On the necessity of modelling fluid–structure interaction for stented coronary arteries

Although stenting is the most commonly performed procedure for the treatment of coronary atherosclerotic lesions, in-stent restenosis (ISR) remains one of the most serious clinical complications. An important stimulus to ISR is the altered hemodynamics with abnormal shear stresses on endothelial cells generated by the stent presence. Computational fluid dynamics is a valid tool for studying the local emodynamics of stented vessels, allowing the calculation of the wall shear stress (WSS), which is otherwise not directly possible to be measured in vivo. However, in these numerical simulations the arterial wall and the stent are assumed to be rigid and fixed, and then influencing the WSS and flow patterns. Therefore, the aim of this work is to perform fluid-structure interaction (FSI) analyses of a stented coronary artery in order to understand the effects of the wall compliance on the hemodynamic quantities. Two different standard stents are considered: cobalt-chromium (CoCr) and polymeric (poly-L-lactide - PLLA). The results of the FSI and the corresponding rigid-wall models are compared, especially focusing on the analysis of the WSS distribution. Results showed similar trends in terms of instantaneous and time-averaged WSS between compliant and rigid-wall cases. In particular, the difference between the percentage area exposed to time-averaged WSS lower than 0.4 Pa in the stented region was small for the CoCr (about 1.5%) and PLLA (about 1.0%) cases. The results indicate that, for idealized models of stented coronary artery, rigid-wall assumption for fluid dynamic simulations is adequate when the aim of the study is the analysis of near-wall quantities like WSS.