Changes in Doppler ultrasound sonagrams at varying distances from stenoses.

The effect of different degrees of arterial stenosis on Doppler ultrasound sonagrams recorded from various distances downstream has been investigated in a canine model. It has been found that even mild stenoses give rise to considerable disturbances close to the stenosis, and that more severe stenoses give rise to greater disturbances which propagate further downstream. The distance the disturbances travelled was not related to stroke volume, and it was only for stenoses of 88% area reduction and greater that such disturbances ever propagated beyond one stroke-length. Quantitative assessment of moderate degrees of proximal stenosis using continuous wave Doppler ultrasound will not be reliable unless the distance between the major stenosis and the recording site is known.