Background: Carotid intima-media thickness (CIMT), an ultrasonographic marker of cardiovascular risk, is increasingly used in adults and children. The choice of specific images used to quantify CIMT from a cine sequence is often based on image quality rather than on a consistent point in the cardiac cycle. This methodological study quantified the imprecision that may be introduced by variation of CIMT during the cardiac cycle.
Probands and methods: Data from four-year-olds, 11 to 12-year-olds, and adults (n=30 each age group) were selected retrospectively from two population-derived studies. Far wall CIMT of the right common carotid artery was measured at end-diastole and peak systole using standardized protocols. All images were analysed using semi-automated edge-detection software.
Results: In all age groups CIMT varied significantly during the cardiac cycle and was largest at end-diastole. The mean difference in CIMT between end-diastole and peak systole was greater in four-year-olds (38 μm; 95 % confidence interval (CI) 33 to 43 μm) and 11 to 12-year-olds (31 μm; CI 26 to 36 μm) than in adults (18 μm; CI 16 to 22 μm). Carotid IMT increased by 8.8 % (CI 7.7 to 9.8 %), 6.9 % (CI 5.8 to 8.1 %), and 3.8 % (CI 3.1 to 4.5 %) between minimum and maximum arterial diameter in four-year-olds, 11 to 12-year-olds, and adults, respectively. The greatest variation in CIMT during the cardiac cycle was observed in children (up to 14 %).
Conclusions: Inconsistent timing of CIMT measurement during the cardiac cycle is an avoidable source of imprecision, especially in children, in whom inter-individual differences are smallest. As CIMT is largest at end-diastole, this is the most appropriate time point for consistent and comparable measurements to be made.
Keywords: Carotid artery intima-media thickness; adult; atherosclerosis.; cardiac cycle; carotid artery ultrasound; child.