Viscoelastic changes in the blood and vascular wall in a pulsating circular flow
Altered flow conditions, such as separation and recirculationg zones, low and oscillatory shear stress, play an important role in the development of arterial disease. Endothelial denudation by the blood flow is the first step in atherosclerosis. The description of blood flow in vivo is complicated due to the viscoelasticity of vessel walls. However, conventional researches of the effect of the blood vessel viscoelasticity on the blood pressure wave propagation using non-linear one-dimensional models do not take into account the viscoelasticity, despite it being importance in the analysis of pulse wave propagation in arteries.
The purpose of this paper is to study the impact of the arterial pulse wave on the viscoelastic blood flow and initial factors of atherosclerosis.
In 12 healthy men (25-39 years of age) peak velocity, mean velocity, mean flow and net flow in the aorta have been investigated by MR angiography.
Initial velocity was registered after 43msec of the ECG-R wave, and it differed from zero at all sites of the aorta, although net flow was equal to zero. Womersley's number from the ascending to the thoracic aorta decreased from 12.5 ± 1.5 to 7.3 ± 1.2; flow modified from inertio-elastic to viscous. Pulse pressure wave move on artery walls fifteen or more times more rapidly than the blood flow. In the aortic arch in protodiastole blood flow separated into the opposite directed streams resulting in wave superposition with the high net flow. At the isthmus area separated waves interferences and reflects to anterograde direction.
Pulse oscillation increases strain rate to the contiguous vessel wall flow layers. At the sites with the flow wave negative interference vessel pulse oscillation attenuates and at the boundary reflection flow wave can shift the vessel wall.