  The traditional view is that low shear stress of blood flow accelerates
atherosclerosis. How does a low shear stress damage the vessel or aggravate
atherosclerosis? It is a puzzling question. Furthermore, shear stress of veins
is similar to that of Relatively Vulnerable Zones (RVZ) of arteries, while
intimal thickening of veins is not obvious as the arteries. There are many
places in arterioles with lower shear stress as the decrease of blood velocity,
while the thickening of arterioles is not as obvious as that of the
medium-sized arteries. These issues make it unconvincing for us to explain
atherogenesis with lower shear stress. According to Bernoulli fluid equation
(P+1/2\r{ho}v^2+\r{ho}gh=constant), in a closed pipe full of flowing blood, at
the same height, the hydrostatic pressure is inversely proportional to the
second power of blood velocity. At any point of per unit mass of fluid micro
cluster here, the reduction of 1/2\r{ho}v^2 would be converted into P.
Therefore, hydrostatic pressure(P) is inversely proportional to v^2 in a very
short distance or in the same transection of the artery. When blood micro
cluster flows over a very short distance or the same transection of the artery,
previous studies did not consider the conversion between 1/2\r{ho}v^2 and P.
Therefore, low shear stress aggravates atherosclerosis is an appearance, and
the essence is that these areas with smaller blood velocity have much bigger
hydrostatic pressure, which aggravates atherosclerosis. This perfectly explains
the predisposing sites of atherosclerosis.
