Pressure-flow relationships and vascular impedance in man

Mills, Christopher; Gabe, I. T.; Gault, James H.; Mason, Dean T.; Ross, Jr J; Braunwald, E.; Shillingford, John

doi:10.1093/cvr/4.4.405

Cited by 324 publications

(165 citation statements)

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“…This dependence reflects the fact that the intrarenal flow pulsation is determined by the aortic pressure pulsation (Mills et al 1970;Tublin et al 1999). The dependence of renal RI on the central hemodynamics has been suggested also by a recent study of renal transplant recipients, which showed an association between renal RI and recipient age (related to aortic stiffness) but not renal allograft histologic features (Naesens et al 2013).…”

Section: Elastic Aorta Stiff Aortamentioning

confidence: 84%

Central Hemodynamics and Target Organ Damage in Hypertension

Hashimoto

2014

Tohoku J. Exp. Med.

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Recent advances in technology have enabled the noninvasive evaluation of pulsatile hemodynamics in the central aorta; namely, central pressure and flow measurements. The central blood pressure represents the true load imposed on the heart, kidney and brain, and the central blood flow influences the local flow into these vital organs. An elevation of the central blood pressure has a direct, adverse impact on the target organ and, thus, the cardiovascular prognosis in patients with hypertension. A decrease in the central blood flow can cause organ dysfunction and failure. The central pressure and flow dynamics were conventionally regarded as unidirectional from the heart to the periphery. However, current evidence suggests that it should be recognized as a bidirectional interplay between the central and peripheral arteries. Specifically, the pressure pulse wave is not only transmitted forward to the periphery but also reflected backward to the central aorta. The flow pulse wave is also composed of the forward and reverse components. Aortic stiffening and arteriolar remodeling due to hypertension not only augment the central pressure by increasing the wave reflection but also may alter the central bidirectional flow, inducing hemodynamic damage/dysfunction in susceptible organs. Therefore, central hemodynamic monitoring has the potential to provide a diagnostic and therapeutic basis for preventing systemic target organ damage and for offering personalized therapy suitable for the arterial properties in each patient with hypertension. This brief review will summarize hypothetical mechanisms for the association between the central hemodynamics and hypertensive organ damage in the heart, kidney and brain.

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Section: Elastic Aorta Stiff Aortamentioning

confidence: 84%

Central Hemodynamics and Target Organ Damage in Hypertension

Hashimoto

2014

Tohoku J. Exp. Med.

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“…Mills et al, 18 Gosling et al,21 and Murgo and colleagues '9 have argued that the major reflection site in the abdominal aorta is located at the aortoiliac bifurcation, whereas more recently, a careful study by Latham et al10 on subjects in the age range of 35-61 years has shown that no significant reflections occur between the renal arteries and the bifurcation. Our results confirm this latter observation, at least in specimens 30-60 years old.…”

Section: Resultsmentioning

confidence: 99%

Effect of age on the in vitro reflection coefficient of the aortoiliac bifurcation in humans.

1990

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The local reflection coefficient (r) at the aortoiliac junction was estimated in vessels removed at autopsy from 15 females and 31 males aged 2 months to 88 years by calculating the characteristic impedance (ZJ) of the abdominal aorta and the two common iliac arteries. Z, was evaluated for each vessel by measuring cross-sectional area from radiographs and propagation velocity of an isolated pressure impulse generated by a solenoid-driven piston connected to the distal end of the abdominal aorta, and detected at several sites a known distance from the junction. Attenuation coefficients in the aorta were estimated from the peak amplitude of the impulse at these several sites. We observed significant decreases with age in abdominal aortic attenuation coefficient ( In children, a significant positive reflection at the distal end of the aorta will amplify the pulse wave in this region. As this vessel becomes stiffer with increasing age, amplification will increase, whereas the increasingly negative value of r will partially offset this rise, reducing pulse pressure on either side of the junction. These processes might help to minimize the adverse effects of increased vascular stiffness due to aging and disease in this part of the circulation. (Circulation 1990;82:114-123) T he magnitude of measured pressure and flow waves in the cardiovascular system is determined by the interaction of incident waves generated by the heart and one or more reflections due to junctions and, in diseased vessels, occlusive or aneurysmal lesions. Constricted muscular vessels in the peripheral circulation can cause additional reflections. Thus, to measure the magnitude of reflection coefficients, it is necessary to resolve the From measured pressure and flow wave into its generated component traveling away from the heart, a reflected wave traveling back toward the heart and, possibly, one or more rereflected waves traveling in either direction.The different approaches to this problem described in the literature can be divided into two types.' First, those in which the magnitude of all reflections distal to the measurement site are determined.2-8 These methods do not, in general, give any information about the location of particular sites of reflection but allow the calculation of a global reflection coefficient together with propagation constants (phase velocity and attenuation coefficient) of the vessel in which the measurements are made. The second class of measurements is based on the prop-

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“…The time-dependent fully developed laminar flow velocity and the time-dependent pressure wave-forms, as suggested by Mills et al, were applied at the inlet and outlet of the fluid domain, respectively [66]. Peak systolic pressure occurs at t = 0.53 s (15,594.5 kg/m s 2 ) and peak systolic flow is obtained at t = 0.45 s (0.437886 m/s).…”

Section: Boundary Conditionsmentioning

confidence: 99%

Investigation of material modeling in fluid–structure interaction analysis of an idealized three-layered abdominal aorta: aneurysm initiation and fully developed aneurysms

Şimşek

Kwon

2015

J Biol Phys

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Different material models for an idealized three-layered abdominal aorta are compared using computational techniques to study aneurysm initiation and fully developed aneurysms. The computational model includes fluid-structure interaction (FSI) between the blood vessel and the blood. In order to model aneurysm initiation, the medial region was degenerated to mimic the medial loss occurring in the inception of an aneurysm. Various cases are considered in order to understand their effects on the initiation of an abdominal aortic aneurysm. The layers of the blood vessel were modeled using either linear elastic materials or Mooney-Rivlin (otherwise known as hyperelastic) type materials. The degenerated medial region was also modeled in either linear elastic or hyperelastic-type materials and assumed to be in the shape of an arc with a thin width or a circular ring with different widths. The blood viscosity effect was also considered in the initiation mechanism. In addition, dynamic analysis of the blood vessel was performed without interaction with the blood flow by applying time-dependent pressure inside the lumen in a three-layered abdominal aorta. The stresses, strains, and displacements were compared for a healthy aorta, an initiated aneurysm and a fully developed aneurysm. The study shows that the material modeling of the vessel has a sizable effect on aneurysm initiation and fully developed aneurysms. Different material modeling of degeneration regions also affects the stressstrain response of aneurysm initiation. Additionally, the structural analysis without considering FSI (called noFSI) overestimates the peak von Mises stress by 52% at the interfaces of the layers.

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Pressure-flow relationships and vascular impedance in man

Cited by 324 publications

References 0 publications

Central Hemodynamics and Target Organ Damage in Hypertension

Central Hemodynamics and Target Organ Damage in Hypertension

Effect of age on the in vitro reflection coefficient of the aortoiliac bifurcation in humans.

Investigation of material modeling in fluid–structure interaction analysis of an idealized three-layered abdominal aorta: aneurysm initiation and fully developed aneurysms

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