Evaluation of shear stress accumulation on blood components in normal and dysfunctional bileaflet mechanical heart valves using smoothed particle hydrodynamics S. Shahriari a,b , H. Maleki a , I. Hassan a , L. Kadem a,n a Department of Mechanical and Industrial Engineering, Concordia University, Montreal, Quebec, Canada b Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center (CRCHUM), Montreal, Quebec, Canada article info Article history: Accepted 9 August 2012 Keywords: Fully Lagrangian meshfree method Smoothed particle hydrodynamics Bileaflet mechanical heart valve Hemodynamics Shear stress accumulation Blood components damage abstract Evaluating shear induced hemodynamic complications is one of the major concerns in design of the mechanical heart valves (MHVs). The monitoring of these events relies on both numerical simulations and experimental measurements. Currently, numerical approaches are mainly based on a combined Eulerian–Lagrangian approach. A more straightforward evaluation can be based on the Lagrangian analysis of the whole blood. As a consequence, Lagrangian meshfree methods are more adapted to such evaluation. In this study, smoothed particle hydrodynamics (SPH), a fully meshfree particle method originated to simulate compressible astrophysical flows, is applied to study the flow through a normal and a dysfunctional bileaflet mechanical heart valves (BMHVs). The SPH results are compared with the reference data. The accumulation of shear stress patterns on blood components illustrates the important role played by non-physiological flow patterns and mainly vortical structures in this issue. The statistical distribution of particles with respect to shear stress loading history provides important information regarding the relative number of blood components that can be damaged. This can be used as a measure of the response of blood components to the presence of the valve implant or any implantable medical device. This work presents the first attempt to simulate pulsatile flow through BMHVs using SPH method. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Valve replacement by a prosthetic heart valve is a viable solution in symptomatic patients with severe valve stenosis. The prosthetic heart valves can be either biological or mechanical. A biological valve is more biocompatible than a mechanical valve and patients with biological valve implanted do not need life-long anticoagulant therapy. Instead, a mechanical heart valve (MHV) has higher structural durability but has more post-surgical complications. Thrombus formation and hemolysis are the major life-threatening complications associated with MHVs. Moreover, pannus and thrombus formation around the structure of the valve can hinder its performance and lead to dysfunction in one or both leaflets for bileaflet MHVs (BMHVs) (Baumgartner et al., 1993). Their prevalence is around 0.2–6% patients/yr (Montorsi et al., 2003). Several in vivo, in vitro and in silico studies have been dedicated to the investigation of flow characteristics downstream of MHVs. A review on these studies, the current challenges and future directions can be found in (Yoganathan et al., 2005; Sotiropoulos and Borazjani, 2009). Despite decades of improvements in the design of MHVs, damage to platelet and red blood cells (RBCs) are still drawbacks to their use. In vivo evaluation of such shear induced hemody- namic events is still a difficult task. As a consequence, most studies rely on in vitro tests and numerical simulations, with a preference towards numerical simulations since they can provide a large spectrum of flow characteristics with a significantly high spatial resolution. The accumulative shear stress loading can then be evaluated using linear (Hellums et al., 1987; Bluestein et al., 1997; Bluestein et al., 2000) or nonlinear models (Jesty et al., 2003). Almost all in silico studies investigating thrombus and hemo- lysis events in MHVs rely on simulations based on a combined Eulerian–Lagrangian approach. An accurate evaluation of such events has to take into account the loading history and the cumulative effect on blood components (Grigioni et al., 2005) and therefore to analyze the Lagrangian dynamics of blood components trajectories in the unsteady flow field (Yoganathan et al., 2005). Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com Journal of Biomechanics 0021-9290/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jbiomech.2012.08.009 n Corresponding author. Laboratory of Cardiovascular Fluid Dynamics, Department of Mechanical and Industrial Engineering, Concordia University, 1455 de Maisonneuve Blvd W, Montreal, Quebec, Canada H3G 1M8. Tel.: þ1 514 848 2424; fax: þ1 514 848 3175. E-mail address: kadem@encs.concordia.ca (L. Kadem). Journal of Biomechanics 45 (2012) 2637–2644