Modeling Aortic Stenosis to Investigate the Effect of Leaflet Thickness on Frequency Content

The effect of leaflet thickness on acoustic frequencies and their interactions in a pulsatile flow is investigated in a model system inspired by aortic stenosis, a valvular heart disease where the leaflets of the aortic valve thicken and calcify. In the model system, blood flow through the aortic valve is simulated using water and a pulsatile pump. Flexible trileaflet valves, modeled after the geometry of the aortic valve, are 3D printed in various thicknesses to simulate a range of calcification from healthy to severe stenosis. Dynamic similarity between the model setup and biological systems is maintained by matching Reynolds and Womersley numbers to physiological values. The sounds produced by the leaflets in the flow are recorded by a contact microphone, analogous to an electronic stethoscope. The signals are decomposed into energy spectra to show the energy content across frequencies, and the bicoherence of the signals is calculated from the Fourier transform to evaluate interactions between frequencies. The short time Fourier transform is used to investigate how the distribution of energy across frequencies evolves over the duration of a pulse. Results show that thicker leaflets correlate with enhanced energy content at higher frequencies and decreased bicoherence in the signals, matching results from real heart murmur data. This study aims to develop predictive markers based on acoustic signals that can enhance real diagnostic capabilities.