presence or absence of recurrent restenosis: no recurrent restenosis group (n = 56) and recurrent restenosis group (n = 11). The coronary angiography data during first and second SES implantation were compared between the groups. Minimal lumen diameter (MLD) was smaller before first and second percutaneous coronary interventions (PCI) with SES implantation in the recurrent restenotic group compared with no recurrent restenosis group (first PCI, 0.28 ± 0.19 mm vs. 0.54 ± 0.42 mm, P = 0.040; second PCI, 0.44 ± 0.36 mm vs. 0.69 ± 0.39 mm, P = 0.036, respectively). Acute stent recoil after second SES implantation was significantly greater in the recurrent restenosis group compared with no recurrent restenosis group (0.08 ± 0.17 mm vs. 0.20 ± 0.22 mm, P = 0.049, respectively). Multivariate analysis showed preprocedural MLD at first PCI and acute stent recoil at second PCI as independent predictors of recurrent restenosis. Preprocedural smaller MLD at first PCI and acute stent recoil at second PCI are predictors of recurrent restenosis treated on two previous occasions with SES.

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.

TCT-633: Stent Recoil and Angiographic Outcome in Drug Eluting Stents. Results of the STEREO-DES pilot study

TCT-633: Stent Recoil and Angiographic Outcome in Drug Eluting Stents. Results of the STEREO-DES pilot study

TCT-621: Long-term (5 years) Serial in vivo Evaluation of Chronic Stent Recoil after Drug-Elutig Stent Implantation: Does it exits?

TCT-621: Long-term (5 years) Serial in vivo Evaluation of Chronic Stent Recoil after Drug-Elutig Stent Implantation: Does it exits?

Avaliação do recolhimento elástico tardio de stents farmacológicos de primeira e segunda gerações

BACKGROUND: Radial expansion and vessel wall scaffolding properties of stainless steel stents have improved the outcomes of coronary balloon angioplasty. Thinner struts and new platform designs are characteristic of more contemporaneous stents, but it is not clear whether these changes may result in devices with less radial strength, susceptible to elastic recoil, especially in the very late follow-up. This study was aimed at assessing late stent recoil in two generations of drug-eluting stents (DES) using serial intravascular ultrasound (IVUS) analysis. METHODS: Twenty-five patients with single de novo coronary lesions, treated with DES (12 CypherTM and 13 BioMatrixTM), were included and serial IVUS analysis was performed after stent implantation and at 4-6-months and 4-5 years of follow-up. Stent volume index was compared between the procedure and the mid and long-term follow-ups. Stent recoil was defined as a decrease > 10% of the stent volume index. RESULTS: Most of the patients were male (52%), with mean age of 58.8 ± 7.6 years, and 28% were diabetic. Stent volume index, the primary objective of this study, was 7.7 ± 1.5 mm3/mm post-procedure, 7.7 ± 2.1 mm3/mm at 4-6 months and 7.8 ± 1.6 mm3/mm at 4-5 years, with a delta of -0.02 ± 1.6 mm3/mm (P = 0.97). The long-term delta stent volume index was 0.13 ± 1.8 mm3/mm (1.7%) for the CypherTM stent and -0.05 ± 1.3 mm3/mm (-0.6%) for the BioMatrixTM stent (P = 0.78). CONCLUSIONS: Serial IVUS analysis showed that stainless steel DES of different generations did not show evidence of long-term elastic recoil.

Comparison of in vivo acute stent recoil between the bioresorbable everolimus‐eluting coronary scaffolds (revision 1.0 and 1.1) and the metallic everolimus‐eluting stent

The ABSORB cohort A trial using the bioresorbable everolimus-eluting scaffold (BVS revision 1.0, Abbott Vascular) demonstrated a slightly higher acute recoil with BVS than with metallic stents. To reinforce the mechanical strength of the scaffold, the new BVS scaffold (revision 1.1) with modified strut design was developed and tested in the ABSORB cohort B trial. This study sought to evaluate and compare the in vivo acute scaffold recoil of the BVS revision 1.0 in ABSORB cohort A and the BVS revision 1.1 in ABSORB cohort B with the historical recoil of the XIENCE V® everolimus-eluting metal stent (EES, SPIRIT I and II). In the ABSORB cohort B trial, 101 patients with one or two de-novo lesions were enrolled at 10 sites. In ABSORB cohort A, 27 patients treated with a BVS 1.0 were analyzed and compared with EES. Acute absolute recoil, assessed by quantitative coronary angiography, was defined as the difference between mean diameter of the last inflated balloon at the highest pressure (X) and mean lumen diameter of the stent immediately after the last balloon deflation (Y). Acute percent recoil was defined as (X - Y)/X and expressed as a percentage. Out of 101 patients enrolled in the ABSORB cohort B trial, 88 patients are available for complete analysis of acute recoil. Absolute recoil of BVS 1.1 (0.19 ± 0.18 mm) was numerically higher than metallic EES (vs. 0.13 ± 0.21 mm) and similar to BVS 1.0 (0.20 ± 0.21 mm) but the differences did not reach statistical significance (P = 0.40). The acute percent recoil demonstrated the same trend (EES: 4.3% ± 7.1%, BVS 1.0: 6.9% ± 7.0%, BVS 1.1: 6.7% ± 6.4%, P = 0.22). In the multivariate regression model, high balloon/artery ratio (>1.1) (OR 1.91 [1.34-2.71]) was the predictive for high absolute recoil (>0.27 mm) while (larger) preprocedural MLD was protective (OR 0.84 [0.72-0.99]). The stent/scaffold type was not a predictor of acute recoil. The average in vivo acute scaffold recoil of the BVS 1.1 is slightly higher than the metallic EES. However, the scaffold/stent type was not predictive of high acute recoil, while implantation in undersized vessels or usage of oversized devices might confound the results.

Double stenting: a method for treating acute stent recoil and luminal filling defects

Acute stent recoil and luminal filling defects can result in a suboptimal angiographic result following stent deployment and are associated with an increased risk of adverse outcomes. We aimed to evaluate the effect of double stenting, deployment of a second stent within the first, in the treatment of these conditions and to review the literature on this procedure. Thirteen cases of double stenting performed by a single operator at the Manchester Royal Infirmary over a three year period were identified and quantitative coronary angiography was performed. The indication for double stenting was acute stent recoil in eight cases, luminal filling defects in three cases and a combination of recoil and filling defects in two cases. There was a high frequency of target vessel calcification (77%) and ostial lesions (23%). Following double stenting, mean minimum lumen diameter increased significantly from 2.5 mm to 3.5 mm (p <0.001). There were no procedural complications. At mean clinical follow-up of 19 months (range six to 37 months), there were no major adverse cardiac events. Double stenting can significantly improve angiographic outcome in cases of acute stent recoil and luminal filling defects, with excellent clinical results in the medium term.

Impact of Hinge Motion on In-Stent Restenosis After Sirolimus-Eluting Stent Implantation

A tortuous lesion with hinge motion is reportedly a risk factor for in-stent restenosis (ISR) after bare metal stent implantation. Sirolimus-eluting stents (SESs) implantation has dramatically reduced ISR. However, SES is a closed-cell design stent, which has low conformability and flexibility. Several studies have reported a relationship between tortuous lesions and stent fracture, which is one of the causes of ISR. The efficacy of SES in a tortuous lesion with hinge motion has not been fully evaluated. The aim of this study was to investigate the relationship between tortuous lesions and ISR after SES implantation. Three year clinical follow-up data after SES implantation, including 6-9 month scheduled follow-up coronary angiography in 399 consecutive patients with 537 lesions, were obtained. Δangle was defined as the difference in the angle of the target lesion between the diastole and systole before the procedure. The incidence of ISR was 8.2%. The mean maximal angle and Δangle were larger in the ISR group (47 ± 22° vs. 37 ± 21°, P=0.004 and 20 ± 13° vs. 13 ± 10°, P < 0.0001, respectively). Independent predictors of ISR were Δangle, hemodialysis, aortic ostium stenting, and diabetes mellitus. Hinge motion-associated ISR (Δangle ≥ 16°) occurred in 28 lesions: stent fracture in 9, stent recoil in 6, edge injury in 10, and others in 3. The amount of hinge motion in tortuous lesions should be considered in the selection of drug eluting stent types.

Research on Constructing Surrogate Model of Coronary Stent Mechanical Property

Coronary stents are small tube-like structures expanded into stenotic arteries to restore blood flow perfusion to the downstream tissues. In this paper, based on the finite element analysis (FEA), both the response surface model (RSM) and radial basis function neural network (RBFNN) are used to construct the surrogate model for stent recoil performance. Precision between these two surrogate models are compared. The results show that the surrogate model with RBFNN is more reliable and efficient.

EFFECTS OF BALLOON LENGTH AND COMPLIANCE ON VASCULAR STENT EXPANSION

Vascular stents are used to dilate arteries that are narrowed or clogged by plaque. However, in-stent restenosis is still one of the major causes of the clinical failure. It is believed that vessel trauma imposed during stent deployment is closely correlated to restenosis. Clinical observations show that the longitudinal and axial geographic miss in pre/post-dilation are responsible for the vessel trauma. The interactions between the stent-strut and the artery are difficult to measure in vivo or clinically and reported results are very limited. A numerical approach that leverages on computing power can provide new insights into the stent implantation process. In this study, the effects of balloon length and compliance that play important roles during stent expansion were investigated. Areas in the vessels with high stress concentrations were identified as these were weaknesses that might have a high possibility of vascular injury. Two different types of numerical models were constructed: a simplified model that considered only the balloon and stent and a more comprehensive model that consisted of the balloon, stent, plaque, and artery. Virtual stent implantation trials were simulated and the phenomena of stent recoil, dogboning and foreshortening were observed and examined. It was found that balloons which were slightly longer than the stent and less compliance would be more likely to eliminate dogboning. Furthermore, a new parameter, namely the Ectropion angle, was introduced to describe the turning effect of the stent end in situations when dogboning could not adequately characterize this phenomenon. The present study could provide guidance for the placement of stents by clinical practitioners.