Influence of plaque properties and constitutive modeling approach on the simulation of percutaneous angioplasty of chronic total occlusions

Clinical treatment of Chronic Total Occlusion (CTO) of an artery often involves percutaneous procedures, like sub-intimal balloon angioplasty, in which the controlled inflation of a balloon restores the lumen by compression ofatherosclerotic plaque. Realistic simulations of these challenging techniques could provide valuable information for clinician, but characterization of CTO in human studies is problematic. Reported data are highly variable and the few published models employed different approaches to fit (apparently) the same experimental tests. Moreover, atherosclerotic plaques are commonly assumed as elastic and incompressible, but in angioplasty procedures they may be subjected to large and not physiological overstretch. Permanent plaque damage after balloon inflation is expected, suggesting that some form of inelastic behavior should be considered. Thus, the goal of the present work is to investigate the influence of changing plaque properties and constitutive modeling assumptions, on the predicted outcomes of a simulation of CTO percutaneous angioplasty. To this aim, a finite element model of the compression of a total occlusion inside an artery was implemented. Different forms of hyperelastic constitutive laws proposed in literature were compared in presence of the complex stress state resulting from sub-intimal angioplasty. The degree of compressibility and the threshold for a permanent damage, introduced in the form of a plastic yield limit, were varied. Overall, results demonstrated that the choice of different data sets or constitutive modeling approaches for plaque has a primary influence. Some common assumptions for plaque modeling may lead to highly variable or even unrealistic predictions for the extreme case of total occlusion treatment. In this sense, more specific experimental investigations on the properties of plaque constituents as a function of heterogeneous CTO composition, are necessary in order to exploit the potential usefulness of the method as a patient-specific predictive tool.