Ultrasonic Tissue Characterization of Carotid Plaque Improves the Prediction of Cardiovascular Events in Diabetic Patients: A pilot study

OBJECTIVE: The aim of this study is to evaluate whether noninvasive ultrasonic tissue characterization of carotid plaque using integrated backscatter (IBS) analysis can be a predictor of future cardiovascular events (CVE) in asymptomatic type 2 diabetic patients. RESEARCH DESIGN AND METHODS: We prospectively evaluated the association between Calibrated-IBS value, an ultrasonic marker for tissue characteristics of carotid plaque, and CVE in 85 asymptomatic type 2 diabetic patients with carotid plaque. RESULTS: The median follow-up period was 7.9 years, and there were 20 new CVE. The risk of CVE was significantly higher in the subjects with low Calibrated-IBS values (<−17.1 dB; n = 42) as compared with those with high values (≥−17.1 dB; n = 43) (P = 0.004, log-rank test). Cox proportional hazards regression analysis revealed that both Calibrated-IBS value (hazard ratio [HR] 0.802 [95% CI 0.710–0.906]; P < 0.0001) and plaque thickness (1.938 [1.170–3.213]; P = 0.010) were independently associated with CVE, even after adjustment for the 10-year risk for a general cardiovascular disease estimated by Framingham risk scoring (FRS). Time-dependent receiver operating characteristic curve analysis for CVE at 10 years after the baseline examinations revealed that area under the curve for Calibrated-IBS was 0.76 (0.60–0.90) and substantially higher than those for plaque thickness (0.60 [0.45–0.79]) and FRS (0.60 [0.40–0.78]). These analyses also revealed that the addition of both plaque thickness and Calibrated-IBS value to conventional risk factors significantly improved the event prediction. CONCLUSIONS: Calibrated-IBS value could improve the risk prediction of CVE in asymptomatic type 2 diabetic patients with carotid plaque.