AJP - Heart and Circulatory Physiology, Vol 247, Issue 5 699-H708, Copyright © 1984 by American Physiological Society
Left ventricular function and muscle mechanics in hypertrophied rabbit heart
T. Okada, H. Okuyama, H. Mashima, H. Sato and K. Kitamura
Ventricular contractile performance was studied in relation to wall muscle
mechanics in isolated rabbit left ventricles during pressure-overloaded
hypertrophy. The isovolumic pressure-volume relation of the hypertrophied
ventricle (LVH) shifted to the left and upward from the normal control (NC)
(P less than 0.001), but calculated wall stress at each normalized
circumferential length decreased in LVH. The pressure-ejection rate
relation, determined accurately by velocity control technique, could be
adequately approximated by a hyperbola. In LVH, the maximum pressure (Po)
was larger (154.3 +/- 17.0 mmHg), whereas the maximum ejection rate (Vej
max) was smaller (13.7 +/- 4.2 ml/s, P less than 0.001) than those for NC
(127.7 +/- 23.3 mmHg and 22.3 +/- 5.7 ml/s, respectively). The
pressure-stiffness relation was linear in both groups, but the vertical
axis intercept increased, indicating increased resting stiffness in LVH.
Ventricular volume stiffness vs. the mean wall stress relationship of LVH
shifted upward, whereas the normalized wall muscle stiffness vs. the mean
wall stress relationship of LVH showed a smaller slope. Thus the
hypertrophied ventricle can maintain its pumping ability at normal or
augmented levels with depressed contractile function of the wall muscle.
