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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. [ABSTRACT FROM AUTHOR]

Aims: The intra-aortic balloon pumping (IABP) changes pressure and increases the aorta shear stress reversal (SSR) and oscillatory (SSO) components. Hence, IABP-dependent changes in aortic biomechanics would be expected, because of vascular smooth muscle (VSM) tone (i.e. flow-induced endothelium-dependent response, related to SSR and SSO variations) and/or pressure changes. To characterize: (i) the IABP effects on the aortic and global (systemic circulation) biomechanics, analysing their dependence on pressure and VSM basic tone changes and (ii) the relation between the SSR and SSO and the aortic biomechanical changes associated with the VSM tone variations. Methods: Aortic flow, pressure and diameter were measured in eight sheep during basal, augmented and assisted beats (1 : 1 and 1 : 2 IABP modalities). Calculations: (i) aortic effective and isobaric elasticity, viscosity, circumferential stress, pulse wave velocity, shear stress and buffer and conduit functions, (ii) peripheral resistance, global compliance, reflection coefficient and wave propagation times and (iii) the relation between SSR and SSO and biomechanical changes associated with variations in the aortic VSM tone. Results: Augmented and assisted beats showed: global VSM relaxation pattern (reduced peripheral resistance and reflection coefficient; increased propagation times) and local VSM contraction pattern (increased viscosity; reduced diameter, elasticity and circumferential stress), associated with SSR and SSO, levels and changes. The vascular changes reduced the ventricle afterload determinants, increased the vascular buffer performance and kept the conduit capability. Conclusion: In addition to pressure-dependent changes, IABP determined biomechanical changes related to variations in the VSM tone. The increased SSR and SSO were associated with the aortic VSM contraction pattern and biomechanical changes. [ABSTRACT FROM AUTHOR]

Aim: An adventitia dependent regulation of the vascular smooth muscle tone has been described. However, if the adventitia plays an active role on arterial wall biomechanical behaviour and functions remains to be established. Our aim was to characterize the influence of adventitia on arterial wall mechanical properties and the arterial conduit and buffer functions. Methods: Ovine brachiocephalic arteries were studied in vivo ( n = 8) and in vitro (with null tone) in a circulation mock ( n = 8). Isobaric, isoflow and isofrequency studies were performed. In each segment, pressure and diameter waves were assessed before and after adventitia removal. From the arterial stress–strain relationship, we derived the elastic and the viscous modulus. The buffering and conduit functions were calculated using the Kelvin–Voigt's time constant and the inverse of the characteristic impedance, respectively. Results: In in vivo studies arterial diameter decreased after adventitia removal ( P < 0.05). Elastic and viscous modulus in in vivo studies were significantly higher in adventitia-removed arteries, compared with values in intact vessels ( P < 0.05). This behaviour was not observed in in vitro experiments. An impairment of buffer and conduit functions was observed in vivo after adventitia removal ( P < 0.05), while both functions remain unchanged in in vitro studies ( P > 0.05). Conclusions: Arterial wall viscosity and elasticity were influenced by adventitia removal in in vivo studies, possibly by a smooth muscle-dependent mechanism, since it was not present in in vitro experiments. Adventitia would be involved in a physiological mechanism of arterial wall viscous and elastic properties regulation, that could influence arterial buffering and conduit functions. [ABSTRACT FROM AUTHOR]