Hemodynamic flow characteristics at stenosed artery: Numerical analysis of three-dimensional patient-specific aortic–cerebral vasculature exposed to progressive carotid stenosis

Abstract

Progression of carotid stenosis (CS) significantly reduces blood flow in the affected arteries and alters both proximal and distal hemodynamics. While conventional studies consider only the stenosis region for analysis, an extended larger arterial domain of aortic–cerebral vasculature is used to avoid artificial modeling of the inlet condition to the carotid region and facilitate automatic flow redistribution during CS progression. The fluid domain was constructed and simulated using an open-source package SimVascular, and three patient models with five stenosis cases each were created using medical images. Newtonian, incompressible, and rigid-wall conditions were assumed because of the high computational burden, and boundary conditions of the lumped Windkessel and pulsatile flow rate were implemented for the outlets and inlet, respectively. We present a novel index called circulation core fraction (CCF) to quantify and visualize the stenosis-driven hemodynamics; the CCF is developed from the benchmark backward-facing step problem and compares the representative recirculation to the total volume. Thus, CCF in the post-stenotic region increases during CS progression regardless of patient-specific features whereas that in the pre-stenotic region exhibits patient-specific nature despite the incremental tendency. Streamlines with custom sources show a helical vortex with recirculation and artery-wise flow streams that vary during CS progression. We also report transitional patterns in both the pulsatility index (PI) contours and Q-criterion, where the PI values shift from high–low–high to high–low–low across the stenosis, and the latter is nearly absent at 0% and 95% but mostly present at 50% and 75% CS.

Evidence And Mechanisms For Embolic Stroke In Contralateral Hemispheres From Carotid Artery Sources

“…First, we assumed that the carotid sites did not have severe stenosis. Presence of a severe stenosis will alter flow patterns through the carotid arteries into the CoW [47], which makes it difficult to isolate the effects of embolus-flow interactions at the CoW vessels alone. However, the approach presented here can be extended in future studies to specifically account for stenosis of varying severity and its influence on cerebral embolic events.…”

Evidence and Mechanisms for Embolic Stroke in Contralateral Hemispheres From Carotid Artery Sources

“…First, we assumed that the carotid sites did not have a visible severe stenosis. Presence of a severe stenosis will alter flow patterns through the carotid arteries into the CoW, 47 which makes it difficult to isolate the effects of embolus‐flow interactions at the CoW vessels alone. Furthermore, carotid arteries can be suspect to varying forms of embolization such as postoperative embolic showers after carotid endarterectomy 48 or endothelial trauma during catheterization, where stenosis severity will be low yet embolic phenomena may occur.…”