Preoperative in silico analysis of atherosclerotic calcification vulnerability in carotid artery stenting using finite element analysis by considering agatston score

Abstract

The role of calcification inside fibroatheroma during carotid artery stenting operation is controversial. Cardiologists face a major problem of “plaque vulnerability” during the placement of both balloon and stent, with stiff plaques containing advanced calcifications that break the arterial wall or give rise to unstable thromboembolic stroke. The aim of this work is to evaluate the role of calcification (in terms of material and mechanical properties) in plaque vulnerability and wall rupture and to find plaque maximum resistance before breaking. Image-based models of carotid artery stenting were used and Finite Element Analysis (FEA) was performed to simulate the impact of balloon and stent expansion in the presence of calcified plaques. In detail, a nonlinear static structural analysis was performed on 20 patients acquired using in vivo MDCT angiography. The Agatston Calcium score was obtained for each patient and subject-specific local Elastic Modulus was calculated. The in silico results showed that by imposing maximum ultimate external load of 1.2MPa and 4.2MPa on balloon and stent respectively, average ultimate stress of 55.7±41.2kPa and 171±41.2kPa as well as average Plaque Wall Stress of 19.03 ± 16.05kPa and 64.3 ± 63.3kPa were obtained on calcifications, respectively. Elastic and plastic strain average values of 0.03±0.02 and 0.006 ± 0.01, respectively, were obtained on the calcified plaques after stent expansions. These average data are in good agreement with results obtained by other research groups relative to the values of compressive Elastic Modulus of atherosclerotic plaques and its ultimate stress, strain values after performing carotid artery stenting. Even if our findings are markedly influenced by local geometry and plaque shape, this study enriches the literature in pre-operative prediction of ultimate mechanical parameters in stenting operation to prevent rupture before balloon/stent expansion.