Modelling pulse wave propagation in the rabbit systemic circulation to assess the effects of altered nitric oxide synthesis

Alastruey, Jordi; Nagel, Simon R.; Nier, Bettina A.; Hunt, Anthony A. E.; Weinberg, Peter D.; Peiró, Joaquim

doi:10.1016/j.jbiomech.2009.05.028

Cited by 25 publications

(32 citation statements)

References 19 publications

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“…We believe, however, that mechanical-based algorithms, as those described here, should first be used to determine the total compliance and net resistance of the system, outflow pressures, and local compliances and viscous moduli at as many locations as possible. For example, knowledge of the wave speed, c i , and luminal area at a few locations allows us to relate them through a least-squares fitting [25,31,50], so that c i can be inferred elsewhere in the system given local areas from medical images. Once the net peripheral resistance and compliance are known, we can distribute them among the terminal branches based on mechanical principles [8,33].…”

Section: Discussionmentioning

confidence: 99%

Physical determining factors of the arterial pulse waveform: theoretical analysis and calculation using the 1-D formulation

et al. 2012

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The shape of the arterial pulse waveform is intimately related to the physical properties of the cardiovascular system. It is clinically relevant to measure those properties that are related to cardiovascular function, such as the local elasticity and viscosity of the arterial wall, total compliance and net peripheral resistance of the systemic arterial tree. Most of these properties cannot be directly measured in vivo, but they can be calculated from pressure, flow and wall displacement measurements that can be obtained in vivo. We carry out a linear analysis of the one-dimensional (1-D) equations of blood flow in Voigt-type visco-elastic vessels to study the effects on pulse wave propagation of blood viscosity, flow inertia, wall visco-elasticity, total arterial compliance, net resistance, peripheral outflow pressure, and flow rate at the aortic root. Based on our analysis, we derive methods to calculate the local elastic and viscous moduli of the arterial wall, and the total arterial compliance, net resistance, time constant and peripheral outflow pressure of the systemic arterial tree from pressure, flow and wall displacement data that can be measured in vivo. Analysis of in vivo data is beyond the scope of this study, and therefore, we verify the results of our linear analysis and assess the accuracy of our estimation methods using pulse waveforms simulated in a nonlinear visco-elastic 1-D model of the larger conduit arteries of the upper body, which includes the circle of Willis in the cerebral circulation.

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Section: Discussionmentioning

confidence: 99%

Physical determining factors of the arterial pulse waveform: theoretical analysis and calculation using the 1-D formulation

et al. 2012

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“…Average maps are shown in Cremers et al 6 conditions do not substantially alter the WSS patterns. Thirdly, many recent experimental studies highlight the importance of flow reversal as an initiating factor for atherosclerosis, 12 suggesting that the pulsatility of the flow is decisive for the development of particular disease patterns; an increasing number of computational studies compare lesion distributions against time-dependent flow metrics such as OSI. 14,15 However, the patterns of TAWSS and OSI we derived from the simulations of unsteady flow in 4 aortic geometries were very similar to the steady WSS patterns.…”

Section: Discussionmentioning

confidence: 99%

“…For the time-dependent simulation, steady-state boundary conditions at the aortic root and branches were modulated using a velocity waveform that was computed at the proximal descending aorta in a 1D pulse wave propagation model. 12 The waveform was selected at this location to accurately model flow in the descending aorta.…”

Section: S13 Modelling Parameters and Assumptionsmentioning

confidence: 99%

“…Their data suggested a positive correlation of WSS with lesion prevalence, in contrast to the current consensus that low or low oscillatory WSS promotes plaque formation. 7,12 Computational Fluid Dynamics (CFD) is widely used in the field of bioengineering to compute arterial WSS. [13][14][15] It has been used in this context to study flow in an idealised model of a single intercostal artery branching off the thoracic aorta 16 and in a geometrically accurate model of one (mature) rabbit thoracic aorta, 17 but it has not been applied to evaluate age-related changes in blood flow characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Effect of aortic taper on patterns of blood flow and wall shear stress in rabbits: Association with age

et al. 2012

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Objective -The distribution of atherosclerotic lesions changes with age in human and rabbit aortas. We investigated if this can be explained by changes in patterns of blood flow and wall shear stress. Methods -The luminal geometry of thoracic aortas from immature and mature rabbits was obtained by micro-CT of vascular corrosion casts. Blood flow was computed and average maps of wall shear stress were derived. Results -The branch anatomy of the aortic arch varied widely between animals. Wall shear was increased downstream and to a lesser extent upstream of intercostal branch ostia, and a stripe of high shear was located on the dorsal descending aortic wall. The stripe was associated with two vortices generated by aortic arch curvature; their persistence into the descending aorta depended on aortic taper and was more pronounced in mature geometries. These results were not sensitive to the modelling assumptions.Conclusions -Blood flow characteristics in the rabbit aorta were affected by the degree of taper, which tends to increase with age in the aortic arch and strengthens secondary flows into the descending aorta. Previouslyobserved lesion distributions correlated better with high than low shear, and age-related changes around branch ostia were not explained by the flow patterns.

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“…Applying this to a thin shell cylinder model, 18 the following relationship between TMP and aortic diameter Ø can be derived 19 :…”

Section: Theoretical Modelmentioning

confidence: 99%

Altered Dependence of Aortic Pulse Wave Velocity on Transmural Pressure in Hypertension Revealing Structural Change in the Aortic Wall

et al. 2015

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Stiffening of the aorta, a ubiquitous feature of cardiovascular ageing, imposing adverse loading on the left ventricle and generating high pulse pressure, predisposes to cardiovascular events independent of traditional risk factors.1,2 The determinants of aortic stiffening are, however, poorly understood. Aortic pulse wave velocity (aPWV, the measure of aortic stiffening with most prognostic impact) is only weakly, if at all, associated with traditional risk factors for cardiovascular disease other than age and blood pressure.3,4 By contrast, aPWV is closely associated with concurrent levels of blood pressure 5 implicating hypertension in the etiology of aortic stiffening. However, it is unclear whether the relation of aPWV to blood pressure is simply because of the aorta becoming stiffer as it is stretched by a higher transmural distending pressure (TMP, usually equal to intra-aortic blood pressure) 6 or whether it results from a structural change in the aortic wall associated with and contributing to a sustained elevation in blood pressure (ie, hypertension). Previous attempts to address this question by obtaining indirect estimates of isobaric stiffness have yielded conflicting results. 7-10However, isobaric stiffness does seem to be of prognostic significance. 11 In the present study, we have exploited a novel technique to modulate TMP independent of blood pressure by controlled variation of intrathoracic pressure (ITP) around the adventitial surface of the aorta. We used this to examine the relation of aPWV to TMP in normotensive and hypertensive subjects, reasoning that if aPWV in hypertension is because of a higher TMP, then aPWV in hypertensive subjects would equal that in normotensive subjects when measured at the same TMP. We then used a theoretical model to examine whether aPWV-TMP relationships may be explained by recruitment of collagen fibers in an elastin/collagen matrix when the aorta is distended by increased TMP.Abstract-Aortic pulse wave velocity (aPWV), a major prognostic indicator of cardiovascular events, may be augmented in hypertension as a result of the aorta being stretched by a higher distending blood pressure or by a structural change. We used a novel technique to modulate intrathoracic pressure and thus aortic transmural pressure (TMP) to examine the variation of intrathoracic aPWV with TMP in hypertensive (n=20; mean±SD age, 52.1±15.3 years; blood pressure, 159.6±21.2/92.0±15.9 mm Hg) and normotensive (n=20; age, 55.5±11.1 years; blood pressure, 124.5±11.9/72.6±9.1 mm Hg) subjects. aPWV was measured using dual Doppler probes to insonate the right brachiocephalic artery and aorta at the level of the diaphragm. Resting aPWV was greater in hypertensive compared with normotensive subjects (897±50 cm/s versus 784±43 cm/s; P<0.05). aPWV was equal in hypertensive and normotensive subjects when measured at a TMP of 96 mm Hg. However, dependence of aPWV on TMP in normotensive subjects was greater than that in hypertensive subjects (9.6±1.6 versus 3.8±0.7 cm/s per mm Hg increase in TMP, respe...

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Modelling pulse wave propagation in the rabbit systemic circulation to assess the effects of altered nitric oxide synthesis

Cited by 25 publications

References 19 publications

Physical determining factors of the arterial pulse waveform: theoretical analysis and calculation using the 1-D formulation

Physical determining factors of the arterial pulse waveform: theoretical analysis and calculation using the 1-D formulation

Effect of aortic taper on patterns of blood flow and wall shear stress in rabbits: Association with age

Altered Dependence of Aortic Pulse Wave Velocity on Transmural Pressure in Hypertension Revealing Structural Change in the Aortic Wall

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