Vortical Structures Promote Atheroprotective Wall Shear Stress Distributions in a Carotid Artery Bifurcation Model

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Fluid Dynamics

Background:

• Carotid artery diseases, including atherosclerosis, are a leading cause of mortality in the US.
• Wall shear stress is implicated in plaque formation, but underlying flow structures remain poorly understood, especially in high-risk patients.
• A 'pre-disposed' carotid artery model representing pathological anatomy was developed.

Purpose of the Study:

• To investigate complex flow structures and their relationship with wall shear stress in healthy versus pre-disposed carotid artery bifurcations.
• To understand how altered hemodynamics contribute to atherosclerotic plaque development.

Main Methods:

• Computational fluid dynamics (CFD) simulations were employed.
• Physiological blood flow data from healthy human subjects were used.
• Two distinct carotid artery bifurcation models were simulated: a 'healthy' model and a 'pre-disposed' pathological model.

Main Results:

• A significant hairpin vortical structure was identified in the internal carotid artery sinus of the healthy model, increasing local wall shear stress.
• In the pre-disposed model, this vortex initiated earlier and was shorter-lived, with secondary flow structures dominating the latter half of the cardiac cycle.
• The pre-disposed geometry exhibited weaker favorable axial pressure gradient peaks.

Conclusions:

• A strong correlation exists between vortical structures and wall shear stress in the carotid artery.
• An intact internal carotid artery sinus hairpin vortex plays a protective physiological role by enhancing local wall shear stress.
• The disruption of this beneficial vortex structure is a key factor in the initiation and progression of atherosclerotic plaque formation.