Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Numerical Simulation of Transport Through Polymer Layer and Porous Arterial Wall of Sirolimus and Paclitaxel in Drug-eluting Stents
Submission Author:
Haroldo Rosman Junior , RJ
Co-Authors:
Haroldo Rosman Junior, Rachel Manhães de Lucena, Norberto Mangiavacchi, José da Rocha Miranda Pontes, Sean McGinty
Presenter: Haroldo Rosman Junior
doi://10.26678/ABCM.COBEM2021.COB2021-2117
Abstract
The cardiovascular diseases (CVDs) is one of the main causes of deaths in the world, according to the World Health Organization (2017). Close to 40% of CVDs deaths are due to coronary artery disease (CAD). The CAD is the result of obstruction of the coronary arteries - the blood vessels that supply the heart muscle. One of CAD treatments employs stents, which are tiny expansible wire tubes that are inserted in the obstructed coronary artery to maintain the passage free. However, bare-metal stents have shown the occurrence of restenosis, which is the obstruction of the artery due to arterial tissue regrowth. There are many works related to Drug-eluting stents (DES), which are coated with a polymer that slowly releases a drug that controls the arterial wall regrowth. Even though DES are successful in avoiding restenosis, they are frequently associated with the occurrence of late stent thrombosis. Thus, the correct concentration of the eluted drug is very important to reduce the risk of both restenosis and thrombosis, and has motivated many studies. This paper aims to analyze the drug elution from the polymer coating, transport, specific and non-specific binding in the artery wall for two different drugs, sirolimus and paclitaxel. The elution for two different release regimes, fast and slow, associated with two different polymer diffusion coefficients, was analyzed. In this paper a computational model is developed employing the Finite Element Method on an unstructured mesh. We consider the model of dissolution, transport and binding of the drug on an axisymmetric domain representing the polymer coating layer and the porous artery wall in the vicinity of a stent strut. We employ a nonlinear dissolution model for the dynamics of sirolimus or paclitaxel in the polymer coating, and a nonlinear saturable binding model that includes both specific and non-specific binding in the arterial wall as separate phases. The transport of the eluting drug in the artery wall is modeled considering an anisotropic diffusion tensor. The presence of the stent causes the compression and realignment of tissue fibers, such that they are parallel to the stent surface in its proximity. So, the principal directions of the diffusion tensor are re-oriented in the vicinity of the stent to properly account for this stent-artery interaction. Simulations performed with the developed computational model allow to fine-tune the polymer diffusion coefficient, and other geometric tunable parameters, in order to obey the required restraints for a safe DES utilization.
Keywords
drug-eluting stents, Darcy's law, convection-diffusion-reaction equations, anisotropic diffusion, Finite Element Method
