NUMERICAL MODELLING OF STENTING PROCEDURES IN CORONARY BIFURCATIONS: A STRUCTURAL AND FLUID DYNAMIC COMBINED APPROACH

摘要

Stenting procedures give the opportunity to treat cardiovascular diseases with a time saving, cost effective and minimally invasive procedure if compared to coronary artery by-pass, ensuring at the same time better clinical results than balloon angioplasty. Despite their success, stenting procedures are still associated to some clinical problems like sub-acute thrombosis (ST) and in-stent restenosis (ISR) whose main outcome is the re-narrowing of the coronary vessels and the necessity of a new treatment to restore blood flow and perfusion to downstream tissues. Their mechanisms and causes are still not fully understood but clinical and biological studies agree the idea that these are caused by a combination of both structural and hemodynamic factors [1,2]. Numerical models have been widely used to investigate the biomechanical aspects of stenting procedures but always analyzing the phenomenon from a purely structural or a fluid dynamic point of view. To overcome this limitation, the primary goal of this study is the combination of structural and fluid dynamic models by using the realistic geometrical configurations obtained through structural simulations as a fluid domain for the fluid dynamic analyses. This process leads to a more realistic estimate of the local blood flow pattern and a more accurate investigation of the hemodynamic forces acting on the endothelial cells. This combined approach has been applied to the provisional side branch approach (PSB), the most commonly used stenting procedure for coronary bifurcations. Then, looking at the results obtained, three main aspects have been discussed: the process of atherogenesis, the biomechanical influence of the final kissing balloon (FKB) inflation (simultaneous expansion of two balloons) and the behavior of a newly designed dedicated tapered balloon.