Objective: to determine the relative significance of ultrasonographic parameters of carotid plaques to develop an Activity Index (AI) which could correlate with clinical findings.
Method: two hundred and fifteen plaques in 141 patients underwent ultrasonography and computer-assisted structural analysis. In half the patients (group 1), plaques were classified as either homogeneous and heterogeneous and ultrasonographic appearances related symptomatic (SP) or asymptomatic (AP) station. The probability of SP for each ultrasound parameter was used to define an Activity Index (AI). The AI was then applied the second half of patients (Group 2) to assess the value of AI in determining symptomatic station.
Results: the parameters with highest morbility were surface disruption, severe stenosis and low grey scale median and, additionally in heterogenous plaques heterogeneity and the presence of a juxta-luminal echolucent area. The power in group 2 of AI to identify symptomatic plaques was determined. Mean AI was for SP-75 (41-100) and for AP-43 (22-100); 78% of SP have AI>60 and 70% of AP have AI<50. The cut-off point between the two groups was 52. ROC curve analysis of the AI were obtained to determine its diagnostic accuracy.
Conclusion: Activity Index is an objective parameter of plaque echostructure that positively correlates with symptoms. AI may contribute to better selection for treatment of patients with carotid artery disease.