Thromboembolic complications (TECs) of bileaflet mechanical heart valves (BMHVs) are believed to be due to the nonphysiologic mechanical stresses imposed on blood elements by the hinge flows. Relating hinge flow features to design features is, therefore, essential to ultimately design BMHVs with lower TEC rates. This study aims at simulating the pulsatile three-dimensional hinge flows of three BMHVs and estimating the TEC potential associated with each hinge design. Hinge geometries are constructed from micro-computed tomography scans of BMHVs. Simulations are conducted using a Cartesian sharp-interface immersed-boundary methodology combined with a second-order accurate fractional-step method. Leaflet motion and flow boundary conditions are extracted from fluid-structure-interaction simulations of BMHV bulk flow. The numerical results are analyzed using a particle-tracking approach coupled with existing blood damage models. The gap width and, more importantly, the shape of the recess and leaflet are found to impact the flow distribution and TEC potential. Smooth, streamlined surfaces appear to be more favorable than sharp corners or sudden shape transitions. The developed framework will enable pragmatic and cost-efficient preclinical evaluation of BMHV prototypes prior to valve manufacturing. Application to a wide range of hinges with varying design parameters will eventually help in determining the optimal hinge design.
Bibliographical noteFunding Information:
This study was partially supported by a grant from the National Heart, Lung and Blood Institute (R01-HL-070262), a research funding donation from Tom and Shirley Gurley, and the Minnesota Supercomputing Institute. The authors also wish to thank Dr. Iman Borazjani for providing the numerical boundary conditions from the large scale simulations, and Dr. Hwa-Liang Leo for providing experimental insights on the influence of hinge designs on the microscopic flow fields.
- Computational fluid dynamics (CFD)
- Design parameters
- Fluid mechanics
- Physiologic conditions
- Prosthetic heart valve
- Pulsatile numerical simulations