TITLE:
Wave Reflection at the Boundary Layer and Initial Factors of Atherosclerosis
AUTHORS:
Guram Beraia, Merab Beraia
KEYWORDS:
Shear Stress, Boundary Layer, Viscoelasticity, Resonance, Wave Reflection
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.3 No.2,
May
8,
2014
ABSTRACT: The aim is to study
the blood flow and vessel wall viscoelastic alterations at the boundary layer. Methods
and Results: In 12 healthy men (18 - 52 years of age) at the different sites of
the aorta peak velocity, net flow, flow acceleration has been investigated by
Magnetic Resonance Angiography. In the aortic arch in the end systole blood
flow separates into the opposite directed streams resulting in the wave
superposition. At the outer curvature of the isthmus, flow acceleration in
the initial diastole is 6.26 times higher than that in systole. Net flow from
systole to diastole increases 2.5 ± 0.5 folds. From the end systole to the
initial diastole there is a plateau on the net flow graph. At the outer
curvature of isthmus, group wave at the boundary reflection, changes in phase
at 180o. Herewith, flow wave oscillation frequency at the outer curvature is
two times higher (2.5 Hz) than that at the inner (1.25 Hz). Conclusion: During
the heart cycle, blood motion at the boundary layer, forms the surface wave and
facilitates the blood structural rearrangement and flow. At the end systole, at
the outer curvature of the isthmus, pulse pressure at the reflection is in the
resonance with the end systolic pressure drop. Amplitude of the wall stress
increases. Forming standing wave leads to the dissipation of the wall
mechanical energy. Here, in the initial diastole, group wave, due to the wave
reflection and frequency dispersion, facilitates the structural
rearrangement/denudation of the vessel wall. By the removing resonance
oscillation during the end systole/initial diastole between the heart and
vessel wall, atherosclerosis can be avoided.