Abstract
Recent studies showed that wave intensity analysis (WIA) provides clinically valuable information about local and global cardiovascular function. Wave intensity (WI) is computed as the product of the pressure change and the velocity change during short time intervals. The major limitation of WIA in clinical practice is the need for invasive pressure measurement. Since vessel wall displacement can be measured non-invasively, the usage of WI will be expanded if the vessel wall dilation is used instead of pressure in derivation of WI waveform. Our goal in this study is to investigate the agreement between wall displacement-based WI and the pressure-based WI for different vessel wall models including linear elastic, nonlinear and viscoelastic cases. The arbitrary Eulerian Lagrangian finite element method is employed to solve the coupled fluid-structure interaction (FSI). Our computational models also include two types of vascular disease-related cases with geometrical irregularities, aneurysm and stenosis. Our results show that for vessels with linear elastic wall, the displacement-based WI is almost identical to the pressure-based WI. The existence of vessel irregularities does not impact the accuracy of displacement-based WI. However, in a viscoelastic wall where there is a phase difference between pressure and vessel wall dilation, displacement-based WI deviated from pressure-based WI. The error associated with this phase difference increased nonlinearly with increasing viscosity. This results in a maximum error of 6.8% and 7.13% for a regular viscoelastic vessel wall and an irregular viscoelastic vessel wall, respectively. A separate analysis has also been performed on the agreement of backward and forward running waves extracted from a decomposition of the displacement-based and pressure-based WI. Our findings suggest that displacement-based WI is a reliable method of WIA for large central arteries that do not show viscoelastic behaviors. This can be clinically significant since the required information can be measured non-invasively.
Highlights
It is well accepted that arterial waveform analysis provides clinically valuable information about local and global cardiovascular function
Our results suggest that for large arteries demonstrating linear elastic behavior, the displacement-based Wave intensity (WI) is almost identical to the pressurebased WI
Our results indicate that the existence of vessel wall abnormalities such as an aneurysm or stenosis does not impact the accuracy of displacement-based wave intensity
Summary
It is well accepted that arterial waveform analysis provides clinically valuable information about local and global cardiovascular function. Understanding the physics of these forward and backward waves is necessary for extracting physiological information relevant to clinical practice. Several methods such as Fourier (impedance) methods and wave intensity analysis (WIA) have been introduced for decomposing hemodynamic waves in the arterial system into their forward and backward components. The Fourier analysis method (impedance method), in particular, relies on the normal periodicity of the cardiac cycle to compute the hemodynamic impedance in the frequency domain [2] This method is not useful for many applications in which the timeline of certain events is important [3]. This method assumes a linear relation between the pressure and flow rate at each harmonic frequency
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