The ambulatory arterial stiffness index is not a measure of arterial stiffness in childhood

BackgroundThe ambulatory arterial stiffness index (AASI) has emerged as an ambulatory blood pressure monitoring (ABPM) measure of stiffness and is supposedly useful in younger subjects. The objective of our cross-sectional study was to evaluate the relationships between the AASI and indices of arterial stiffness in a pediatric population at risk of hypertension. MethodsThis was a cross-sectional study of children/adolescents (8-18 years) whose pulse wave velocity (PWV: carotid-to-femoral cf-PWV and heart-finger hf-PWV), augmentation index (AIx; normalized at 75 bpm: AIx75), systemic arterial stiffness (aortic pulse pressure/stroke volume, measured via pulse contour analysis) and ABPM were measured on the same day. At-risk populations were vascular remodeling (preterm birth, n=44 and chronic kidney diseases, n=7) and hyperkinetic causes (congenital central hypoventilation syndrome, n=14 and psychostimulant treatment, n=10). ResultsThe mean age of the 75 participants was 12.3 {+/-} 2.5 years (34 girls), and their mean AASI was 0.33 {+/-} 0.17. AASI did not correlate with cf-PWV, hf-PWV, AIx or systemic arterial stiffness. In contrast, the AASI significantly correlated with both systolic and diastolic BP at night (R= -0.23; p=0.048 and R= -0.33; p=0.004, respectively). Systemic arterial stiffness correlated with hf-PWV and AIx75 (R= 0.35; p=0.004 and R= -0.34; p=0.013, respectively). Based on ABPM, 15/75 (20%) participants had hypertension, and they had higher cf-PWV than participants without hypertension (5.64 {+/-} 0.70 vs 4.92 {+/-} 0.78 m/s, p=0.002) and not different AASI values (0.34 {+/-} 0.14 vs 0.32 {+/-} 0.18, p=0.756). ConclusionAASI is not a measure of arterial stiffness in childhood.