Dynamic Fluid Shear Stress Measurements on the Normal Aortic Valve Leaflet Using Laser Doppler Velocimetry
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Aortic valve (AV) calcification is a major cause of mortality and morbidity. This disease involves the chronic inflammation of the AV leaflets and calcium deposition, resulting in valve stenosis and regurgitation. The exact cause of aortic valve calcification is unknown but previous studies have shown that adverse mechanical forces play a role.1 Unfortunately, the mechanical environment of the AV is not well known. Thus, the objective of this project was to make experimental measurements of the fluid shear stress mechanical environmental of the native aortic valve. Native aortic valves were excised from porcine hearts, sutured onto stented rings, and tested in an in vitro pulsatile flow loop. Laser Doppler Velocimetry (LDV) was used to measure shear stresses on the aortic surface of the valve leaflet. Two fluid shear stress experiments were run to understand the effects of hemodynamics on fluid shear stress: varying stroke volumes at a constant heart rate and varying heart beats at a constant stroke volume. As the stroke volume increased, fluid shear stresses increased due to the stronger sinus fluid motion. As the heart rate increased, fluid shear stresses decreased due to reduced systolic duration which restricted strong sinus flow formations. These results show that a higher heart rate can potentially elicit sclerotic responses from the AV and a higher velocity may reduce sclerotic responses from the AV. This data can be used to further understand AV biological response to shear stresses and to create improved computational simulations of flow dynamics in an aortic valve.