Influence of geometrical parameters on radial force during self-expanding stent deployment. Application for a variable radial stiffness stent.

The goal of this work is to study the influence of the main geometrical parameters on the radial force of a self-expanding stent, and using them to advance towards a new design of a variable radial force stent to improve the interaction vessel-device. Using finite element simulations, a parametric analysis of a commercial stent model (Acculink, Abbot Vascular) was developed to estimate the influence of geometrical variables, mainly radial and circumferential strut thicknesses and the initial diameter of the stent. The radial expansion force was compared for the different values of each geometrical variable. The previous results were used to propose a new stent design with variable radial stiffness. Their effects on healthy and atheromatous vessels were studied and compared for both stent models, constant and variable radial stiffness respectively. The developed analysis reveals a notable decrease of the contact pressure over the inner arterial wall in healthy areas using a variable radial force (VF) stent with respect to the same model with a constant expansion force (CF) stent. In the case of a vessel model with a fibrotic core plaque, the lumen healthy areas that suffer a contact pressure higher than 0.25 MPa are reduced from 36.86% to 22.38% for the left healthy area (LHA), and from 40.13% to 21.36% in the right healthy area (RHA). Furthermore, this pressure reduction in the healthy areas does not cause a decrease in the expansion pressure in an atheromatous section, where it is necessary to maintain a recovery of the lumen section. In the case of lipid core, the flow section with plaque is 70.8% of the healthy flow section using a VF stent, and 70.9% with a CF stent, while 66.87% and 66.89% were found respectively in the case of a calcified core.