Correlation between severity of a modeled aortic valve stenosis and its acoustic spectrum

Aortic stenosis is one of the most common heart valve diseases that occurs due to the narrowing of the aortic valve. Heart murmurs are abnormal sounds caused by turbulent blood flow due to the narrowing of the valve. This study seeks to understand the relationship between stenosis severity and energy content at different frequencies. The experimental setup includes two distinct cases; a circular narrowing and a simplified semi triangular shape to mimic an opened aortic valve. Each shape is 3D printed with eight matched restrictions ranging from 0% to 82% blockage ratio. A pulsatile pump regulates the flow and a contact microphone collects the sound pressure levels at the narrowing for all conditions. Flow rates in all test cases have been set to match the Reynolds numbers through the opening which are based on healthy human heart conditions. A spectral analysis shows the energy content is influenced by both the stenosis severity and the Reynolds number of the flow. As the restrictions become increasingly narrow, the energy present at higher frequencies increases, most notably in the 300-500 Hz range. The same trend is present with increasing Reynolds number. This provides a general look into identifying characteristic frequencies that indicate the severity of a restriction in this modeled pulsatile flow, and highlights the interactions of parameters that increase the complexity of identifying stenosis.