Effects of surrounding tissue on the sound spectrum of arterial bruits in vivo.

Abstract

SUMMARY Turbulent flow distal to arterial stenoses produces bruits with a characteristic sound spectrum, analysis of which has permitted accurate non-invasive assessment of the residual lumen diameter of the stenosis in the case of the human carotid artery. In contrast, investigators working with In vitro elastic models of arteries or with excised vessels have reported finding mainly resonant spectra of bruits recorded distal to stenoses. We have studied tbe effects of turbulent flow on tbe sound spectrum produced at the arterial wall and the influence of surrounding tissue on this spectrum. Aortic, carotid, and femoral stenoses were produced in dogs by external banding of the arteries with 5mm wide Teflon bands. Recordings of bruits made directly on the vessel wall had a sound spectrum made up of 2 components, one due to turbulent flow, and the second to a superimposed resonant spectrum from arterial wall vibration. This was true of 3 kinds of vessels studied. The effects of surrounding tissue on tbe sound spectrum of arterial bruits was sbown by comparing the spectra of bruits recorded directly on the vessel wall, on tbe freshly closed wound and on tbe healed wound. The sound properties of the artery in situ are very different from those of exposed or excised vessels or elastic tubes. Although intravascular turbulence may be accurately appreciated at the skin surface, arterial wall resonance in the intact animal is extensively damped by tbe normal coupling of the artery to its surrounding tissue. Stroke, Vol 11, No 4, 1980ALTHOUGH AUSCULTATION of arterial bruits has been taught since the time of Laennec, only recently has quantitative information been derived concerning the extent of arterial disease. Lees and Dewey 1 in 1970 showed that flow through a significant arterial stenosis resulted in a spectrum of pressure fluctuations at the surface of the skin remarkably similar to wall pressure fluctuations in fully turbulent pipe flow at a high Reynolds number, and that quantitative information about the size of the residual lumen at the stenosis could be obtained by spectral analysis of the bruit recorded at the skin surface overlying the artery. In later studies, Lees and collaborators showed that accurate clinical diagnosis of the extent of carotid stenosis could be made non-invasively by quantitative analysis of bruit spectra. '" 4 The analytical method depends upon the recognition of a single frequency peak beyond which sound intensity drops sharply with increasing frequency.By contrast, Boughner and Roach showed that isolated arteries studied ex vivo resonate when excited by a sound stimulus at certain characteristic frequencies.0 Kim and Corcoran* showed that turbulent flow in latex tubes produced 2 spectra superimposed on one another -a turbulent spectrum caused by disturbed fluid flow and a resonant spectrum resulting from the natural frequency of the tube itself, which was set in vibratory motion by the turbulent flow.The present study was designed to investigate whether turbulent blood flow in art...

A Coupled CFD-FEA study of the Sound Generated in a Stenosed Artery and Transmitted Through Tissue Layers

“…These interactions with the elastic blood vessel may introduce resonance peaks in the sound spectrum [51]. However, these resonance peaks are generally vanished due to the damping associated with the surrounding tissue and may not have important components in the sounds detected at the skin surface [26,51]. The acoustic domain in the current study includes not only the lumen surface but also the arterial wall (blood vessel) and the surrounding tissue layers.…”

“…3 shows the simulation methodology in the current study: In the current study, the fluid-structure interaction of blood flow with the arterial wall was also considered; however, it was neglected in the previous study [26]. These interactions with the elastic blood vessel may introduce resonance peaks in the sound spectrum [51]. However, these resonance peaks are generally vanished due to the damping associated with the surrounding tissue and may not have important components in the sounds detected at the skin surface [26,51].…”