STROKE VOLUME AND CARDIAC-OUTPUT IN NORMOTENSIVE CHILDREN AND ADULTS - ASSESSMENT OF RELATIONS WITH BODY-SIZE AND IMPACT OF OVERWEIGHT

Background Relations between organs and body size are not linear but r ather follow allometric (growth) relations characterized by their powe rs (exponents). Methods and Results Stroke volume (SV) by M-mode echoc ardiography was related to height, weight, body surface area (BSA), an d ideal BSA (derived from ideal body weight for given height) in 970 n ormotensive individuals (1 day to 85 years old; 426 <18 years old; 204 overweight to obese; 426 female). In normal-weight children, adults, and the entire population, SV was related by allometric relations to B SA (power=0.82 to 1.19), body weight (power=0.57 to 0.71), and height (power=1.45 to 2.04) (all P<.0001). Relations of cardiac output to mea sures of body size had lower allometric powers than those for SV in th e entire population (0.41 for body weight, 0.62 for BSA, and 1.16 for height). In overweight adults, observed SVs were 17% greater than pred icted for ideal BSA, a difference that was approximated by normalizati on of SV fur height to age-specific allometric powers. Similarly, obse rved cardiac output was 19% greater than predicted for ideal BSA, a di fference that was accurately detected by use of cardiac output/height to age-specific allometric powers but not of BSA to the first power. C onclusions Indexations of SV and cardiac output for BSA are pertinent when the effect of obesity needs to be removed, because these indexati ons obscure the impact of obesity. To detect the effect of obesity on LV pump function, normalization of SV and cardiac output for ideal BSA or for height to its age-specific allometric power should be practice d.