Abstract 20291: Preservation of Generated Cardiac Spiral Flow Structures is Valve-Type Dependent
Introduction: Non-invasive imaging modalities (e.g. 3D echo, 4D MRI) have demonstrated prevalence of spiral blood flow in the cardiovascular system. Fluid spirality imparts flow stability, minimizes near-wall flow stasis, and may be atheroprotective by normalizing wall shear stress. The heart’s helical fiber architecture and torsional contraction is responsible for generating complex blood flow. Valve replacement (bileaflet mechanical or trileaflet biological) may differentially alter the generated spiral flow structures.
Hypothesis: The purpose of this study was to test the hypothesis that spiral flow is characteristically dissipated by bileaflet mechanical valves in comparison to trileaflet valves.
Methods: Computer aided design was used to combine cardiac spiral flow generators with the two valve types. Computational fluid dynamics (CFD) was used to evaluate the progression of spiral flow through the valves. The fluid was assumed to be Newtonian with a viscosity and density of blood.
Results: With bulk flow along the z-axis (axial), the transverse (x-component) velocities at the outflow ranged from -0.032 to 0.033 m/s for the bileaflet valve and -0.063 to 0.064 m/s for the trileaflet valve (Figure), despite identical inflow spirality. Y-component outflow velocities ranged from -0.032 to 0.032 m/s (bileaflet) and -0.074 to 0.043 m/s (trileaflet). The results demonstrated that bileaflet mechanical valves alter spiral flow dynamics differentially, effectively functioning as a flow diffuser.
Conclusion: The preservation and propagation of generated spiral flow is dependent on valve type; the valve orifice geometry and leaflets play a crucial role in flow-pattern modulation. The unraveling of spiral flow may adversely impact circulation through complex vessels (e.g. aortic arch, bifurcation) and affect endothelial shear stress mediated mechanotransduction, contributing to undesirable (atherogenesis, thrombogenesis) vascular-wall response.
Author Disclosures: P.S. Huang Zhang: None. C.D. Tkatch: None. J. Kresh: None.
- © 2016 by American Heart Association, Inc.