The identification of the high risk carotid plaque.

OBJECTIVE: To determine the influence of carotid plaque morphology and severity of stenosis on symptoms of cerebrovascular disease and cerebral infarction. PATIENTS AND METHODS: One hundred and ninety patients with 329 carotid plaques producing 50-99% stenosis were studied. Carotid plaque echogenicity on ultrasonography was evaluated using computerised measurement of the median of the overall grey scale content (GSM). Heterogeneity was evaluated as the difference between the GSMs of the most echogenic and the most echolucent areas within each plaque and expressed as the heterogeneity index (HI). All patients had a CT brain scan and the presence of ipsilateral cerebral infarction noted.
RESULTS: Cerebral infarction was more common in symptomatic than asymptomatic plaques (42% vs. 29%, p<0.02) and in echolucent than echogenic plaques (mean GSM of 37.8 vs. 29.7, p<0.01). Plaques with GSM below or equal to 32 were associated with a higher incidence of cerebral infarction as compared to those above this level, this was significant in both symptomatic and asymptomatic plaques. Symptomatic carotid plaque were less heterogenous than asymptomatic plaques. Plaques associated with cerebral infarction were less heterogenous than those not associated with infarction.
CONCLUSION: This study has shown that the identification of the high risk carotid plaques, i.e. those associated with a high incidence of cerebral infarction is possible both in symptomatic and asymptomatic patients. The potential of such analysis in the identification of patients with asymptomatic carotid stenosis with high and low risk of stroke should be explored in a natural history study.