AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 1 40-R48, Copyright © 1984 by American Physiological Society
Left ventricular size, output, and structure during guinea pig pregnancy
M. Morton, H. Tsang, R. Hohimer, D. Ross, K. Thornburg, J. Faber and J. Metcalfe
We investigated left ventricular (LV) hemodynamics, pressure-volume
relations, and morphometry to determine what cardiac changes characterize
pregnancy in the guinea pig. Time-bred virgin guinea pigs were paired by
weight with unbred controls. Hemodynamic studies and LV pressure-volume
relations were obtained on days 59-68 of the 68-day gestation. Weight of
control sows increased from 817 to 902 g (P less than 0.01) and pregnant
sows from 810 to 1,251 g (P less than 0.01). LV weights were not different.
When indexed for maternal weight minus uterus and contents, pregnancy
produced increases in O2 consumption, +48% (P less than 0.01); cardiac
output, +32% (P less than 0.05); and stroke volume, +46% (P less than
0.025). Passive LV pressure-volume curves (dP/dV) were shifted to the right
(P less than 0.025), but dP/dV at constant pressure was unchanged. Using a
thin-walled spherical model, elastic modulus at constant stress was not
different. The percent LV inter- and intracellular volumes and myocyte
myofibril and organelle volumes were unchanged during pregnancy. In the
guinea pig, pregnancy increases LV output, stroke volume, and size without
changes in LV mass, morphometry, or elastic modulus.
