Ultrasound characteristics of recurrent carotid disease: hypothesis explaining the low incidence of symptomatic recurrence.

The true incidence of recurrent disease after carotid endarterectomy (CENDX) is unknown, but noninvasive hemodynamic testing shows a paradox between the incidence of hemodynamically significant recurrent stenosis (RS) and the presence of symptomatic disease. We have shown that real-time B-mode ultrasound imaging can demonstrate the gross pathology of the arterial wall and plaque and their surface characteristics. Therefore we reviewed the clinical data and B-mode studies performed 6 months to 15 years after 276 carotid endarterectomies. Preoperative and perioperative risk factors and associated symptoms on follow-up were stored on computer. The patients were divided into three groups by the anatomy of their B-mode study. The majority of the studies were normal (203 [73.5%]), 42 (15.2%) showed mild disease, and 34 (12.3%) demonstrated significant RS. The RS group had a statistically significant increase in incidence of known lipid abnormalities (p less than 0.05), associated peripheral vascular disease, previous myocardial infarctions, and ulcerated plaque on the original carotid endarterectomy (p less than 0.01). The site of RS appeared related to the time of detection by B-mode ultrasound imaging. Internal carotid RS developed late (greater than 4 years), as did RS of the bifurcation. By contrast, stenosis at the common carotid level developed earlier. These findings suggest different pathogenic mechanisms--for the former, redevelopment of atherosclerosis; for the latter, accentuation of preexisting atherosclerosis perhaps by hemodynamic factors. Finally, in the 26 vessels with RS without occlusion, there was an 8% incidence of plaque ulcer or hemorrhage vs. a 62% incidence in 79 primary atherosclerotic plaques previously studied by both B-mode and pathologic examination. The low incidence of plaque characteristics associated with symptomatic disease may account for the low incidence of symptomatic disease associated with RS.