RESUMO
The aims of the study were to determine (1) whether the presence of High blood pressure (HBP) states in the youth associate a steeper rate of age-related change in arterial geometrical and wall properties with respect to subjects with no previous cardiovascular risk factor (CRF) exposure, (2) in which parameters and in what magnitude, and (3) the existence of a gender-related difference in the impact of this condition on arterial properties. 300 individuals (mean/range: 15/4-29 years; 133 females) were included. Two groups were assembled: (1) Reference: nonprevious exposure to traditional CRF and (2) HBP: subjects with arterial hypertension and/or elevated blood pressure (BP) levels during the study. Additionally, HBP subjects were separated in BP-related subgroups. Measured parameters were (1) central (aortic) arterial BP and aortic pulse wave analysis parameters, (2) carotid and femoral artery local (pressure-strain elastic modulus) and regional (pulse wave velocity; PWV) stiffness, and (3) arterial diameters and carotid intima-media thickness (CIMT). Age-related changes in these parameters (absolute values and z-scores) were explored by obtaining simple linear regression models for each group. HBP presented a steeper rate of change (accelerated vascular aging; VA) for most of the parameters assessed, mainly in central (aortic) hemodynamics. VA increased as the HBP level got higher. Both males' and females' aging rates were affected by this condition, but females presented a more marked relative age-related increase with HBP exposure. HBP states in the youth gradually associate accelerated VA, with a progressive hemodynamic-structural-functional onset of damage, with females presenting a more marked relative HBP-associated arterial repercussion.
Assuntos
Envelhecimento , Artérias/fisiopatologia , Hipertensão/fisiopatologia , Doenças Vasculares/fisiopatologia , Adolescente , Adulto , Aorta/fisiopatologia , Pressão Arterial , Artérias Carótidas/fisiopatologia , Espessura Intima-Media Carotídea , Criança , Pré-Escolar , Feminino , Artéria Femoral/fisiopatologia , Hemodinâmica , Humanos , Masculino , Análise de Onda de Pulso , Fluxo Sanguíneo Regional , Fatores de Risco , Fatores Sexuais , Rigidez Vascular , Adulto JovemRESUMO
The aims of our work were to determine normal aging rates for structural and functional arterial parameters in healthy children, adolescents, and young adults and to identify gender-related differences in these aging rates. Methods. 161 subjects (mean: 15 years (range: 4-28 years), 69 females) were studied. Subjects included had no congenital or chronic diseases, nor had they been previously exposed to traditional cardiovascular risk factors. Arterial parameters assessed were (1) central blood pressure (BP) and aortic pulse wave analysis, (2) arterial local (pressure-strain elastic modulus) and regional (pulse wave velocity, PWV) stiffness, and (3) arterial diameters and carotid intima-media thickness (CIMT). Simple linear regression models (age as the independent variable) were obtained for all the parameters and the resulting rates of change were compared between genders. Results. No gender-related differences were found in mean values of arterial structural and functional parameters in prepubertal ages (4-8 years), but they started to appear at ~15 years. Boys showed a greater rate of change for central systolic BP, central pulse pressure, CIMT, and carotid-femoral PWV. Conclusion. Gender-related differences in arterial characteristics of adults can be explained on the basis of different growing-related patterns between boys and girls, with no existing differences in prepubertal ages.
RESUMO
UNLABELLED: Flow-mediated dilatation (FMD) is the most accepted technique for the evaluation of endothelial function. However, it has been show a great inter-subject variability limiting its clinical use. Carotid-radial pulse wave velocity (PWVcr) was proposed as an alternative tool for the evaluation of endothelial function. At the present, there is no doubt that PWVcr reduces its values in response to reactive hyperemia test (RHT) in healthy subjects. AIMS: a) to determine simultaneously the temporal profile of FMD, PWVcr and shear rate in response to RHT and b) to describe and analyze how subjects "FMD responders" or "non-responders" behave regards to PWVcr changes. METHODS: 34 Healthy young subjects were included. The PWVcr (strain gauge mechanotransducers), brachial diameter (B-Mode ultrasound and blood flow velocity (Doppler ultrasound) were measured before (baseline) the cuff was inflated and after its deflation (5 minutes). 10(th) percentiles FMD and PWVcr changes in the population were used for the definition of the subjects ("responders and non-responders"). RESULTS: Changes in PWVcr, brachial arterial diameter and shear rate were evidenced after the cuff release (p<0.05). There were differences in the PWV and FMD temporal profiles. Within "FMD responders" there were "PWV responders and non-responders". CONCLUSION: Assessing RHT-related changes in PWVcr in the context of a FMD evaluation, could be useful as a discriminator of intrinsic wall alterations giving additional information of vascular dynamics.
Assuntos
Artérias Carótidas/patologia , Adulto , Algoritmos , Velocidade do Fluxo Sanguíneo/fisiologia , Pressão Sanguínea , Artéria Braquial/patologia , Sistema Cardiovascular , Dilatação , Endotélio Vascular/patologia , Feminino , Humanos , Hiperemia/patologia , Masculino , Resistência ao Cisalhamento , Estresse Mecânico , Fatores de Tempo , Vasodilatação/fisiologiaRESUMO
The early detection of biomechanical modifications in the arterial wall could be used as a predictor factor for various diseases, for example hypertension or atherosclerosis. In this work a transient elastography technique is used for the in vitro evaluation of the arterial wall elasticity. The obtained Young modulus is compared with the one obtained by a more classical approach: pressure-diameter relationships. As a sample an arterial phantom made of PolyVinyl Alcohol (PVA) gel was used. Diameter variation due to pressure variation inside the phantom was recorded by means of ultrasound. Through both techniques similar Young modulus estimations are obtained showing in this way the feasibility of applying transient elastography for the arterial wall elasticity assessment.
Assuntos
Artérias/diagnóstico por imagem , Técnicas de Imagem por Elasticidade/métodos , Processamento de Imagem Assistida por Computador/métodos , Modelos Cardiovasculares , Algoritmos , Módulo de Elasticidade , Estudos de Viabilidade , Imagens de Fantasmas , Álcool de Polivinil , VibraçãoRESUMO
In this present paper, we showed that wavelet analysis (WA) has the potential for extracting specific features from measured arterial diameter and pressure waveforms. The fifth detail of the Daubechies 4 (Db4) wavelet appears to be the most appropriate level for application, in order to analyze artery waveforms and was used to characterized arterial de-endothelization (DE). Raises in smooth muscle tone induced by (DE) tended to increase arterial stiffness and therefore that WA details embed the information of the diameter and pressure pulse that contains the signature of effects of wave travel and reflection affected by arterial stiffness.
Assuntos
Artérias/anatomia & histologia , Artérias/fisiologia , Determinação da Pressão Arterial/métodos , Pressão Sanguínea/fisiologia , Diagnóstico por Computador/métodos , Embolização Terapêutica , Endotélio Vascular/anatomia & histologia , Endotélio Vascular/fisiologia , Análise de Ondaletas , Animais , Artérias/cirurgia , Endotélio Vascular/cirurgia , Masculino , OvinosRESUMO
UNLABELLED: The analysis of carotid-radial pulse wave velocity (PWVcr) changes in response to forearm transient ischemia (TI) has been proposed as an alternative approach to evaluate endothelial function. Consider flow mediated dilatation tests, PWVcr changes are characterized after 5 minutes of TI. It is unknown if lower TI times could be used and if different TI times would result in different PWVcr responses (levels and/or kinetics). OBJECTIVE: To determine PWVcr changes associated with the reactive hyperemia in response to 1, 3 or 5 minutes of forearm TI. METHODS: We measured left PWVcr change using mechano-transducers in healthy volunteers (22 ± 2 years old) before (basal) and after 1 (n=14), 3 (n=14) and 5 (n=15) minutes of TI (forearm cuff inflation), respectively. The change of level and rate in PWVcr were recorded at 15, 30, 45 and 60 seconds after cuff release. Right brachial pressure was measured. RESULTS: There were no changes in heart rate or blood pressure during the studies. Regardless of the occlusion length, TI resulted in PWVcr reduction (p < 0.05). The groups showed similar maximum PWVcr reduction. However, there were differences in the immediate PWVcr changes (-4.9 ± 0.2%; -6.8 ± 0.3% and -8.3 ± 0.5% for 1, 3 and 5 minutes of TI, respectively) (p < 0.05). Then, the immediate rate of PWVcr change differed (p < 0.05) among the different ischemia times considered. Thereafter, the differences diminished and a minute after TI the groups showed similar levels and mean rate of PWVcr reduction. CONCLUSION: Similar maximum PWVcr responses can be obtained after 1, 3, or 5 minutes of TI. Different TI times resulted in dissimilar immediate, but not later, PWVcr changes.
Assuntos
Artérias Carótidas/patologia , Hiperemia/diagnóstico , Hiperemia/fisiopatologia , Isquemia , Adulto , Algoritmos , Fenômenos Biomecânicos , Determinação da Pressão Arterial , Frequência Cardíaca , Humanos , Cinética , Processamento de Sinais Assistido por Computador , Software , Esfigmomanômetros , Fatores de Tempo , TransdutoresRESUMO
Atherosclerotic plaque complication is a major cause of vascular accidents. Although a variety of factors have been proposed as key factors in these process, the mechanism that contribute to this problem remain to be characterized. Previously we demonstrated that changes in arterial wall viscous and elastic properties and/or in the filtering function (FF) could be part of the arterial wall alterations basis. If these properties are altered in arteries with atherosclerotic plaques remains to be analyzed. Our aims were 1) to analyze the arterial wall visco-elasticity and FF of carotid and femoral segments with atherosclerotic plaques, 2) to compare them with the mechanical behavior of segments without plaques (from the same artery) and of healthy arteries studied non-invasively. To this end, in each arterial segment, pressure and diameter signals were obtained, in vitro (circulation mock) and in vivo (non-invasive recordings). In atherosclerotic arteries recordings were performed on plaques and near regions without plaques. In each segment, the elasticity, the viscosity, and the wall FF were quantified. Atherosclerotic vessels, and particularly plaque regions, showed a reduced viscosity and FF. At the light of our results, hypothetical links between plaque events and changes in visco-elasticity and FF were discussed.
Assuntos
Aterosclerose/patologia , Artéria Carótida Primitiva/patologia , Artéria Femoral/patologia , Placa Aterosclerótica/patologia , Adulto , Fenômenos Biomecânicos , Elasticidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Cardiovasculares , Modelos Estatísticos , Processamento de Sinais Assistido por Computador , ViscosidadeRESUMO
In several clinical and experimental circumstances, it is widely necessary to characterize the bio-mechanical changes induced by atherosclerosis to the arterial wall. In this context, the purpose of this paper is twofold. Firstly, to propose a low cost ultrasound setup to improve artery radii determination in elasticity experiments, based on two transducers using a single channel ultrasound hardware. Secondly, to present an in vitro artificial heart system developed in our laboratory, which provides a wide range of hemodynamic parameters in arterial elasticity assessment experiments. It can be used in a liquid, stand alone mode or blowing air to a Jarvik device. This system will be integrated in future works with the proposed ultrasound setup to provide real time elasticity measurements.
Assuntos
Artérias/diagnóstico por imagem , Coração Artificial , Ultrassonografia/métodos , Algoritmos , Fenômenos Biomecânicos , Calibragem , Ecocardiografia/métodos , Elasticidade , Técnicas de Imagem por Elasticidade/métodos , Desenho de Equipamento , Hemodinâmica , Humanos , Processamento de Imagem Assistida por Computador , Técnicas In Vitro , Pressão , TransdutoresRESUMO
Although a variety of factors have been proposed as key factors of the atherosclerotic plaque vulnerability, the mechanisms that contribute to this problem are not yet fully characterized. In previous works we demonstrated that changes in arterial wall viscosity and elasticity and/or in the filtering function (FF) could be in the basis of arterial wall alterations. If these properties are altered in arterial wall with atherosclerotic plaques remain to be analyzed. Our aims were to analyze, the arterial wall visco-elasticity and FF of human carotid arteries with atherosclerotic plaques. To this end, instantaneous arterial diameter waveforms were obtained non-invasively (B-Mode Echography), in five sites (S1-S5) on the carotid artery. After that, diameter waveform obtained in S1 (first segment of the common carotid artery) was calibrated using pressure values, and used to quantify the pressure-diameter relationship for each segment. From pressure-diameter relationships, viscosity, elasticity and FF were quantified. Central portions of atherosclerotic plaques showed a reduced FF. At least in theoretical terms, the FF reduction could be related with the plaque vulnerability.
Assuntos
Aterosclerose/diagnóstico , Aterosclerose/patologia , Artérias Carótidas/patologia , Idoso , Calibragem , Ecocardiografia/métodos , Elasticidade , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Estatísticos , Placa Aterosclerótica/diagnóstico , Placa Aterosclerótica/patologia , Pressão , Software , Ultrassonografia/métodos , ViscosidadeRESUMO
Biomechanical and functional properties of tissue engineered vascular grafts must be similar to those observed in native vessels. This supposes a complete mechanical and structural characterization of the blood vessels. To this end, static and dynamic mechanical tests performed in the sheep thoracic and abdominal aorta and the cava vein were contrasted with histological quantification of their main constituents: elastin, collagen and muscle cells. Our results demonstrate that in order to obtain adequate engineered vascular grafts, the absolute amount of collagen fibers, the collagen/elastin ratio, the amount of muscle cells and the muscle cells/elastic fibers ratio are necessary to be determined in order to ensure adequate elastic modulus capable of resisting high stretches, an adequate elastic modulus at low and normal stretch values, the correct viscous energy dissipation, and a good dissipation factor and buffering function, respectively.