Abstract
Theoretically emboli, both gaseous and solid, would be expected to appear in the Doppler spectrum as short duration high intensity signals. Experimental studies have confirmed the sensitivity of the technique. Embolic signals have been detected in patients with a variety of embolic sources including prosthetic cardiac valves and carotid stenosis. In the latter group they appear to be clinically relevant correlating with time since symptoms, the degree of stenosis and plaque ulceration, and being reduced or abolished after carotid endarterectomy. However early studies have given very different frequencies of embolic signals. This may partly reflect different patient populations but also emphasizes the importance of technical factors. These are discussed in this review. A number of automated systems have been developed to detect embolic signals but none yet developed have sufficient sensitivity and specificity for routine use.
