Finite element analysis of a rupture-induced deformation of a carotid atherosclerotic plaque with intraplaque hemorrhage

Intraplaque hemorrhage (IPH), bleeding in a plaque, is caused by a neocapillary rupture in an atherosclerotic plaque. We used contrast-enhanced ultrasonography to diagnose carotid atherosclerotic plaques before carotid endarterectomy (CEA), a surgical operation to remove an arterial intimal layer including a plaque lesion. We found lumenward (inward) deformation in some cases of ruptured plaques with IPH. The aim of this study was to evaluate the mechanical effects of infiltrated blood in the lipid core on the luminal shape of the ruptured plaque in the short-axis view. We created a finite element model of a carotid artery bifurcation with a ruptured plaque based on a sample obtained from CEA. As physiological loads, we assigned pressures on the surfaces of the lumen and the lipid core, the sum of a gradual pressure drop in the artery obtained from computational fluid dynamics analysis and a uniform pressure, and a constant longitudinal stretch. In the simulation, the fibrous cap in the ruptured model became almost flat in the short-axis view with lumenward deformation, being less deformed than that observed in ultrasonography. The simulation results show that inward deformation of the fibrous cap is correlated with an equal pressure in the lumen and the lipid core. In comparison, a hyperelastic model of soft unruptured plaque reproduced a round lumen. A better understanding of contrast-enhanced ultrasonography images from a mechanical perspective may facilitate the morphological identification of plaque rupture with IPH.