Geometry and Flow Properties Affect the Phase Shift between Pressure and Shear Stress Waves in Blood Vessels

Abstract

The phase shift between pressure and wall shear stress (WSS) has been associated with vascular diseases such as atherosclerosis and aneurysms. The present study aims to understand the effects of geometry and flow properties on the phase shift under the stiff wall assumption, using an immersed-boundary-lattice-Boltzmann method. For pulsatile flow in a straight pipe, the phase shift is known to increase with the Womersley number, but is independent of the flow speed (or the Reynolds number). For a complex geometry, such as a curved pipe, however, we find that the phase shift develops a strong dependence on the geometry and Reynolds number. We observed that the phase shift at the inner bend of the curved vessel and in the aneurysm dome is larger than that in a straight pipe. Moreover, the geometry affects the connection between the phase shift and other WSS-related metrics, such as time-averaged WSS (TAWSS). For straight and curved blood vessels, the phase shift behaves qualitatively similarly to and can thus be represented by the TAWSS, which is a widely used hemodynamic index. However, these observables significantly differ in other geometries, such as in aneurysms. In such cases, one needs to consider the phase shift as an independent quantity that may carry additional valuable information compared to well-established metrics.

Numerical Investigation of Physical Parameters in Cardiac Vessels as a New Medical Support Science for Complex Blood Flow Characteristics

“…Also, the velocity description is almost similar to the tube diameter, with a narrow layer on the wall. Higher harmonic components of similar waveforms with higher results will show the same treatment 33 .…”

On the Potential Self-Amplification of Aneurysms Due to Tissue Degradation and Blood Flow Revealed From FSI Simulations

“…Although intra-aneurysm flow patterns and hemodynamic quantities depend on the specific geometry (Varble et al, 2016;Wang et al, 2020Wang et al, , 2021aKhan et al, 2021), effects of tissue degradation turn out to be qualitatively similar in all the investigated cases, i.e., for different geometries, degradation intensities, heart rates and blood pressures: at low-WSS sites, degradation leads to a lower TAWSS and at the same time a higher OSI.…”

“…Aneurysms are vascular diseases characterized by excessive tissue degradation and chronic inflammation (Frösen, 2014). There are relations among aneurysmal geometry, intra-aneurysmal hemodynamics (flow), and aneurysm pathobiology (Meng et al, 2014): Geometry instantaneously alters flow conditions (short-term effect) (Wang et al, 2020(Wang et al, , 2021a; abnormal-flow-induced hemodynamic-biomechanical triggers are transduced into biological signals and lead to the degradation, growth and/or remodeling of aneurysms via pathobiology (Meng et al, 2014); the interplay between the local flow environment and aneurysm pathobiology dominates the growth and geometric changes of the aneurysm (longterm effect) (Tarbell et al, 2014). Within an aneurysm wall, constructive (eutrophic) changes (cell proliferation and extracellular matrix production) and destructive (degradative) changes (cell death and extracellular matrix degradation) are ongoing concurrently (Frösen et al, 2012;Frösen, 2014;Meng et al, 2014).…”

Fluid-structure interaction simulation of tissue degradation and its effects on intra-aneurysm hemodynamics

“… 2018 ; Wang et al. 2020 , 2021 ) for the above-described observation, we have conducted simulations of pulsatile flow through a curved tube without aneurysm (Fig. 8 ) and a different ideal aneurysm (Fig.…”