Prediction of Turbulent Shear Stresses through Dysfunctional Bileaflet Mechanical Heart Valves using Computational Fluid Dynamics

TL;DR

This computational study analyzes how dysfunction in bileaflet mechanical heart valves affects flow dynamics, revealing increased velocities and shear stresses that pose risks to blood cells, aiding in better valve design and risk assessment.

Contribution

It provides detailed CFD analysis of flow and shear stresses in dysfunctional bileaflet valves, highlighting risks and informing improved designs.

Findings

Maximum velocities increased with dysfunction from 2.05 to 4.49 m/s.

Turbulent shear stresses rose from 90 to 800 N/m² with dysfunction.

Regions of high stress correlated with high jet velocities and helical flow structures.

Abstract

There are more than 300,000 heart valves implanted annually worldwide with about 50% of them being mechanical valves. The heart valve replacement is often a common treatment for severe valvular disease. However, valves may dysfunction leading to adverse hemodynamic conditions. The current computational study investigated the flow around a bileaflet mechanical heart valve at different leaflet dysfunction levels of 0%, 50%, and 100%, and documented the relevant flow characteristics such as vortical structures and turbulent shear stresses. Studying the flow characteristics through these valves during their normal operation and dysfunction can lead to better understanding of their performance, possibly improved designs, and help identify conditions that may increase the potential risk of blood cell damage. Results suggested that maximum flow velocities increased with dysfunction from 2.05 to 4.49 ms-1 which were accompanied by growing eddies and velocity fluctuations. These fluctuations led to higher turbulent shear stresses from 90 to 800 N.m-2 as dysfunctionality increased. These stress values exceeded the thresholds corresponding to elevated risk of hemolysis and platelet activation. The regions of elevated stresses were concentrated around and downstream of the functional leaflet where high jet velocity and stronger helical structures existed.