This paper presents a theoretical study of pulse wave propagation in arteries, with consideration of a full set of arterial wall properties: elasticity, viscosity, and axial and circumferential initial tensions. Pulse wave propagation in an artery is formulated as governing equations of the arterial wall and flowing blood in the artery and their interface conditions. A free wave analysis is conducted on the formulated problem, giving rise to a frequency equation. The solution to the frequency equation indicates the co-existence of two waves: Young wave and Lamb wave, propagating in the arterial tree. With the related values at the carotid artery (CA) and the ascending aorta (AA), wave velocity and transmission of each wave at the CA and the AA are estimated and the influence of arterial wall properties on wave velocity and transmission is examined. Physiological implications of such influence are discussed. &nbsp;The advancement of medical instruments has allowed investigations of a wide range of parameters in the cardiovascular (CV) system for their clinical values in detection of arterial abnormalities (e.g., atherosclerosis). For instance, clinical studies on axial motion of the arterial wall at the CA and the AA, arterial viscosity, isolated diastolic hypertension (i.e., circumferential initial tension), and axial initial tension have identified their clinical values. Yet, the theory on pulse wave propagation utilized in clinical studies considers only radial motion of the arterial wall and arterial elasticity. As such, there is a need to develop a more comprehensive theory on pulse wave propagation in arteries that accounts for the full suite of arterial wall properties: elasticity, viscosity, and axial and circumferential initial tensions and axial motion of the arterial wall.In this study, the arterial wall is treated as an isotropic, elastic, thin-walled circular membrane, and flowing blood is considered as an incompressible viscous/inviscid fluid. Pulse wave propagation in arteries is formulated by a combination of 1) the governing equations of the arterial wall for two variables: radial displacement and axial displacement, 2) the governing equations of flowing blood for three variables: axial velocity, radial velocity, and pulsatile pressure, and 3) blood-wall interface conditions at the inner radius of the arterial wall. By representing all the five variables with their own wave expressions, a free wave analysis is conducted on the formulated problem, which gives rise to a frequency equation. This frequency equation is a quadratic equation of the square of the wave velocity with arterial wall properties as coefficients. The solution to the frequency equation is two complex roots. While the first root is associated with the Young wave – a fluid-dominant wave, the second root is related to the Lamb wave – a wall-dominant wave. The wave velocity and transmission per wavelength of each wave correspond to the real value of each complex root and its ratio of the real value to the imaginary value, respectively. With the related values at the CA and the AA, wave velocity and transmission of each wave at the two arterial locations are estimated. The influence of blood viscosity, and each arterial property: elasticity, viscosity, and axial and circumferential initial tensions, on wave velocity and transmission at the two arterial locations is separately examined. With the aid of the related clinical findings, physiological implications of such influence are further discussed.

Pulse Wave Velocity and Transmission at the Carotid Artery and the Ascending Aorta

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.