Carotid artery intima-media thickness measurement in children with normal and increased body mass index: a comparison of three techniques.

ABSTRACT

BACKGROUND: Common carotid artery intima-media thickness is a marker of subclinical atherosclerosis. In children, increased intima-media thickness is associated with obesity and the risk of cardiovascular events in adulthood. OBJECTIVE: To compare intima-media thickness measurements using B-mode ultrasound, radiofrequency (RF) echo tracking, and RF speckle probability distribution in children with normal and increased body mass index (BMI). MATERIALS AND METHODS: We prospectively measured intima-media thickness in 120 children randomly selected from two groups of a longitudinal cohort normal BMI and increased BMI, defined by BMI ≥85th percentile for age and gender. We followed Mannheim recommendations. We used M'Ath-Std for automated B-mode imaging, M-line processing of RF signal amplitude for RF echo tracking, and RF signal segmentation and averaging using probability distributions defining image speckle. Statistical analysis included Wilcoxon and Mann-Whitney tests, and Pearson correlation coefficient and intra-class correlation coefficient (ICC). RESULTS: Children were 10-13 years old (mean 11.7 years); 61% were boys. The mean age was 11.4 years (range 10.0-13.1 years) for the normal BMI group and 12.0 years (range 10.1-13.5 years) for the increased BMI group. The normal BMI group included 58% boys and the increased BMI group 63% boys. RF echo tracking method was successful in 79 children as opposed to 114 for the B-mode method and all 120 for the probability distribution method. Techniques were weakly correlated ICC=0.34 (95% confidence interval [CI] 0.27-0.39). Intima-media thickness was significantly higher in the increased BMI than normal BMI group using the RF techniques and borderline for the B-mode technique. Mean differences between weight groups were B-mode, 0.02 mm (95% CI 0.00 to 0.04), P=0.05; RF echo tracking, 0.03 mm (95% CI 0.01 to 0.05), P=0.01; and RF speckle probability distribution, 0.03 mm (95% CI 0.01 to 0.05), P=0.002. CONCLUSION: Though techniques are not interchangeable, all showed increased intima-media thickness in children with increased BMI. RF echo tracking method had the lowest success rate at calculating intima-media thickness. For patient follow-up and cohort comparisons, the same technique should be used throughout.