How Critical Is Fibrous Cap Thickness to Carotid Plaque Stability?

Abstract

Background and Purpose-Acute cerebral ischemic events are associated with rupture of vulnerable carotid atheroma and subsequent thrombosis. Factors such as luminal stenosis and fibrous cap thickness have been thought to be important risk factors for plaque rupture. We used a flow-structure interaction model to simulate the interaction between blood flow and atheromatous plaque to evaluate the effect of the degree of luminal stenosis and fibrous cap thickness on plaque vulnerability. Methods-A coupled nonlinear time-dependent model with a flow-plaque interaction simulation was used to perform flow and stress/strain analysis in a stenotic carotid artery model. The stress distribution within the plaque and the flow conditions within the vessel were calculated for every case when varying the fibrous cap thickness from 0.1 to 2 mm and the degree of luminal stenosis from 10% to 95%. A rupture stress of 300 kPa was chosen to indicate a high risk of plaque rupture. A 1-sample t test was used to compare plaque stresses with the rupture stress. Results-High stress concentrations were found in the plaques in arteries with Ͼ70% degree of stenosis. Plaque stresses in arteries with 30% to 70% stenosis increased exponentially as fibrous cap thickness decreased. A decrease of fibrous cap thickness from 0.4 to 0.2 mm resulted in an increase of plaque stress from 141 to 409 kPa in a 40% degree stenotic artery. Conclusions-There is an increase in plaque stress in arteries with a thin fibrous cap. The presence of a moderate carotid stenosis (30% to 70%) with a thin fibrous cap indicates a high risk for plaque rupture. Patients in the future may be risk stratified by measuring both fibrous cap thickness and luminal stenosis.

The Effect of Carotid Plaque Morphology on Longitudinal Fibrous Cap Stress Levels

“…Links between stenosis severity, fibrous cap thickness, and mechanical stress levels have previously been reported by Li et al [3]. The severe influence of fibrous cap thickness on first principal stresses was confirmed in the present study, whereas the significant impact of the degree of stenosis was lacking.…”

“…Previous studies have used principal stres and cess of 300 kPa to be predictive of plaques at high risk of rupture [1,3,4]. The choice of material model and parameters may substantially affect simulated stress levels.…”

“…Rupture of vulnerable carotid atherosclerotic plaques is a major source of strokes and transient ischemic attacks [1][2][3][4]. Carotid endarterectomy (CEA) has been proven beneficial in symptomatic patients with high degrees of stenosis [5][6][7][8].…”

Asymptomatic carotid plaque rupture with unexpected thrombosis over a non-canonical vulnerable lesion

“…Subendothelial calcified nodules in asymptomatic patients are usually localized in the context of thin cap plaques and mildly stenotic segments. Both these conditions, according to Laplace law, make these plaques highly susceptible to rupture [13,31]. Moreover, it has to be emphasized that these calcified nodules, protruding into the vascular lumen, can induce flow disturbances, increase the stiffness and reduce the elasticity of the vessel wall [32].…”

Atherosclerosis Initiation Modeled as an Inflammatory Process

“…Indeed the fibrous cap changes the geometry of the vasculature and modifies the blood flow. The interaction between the flow and the cap may lead to a thrombus, or to the degradation and rupture of the plaque liberating dangerous solid parts in the flow [4,5]. In this study we do not address the fluid-structure interaction between the blood flow and the plaque, and only consider the set up of the chronic inflammatory reaction with its biochemical and mechanical inhibitions.…”