Estimation of Degradation Velocity of Biocompatible Damaged Stents due to Blood Flow

Objective: Bioresorbable materials represent a promising technology for the treatment of coronary disease. Among the different materials employed, magnesium stents display favourable mechanical properties. One of the main uncertainties regarding use is their behaviour when deployed on coronary bifurcations, especially when their retardant coating has been damaged during the implantation process. This paper analyses the temporal evolution of the degradation of a damaged magnesium stent inserted into a coronary bifurcation. Methods: The rate of erosion-corrosion and the effect of the flow configuration on the mass transfer coefficient were estimated on the basis of previous experimental studies and numerical simulations. This coefficient has been employed to reproduce the conditions that can appear in real stent configurations, and computational fluid dynamics simulations were performed. Results: The diffusion coefficient for this particular case has been calculated from the mass transfer coefficient and the Sherwood number. The results of the simulation show how the presence of the inner artery wall has a positive effect, preventing a premature degradation of the stent, and how the distal strut is protected by the presence of the proximal struts. Conclusions: This study demonstrates the usefulness of the proposed methodology to evaluate the temporal evolution of the degradation of struts made of magnesium alloys. In addition, this methodology can be applied to a study of different materials and geometric configurations. Significance: The proposed technique can contribute to expanding existing knowledge concerning bioresorbable stent flow-corrosion, thus improving their design and implantation.