On-X Heart Valve Prosthesis: Numerical Simulation of Hemodynamic Performance in Accelerating Systole NIMA MIRKHANI, 1 MOHAMMAD REZA DAVOUDI, 2 PEDRAM HANAFIZADEH, 1 DARYOOSH JAVIDI, 3 and NILOOFAR SAFFARIAN 4 1 Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran; 2 Biomedical Engineering, Katholieke Universiteit Leuven, Louvain, Belgium; 3 Department of Cardiac Surgery, Pars Hospital, Tehran, Iran; and 4 Cardiovascular Department, Pars Hospital, Tehran, Iran (Received 29 January 2016; accepted 26 April 2016) Associate Editor Ajit P. Yoganathan oversaw the review of this article. Abstract—Numerical simulation of the bileaflet mechanical heart valves (BMHVs) has been of interest for many researchers due to its capability of predicting hemodynamic performance. A lot of studies have tried to simulate this three-dimensional complex flow in order to analyze the effect of different valve designs on the blood flow pattern. However, simplified models and prescribed motion for the leaflets were utilized. In this paper, transient complex blood flow in the location of ascending aorta has been investigated in a realistic model by fully coupled simulation. Geometry model for the aorta and the replaced valve is constructed based on the medical images and extracted point clouds. A 23-mm On-X Medical BMHV as the new generation design has been selected for the flow field analysis. The two-way coupling simulation is conducted throughout the accelerating phase in order to obtain valve dynamics in the opening process. The complex flow field in the hinge recess is captured precisely for all leaflet positions and recirculating zones and elevated shear stress areas have been observed. Results indicate that On-X valve yields relatively less transvalvular pressure gradient which would lower cardiac external work. Furthermore, converging inlet leads to a more uniform flow and consequently less turbulent eddies. However, the leaflets cannot open fully due to middle diffuser-shaped orifice. In addition, asymmetric butterfly-shaped hinge design and con- verging orifice leads to better hemodynamic performance. With the help of two-way fluid solid interaction simulation, leaflet angle follows the experimental trends more precisely rather than the prescribed motion in previous 3D simula- tions. Keywords—Fluid solid interaction, Hemodynamic perfor- mance, Bileaflet mechanical heart valve. INTRODUCTION Surgical operation and replacement of the diseased native heart valves is a common procedure for the patients who suffer from heart valve disease. Mal- functioning valves are usually replaced by artificial heart valves, for which an increasing demand is seen each year. Considering the fact that about 55% of the diseased heart valves are substituted by artificial mechanical ones, this type of the prosthetic valves are recently the choice for many surgeons. It has been reported that about 80% of the implanted mechanical heart valves in the aortic position are bileaflet mechanical heart valves (BMHVs). 20,43,45 BMHVs are mainly constructed with artificial materials like pyr- olytic carbon and therefore they show accept- able strength and durability, however patients with these implants require long-term anticoagulant ther- apy. 12,13,41 This phenomenon is attributed to the non- physiological blood flow pattern which is created by this artificial organ in the heart. 21 On the other hand, Computational Fluid Dynamics (CFD) are among the powerful tools generally for the study of cardiovascular risk factors 15 and especially those related to the mechanical performance of the artificial valves. 12,23,42 In the case of BMHVs, the dy- namic of the leaflets play an important role in the flow pattern through the valve and its motion is fully cou- pled with the physiologic blood flow. Therefore, here comes the turn to the Fluid Solid Interaction (FSI) simulation which accounts for this coupled physics associated with this problem. 41 This numerical simu- lation is capable of transfer data between the solid boundaries, i.e., valve leaflets, and the fluid domain which is blood flow in the ascending aorta for this case. Address correspondence to Pedram Hanafizadeh, Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran. Electronic mail: hanafizadeh@ut.ac.ir Cardiovascular Engineering and Technology (Ó 2016) DOI: 10.1007/s13239-016-0265-y Ó 2016 Biomedical Engineering Society