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 echoc ardiographic (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 wi th 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 o f the arterial tree, we used ANCOVA to adjust SV/PP for body size. Bod y size-adjusted SV/PP ratio was no longer related to age in children, whereas the negative relation with aging in adults remained statistica lly significant (r=-.19, P<.0002). Heart rate was negatively related t o SV/PP ratio in both children and adolescents and adults, but this re lation did not influence the relation with age. In multivariate analys is, high SV/PP ratio was predicted by greater height (P<.002) and weig ht (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 adult hood through old age; (2) arterial compliance decreases progressively with aging; (3) the apparent difference between males and females migh t be due to their different body sizes.