ALLOMETRIC SCALING OF LEFT-VENTRICULAR MASS BY BODY DIMENSIONS IN MALES AND FEMALES

Physiological variables must often be scaled for body size differences to permit meaningful comparisons between subjects or groups. This stu dy aimed to determine the proper relationship between body dimensions and left ventricular mass (LVM) via allometric scaling (AS) in 142 sub jects (78 males, 64 females; ages 18-40). A cubic formula was used to estimate LVM from wall thicknesses and left ventricular internal dimen sions derived from M-mode echocardiography. Fat free mass (FFM) was pr edicted from anthropometry. ''Best compromise'' allometric equations ( y = a . x(b)) revealed a common body mass (BM) exponent of 0.78 (95% C I, 0.65-0.91). The widely adopted ratio scaling (RS) method assumes th at the exponent b = 1. In this sample, use of RS would penalize heavie r subjects by overcorrecting for BM. The equivalent mean FFM exponent of 1.07 was not different from unity (95% CI, 0.92-1.22). Hence, RS us ing BM would appear to penalize those subjects who are heavier owing t o excess fat not excess FFM. Gender differences in LVM were 70, 44, an d 18%, for absolute values per BM(0.78) and per FFM(1.07), respectivel y (P < 0.05). This reveals quantitative differences in heart size inde pendent of body dimensions. We conclude that sample specific AS permit s meaningful intersubject or intergroup comparisons.