Phonoangiography: qualitative and quantitative.

Bruit analysis (phonoangiography) has been performed for many years as a method of characterizing arterial disease. Time displays of arterial bruits, particularly at the carotid bifurcation, have been used in an attempt to quantitate arterial narrowing. Despite the generalization that longer bruits and bruits which look and sound higher in frequency are often associated with severe disease, prospective studies have shown no useful predictive value for qualitative phonoangiography. In marked contrast, spectral bruit analysis or quantitative phonoangiography has been quite accurate in predicting the location and extent of carotid stenosis, and in distinguishing intrinsic from transmitted bruits. With this method, the peak systolic portion of the bruit is subjected to fast Fourier transform analysis. The peak frequency, beyond which amplitude drops as frequency increases further, is directly related to the residual lumen diameter of the stenotic common or internal carotid artery. Several blinded trials of this method have given results accurate to within 1 mm of angiographic values in 83-93% of cases studied. When used in conjunction with duplex doppler ultrasound scanning, 95% accuracy in diagnosis of patients with and without bruits may be achieved. This completely noninvasive method deserves more widespread use and may also be applicable to other cardiovascular sounds.