Impulse propagation in normal and stenosed vessels.

The propagation of a transient pressure impulse in a viscoelastic medium was investigated by experiments using water-filled latex rubber tubing and the aorta of anaesthetised dogs. A 5 ms pressure impulse was produced by the impact of a solenoid driven hammer. The propagation characteristics of the impulse (attenuation and propagation velocity) along the vessel were determined by means of a catheter-tip pressure manometer placed at various distances distal to the impulse generator. The presence of stenoses of varying degrees of severity resulted in reflection of the impulse and the appearance of reflected pulses whose magnitude depended on the stenotic severity. The experiments suggest that for the technique to be used in the detection of local reflecting sites such as might result from vascular occlusive disease, the lesions should occlude at least 70% of the lumen and should be no more than 0.20 m distal to the impulse generator.