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Carotid-artery Bifurcation

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Because of its cross-sectional area, the carotid-artery sinus tends to fall between two regimes of fluid flow. Even in healthy induviduals, a standing vortex, or recirculation zone, that could play a role in the initiation of atherosclerotic desease, may form in the sinus. This zone shows up clearly in the images. The filming of tracer particles reveals streamlines (blue) that diverge at the befurcation and form spiral secondary flows.

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Figure 3: Mechanical stress is known to play a role in the formation of aneurysms and may also play a role in the formation of atherosclerotic plaque. Because the internal and external carotids tend to "pull" on the common carotid, stress is concentrated at the apex of the bifurcation. Stress is also concentrated in the sinus bulb, where the artery wall thins. The stress contours shown here are based on analyses of stress on the inner-wall surface. Numerical (finite-element) models of carotid-artery bifurcations, whose geometry and physical chaaracteristics were based on measurements of cadaver specimens (with stenoses as indicated in small diagrams), were subjected to a mechanical load at right angles to the vessel wall to represent the pulse and to longitudinal loads to mimic the traction of the vessels on one another. Stress magnitudes ranged from 0.0187 to 0.6796 kilopascals in the upper artery and from 0.0237 to 0.7296 kilopascals in the lower specimen. Stress contours range from white and blue (nominal) to bright orange and yellow (maximum).

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Figure 7: Blood flows smoothly through most vessels most of the time, but vortices or turbulence can sometimes develop. In physics, the "character" of flow is predicted by the Reynolds number, which expresses the ratio of the inertial and the viscous forces acting on a parcel of fluid.  As the Reynolds number increases--as it would, for example, if the fluid sped up--the flow is smooth at low Reynolds numbers; then a pair of counter-rotating eddies form downstream of the cylinder; then the vortices alternately detach, forming which is called a Von Karman trail; and finally the cylinder's wake becomes turbulent. Vortices can develop in the carotid sinus of a healthy individual and turbulence in a vessel partially blocked by atherosclerotic plaque.

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Before treatment with Amyloxine®

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       Before Amyloxine® Treatment                                 Graph Enhanced Digital

Figure 3: The carotid-artery bifurcation, like most arterial bifurcations, is a common site of atherosclerotic disease. The common carotid artery divides in the neck into the external and internal carotid arteries. The external carotid supplies the face, scalp, neck and throat tissues with freshly oxygenated blood from the heart, and the internal carotid supplies the anterior portion of the brain. Immediately above the bifurcation, there is a sinus, or swelling, in the internal carotid that plays an important role in its hemodynamics. In the color Doppler ultrasound closeup (center) and magnetic-resonance image (bottom) of a normal carotid in the area of the bifurcation, the area denoted by the blue color and small arrow, respectively, is an area of low-velocity blood flows. The Doppler image was created by ultrasonic waves reflected from the blood; the apparent change in frequency of these waves can be used to derive the velocity of the fluid from which they were reflected.

After treatment with Amyloxine® 8 Weeks.

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      After   Amyloxine® Treatment Eight  Weeks                                Graph Enhanced Digital

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