Mapping the cardiac acousteome: An overview of technologies, tools and methods

Journal of Biomechanical Engineering

Mittal

2019

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In this study, coupled hemodynamic–acoustic simulations are employed to study the generation and propagation of murmurs associated with aortic stenoses where the aorta with a stenosed aortic valve is modeled as a curved pipe with a constriction near the inlet. The hemodynamics of the poststenotic flow is investigated in detail in our previous numerical study (Zhu et al., 2018, “Computational Modelling and Analysis of Haemodynamics in a Simple Model of Aortic Stenosis,” J. Fluid Mech., 851, pp. 23–49). The temporal history of the pressure on the aortic lumen is recorded during the hemodynamic study and used as the murmur source in the acoustic simulations. The thorax is modeled as an elliptic cylinder and the thoracic tissue is assumed to be homogeneous, linear and viscoelastic. A previously developed high-order numerical method that is capable of dealing with immersed bodies is applied in the acoustic simulations. To mimic the clinical practice of auscultation, the sound signals from the epidermal surface are collected. The simulations show that the source of the aortic stenosis murmur is located at the proximal end of the aortic arch and that the sound intensity pattern on the epidermal surface can predict the source location of the murmurs reasonably well. Spectral analysis of the murmur reveals the disconnect between the break frequency obtained from the flow and from the murmur signal. Finally, it is also demonstrated that the source locations can also be predicted by solving an inverse problem using the free-space Green's function. The implications of these results for cardiac auscultation are discussed.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Computational Modeling and Analysis of Murmurs Generated by Modeled Aortic Stenoses

Zhu

Journal of Biomechanical Engineering

Mittal

2019

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“…At the end of each Runge-Kutta sub-steps, the boundary conditions are imposed by updating the ghost-cell values using Eqs. (17)(18)(19). After the final Runge-Kutta step, the spatial filtering, Eq.…”

Section: Solution Proceduresmentioning

confidence: 99%

“…The availability of ultra-sensitive, low-power, low-cost compact acoustic sensors and sophisticated signal analysis algorithms has rekindled the possibility of developing effective systems for automated cardiac auscultation [17,18]. Such a diagnostic modality would be non-invasive and inexpensive, and could be highly effective in the screening for particular heart conditions, longitudinal (tracking over time) assessment of cardiac health, 24/7, continuous, at-home health monitoring; and cardiac health assessment in rural and underdeveloped areas where access to specialists is limited.…”

Section: Introductionmentioning

confidence: 99%

A method for the computational modeling of the physics of heart murmurs

Journal of Computational Physics

Bakhshaee

Garreau

et al. 2017

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A computational method for direct simulation of the generation and propagation of blood flow induced sounds is proposed. This computational hemoacoustic method is based on the immersed boundary approach and employs high-order finite difference methods to resolve wave propagation and scattering accurately. The current method employs a two-step, one-way coupled approach for the sound generation and its propagation through the tissue. The blood flow is simulated by solving the incompressible Navier-Stokes equations using the sharp-interface immersed boundary method, and the equations corresponding to the generation and propagation of the three-dimensional elastic wave corresponding to the murmur are resolved with a high-order, immersed boundary based, finite-difference methods in the time-domain. The proposed method is applied to a model problem of aortic stenosis murmur and the simulation results are verified and validated by comparing with known solutions as well as experimental measurements. The murmur propagation in a realistic model of a human thorax is also simulated by using the computational method. The roles of hemodynamics and elastic wave propagation on the murmur are discussed based on the simulation results.

“…Even though this noninvasive and inexpensive technique can provide valuable diagnostic information, the practice of auscultation is virtually unchanged since the invention of the stethoscope and suffers from a lack of specificity and sensitivity. Fortunately, the emergence of low-power, low-cost compact acoustic sensors, advanced signal analysis algorithm, and powerful portable computational devices provides the technological support needed to transform this technique into a more accurate automated diagnostic modality that could potentially play a role in traditional medicine as well as telemedicine [6]. Compared with traditional auscultation, automated auscultation could extract more useful information from these bruits.…”

Section: Introductionmentioning

confidence: 99%

A Computational Method for Analyzing the Biomechanics of Arterial Bruits

Zhu

Journal of Biomechanical Engineering

Bakhshaee

et al. 2017

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A computational framework consisting of a one-way coupled hemodynamic-acoustic method and a wave-decomposition based postprocessing approach is developed to investigate the biomechanics of arterial bruits. This framework is then applied for studying the effect of the shear wave on the generation and propagation of bruits from a modeled stenosed artery. The blood flow in the artery is solved by an immersed boundary method (IBM) based incompressible flow solver. The sound generation and propagation in the blood volume are modeled by the linearized perturbed compressible equations, while the sound propagation through the surrounding tissue is modeled by the linear elastic wave equation. A decomposition method is employed to separate the acoustic signal into a compression/longitudinal component (curl free) and a shear/transverse component (divergence free), and the sound signals from cases with and without the shear modulus are monitored on the epidermal surface and are analyzed to reveal the influence of the shear wave. The results show that the compression wave dominates the detected sound signal in the immediate vicinity of the stenosis, whereas the shear wave has more influence on surface signals further downstream of the stenosis. The implications of these results on cardiac auscultation are discussed.