Age dependency of stiffness of the abdominal aorta and the mechanical properties of the aorta in Kawasaki disease in children

Measuring aortic distensibility has been shown to be useful in adults as a noninvasive method in the early detection of atherosclerosis. This study had two purposes: to assess the stiffness of the abdominal aorta by using two-dimensional echocardiography (2DE) in healthy neonates, children, and adults and to assess aortic distensibility in children with Kawasaki disease in acute and subacute phases. The study comprised 168 healthy subjects and 40 patients with Kawasaki disease. We recorded systolic (P-s) and diastolic (P-d) blood pressure and measured aortic diameter (D-d) at both minimum diastolic pressure and maximum systolic expansion (D-s) by 2DE. These measurements were used to determine (1) aortic strain (S) = (D-s - D-d)/D-d, (2) pressure strain elastic modulus (E-p) = (P-s - P-d)/S, and (3) normalized E-p (E-p*) = E-p/P-d. Significant correlations were found between S and age, E-p and age, and E-p* and age. In Kawasaki disease, E-p and E-p* showed negative correlations to day after onset. The aorta was less distensible in infants. became soft in 12- to 16-year-olds, and then stiffened with increasing age among normal subjects. In Kawasaki disease, aortic stiffness was high at the acute phase and normal at the subacute phase. These tendencies may be related to the biological characteristics of smooth muscle cells.