AJP - Heart and Circulatory Physiology, Vol 243, Issue 6 941-H947, Copyright © 1982 by American Physiological Society
Use of tibial length to quantify cardiac hypertrophy: application in the aging rat
F. C. Yin, H. A. Spurgeon, K. Rakusan, M. L. Weisfeldt and E. G. Lakatta
Fluctuations in body weight as occur with aging make body weight an
unreliable reference for normalizing heart weight. We compared heart weight
normalized by tibial length, which remains constant after maturity, with
that normalized by body weight in 5- to 28-mo-old male Wistar rats. When
normalized by tibial length or body weight, relative to the 5-mo heart, the
senescent left ventricle undergoes 17 vs. 38% hypertrophy, respectively,
and the right ventricle undergoes 0 vs. 28% hypertrophy, respectively.
Histological measurements in the 25- compared with the 5-mo-old left
ventricles reveal 6% larger myocyte diameters and 12% larger cellular
cross-sectional areas, indicating about 15% hypertrophy; this value agrees
more closely with the estimates based on tibial length than with those
based on body weight. To allow prediction of left ventricular weight in a
living rat, a regression equation using body weight, age, and tibial length
was derived. This enabled us to perform a longitudinal aging study that
verified that the above results were not biased by selective survival.
Thus, in conditions in which body weight changes, cardiac hypertrophy can
be more accurately quantified by relating heart weight to tibial length
than to body weight. This approach may have applicability for assessing
relative sizes of other organs as well.
