A Model Experiment of Aortic Valve Stenosis to Correlate Narrowness With the Acoustic Spectrum

Abstract

A model experiment is used to investigate the relationship between a narrowing in a pulsatile flow and the relative energy contained in the measured acoustic spectrum. Inspired by studies of aortic stenosis, this experiment models increasingly severe narrowings in an internal flow with a semi-triangular opening to mimic the shape of an open tricuspid valve. A baseline case is attained through use of dynamic similarity to the average flow through an unrestricted aortic valve. Normalized spectra for each case provides an indication of relative energy in each frequency band which shows how the distribution of energy changes with each restriction. Increasing narrowness of the model valve opening results in enhanced energy content across all frequency bands up to 400Hz. Frequency bands identified as relevant to more extreme cases of stenosis in actual heart valves, such as the 40Hz–80Hz band, show significantly increased overall energy in these model cases. While all restricted cases demonstrate a nominal amount of increased energy, there appears to be more significant changes when the narrowing exceeds an area reduction of 40%.