Vascular diameter and intima-media thickness to diameter ratio values of the carotid artery in 642 healthy children.

In children, arterial alterations occur with increased intima-media thickness as well as vascular diameter enlargement. Both conditions correlate with higher cardiovascular risk in adults, and both the array and proportion of these alterations are important hemodynamic parameters. In terms of functional adaptation processes, they influence several arterial wall properties as for example the shear and tensile stress of the vessel. There are no reference values for the vascular diameter and intima-media thickness/diameter ratio of the carotid artery in children. Therefore, this study aimed to assess vascular diameter, intima-media thickness/diameter ratio and related tensile stress values in children and to further investigate the influence of sex, age, body mass index, and blood pressure. The parameters were measured with high-resolution semi-automated ultrasound. Sex- and age-dependent values were calculated with the LMS method for a cross-sectional sample of 642 healthy, non-obese children aged 8-17 years. The mean vascular diameter was 5.45 ± 0.46 mm; the median intima-media thickness/diameter ratio was 0.085 (0.079-0.092); the median tensile stress was 105.4 (95.2-116.4) kPa. The vascular diameter and the tensile stress were higher, and the intima-media thickness/diameter ratio was lower in boys than in girls. In comparison to the normal weight study population the excludedobese children had a significantly higher diameter, a lower intima-media thickness/diameter ratio, and a higher tensile stress. In multiple regression analyses of diameter, intima-media thickness/diameter ratio, and tensile stress, all parameters were influenced by sex and body mass index. Furthermore, systolic and diastolic blood pressure significantly influenced the vascular diameter, and systolic blood pressure significantly influenced the intima-media thickness/diameter ratio. Conclusion: This study is the first to report values for the diameter, the intima-media thickness/diameter ratio of the carotid artery, and the related tensile stress allowing a more differentiated view of cardiovascular adaptations as it combines structural and functional vascular parameters. What is known: • Intima-media thickness and vascular diameter are related to a higher cardiovascular risk in adults • The intima-media thickness/diameter ratio gives information about hemodynamic and functional vessel adaptation What is new: • Values for vascular diameter, intima-media thickness/diameter ratio, and tensile stress of the carotid artery in children are presented in this study • Intima-media thickness as a surrogate marker for arterial health in children should be complemented by intima-media thickness/diameter ratio measurement.

Reduced arterial stiffness in very fit boys and girls.

Low cardiorespiratory fitness is associated with higher cardiovascular risk, whereas high levels of cardiorespiratory fitness protect the cardiovascular system. Carotid intima-media thickness and arterial distensibility are well-established parameters to identify subclinical cardiovascular disease. Therefore, this study investigated the influence of cardiorespiratory fitness and muscular strength on carotid intima-media thickness and arterial distensibility in 697 children and adolescents (376 girls), aged 7-17 years. Cardiorespiratory fitness and strength were measured with the test battery FITNESSGRAM; carotid intima-media thickness, arterial compliance, elastic modulus, stiffness index ß, and pulse wave velocity ß were assessed by B- and M-mode ultrasound at the common carotid artery. In bivariate correlation, cardiorespiratory fitness was significantly associated with all cardiovascular parameters and was an independent predictor in multivariate regression analysis. No significant associations were obtained for muscular strength. In a one-way variance analysis, very fit boys and girls (58 boys and 74 girls>80th percentile for cardiorespiratory fitness) had significantly decreased stiffness parameters (expressed in standard deviation scores) compared with low fit subjects (71 boys and 77 girls<20th percentile for cardiorespiratory fitness): elastic modulus -0.16±1.02 versus 0.19±1.17, p=0.009; stiffness index ß -0.15±1.08 versus 0.16±1.1, p=0.03; and pulse wave velocity ß -0.19±1.02 versus 0.19±1.14, p=0.005. Cardiorespiratory fitness was associated with healthier arteries in children and adolescents. Comparison of very fit with unfit subjects revealed better distensibility parameters in very fit boys and girls.

Beyond intima-media-thickness: Analysis of the carotid intima-media-roughness in a paediatric population.

BACKGROUND AND AIMS: Subclinical atherosclerosis assessed by sonographic intima-media-thickness measurement of the carotid artery (cIMT) is considered to be an early precursor of cardiovascular disease already in childhood. Structural analysis of the carotid intimal layer (carotid intima-media-roughness, cIMR) improves cardiovascular risk profiling for the adult patient and has been shown to be increased also in paediatric patients with elevated cardiovascular risk. To date, normal values for the paediatric age are lacking. Thus, we present normative data for a paediatric age group. METHODS: 602 healthy German school children (age 8-18 y) were studied, and cIMT and cIMR calculated; reference values were given for three age groups (group 1: 8-10.99 years; group 2: 11-13.99 years; group 3: 14-17.99 years). RESULTS: cIMT values were: 0.48 ± 0.03 mm for girls and boys in age group 1, 0.49 ± 0.03 mm for girls and boys in age group 2; and 0.45 ± 0.03 mm for girls and 0.49 ± 0.03 mm for boys in age group 3; cIMR was 0.04 ± 0.01 mm for both sexes in age group 1 and 3; while in age group 2, both sexes showed a cIMR of 0.03 ± 0.01 mm. Physical fitness was significantly negatively correlated with cIMR (r = - 0.212, p < 0.0001) and a strong predictor for cIMR increase. CONCLUSIONS: The normative data of cIMR for a paediatric age group presented here allow for the identification of patients at elevated cardiovascular risk. By including cIMR as surface analysis of the arterial wall, the individual risk stratification may be improved compared to thickness-analysis of the Intima-Media-Layer (cIMT) also at a paediatric age.

Intima-Media Thickness Does Not Differ between Two Common Carotid Artery Segments in Children.

Carotid intima-media thickness (cIMT) is a surrogate marker of early atherosclerotic changes in children. cIMT-studies are hard to compare, due to variations in ultrasound protocols, especially regarding the common carotid artery (CCA) segment measured in relation to the bulb. This study's purpose was therefore to compare two distinct CCA segments in children, to see if cIMT values differ substantially according to the site of measurement. cIMT was assessed after power calculation in 30 children (15 girls) aged 8-17, using B-Mode ultrasound (5-13 MHz) at two CCA locations. The first measurement was performed over a distance of 1 cm immediately after the bulb (A), the second 1cm proximal the bulb (B) over the same distance of 1cm length. Means of end-diastolic far wall cIMT were compared between measurement A and B. cIMT in 30 participants was 0.51±0.06 mm for measurement A and 0.51±0.05 mm for measurement B. Results did not differ significantly (p = .947) over a distance of 2 cm after the bulb. According to our results, studies measuring CCA IMT within the first 2 cm, either close to the bulb or further proximal, can be compared. This will improve interpretation of data and application of reference values.

Increased intima-media thickness is not associated with stiffer arteries in children.

OBJECTIVE: Subclinical atherosclerosis can be assessed via sonographic measurement of intima-media thickness and carotid artery distensibility, both may already be pathologically altered in childhood. Therefore, the purpose of this study was to provide reference percentiles and investigate possible associations between alterations of intima-media thickness and distensibility. METHODS: Carotid intima-media thickness and distensibility was measured via B- and M-mode ultrasound. Distensibility was defined by arterial compliance, elastic modulus, stiffness parameter ß, and local pulse wave velocity ß. Age- and height-dependent reference values were calculated separately for boys and girls among 690 (intima-media thickness) and 870 (distensibility) non-obese children aged 7-17 years. RESULTS: Intima-media thickness and distensibility did not increase significantly with age or differ between boys and girls. Systolic blood pressure and body mass index were independent predictors of intima-media thickness, while an increased systolic blood pressure or pulse pressure was associated with stiffer arteries. Increased intima-media thickness was accompanied by higher arterial compliance and lower stiffness. CONCLUSION: Using this healthy cohort, we describe a functional and non-pathological arterial adaptation wherein an increase in intima-media thickness is not associated with stiffer arteries.

Intima-media thickness and arterial function in obese and non-obese children.

BACKGROUND: Obesity is an independent cardiovascular risk factor that contributes to the development of atherosclerosis. Subclinical forms of the disease can be assessed via sonographic measurement of carotid intima-media thickness (cIMT) and distensibility - both may already be altered in childhood. As childhood obesity increases to an alarming extent, this study compares vascular data of obese with normal weight boys and girls to investigate the influence of obesity on cIMT and distensibility of the carotid arteries. METHODS: cIMT and distensibility of 46 obese children (27 girls) aged 7-17 years were compared with measures of 46 sex- and age-matched normal weight controls. cIMT and distensibility were measured by B- and M-mode ultrasound and expressed as standard deviation scores (SDS). Arterial distensibility was defined by arterial compliance (AC), elastic modulus (Ep), stiffness index ß (ß), and local pulse wave velocity ß (PWV ß). RESULTS: Obese girls had significantly stiffer arteries compared with normal weight girls (Ep SDS 0.64 ± 1.24 vs. 0 ± 1.06, ß SDS 0.6 ± 1.17 vs. -0.01 ± 1.06 p < .01, PWV ß 0.54 ± 1.2 vs. -0.12 ± 1.05 p < .05). No significant differences were observed for boys. In multiregression analysis, BMI significantly influenced Ep, ß and PWV ß but not cIMT and AC. CONCLUSIONS: Obese girls seemed to be at higher cardiovascular risk than boys, expressed by stiffer arteries in obese girls compared with normal weight girls. Overall, BMI negatively influenced parameters of arterial stiffness (Ep, ß and PWV ß) but not compliance or cIMT.