Fluid structure interaction analysis to stratify the behavior of different atheromatous carotid plaques
Saturday 24th April 2021
Domanin, M.; Bennati, L.; Vergara, C.; Bissacco, D.; Malloggi, C.; Silani, V.; Parati, G.; Trimarchi, S.; Casana, R.
Objectives: Different plaque types could have different hemodynamic and structural behaviors in asymptomatic carotid stenosis (ACS), increasing the risk of instability. Methods: The vessel lumen, the wall, and the geometries of three different types of carotid plaques, namely lipid (LP), fibrous (FP), and calcific (CP) were reconstructed starting with CTA images from 15 candidate patients for carotid revascularization with ACS >70%, in order to obtain 5 models for each type. Fluid structure interaction (FSI) analyses were performed to describe hemodynamic and structural behavior in different types of plaques by computing wall shear stresses (WSS), plaque displacements (D), von Mises stresses (VMS), and absorbed elastic energy (AEE) spatial distribution and their maximum-in-space values at the systolic peak, namely WSSsyst, Dsyst, VMSsyst and AEEsyst. Results: WSSsyst resulted significantly lower in LP, whereas in FP we found intermediate values (+33%) and the highest WSSsyst (+157%) in CP. The highest values of Dsyst were observed in LP, with a different spatial distribution, being localized mainly in the inner region of the thin fibrous cap, at the shoulder of the stenosis, whereas for FP and CP the values were -250% and -480% lower, respectively. VMSsyst in the LP group was again localized to the inner region of the thin fibrous cap, whereas FP and CP had lower values, -150% and -400%, respectively, without spatial concentration of peak stresses. AEEsyst was determined to be focused at the fibrous cap, and capable of storing elevated values of energy due to the compliant nature of the inner core in LP, while lower values were found for FP and CP, -470% and -2240%, respectively. Conclusions: Depending upon their nature, plaques store different amounts of mechanical energy. The deformation causes different distributions of internal forces inside the plaque, thus influencing vulnerability properties, especially for LP.