Relations of Left Ventricular Mass to Fat-Free and Adipose Body Mass
To the Editor:
We read with great interest the recent article by Bella et al,1 which reported as its principal finding that fat-free mass (FFM) was the strongest correlate of left ventricular mass (LVM) in a large cross-sectional study of Native Americans (the Strong Heart Study). Their article agrees in many aspects with our report of a large Caucasian adult population survey (the MONICA Augsburg study), which was published earlier in 1998.2 Body impedance analysis was used in both studies to determine the FFM. Interestingly, despite the use of different equipment for body impedance analysis, different equations, and the major differences in the anthropometric characteristics of the 2 populations, the results of these 2 investigations are impressively consistent. Our study supports the principal finding of Bella et al1 ; we could demonstrate that substantial reductions in the association of adiposity with ventricle mass were obtained by indexing LVM to FFM. This reduction was significantly stronger than that observed by indexing for height, various exponentials of height, or body surface. However, a remarkable difference existed between the 2 studies.
The sex difference in heart mass, which is traditionally reported as higher in adult men than women, was almost completely eliminated when LVM was indexed to FFM in the MONICA Augsburg study (men, 3.4 g/kg; women, 3.3 g/kg; P=0.06).2 Bella et al1 present sex-specific criteria for LV hypertrophy based on the LVM/FFM ratio that were even lower for men (3.6 g/kg) than for women (4.4 g/kg [according to Table 6] or 4.86 g/kg [according to the text on pages 2541 and 2542]). This could indicate that in the Strong Heart Study, the whole distribution of the LVM/FFM values of women shifted to values that were higher than those in men. Alternatively, the inverted order of the partition values may be due to the comparatively few subjects in the healthy reference population and reflect the sensitivity of the 97.5th percentile partition criteria to extreme values in such a situation. A more detailed description of the Strong Heart population including, for example, mean values of LVM and LVM/FFM, would help to elucidate these associations and resolve open questions. It may help to further support the notion that fat-free body mass is the dominating anthropometric determinant of LVM in adult men and women.
- Copyright © 1999 by American Heart Association
We thank Drs Hense and Schunkert for their interest in our report from the Strong Heart Study (SHS), which indicated that left ventricular (LV) mass is more strongly related to fat-free mass (FFM) than to adipose mass or height-based surrogates for FFM.R1 We read their article, which was published after ours was in press, with great interest,R2 and we are delighted that both the Augsburg and SHS studies identified FFM as the strongest correlate of LV mass. The differences between the SHS and Augsburg results reflect both differences in data presentation and in study populations. In the SHS cohort of American Indians aged 47 to 81 years, we found that men had thicker LV walls and larger LV chamber diameters than women. As a consequence, unindexed LV mass was greater in men than in women (mean, 167.7 versus 143.0 g), as was LV mass/body surface area (83.4 versus 78.8 g/m2; both P<0.001). However, FFM was much higher in SHS men than SHS women (63.3 versus 46.4 kg). As a result, mean LV mass/FFM was higher in women than men (3.13 versus 2.71 g/kg), as was the prognostically-validated indexation of LV mass for height2.7 (40.7 versus 38.1 g/m2.7; both P<0.001).
Although the results of both studies agree on the strong relationship of FFM to LV mass, the contrasting findings with regard to LV mass/FFM in women and men indicate that this ratio is influenced by other variables. A potential candidate for such a role is the considerably lower age limit for the Augsburg population (25 versus 47 years in the SHS study), which facilitated the inclusion of individuals (disproportionately men) in the population who engaged in leisure-time athletics or physically demanding work. In addition, the difference in adipose mass between women and men was more than 3 times as great in the SHS (8.0 kg) than in the Augsburg study (2.6 kg), which potentially allowed the small contribution of body fat to LV mass to raise the LV mass/FFM ratio in SHS women. Further studies are needed to assess the impact of age, physical activity, weight, and sex on LV mass within and across populations.
Bella JN, Devereux RB, Roman MJ, O’Grady MJ, Welty TK, Lee ET, Fabsitz RR, Howard BV, for the Strong Heart Study Investigators. Relations of left ventricular mass to fat-free and adipose body mass: the Strong Heart Study. Circulation. 1998;98:2538–2544.
Hense H-W, Gneiting B, Muscholl M, Broeckel U, Kuch B, Doering A, Riegger GAJ, Schunket H. The associations of body size and body composition with left ventricular mass: impacts for indexation in adults. J Am Coll Cardiol. 1998;32:451–457.