Comportamiento mecánico ante la sobrexpansión de stents de cromo-cobalto comparados con stents de acero inoxidable, implantados en la aorta abdominal de conejos hipercolesterolémicos

Introducción: La fisiopatología de la disfunción diastólica del ventrículo izquierdo incluye alteraciones de la relajación ventricular, rigidez elástica pasiva o una combinación de ambos mecanismos. Mediante el eco-Doppler es posible evaluar parámetros relacionados con la relajación ventricular, pero no de la rigidez elástica pasiva. El estrés parietal diastólico evalúa la rigidez elástica pasiva a través de la disminución de la compresión del miocardio al final de la diástole. Objetivo: Evaluar la rigidez elástica pasiva mediante el estrés parietal diastólico en pacientes con estenosis aórtica grave con fracción de eyección preservada y su relación con la presencia de insuficiencia cardíaca grado III-IV. Material y métodos: Se estudiaron 76 pacientes (edad promedio 67 ± 11 años) portadores de estenosis aórtica grave (índice de área valvular aórtica <0,6 cm2/m2) y fracción de eyección mayor o igual al 50%. El estrés parietal diastólico fue calculado como: (espesor sistólico de pared posterior – espesor diastólico) / espesor sistólico en modo M. Se calculó por métodos no invasivos la relación E/e´, presión de fin de diástole y presión de fin de diástole / volumen de fin de diástole. Los pacientes fueron ordenados en 2 grupos: Grupo 1: insuficiencia cardíaca grado III - IV (n = 5 pacientes) y Grupo 2: sin insuficiencia cardíaca (n = 71 pacientes). Resultados: Los pacientes del grupo 1 presentaron mayor alteración de la rigidez elástica pasiva evidenciada por disminución del estrés parietal diastólico (0,23 ± 0,05 vs. 0,30 ± 0,06 p < 0,01), mayor incremento de E/e´ (20 ± 7 vs. 14 ± 8 p < 0,05), presión de fin de diástole y presión de fin de diástole / volumen de fin de diástole. Conclusión: El estrés parietal diastólico permitiría objetivar alteraciones de la rigidez elástica pasiva en pacientes con estenosis aórtica grave, fracción de eyección preservada e insuficiencia cardíaca que no pueden ser evaluadas mediante los parámetros de función diastólica habituales.Objectives: The aim of this study was to analyze the behavior to overexpansion of cobalt chromium stents compared with stainlesssteel stents.Methods: Twenty New Zealand rabbits were used, fed with a diet supplemented with 1% cholesterol. Animals were divided into twogroups. Group 1 (n=10) received 3.0 mm cobalt chromium stents overexpanded at 20 atmospheres and group 2 (n=10) 3.5 mm stentsdeployed at 10 atmospheres. These stents were compared with a previous series of 20 animals with stainless steel stents, dividedinto the same two groups. A third group with conventional diet was used as control. Intravascular ultrasound (IVUS) was performedto assess the degree of elastic recoil and also the degree of symmetry using ?intertrust angles?.Results: In group 1 of cobalt chromium stents, mean elastic recoil was 0.11±0.13 mm, (3.21% recoil) and in group 2 this was0.3±0.12 mm, (8.26% recoil) (p=0.002). In group 1 of stainless steel stents mean elastic recoil was 0.28±0.18 mm (8.21% recoil) andin group 2 this was 0.10±0.11 mm (2.79% recoil) (p <0.001).Conclusions: In cobalt chromium stents, elastic recoil was lower in overexpanded stents, whereas in stainless steel stents, elasticrecoil was higher in overexpanded stents. No differences in symmetry were observed between the different groups.Fil: Fernandez, Alejandro. Hospital Italiano; ArgentinaFil: Mele, Esteban. Hospital Italiano; ArgentinaFil: Renou, Sandra Judith. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Anatomía Patológica; ArgentinaFil: Olmedo, Daniel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Anatomía Patológica; ArgentinaFil: Berrocal, Daniel. Hospital Italiano; ArgentinaFil: Gelpi, Ricardo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Anatomía Patológica; Argentin

Stent implant follow-up in intravascular optical coherence tomography images

The objectives of this article are (i) to utilize computer methods in detection of stent struts imaged in vivo by optical coherence tomography (OCT) during percutaneous coronary interventions (PCI); (ii) to provide measurements for the assessment and monitoring of in-stent restenosis by OCT post PCI. Thirty-nine OCT cross-sections from seven pullbacks from seven patients presenting varying degrees of neointimal hyperplasia (NIH) are selected, and stent struts are detected. Stent and lumen boundaries are reconstructed and one experienced observer analyzed the strut detection, the lumen and stent area measurements, as well as the NIH thickness in comparison to manual tracing using the reviewing software provided by the OCT manufacturer (LightLab Imaging, MA, USA). Very good agreements were found between the computer methods and the expert evaluations for lumen cross-section area (mean difference = 0.11 ± 0.70 mm2; r2 = 0.98, P\ 0.0001) and the stent cross-section area (mean difference = 0.10 ± 1.28 mm2; r2 = 0.85, P value\ 0.0001). The average number of detected struts was 10.4 ± 2.9 per crosssection when the expert identified 10.5 ± 2.8 (r2 = 0.78, P value\0.0001). For the given patient dataset: lumen cross-sectional area was on the average (6.05 ± 1.87 mm2), stent cross-sectional area was (6.26 ± 1.63 mm2), maximum angle between struts was on the average (85.96 ± 54.23), maximum, average, and minimum distance between the stent and the lumen were (0.18 ± 0.13 mm), (0.08 ± 0.06 mm), and (0.01 ± 0.02 mm), respectively, and stent eccentricity was (0.80 ± 0.08). Low variability between the expert and automatic method was observed in the computations of the most important parameters assessing the degree of neointimal tissue growth in stents imaged by OCT pullbacks. After further extensive validation, the presented methods might offer a robust automated tool that will improve the evaluation and follow-up monitoring of in-stent restenosis in patients

CT Coronary Angiography with 100kV tube voltage and a low noise reconstruction filter in non-obese patients: evaluation of radiation dose and diagnostic quality of 2D and 3D image reconstructions using open source software (OsiriX)

INTRODUCTION AND PURPOSE. Computed tomography coronary angiography (CTCA) has seen a dramatic evolution in the last decade owing to the availability of multislice CT scanners with 64 detector rows and beyond. However, this evolution has been paralleled by an increase in radiation dose to patients, that can reach extremely high levels (>20mSv) when retrospective ECG-gating techniques are used. On CT angiography, reduction of tube voltage allows to cut radiation dose with improved contrast resolution due to the lower energy of the X-ray beam and increased photoelectric effect. Our purpose is twofold: 1) to evaluate the radiation dose of CTCA studies carried out using a tube voltage of 100kV and a low noise reconstruction filter, compared with a conventional tube voltage of 120kV and a standard reconstruction kernel; 2) to assess the impact of the 100kV acquisition technique on the diagnostic quality of 2D and 3D image reconstructions performed with open source software (OsiriX). MATERIALS AND METHODS. Fifty-one non-obese patients underwent CTCA on a 64-row CT scanner. Out of them, 28 were imaged using a tube voltage of 100kV and a low noise reconstruction filter, while in the remaining 23 patients a tube voltage of 120kV and a standard reconstruction kernel were selected. All CTCA datasets were exported via PACS to a Macintosh™ computer (iMac™) running OsiriX 4.0 (64-bit version), and Maximum Intensity Projection (MIP), Curved Planar Reformation (CPR), and Volume Rendering (VR) views of each coronary artery were generated using a dedicated plug-in (CMIV CTA; Linköping University, Sweden). Diagnostic quality of MIP, CPR, and VR reconstructions was assessed visually by two radiologists with experience in cardiac CT using a three-point score (1=poor, 2=good, 3=excellent). Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), intravascular CT density, and effective dose for each group were also calculated. RESULTS. Image quality of VR views was significantly better with the 100kV than with the 120kV protocol (2.77±0.43 vs 2.21±0.85, p=0.0332), while that of MIP and CPR reconstructions was comparable (2.59±0.50 vs 2.32±0.75, p=0.3271, and 2.68±0.48 vs 2.32±0.67, p=0.1118, respectively). SNR and CNR were comparable between the two protocols (16.42±4.64 vs 14.78±2.57, p=0.2502, and 13.43±3.77 vs 12.08±2.10, p=0.2486, respectively), but in the 100kV group aortic root density was higher (655.9±127.2 HU vs 517.2±69.7 HU, p=0.0016) and correlated with VR image quality (rs=0.5409, p=0.0025). Effective dose was significantly lower with the 100kV than with the 120kV protocol (7.43±2.69 mSv vs 18.83±3.60 mSv, p<0.0001). CONCLUSIONS. Compared with a standard tube voltage of 120kV, usage of 100kV and a low noise filter leads to a significant reduction of radiation dose with equivalent and higher diagnostic quality of 2D and 3D reconstructions, respectively in non-obese patients

Examination of the coatings of coronary stents

In our study the main properties of coated coronary stents are shown, such as foreshortening, recoil, surface features and failures and the expansion properties. The types and the effects of active and passive coatings are introduced. The results of our examinations with different coated coronary stents are shown as well

A New 3-D automated computational method to evaluate in-stent neointimal hyperplasia in in-vivo intravascular optical coherence tomography pullbacks

Abstract. Detection of stent struts imaged in vivo by optical coherence tomography (OCT) after percutaneous coronary interventions (PCI) and quantification of in-stent neointimal hyperplasia (NIH) are important. In this paper, we present a new computational method to facilitate the physician in this endeavor to assess and compare new (drug-eluting) stents. We developed a new algorithm for stent strut detection and utilized splines to reconstruct the lumen and stent boundaries which provide automatic measurements of NIH thickness, lumen and stent area. Our original approach is based on the detection of stent struts unique characteristics: bright reflection and shadow behind. Furthermore, we present for the first time to our knowledge a rotation correction method applied across OCT cross-section images for 3D reconstruction and visualization of reconstructed lumen and stent boundaries for further analysis in the longitudinal dimension of the coronary artery. Our experiments over OCT cross-sections taken from 7 patients presenting varying degrees of NIH after PCI illustrate a good agreement between the computer method and expert evaluations: Bland-Altmann analysis revealed a mean difference for lumen cross-section area of 0.11 ± 0.70mm2 and for the stent cross-section area of 0.10 ± 1.28mm2

Introduction. Carotid endarterectomy versus carotid stenting. A never-ending story

L'articolo discute le controversie relative all'accettazione in pratica clinica dello stentig carotide

A polymer coated cicaprost-eluting stent increases neointima formation and impairs vessel function in the rabbit iliac artery

Drug-eluting stents have been successful in reducing in-stent restenosis but are not suitable for all lesion types and have been implicated in causing late stent thrombosis due to incomplete regeneration of the endothelial cell layer. In this study we implanted stents coated with cicaprost, a prostacyclin analogue with a long plasma half-life and antiproliferative effects on vascular smooth muscle cells, into the iliac arteries of rabbits. At 28-day follow-up we compared neointima formation within the stented vessels and vascular function in adjacent vessels, to assess if cicaprost could reduce restenosis without impairing vessel function. Arteries implanted with cicaprost eluting stents had significantly more neointima compared to bare metal stents. In adjacent segments of artery, endothelium-dependent relaxation was impaired by the cicaprost-eluting stent but vasodilation to an endothelium-independent vasodilator was maintained. We conclude that the presence of the polymer and sub-optimal release of cicaprost from the stent may be responsible for the increased neointma and impaired functional recovery of the endothelium observed. Further experiments should be aimed at optimising release of cicaprost and exploring different stent polymer coatings

Perfil dos pacientes submetidos à angioplastia trasluminal coronariana com stents farmacológicos no Instituto de Cardiologia de Santa Catarina.

Trabalho de Conclusão de Curso - Universidade Federal de Santa Catarina. Curso de Medicina. Departamento de Clínica Médica

Numerical simulation of Nitinol peripheral stents: from laser-cutting to deployment in a patient specific anatomy

The current clinical trend is to use percutaneous techniques, exploiting Nitinol self-expanding stents, to treat peripheral occluded vessels such as carotid or superficial femoral arteries. Although this class of stents addresses the biomechanical requirements (i.e. flexibility, kink resistance, etc.), it has been observed that many of these stents implanted in peripheral vessels are fractured. Numerical simulations have shown to be very useful in the investigation and optimization of stents and also to provide novel insights into fatigue/fracture mechanics. To date most finite element based stent simulations are performed in a straight simplified anatomy and neglect the actual deployment process; consequently there is a need for more realistic simulations taking into account the different stages of the stent design process and the insertion in the target anatomy into account. This study proposes a virtual framework to analyze numerically Nitinol stents from the laser-cutting stage to the deployment in a (patient specific) tortuous anatomy