Hemodynamics and Mechanical Behaviors of Aortic Heart Valves: A Numerical Evaluation

 

Cheung-Hwa Hsu(1), Ba-Son Nguyen(1), Ha-Ha Vu (2)

1. Department of Mold and Die Engineering National Kaohsiung University of Applied Sciences Kaohsiung, Taiwan, ROC

2. Department of Mechanical Engineering National Kaohsiung University of Applied Sciences Kaohsiung, Taiwan, ROC

Abstract — This study investigates the hemodynamics of aortic heart valves under normal conditions as well as two severe diseases, which would be fundamentals for an assessment of mechanical behaviors of polyurethane (PU) prosthetic heart valves. Analysis results highlight that leaflet opening situation and valve geometry affect the shear stress distribution and vortex flow regime. The interactive impact between low and high wall shear stress on relation to heart valve diseases have been also demonstrated. The results show that low density PU material achieves good hydrodynamic function but produces high stress, while high density PU resists motion of leaflet but reduces the stress significantly. This study also proves that low Young’s modulus PU leaflets achieve good hydrodynamic function while reducing the stress exerted upon the leaflets, and vice versa for high Young’s modulus.

Nowadays, heart valve disease is one of the biggest health problems all over the world. Heart valve diseases occur in all four heart valves, but most frequently affect the aortic valve being responsible for high mortality rates. There are two main processes that can affect the aortic valve including aortic stenosis and aortic insufficiency. The most common treatment for a malfunctioning aortic valve due to stenosis or insufficiency is replacement of the valve, using mechanical valves, or biological prosthetic valves. The viscous drag (shear stress) provided by flowing blood exerts a potent atheroprotective effect. Atherosclerotic lesions preferentially develop in areas with turbulent flow, whereas regions with uniform laminar flow are protected. The endothelial lining is the primary sensor of wall shear stresses, and functions as a transducer of these biomechanical stimuli into biological responses within the vessel wall. The shear stress is highly dependent upon the direction of blood issuing through the orifice of human aortic valve and the location of blood jet impingement. Meanwhile, the orifice shape of aortic valve as well as the location of blood jet impingement could be deformed under influence of valvular diseases. It is a demand to study effects of heart valve disease on blood shear stress.

Shear stress distribution at case 3: (Left) Normal (Mid) Bicuspid (Right) Prolapsed

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