RESUMO
The vascular endothelium plays an important role in the regulation of vascular tone, cell growth, inflammation, and thrombogenicity. Endothelium dysfunction, then, is considered to promote several disorders that initiate the atherosclerosis process. Vascular tone dysfunction can be determined by high-resolution ultrasonographic imaging of the brachial artery, enabling one to assess endothelium-dependent flow-mediated dilation (FMD). It is based on the principle that an increase in blood flow, specifically in shear stress, provokes the release of nitric oxide and then a vasodilation that can be quantified. In this study, brachial artery diameter evolution was continuously followed during baseline and hyperemia after forearm occlusion using a custom designed software. Some techniques used to measure FMD are limited by operator dependence. We present a new, automated, and versatile method of FMD quantification based on B-mode echographic images and edge detection algorithms. Edges for each image in the acquired sequences are recognized as interfaces based on the grey-level profiles of the averaged pixel values. Within-reading and within-subject FMD% coefficients of variation were 7% and 10%, respectively. This technique largely improves manual measurements and was shown to be appropriate for wide clinical use.
Assuntos
Artéria Braquial/fisiologia , Endotélio Vascular/fisiologia , Vasodilatação/fisiologia , Adulto , Algoritmos , Pressão Sanguínea , Artéria Braquial/diagnóstico por imagem , Endotélio Vascular/diagnóstico por imagem , Feminino , Antebraço/irrigação sanguínea , Humanos , Masculino , Pessoa de Meia-Idade , Óxido Nítrico/metabolismo , Variações Dependentes do Observador , Fluxo Sanguíneo Regional , Reprodutibilidade dos Testes , Software , UltrassonografiaRESUMO
BACKGROUND: The reproducibility of brachial artery flow-mediated vasodilatation (FMD) is limited by the operator dependence of most measurement methods. METHODS: A new automated computerized analysis of brachial artery ultrasound scan providing a continuous evolution of the diameter during acute hyperemia, reactive to short hyperemia of the forearm and hand, was tested in 10 normal volunteers and 26 asymptomatic patients with cardiovascular risk factors such as hypertension, hypercholesterolemia, heavy smoking, history of premature coronary heart disease and the metabolic syndrome. FMD was the percentage of the maximum hyperemic diastolic diameter from baseline. Within-reading variations in FMD and diameters were assessed by reading one scan from the same subject twice by two observers. The within-subject variability of FMD was assessed by analysing two repeated measurements in the same subject by the same operator 1 h, 1 week or 1 month apart. RESULTS: Coefficients of variation (CV) of repeated FMD readings were 7.5% in normal volunteers and 6.9% in patients with risk factors. CV of repeated FMD measurements 1 h apart were 7.8% in normal volunteers and 16.5% in patients with risk factors. In normal volunteers, CV of repeated FMD measurements 1 week apart was 9.6%, and in patients with risk factors CV of repeated FMD measurement 1 month apart was 18.1%. CONCLUSION: This method overcomes the variability of FMD measurement seen with conventional manual analysis in normal volunteers, and to a lesser extent in patients with major cardiovascular risk factors, thus supporting its clinical applicability to patients with disease conditions.
Assuntos
Artéria Braquial/diagnóstico por imagem , Doenças Cardiovasculares/diagnóstico , Hiperemia/diagnóstico por imagem , Interpretação de Imagem Assistida por Computador , Software , Vasodilatação , Adulto , Velocidade do Fluxo Sanguíneo , Doenças Cardiovasculares/etiologia , Doenças Cardiovasculares/fisiopatologia , Feminino , Humanos , Hipercolesterolemia/complicações , Hipercolesterolemia/diagnóstico por imagem , Hiperemia/fisiopatologia , Hipertensão/complicações , Hipertensão/diagnóstico por imagem , Masculino , Síndrome Metabólica/complicações , Síndrome Metabólica/diagnóstico por imagem , Variações Dependentes do Observador , Valores de Referência , Reprodutibilidade dos Testes , Projetos de Pesquisa , Fatores de Risco , Fumar/efeitos adversos , Fatores de Tempo , UltrassonografiaRESUMO
Arterial sialic acid (SA) has been shown to attenuate the binding of fibrinogen and low-density lipoproteins (LDL) to the vessel wall, presumably protecting against atherosclerosis. This study was aimed to assess the effect of changes in SA content in intimal thickening, an early step in the development of atherosclerosis. New Zealand white rabbits were subjected to bilateral carotid periarterial collaring, followed by in situ-perfusion with neuroaminidase (random artery) and with vehicle (contralateral control artery). The efficiency of SA removal was evaluated in perfusates and arterial homogenates, and arterial tissue samples were obtained 7 and 14 days after the intervention to assess morphological changes. Neuraminidase significantly reduced SA by 16.7%. Arterial desialylation was associated with a significantly increased neointimal formation. Proliferation of smooth muscle cells (SMCs), assessed by incorporation of bromo-2'-deoxyuridine into replicating DNA was also significantly increased in desialylated arteries. In addition, immunohistochemical studies showed a slightly stronger oxidized-LDL (ox-LDL) immunostaining in neointima of desialylated arteries than in control vessels. A mild reduction of SA increases intimal thickening, at least partly due to an enhanced proliferation of SMCs, and may facilitate the accretion of atherogenic lipoproteins, providing evidence for the potential role of SA in the protection against neointimal development.
Assuntos
Doenças das Artérias Carótidas/metabolismo , Doenças das Artérias Carótidas/patologia , Ácido N-Acetilneuramínico/metabolismo , Animais , Artérias Carótidas/efeitos dos fármacos , Artérias Carótidas/metabolismo , Artérias Carótidas/patologia , Divisão Celular/fisiologia , Imuno-Histoquímica , Lipoproteínas LDL/metabolismo , Masculino , Músculo Liso Vascular/patologia , Neuraminidase/farmacologia , Coelhos , Túnica Íntima/efeitos dos fármacos , Túnica Íntima/metabolismo , Túnica Íntima/patologiaRESUMO
La ateroscleroris es un proceso multifactorial de gran complejidad cuyo origen es aún desconnocido. Sin embargo, eventos característicos de su patogénesis dan evidencias de una disminuición de la densidad de carga eléctrica exnibida normalmente por el glicocáliz de los elementos parietales y sanguíneos implicados en este proceso. Las investigaciones más recientes indican que el espesor del glicocáliz endotelial es función no sólo de sus moléculas polianiónicas superficiales, sino tambíén de la composición del fluido sanguíneo. Teniendo en cuenta esta dependencia respecto de la composicón de la sangre, el objetivo de este trabajo fue investigar la influencia de la concentración electrolítica y del pH plasmáticos sobre las propiedades electrocinéticas en la interfase pared arterial - fluido sanguíneo. Para lograr esto se evaluó experimentalmente utilizando segmentos aórticos porcinos, el efecto electrocinético que ejerce sobre el endotelio arterial, el flujo de soluciones de contenido iónico y pH variables. Los resultados indicaron que el aumento del contenido iónico normal del plasma podría afectar las propriedades eléctricas de aquellos elementos, favoreciendo su acercamiento. Así también, el decremento del valor del pH fisiológico reduciría la proporción de molécular polianiónicas contenidas en el glicocáliz de dichos elementos, disminuyendo la repulsión electrostática entre ellos. De esta forma, el desarrollo aterogénico asociado con un aumento de la captación de componentes de la sangre, podría estar relacionado con una alteración de las propiedades electrocinéticas de los elementos parietales y sanguíneos involucrados, provocada por cambios de pH o concentración electrolítica plasmática
Assuntos
Endotélio Vascular , Técnicas de Laboratório Clínico , Doença da Artéria Coronariana/etiologia , Doença da Artéria Coronariana/sangue , Eletroquímica/instrumentaçãoRESUMO
The role of blood viscosity on arterial wall elasticity before and after deendothelization (DE) was studied. Seven ovine brachiocephalic arteries were studied in vitro under physiological pulsatile flow conditions achieved by a mock circulation loop. Instantaneous pressure and diameter signals were assessed in each arterial segment. Incremental elastic modulus (E(inc)) was calculated using the slope of the pure elastic stress-strain relationship. There was no significant difference between E(inc) values before and after DE (3.11 vs. 3.16 10(7) dyn/cm(2)) at a blood viscosity of 2.00 mPa. s. Increases in blood viscosity (2.50, 3.00, 3.50, and 4.00 mPa. s) always resulted in decreases of E(inc) before DE; inversely, increases in blood viscosity resulted in increases of E(inc) after DE. These values of E(inc), for identical levels of blood viscosity, were always significantly lower (P < 0.05) before DE than those obtained after DE. Arterial wall elasticity assessed through E(inc) was strongly influenced by blood viscosity, probably due to presence or absence of endothelium relaxing factors or to direct shear smooth muscle activation when endothelial cells are removed.