Citation: Marwan, S.H.; Todo, M. Effects of Hysteresis on the Dynamic Deformation of Artificial Polymeric Heart Valve. Prosthesis 2022, 4, 511–523. https://doi.org/10.3390/ prosthesis4040042 Academic Editor: Salvatore Pasta Received: 16 June 2022 Accepted: 18 September 2022 Published: 21 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Effects of Hysteresis on the Dynamic Deformation of Artificial Polymeric Heart Valve Shahrul Hisyam Marwan 1 and Mitsugu Todo 2, * 1 School of Mechanical Engineering, College of Engineering, Universiti Teknologi MARA (UiTM), Terengganu Branch, Bukit Besi Campus, Dungun 23200, Terengganu, Malaysia 2 Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan * Correspondence: todo@riam.kyushu-u.ac.jp Abstract: The deformation behavior of an artificial heart valve was analyzed using the explicit dynamic finite element method. Time variations of the left ventricle and the aortic pressure were considered as the mechanical boundary conditions in order to reproduce the opening and closing movements of the valve under the full cardiac cycle. The valve was assumed to be made from a medical polymer and hence, a hyperelastic Mooney–Rivlin model was assigned as the material model. A simple formula of the damage mechanics was also introduced into the theoretical material model to express the hysteresis response under the unloading state. Effects of the hysteresis on the valve deformation were characterized by the delay of response and the enlargement of displacement. Most importantly, the elastic vibration observed in the pure elastic response under the full close state was dramatically reduced by the conversion of a part of elastic energy to the dissipated energy due to hysteresis. Keywords: artificial heart valve; explicit finite element method; hyperelastic material; hysteresis; cardiac cycle 1. Introduction The aortic valve of the heart is one of the most important organs in our body system. The position of the aortic valve is in between the aorta and the left ventricle, which distributes blood to our body system. The aortic valve is made of three moving thin flaps of tissue called cusps or leaflets that come together in the center of the valve to close it [1] and to ensure only one-directional blood flow through the cardiovascular system [2]. Every year, over 100,000 patients in the United States have to go through surgical procedures to replace their malfunctioning heart valves with artificial heart valves [3]. At present, prosthetic heart valves (PHV) have widely been available commercially in the field of cardiac surgery, including mechanical heart valves (MHV) and bio-prosthetic heart valves (BHV). MHVs are usually made from pyrite carbon (artificial carbon), and the performance is relatively durable but patients are likely to get thromboembolic (blood clotting) problems [4]. Therefore, patients who are using MHVs always need to take an anticoagulant drug, which may cause life-threatening hemorrhages if poorly managed [5]. On the other hand, the natural BHVs have excellent hemodynamic properties (no need for anticoagulant drugs) but they are less durable compared with MHVs [5]. The patients who are using BHVs generally need to experience another surgery after 15 to 20 years. Khan et al. conducted a 20-year post-operation follow-up study on 2533 cases of patients aged 18 years or older who had used MHVs or BHVs [6]. Their study exhibited that in general, there were no survival rates for both types of valves, with similar complications. From this perspective, it is concluded that both types of PHVs have still been suffering from several drawbacks, and an ideal PHV with high durability without thrombotic problems has not been developed yet. Prosthesis 2022, 4, 511–523. https://doi.org/10.3390/prosthesis4040042 https://www.mdpi.com/journal/prosthesis