fluids Article Numerical Study of Bloodstream Diffusion of the New Generation of Drug-Eluting Stents in Coronary Arteries Leandro Marques 1, * and Gustavo R. Anjos 2, *   Citation: Marques, L.; Anjos, G.R. Numerical Study of Bloodstream Diffusion of the New Generation of Drug-Eluting Stents in Coronary Arteries. Fluids 2021, 6, 71. https:// doi.org/10.3390/fluids6020071 Academic Editors: Beatrice Pulvirenti and Mirco Magnini Received: 13 November 2020 Accepted: 2 February 2021 Published: 5 February 2021 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional clai- ms in published maps and institutio- nal affiliations. Copyright: c  2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Graduate Program in Mechanical Engineering, GESAR/Department of Mechanical Engineering, Rio de Janeiro State University, Rio de Janeiro, RJ 20943-000, Brazil 2 COPPE/Department of Mechanical Engineering, Federal University of Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, RJ 21941-914, Brazil * Correspondence: marquesleandro.uerj@gmail.com (L.M.); gustavo.rabello@coppe.ufrj.br (G.R.A.) Abstract: The present work aims at developing a numerical study on the drug diffusion in the bloodstream in a coronary artery with drug-eluting stent implanted. The blood was modeled as a single-phase, incompressible and Newtonian fluid and the Navier–Stokes equation was approxi- mated according to the Finite Element Method (FEM). The dynamics of drug-eluting concentration in bloodstream was investigated using four drug-eluting stents with different mass diffusivities in microchannels with variable cross sections, including a real coronary artery geometry with atheroscle- rosis. The results reveal complex drug concentration patterns and accumulation in the vicinity of the fat buildup. Keywords: angioplasty; cardiovascular disease; drug-eluting stent; real artery geometry; microchan- nels; finite element method 1. Introduction According to the World Health Organization (WHO) [1], cardiovascular diseases have remained the leading death causes globally in the last 15 years. It is estimated that 15.2 million people died from CVD in 2016, representing 26.7% of all deaths in the world. In Brazil, about 38% of deaths due to CVD is in the procutive age range (18 to 65 years) and the estimated costs of CVD were R$ 37.1 billion in 2015, that is, 0.7% GDP [2]. About 60% of CVD deaths occurred due to coronary artery disease (CAD). The main cause of CAD is the atherosclerosis which consists of the accumulation of fat plaques inside the artery wall causing a decrease in lumen diameter. The Atherosclerosis can be prevented with a change in harmful habits such as: cigarette smoking, physical inactivity/low fitness and poor dietary habits [3]. For a corrective approach, however, two treatments can be performed: the Coronary Artery Bypass Graft (CABG) or a procedure minimally invasive called Percutaneous Transluminal Coronary Angioplasty (PTCA) [4], where a wire tube (stent) is placed. In 2001, Hwang, Wu and Edelman [5] presented a simulation of stent implantation coated with a drug in a coronary artery. The simulation presented the close relationship between drug distribution and Peclet number in addition to the importance of developing geometries for stents that enhance the diffusion of the chemical substance. Such procedure proved to be a promising option for the treatment of atherosclerosis and reestonosis. This new type of stent would be known as drug-eluting stent. In the following years, Zunino et al. [6] presented in 2009 a complete overview of mathematical models and finite element numerical simulation applied to the modeling of drug eluting stens and of their interaction with the coronary arteries, take into account the stent expansion, fluid dynamics around the stent and drug release. The numerical simulation showing recirculation zones downstream has important consequences on the drug release process. The smooth and concave shape of stent contours shows that part of the drug released and accumulated in Fluids 2021, 6, 71. https://doi.org/10.3390/fluids6020071 https://www.mdpi.com/journal/fluids