Age-related changes in total arterial capacitance from birth to maturity in a normotensive population

We evaluated the effect of body growth and aging on the ratio of echocardiographic (Teichholz) stroke volume to pulse pressure (SV/PP ratio) in 373 normal-weight, normotensive children to adolescents (1 day to 17 years old; 166 girls, 87 nonwhite) and 393 normal adults (17 to 85 years old; 164 women, 112 nonwhite). Stroke volume increased with age in children (r=.64, P<.0001) and was stable in adults; pulse pressure decreased slightly with age in children (r=-.10, P=.06) and increased in adults (r=.29, P<.0001). As a consequence, SV/PP ratio increased with age in children (r=.51, P<.0001) and decreased in adults (r=-.18, P=.0004). To control for changes in body size that influence the size of the arterial tree, we used ANCOVA to adjust SV/PP for body size. Body size-adjusted SV/PP ratio was no longer related to age in children, whereas the negative relation with aging in adults remained statistically significant (r=-.19, P<.0002). Heart rate was negatively related to SV/PP ratio in both children and adolescents and adults, but this relation did not influence the relation with age. In multivariate analysis, high SV/PP ratio was predicted by greater height (P<.002) and weight (P<.04) and nonwhite race (P<.001) in children and adolescents and by younger age (P<.0001), greater weight (P<.0001), and low heart rate (P<.001) in adults. Sex did not enter the regression models. Thus, (1) SV/PP ratio is a measure of increasing capacity of the arterial tree during growth, whereas it depends on arterial compliance during adulthood through old age; (2) arterial compliance decreases progressively with aging; (3) the apparent difference between males and females might be due to their different body sizes.