Effect of plaque micro-watershed changes on carotid atherosclerosis.

Objective: The study aims to elucidate the mechanisms underlying plaque growth by analyzing the variations in hemodynamic parameters within the plaque region of patients' carotid arteries before and after the development of atherosclerotic lesions.

Methods: The study enrolls 25 patients with common carotid artery stenosis and 25 with tandem carotid artery stenosis. Based on pathological analysis, three-dimensional models of the actual blood vessels before and after the lesion are constructed for two patients within a two-year period. Computational fluid dynamics is employed to conduct unsteady periodic non-Newtonian fluid numerical simulations, enabling an in-depth investigation into the changes in the micro-environment of blood flow.

Results: During the systolic phase of the cardiac cycle, vortex regions are particularly prone to developing at the bifurcation point between the common carotid artery and the distal end of the internal carotid artery. In the early diastolic phase, blood reflux phenomena can be observed within the carotid artery. Towards the end of diastole, there is an expansion of vortex regions at the bifurcation point of the carotid artery. The shoulder region of initial small plaques within the blood vessel is susceptible to developing a low-speed recirculation zone, characterized by significantly reduced shear stress compared to the surrounding areas. Following vascular stenosis, the wall shear stress within the plaque domain generally increases; however, it maintains a consistent pattern of high central values and low upper shoulder values. The shear stress at the upper shoulder of the plaque of tandem carotid stenosis is below 0.4 Pa, whereas the central and lower shoulder regions exhibit shear stress exceeding 40 Pa.

Conclusions: The dynamic parameters of the blood flow micro-environment exhibit variations throughout the cardiac cycle, and temporal disparities exist in local lesions within the carotid artery. Both common and tandem carotid artery stenosis are particularly prone to developing lesions at the shoulder of initial small plaques. The micro-flow characteristics within the plaque domain undergo alterations prior to and following the onset of carotid artery disease. Furthermore, the occurrence of restenosis and rupture is associated with the location of plaque growth.